৪৯তম বিসিএস ⎯ প্রাণ রসায়ন [৬০১]

The famous novel, The Bluest Eye, is written by - American author.

• The Bluest Eye:
- এটি Toni Morrison রচিত।
- এটি একটি novel.
- এটি ১৯৭০ সালে প্রকাশিত হয়।

• Toni Morrison ছিলেন একজন আমেরিকান Novelist, essayist এবং Editor.
- তাছাড়া তিনি Princeton University এর প্রফেসর ছিলেন।

তাঁর উল্লেখযোগ্য সাহিত্যকর্ম গুলো -
- Beloved,
- Song of Solomon,
- The Bluest Eye.

Source: Britannica.

বাংলাদেশের তত্ত্বাবধায়ক সরকার:
- বাংলাদেশের তত্ত্বাবধায়ক সরকার বাংলাদেশের একপ্রকারের শাসন ব্যবস্থা, যার অধীনে দুইটি নির্বাচিত সরকারের মধ্যবর্তী সময়কালে সাময়িকভাবে অনির্বাচিত ব্যক্তিবর্গ কোন দেশের শাসনভার গ্রহণ করে থাকে।
- বিএনপি সরকারের পদত্যাগের পর ১৯৯৬ সালে ত্রয়োদশ সংশোধনের মাধ্যমে সংবিধানে যোগ হয় তত্ত্বাবধায়ক সরকার পদ্ধতি।
- এই সংশোধনীর মাধ্যমে ১৯৯৬ সালে সাংবিধানিকভাবে তত্ত্বাবধায়ক সরকার ব্যবস্থা চালু হয়।
- বিচারপতি মুহাম্মদ হাবিবুর রহমান ছিলেন সেই তত্ত্বাবধায়ক সরকারের প্রধান উপদেষ্টা।
- উপদেষ্টা পরিষদের বাকিরা হলেন: ব্যারিস্টার সৈয়দ ইশতিয়াক আহমেদ, ড. মুহাম্মদ ইউনূস, অর্থনীতিবিদ ড. ওয়াহিদউদ্দিন মাহমুদ, অধ্যাপক মো. শামসুল হক, অধ্যাপক জামিলুর রেজা চৌধুরী, শেগুফতা বখত চৌধুরী, এ জেড এম নাছিরুদ্দিন, সৈয়দ মঞ্জুর এলাহী, অধ্যাপক নাজমা চৌধুরী ও মেজর জেনারেল (অব.) আব্দুর রহমান খান।
- এই তত্ত্বাবধায়ক সরকার মোট ৮৬ দিন ক্ষমতায় ছিল। এই সরকার ১৯৯৬ সালের ১২ জুন জাতীয় সংসদের নির্বাচনের তারিখ ঘোষণা করেন।
- অবশেষে বিপুল উৎসাহ ও উদ্দীপনা মধ্য দিয়ে ১৯৯৬ সালের ১২ জুন তত্ত্বাবধায়ক সরকারের অধীন প্রথম সপ্তম জাতীয় সংসদ নির্বাচন অনুষ্ঠিত হয়।

উল্লেখ্য,
- ১৯৯০ সালে সেনাশাসক হুসেইন মুহম্মদ এরশাদের পতনের পর জাতীয় নির্বাচন আয়োজন পর্যন্ত দায়িত্ব পালনের জন্য গঠন করা হয়েছিল নির্দলীয় প্রথম অন্তর্বর্তীকালীন সরকার।
- প্রধান বিচারপতি শাহাবুদ্দিন আহমেদের নেতৃত্বে ঐ সরকার গঠিত হয়েছিল।

এছাড়াও,
- ৩০ জুন, ২০১১ সালে পঞ্চদশ সংশোধনীর মাধ্যমে বাংলাদেশের সংবিধান থেকে 'তত্ত্বাবধায়ক সরকার ব্যবস্থা' বাতিল করা হয়।

উৎস: ইতিহাস ২য় পত্র, এইচএসসি প্রোগ্রাম, বাংলাদেশ উন্মুক্ত বিশ্ববিদ্যালয়।

তিস্তা মহাপরিকল্পনা:
- তিস্তা মহাপরিকল্পনা বাস্তবায়নে সহায়তা করবে চীন।

⇒ তিস্তা প্রকল্পের প্রথম পর্যায় বাস্তবায়নে ব্যয় হবে ৭৫ কোটি ডলার। এর মধ্যে চীন থেকে ঋণ চাওয়া হয়েছে ৫৫ কোটি ডলার। বাকিটা করা হবে সরকারি অর্থায়নে।
- চীনের রাস্ট্রদূত জানান, তিস্তা প্রকল্পের বিষয়টিতে অর্থ মন্ত্রণালয়ের অর্থনৈতিক সম্পর্ক বিভাগের (ইআরডি) সঙ্গে তারা কাজ করছেন।
- চীনের বিশেষজ্ঞ দল তিস্তা প্রকল্পের সম্ভাবনা যাচাই শেষে অক্টোবর, ২০২৫-এর মধ্যে তিস্তা মহাপরিকল্পনার ডিজাইন চূড়ান্ত হবে।
- ২০২৬ সালে এ প্রকল্পের কাজ শুরু করে ২০২৯ সালে শেষ করার লক্ষ্যমাত্রা নির্ধারণ করা হয়েছে।
- মহাপরিকল্পনায় তিস্তা নদীর ডান-বাম উভয় তীর ঘেঁষে ২২০ কিলোমিটার উঁচু গাইড বাঁধ, রিভার ড্রাইভ, হোটেল-মোটেল-রেস্তোরাঁ, পর্যটন কেন্দ্র, ১৫০ মেগাওয়াট সৌর বিদ্যুতকেন্দ্র, শিল্প-কারখানা, ইপিজেড, ইকোনমিক জোন, কয়েক লাখ হেক্টর কৃষি জমি উদ্ধার, বনায়ন ইত্যাদি রয়েছে।
- এ প্রকল্প বাস্তবায়ন হলে তিস্তা পাড় হয়ে উঠবে পূর্ব চীনের জিয়াংসু প্রদেশের সুকিয়ান সিটির মতো সুন্দর নগরী।

উৎস: i) প্রথম আলো।
ii) দৈনিক ইনকিলাব।

ড্রাগন ফল উৎপাদন:
- কৃষি সম্প্রসারণ অধিদপ্তরের তথ্য অনুযায়ী, ড্রাগন উৎপাদনের শীর্ষে আছে ঝিনাইদহ জেলা।
- ২০২৪-২৫ অর্থবছরে উৎপাদন হয় ৩২ হাজার ৭৬৮ মেট্রিক টন ড্রাগন।

• উৎপাদনের ২য় স্থানে রয়েছে যশোর। ২০২৪-২৫ অর্থবছরে উৎপাদন হয় ১২ হাজার ৫৫৩ মেট্রিক টন ড্রাগন। আর তৃতীয় শীর্ষ জেলা রাজশাহীতে উৎপাদন হয় ৪ হাজার ৪৭৭ মেট্রিক টন ড্রাগন।

⇒ ড্রাগন ফল মূলত আমেরিকার প্রসিদ্ধ একটি ফল যা বর্তমানে আমাদের দেশেও ব্যাপক জনপ্রিয়তা অর্জন করেছে। বাংলাদেশে সর্বপ্রথম ২০০৭ সালে থাইল্যান্ড, ফ্লোরিডা ও ভিয়েতনাম থেকে এই ফলের বিভিন্ন জাত আনা হয়। ড্রাগন ফলের গাছ এক ধরনের ক্যাকটাস জাতীয় গাছ। এই গাছের কোন পাতা নেই। ড্রাগন ফলের গাছ সাধারনত ১.৫ থেকে ২.৫ মিটার পর্যন্ত লম্বা হয়ে থাকে।

⇒ বর্তমানে বাংলাদেশ কৃষি গবেষণা ইন্সিটিউট (বারি) কতৃক উদ্ভাবিত ড্রগন ফলের নতুন জাতটি হলো বারি ড্রাগন ফল-১ যা দক্ষিণ -পূর্ব এশিয়াতে জনপ্রিয় ফল। এ ফলের আকার বড়, পাকলে খোসার রং লাল হয়ে যায় ,শাঁস গাঢ় গোলাপী রঙের, লাল ও সাদা এবং রসালো প্রকৃতির । ফলের বীজগুলো ছোট ছোট কালো ও নরম । একটি ফলের ওজন ১৫০ গ্রাম থেকে ৬০০ গ্রাম পর্যন্ত হয়ে থাকে।

উৎস: i) প্রথম আলো।
ii) কৃষি বাতায়ন।

OIC:
- ইসলামিক সহযোগিতা সংস্থা OIC.
- OIC এর পূর্ণরূপ The Organisation of Islamic Cooperation.
- ইসরাইল কর্তৃক আল আকসা মসজিদে আগুন ধরিয়ে দেওয়ার প্রেক্ষাপটে OIC গঠিত হয়।
- এটি মুসলিম দেশগুলোর একটি রাজনৈতিক জোট যা রাবাত সম্মেলনের মাধ্যমে গঠিত হয়।
- প্রতিষ্ঠার স্থান: মরক্কো।
- প্রতিষ্ঠিত হয়: ২৫ সেপ্টেম্বর, ১৯৬৯ সালে।
- সদর দপ্তর: জেদ্দা, সৌদি আরব।
- বর্তমান মহাসচিব: হুসাইন ইব্রাহিম তাহা (১২ তম)। (অক্টোবর, ২০২৫)
- মহাসচিবের মেয়াদ: ৫ বছর।
- অফিসিয়াল ভাষা: তিনটি (আরবি, ইংরেজি, ফ্রেঞ্চ)।
- বর্তমান সদস্য: ৫৭টি। (অক্টোবর, ২০২৫)

⇒ দক্ষিণ আমেরিকা অঞ্চলের দুটি দেশ OIC এর সদস্য।
• গায়ানা ও
• সুরিনাম।

- ইউরোপ মহাদেশের আলবেনিয়া OIC এর সদস্য।
- বাংলাদেশ ১৯৭৪ সালের ২২-২৪ ফেব্রুয়ারি পাকিস্তানের লাহোরে অনুষ্ঠিত OIC এর দ্বিতীয় শীর্ষ সম্মেলনে সর্বপ্রথম অংশগ্রহণ করে।

তথ্যসূত্র - OIC অফিসিয়াল ওয়েবসাইট।

কার্টাগেনা প্রটোকল (Cartagena Protocol):
- কার্টাগেনা প্রোটকলের পূর্ণনাম - The Cartagena Protocol on Biosafety to the Convention on Biological Diversity.
- কার্টাগেনা প্রটোকল জৈব-নিরাপত্তা বিষয়ক একটি আন্তর্জাতিক চুক্তি।
- এই চুক্তিটি কলম্বিয়ার কার্টাগেনাতে আলোচিত হয়।
- চুক্তি অনুমোদন - ২৯ জানুয়ারি, ২০০০ সাল।
- চুক্তি কার্যকর - ১১ সেপ্টেম্বর, ২০০৩ সাল।

তথ্যসূত্র - কনভেনশন অন বায়ো-ডাইভার্সিটি (CBD) ওয়েবসাইট।

জাতিসংঘ:
- জাতিসংঘের অর্থনৈতিক ও সামাজিক কমিশন (ECOSOC) এর অধীন ৫টি আঞ্চলিক কমিশন রয়েছে।

⇒ এগুলো হলো:
- এশিয়া ও প্রশান্ত মহাসাগরীয় অর্থনৈতিক ও সামাজিক কমিশন (ESCAP),
- পশ্চিম এশীয় অর্থনৈতিক ও সামাজিক কমিশন (ESCWA),
- ল্যাটিন আমেরিকা ও ক্যারিবীয় অর্থনৈতিক কমিশন (ECLAC),
- ইউরোপিয়ান অর্থনৈতিক কমিশন (ECE),
- আফ্রিকান অর্থনৈতিক কমিশন (ECA).

তথ্যসূত্র - UN ওয়েবসাইট।

ইউরোপীয় ইউনিয়ন (EU):
- বিশ্বের সবচেয়ে বড় অর্থনৈতিক জোট ইউরোপীয় ইউনিয়ন (EU)।
- এর সদর দপ্তর বেলজিয়ামের ব্রাসেলসে অবস্থিত।
- প্রতিষ্ঠাতা সদস্য: ৬টি দেশ।
- বেলজিয়াম, ফ্রান্স, জার্মানি, ইতালি, লুক্সেমবার্গ, নেদারল্যান্ডস।
- বর্তমান সদস্য: ২৭টি দেশ। (অক্টোবর, ২০২৫)
- সর্বশেষ সদস্য: ক্রোয়েশিয়া। (অক্টোবর, ২০২৫)
- সর্বশেষ ত্যাগকারী: ব্রিটেন (৩১ জানুয়ারি, ২০২০)।
- এটি ১৯৯৩ সালের ১ নভেম্বরে মাসট্রিচট চুক্তি স্বাক্ষরের মাধ্যমে প্রতিষ্ঠিত হয়েছিল।
- তখন থেকে এটি বিশ্বের বৃহত্তম ট্রেডিং ব্লকে পরিণত হয়।

তথ্যসূত্র - EU ওয়েবসাইট।

‘অপারেশন রাইজিং লায়ন':
- ইসরায়েল কর্তৃক ইরানে চালানো সামরিক অভিযানটির নাম 'অপারেশন রাইজিং লায়ন'।
- 'রাইজিং লায়ন' নামটি বাইবেলের একটি অনুচ্ছেদে সিংহের প্রতীকী পরাক্রমকে তুলে ধরে, ইসরায়েলের যুদ্ধ প্রস্তুতি এবং আত্মবিশ্বাসের প্রতীক।
- ১৩ জুন ২০২৫-এর ভোরে ইসরায়েলি বিমান বাহিনী ও গোয়েন্দা সংস্থা মোসাদ যৌথভাবে 'অপারেশন রাইজিং লায়ন' পরিচালনা করে।
- ইসরায়েল প্রথমে 'ড্রোন' দ্বারা ইরানের আকাশ প্রতিরক্ষা ব্যবস্থা দুর্বল করা, এরপর প্রধান পারমাণবিক ও সামরিক লক্ষ্যবস্তুতে বিমান হামলা করে।

উল্লেখ্য:
- এই হামলার জবাবে ইরান পাল্টা হামলা চালায়।
- এই হামলার নাম দেয়া হয় 'অপারেশন টু প্রমিজ থ্রি’।
- ইরান পাল্টা জবাবে শতাধিক ক্ষেপণাস্ত্র ও ড্রোন ছুড়ে।

তথ্যসূত্র - পত্রিকার রিপোর্ট।

IUCN:
- বিশ্ব জীববৈচিত্র্য সংরক্ষণবাদী সংস্থা (IUCN)।
- IUCN এর পূর্ণরূপ - International Union for the Conservation of Nature.
- প্রতিষ্ঠিত হয়: ১৯৪৮ সালে।
- সদর দপ্তর: গ্লান্ড, সুইজারল্যান্ড।
- এটি নিয়ে বিশ্বের ১৭০ টির অধিক দেশ কাজ করছে।
- উদ্দেশ্য: বিশ্বব্যাপী প্রাকৃতিক সম্পদ সংরক্ষণ করা।

তথ্যসূত্র - IUCN অফিসিয়াল ওয়েবসাইট।

IMF:
- IMF এর পূর্ণরূপ The International Monetary Fund.
- এটি আন্তর্জাতিক মুদ্রা তহবিল।
- প্রতিষ্ঠিত হয়: ১৯৪৪ সাল।
- সদর দপ্তর: ওয়াশিংটন ডিসি, যুক্তরাষ্ট্র।
- প্রতিষ্ঠাতা সদস্য: ৪৪টি।
- বর্তমান সদস্য: ১৯১টি। (অক্টোবর, ২০২৫)
- সর্বশেষ সদস্য: লিচেনস্টাইন। (অক্টোবর, ২০২৫)
- বর্তমান ব্যবস্থাপনা পরিচালক: ক্রিস্টালিনা জর্জিয়েভা। (অক্টোবর, ২০২৫)
- বাংলাদেশ সদস্যপদ লাভ করে: ১৯৭২ সালে।

তথ্যসূত্র - IMF অফিসিয়াল ওয়েবসাইট।

প্রশ্ন: P হচ্ছে Q এর পিতা কিন্তু Q, P এর ছেলে নয়। তাদের সম্পর্কটা কোন ধরনের?

সমাধান:
যেহেতু, P হচ্ছে Q এর পিতা কিন্তু Q, P এর ছেলে নয় সুতরাং Q হলো মেয়ে এবং P হচ্ছে পিতা।

সুতরাং, তাদের সম্পর্কটা মেয়ে-পিতা।

প্রশ্ন: নিচের চিত্রে কয়টি ত্রিভুজ আছে?

সমাধান:

একটি করে ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 1, 2, 3, 4, 5, 6, 7, 8 = ৮ টি
দুইটি করে ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 12, 34, 56, 78, 67, 58 = ৬ টি
চারটি করে ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 1267, 3456 = ২টি
সবগুলো ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 12345678 = ১ টি

সুতরাং, মোট ত্রিভুজ আছে = ৮ + ৬ + ২ + ১ = ১৭ টি

প্রশ্ন: একটি পানি ভর্তি বালতির ওজন ১৪ কেজি। বালতিটি অর্ধেক পানি পূর্ণ থাকলে তার ওজন হয় ৮ কেজি। খালি বালতির ওজন কত?

সমাধান:
দেওয়া আছে,
পানি ভর্তি বালতির ওজন = ১৪ কেজি
অর্ধেক পানি ভর্তি বালতির ওজন = ৮ কেজি
​
​অর্ধেক বালতি পানির ওজন = (১৪ - ৮) কেজি = ৬ কেজি
∴ ​পূর্ণ বালতি পানির ওজন = (৬ × ২) কেজি = ১২ কেজি
​
​আবার,
​পূর্ণ বালতি পানির ওজন + খালি বালতির ওজন = ১৪ কেজি
⇒ ​খালি বালতির ওজন = ১৪ - ​পূর্ণ বালতি পানির ওজন
​⇒ ​খালি বালতির ওজন = ১৪ - ১২ = ২ কেজি

প্রশ্ন: যদি ORANGE = SVERKI হয় তবে GRAPES = ?

সমাধান:
​যদি ORANGE = SVERKI হয় তবে GRAPES = KVETIW
​
​ORANGE শব্দটির বর্ণগুলো থেকে 4 ধাপ এগিয়ে পাওয়া যায়,
O(15) + 4 → S(19)
​R(18) + 4 → V(22)
​A(1) + 4 → E(5)
​N(14) + 4 → R(18)
​G(7) + 4 → K(11)
​E(5) + 4 → I(9)

​অনুরূপভাবে,
GRAPES শব্দটির বর্ণগুলো থেকে 4 ধাপ এগিয়ে গেলে KVETIW শব্দটি পাওয়া যায়। অর্থাৎ,
​G(7) + 4 → K(11)
​R(18) +4 → V(24)
​A(1) + 4 → E(5)
​P(16) + 4 → T(20)
​E(5) + 4 → I(9)
​S(19) + 4 → W(23)
​
অর্থাৎ নির্ণেয় শব্দটি হবে KVETIW

প্রশ্ন: যদি 7 + 3 = 410, 3 + 2 = 15, 6 + 5 = 111 হয়, তবে 8 + 4 = ?

সমাধান:
এখানে
7 + 3 = 410 ⇒ 7 - 3 = 4, 7 + 3 = 10
3 + 2 = 15 ⇒ 3 - 2 = 1, 3 + 2 = 5
6 + 5 = 111 ⇒ 6 - 5 = 1, 6 + 5 = 11

একইভাবে,
8 - 4 = 4, 8 + 4 = 12
সুতরাং, 8 + 4 = 412

প্রশ্ন: A দক্ষিণ দিকে মুখ করে ৪ কি. মি. হাঁটার পর বামদিকে ঘুরল এবং ৫ কি. মি. হাঁটল। আবার ডানদিকে ঘুরে ৮ কি. মি. হাঁটল। এখন যাত্রার স্থান থেকে সরাসরি দূরত্ব কত?

সমাধান:
প্রদত্ত তথ্যগুলোকে চিত্রের মাধ্যমে সাজিয়ে পাই,

এখন, উত্তর-দক্ষিণ দিকে- শুরুতে ৪ কি.মি. দক্ষিণ + পরে আরও ৮ কি.মি. দক্ষিণ = মোট ১২ কি.মি. দক্ষিণ
পূর্ব-পশ্চিম দিকে: শুধু পূর্ব দিকে ৫ কি.মি.

∴ সরাসরি দূরত্ব = √(১২^২ + ৫^২) = √(১৪৪ + ২৫)
= √১৬৯
= ১৩ কি.মি.

প্রশ্ন: (A) চিত্রটির আয়নায় প্রতিবিম্ব কেমন হবে?

সমাধান:


সুতরাং, সঠিক উত্তর (2) নং

Explanation: (b) Tryptophan is decarboxylated to form tryptamine, a precursor to serotonin. Its carbon skeleton can also be broken down to alanine, which is transaminated to form pyruvate, making it glucogenic.

Explanation: (b) Ornithine transcarbamoylase (OTC) is a mitochondrial enzyme that catalyzes the condensation of ornithine with carbamoyl phosphate to form citrulline. Carbamoyl phosphate synthetase I (not OTC) is regulated by N-acetylglutamate.

Explanation: (c) Aspartate can be directly transaminated by aspartate aminotransferase to form oxaloacetate. Alanine (a) transaminates to pyruvate. Glutamate (b) deaminates to α-ketoglutarate. Serine (d) can be converted to pyruvate.

Correct Answer: গ) Chitin
Explanation:
Chitin is a polymer of N-acetylglucosamine with β(1→4) linkages, providing rigidity to fungal cell walls and insect exoskeletons. Chitin is the primary carbohydrate that provides structural support and rigidity to fungal cell walls. It acts as a protective and strengthening component, similar to the role of cellulose in plant cell walls. Chitin, a polysaccharide, is a major constituent of the fungal cell wall, along with glucans and glycoproteins.

Correct Answer: খ) Tyrosine
Explanation: Tyrosine is an amino acid that acts as a building block for proteins and is a precursor for important molecules like neurotransmitters (dopamine, norepinephrine) and thyroid hormones. It's synthesized in the body from the amino acid phenylalanine, and while often considered nonessential, it is sometimes classified as conditionally essential.
Tyrosine is synthesized from phenylalanine, making it non-essential under normal conditions.

B) Toluene.
Explanation: The methyl (−CH3​) group in toluene is an electron-donating group (EDG) that activates the benzene ring toward electrophilic aromatic substitution, making it more reactive than benzene itself. In contrast, the nitro (−NO2​) and chloro (−Cl) groups are electron-withdrawing and deactivate the ring.

B) Benzoic acid.
Explanation: This two-step process first involves the Sandmeyer reaction, where the diazonium salt is converted to benzonitrile (C6​H5​CN). Subsequent hydrolysis of the nitrile group yields benzoic acid (C6​H5​COOH).

B) The resonance stabilization of the phenoxide ion.

Explanation: Phenol is more acidic than aliphatic alcohols because its conjugate base, the phenoxide ion, is stabilized by resonance, which delocalizes the negative charge into the benzene ring.

A) Acetanilide. 

Explanation: The reaction between an aromatic amine like aniline and an acylating agent like acetic anhydride is an acylation reaction. The product is an amide, in this case, acetanilide (C6​H5​NHCOCH3​).

Ans: D) A mixture of o-nitrotoluene and p-nitrotoluene.

Explanation: The methyl group (−CH₃​) is a mild activating group and an ortho, para-director. Therefore, when toluene undergoes nitration, the nitro group (−NO₂​) is directed to the ortho and para positions. Due to steric hindrance, the para product is typically the major product, but a significant amount of the ortho product is also formed.

ঘ) A diazonium salt.
Explanation: The Sandmeyer reaction, which replaces the diazonium group of an aromatic diazonium salt with a halide or cyanide, proceeds through a free-radical mechanism. The diazonium salt is the essential starting material and a key intermediate in the process.

B) Benzene

Explanation: Benzene is a unique molecule due to its delocalized π electron system. This delocalization results in all six carbon-carbon bonds being identical in length, an intermediate between a single and a double bond. The molecule is also perfectly planar, with all bond angles being 120∘.

A secondary alcohol 
Explanation: The reaction of a Grignard reagent (RMgX) with an aldehyde (other than formaldehyde) and subsequent hydrolysis yields a secondary alcohol. Formaldehyde reacts with a Grignard reagent to produce a primary alcohol, while a ketone yields a tertiary alcohol.

Ethanol (CH₃​CH₂​OH)
Explanation: Ethanol has the highest boiling point among the given options due to its ability to form strong intermolecular hydrogen bonds. Neither ethane nor propane can form hydrogen bonds. Dimethyl ether has a polar C-O bond, but its dipole-dipole interactions are much weaker than the hydrogen bonds in ethanol.

B) 2-Bromobutane.
Explanation: The reaction of 1-butene with HBr follows Markovnikov's rule, which states that the hydrogen atom adds to the carbon of the double bond that already has more hydrogens, and the halogen adds to the carbon with fewer hydrogens. This results in the formation of 2-bromobutane.

Answer: B Explanation: The fundamental mechanism of all catalysts, including enzymes, is to provide an alternative reaction pathway with a lower activation energy (Ea). They do this by stabilizing the high-energy transition state. By lowering this energy barrier, they dramatically increase the rate at which the reaction proceeds towards equilibrium, but they do not alter the final equilibrium position or the overall ΔG.

Answer: C
Explanation: Isomerases (EC 5) are enzymes that catalyze structural rearrangements within a single molecule, converting it into an isomer. Since glucose-6-phosphate and fructose-6-phosphate are structural isomers, the enzyme facilitating this conversion is an isomerase.

Answer: B 

Explanation: In feedback inhibition, the end product of a multi-step pathway acts as an allosteric inhibitor for one of the first enzymes in that same pathway. This is an efficient control system; when the cell has enough of the product, the product itself signals for the pathway to shut down, preventing waste of energy and resources.

Explanation: (b) The fumarate released from argininosuccinate is a intermediate of the citric acid cycle (TCA cycle). This provides a direct anaplerotic link between the urea cycle and central carbon metabolism.

Explanation: (b)Urea is synthesized in the urea cycle from ammonia and carbon dioxide, along with ATP and aspartate (which provides the second amino group). The cycle is a series of reactions in the liver that detoxifies ammonia, which is a toxic byproduct of amino acid metabolism, by converting it into urea, a less toxic substance that can be excreted by the kidneys.

Urea, H₂N─C─NH₂, has two nitrogen atoms and one carbon atom. One nitrogen comes from NH₄⁺ (converted via carbamoyl phosphate), the carbon comes from HCO₃⁻ (also via carbamoyl phosphate), and the second nitrogen comes from aspartate.

Answer: ক) Glucose-6-phosphate dehydrogenase

Explanation:
High NADPH levels signal that the cell has enough reducing power, thus inhibiting G6PD to regulate the pathway.
The Pentose Phosphate Pathway (PPP), also called the hexose monophosphate shunt, is a metabolic process that produces NADPH and pentoses, like ribose 5-phosphate, from glucose. It runs parallel to glycolysis and is vital for providing the reducing power (NADPH) needed for fatty acid synthesis, cholesterol synthesis, and combating oxidative stress. Additionally, the pathway generates ribose 5-phosphate, a fundamental precursor for making nucleotides for DNA and RNA.

Answer: ঘ) Both খ and গ

Explanation: The hormone that most prominently promotes gluconeogenesis is glucagon, a pancreatic hormone released in response to low blood glucose levels that stimulates the liver to create glucose from non-carbohydrate sources. Other hormones that promote gluconeogenesis include cortisol, growth hormone, and epinephrine (catecholamines), which act by enhancing intracellular cyclic AMP (cAMP) levels or by interacting with the glucocorticoid receptor to induce gluconeogenic enzymes.

Explanation: (c) Glycerol is phosphorylated to glycerol-3-phosphate, which is then oxidized to dihydroxyacetone phosphate (DHAP). DHAP can enter glycolysis or gluconeogenesis, making glycerol glucogenic. During lipolysis, glycerol is released from triglycerides in adipose tissue and transported to the liver, where it is converted to glucose via gluconeogenesis. The glycerol is first phosphorylated by glycerol kinase into glycerol-3-phosphate, which is then oxidized and enters the gluconeogenic pathway to become glucose.

Explanation: (a) Each cycle of mitochondrial beta-oxidation produces one molecule of acetyl-CoA, one molecule of NADH, and one molecule of FADH2. These molecules are then used in the citric acid cycle and the electron transport chain to generate ATP, the primary energy currency of the cell.

Correct Answer: খ) Benedict's test
Explanation: Benedict's test is a qualitative and semi-quantitative chemical test used to detect the presence of reducing sugars and other reducing substances, such as glucose in urine, by reacting them with Benedict's reagent. The blue Benedict's reagent, containing copper(II) sulfate, turns green, yellow, orange, or brick-red, with the color intensity indicating the concentration of reducing sugar. A brick-red precipitate is a positive result, indicating a high amount of reducing sugar.
Benedict's reagent detects reducing sugars by their ability to reduce Cu²⁺ to Cu⁺, forming a red precipitate of Cu₂O.

Answer: c) It is the structural and catalytic component of the ribosome.

Explanation: rRNA is the most abundant and stable type of RNA. It combines with proteins to form ribosomes, the cellular machinery for protein synthesis. The rRNA component, not the proteins, is responsible for the catalytic activity (peptidyl transferase activity) that forms peptide bonds between amino acids.

Answer: a) A nucleotide contains a sugar, a base, and a phosphate group, while a nucleoside contains only a sugar and a base.

Explanation: The naming convention is straightforward: Nucleoside = Sugar + Base. Nucleotide = Three parts: Triphosphate + Sugar + Base. The phosphate group is the key differentiating component.

Answer: b) Guanine and Cytosine.

Explanation: The complementary base pairing rules dictate that Guanine (G) and Cytosine (C) form three hydrogen bonds, while Adenine (A) and Thymine (T) form two. This difference in bonding strength contributes to the stability of the DNA molecule and affects the melting temperature of a DNA helix.

Answer: a) Glycerol and three fatty acids.

Explanation: A triglyceride (or triacylglycerol) is an ester formed from one molecule of glycerol and three molecules of fatty acids. Hydrolysis breaks these ester bonds, yielding the original components: glycerol and three fatty acid molecules.

Answer: c) Water repellency and protection.

Explanation: Waxes are esters of a long-chain fatty acid and a long-chain alcohol. Their extremely hydrophobic nature makes them ideal for forming protective, water-repellent coatings on leaves, fruits, and animal skin and fur, preventing water loss and microbial invasion.

Answer: c) They are required for the synthesis of prostaglandins and other eicosanoids.

Explanation: Essential fatty acids (EFAs) like linoleic acid (an omega-6) and alpha-linolenic acid (an omega-3) are crucial because the human body cannot synthesize them. They are needed for the formation of important signaling molecules called eicosanoids, which include prostaglandins, leukotrienes, and thromboxanes, involved in inflammation, blood clotting, and other physiological processes.

Answer: c) The entropy of an isolated system always tends to increase.

Explanation: The Second Law of Thermodynamics deals with the direction of natural processes. It can be stated in several ways, one of which is in terms of entropy (S), which is a measure of the disorder or randomness of a system. The law states that the total entropy of an isolated system can never decrease over time. It will either stay constant for a reversible process or increase for an irreversible process. This is why heat naturally flows from hot to cold and why systems tend to move towards a state of greater disorder.

Answer: b) A positive ΔU

Explanation: Internal energy (U) is the sum of all the kinetic and potential energies of the particles within a system. For an ideal gas, internal energy is directly proportional to temperature. Therefore, if the temperature of the system increases (ΔT>0), its internal energy must also increase (ΔU>0). The other options are not necessarily true; for instance, an exothermic reaction could still result in a temperature increase if the heat is not dissipated quickly.

Correct Answer: খ) Pressure

Explanation:
Pressure has little to no effect on the solubility of solids in liquids, whereas temperature, solute-solvent interactions, and common ion effects significantly influence solubility.

Correct Answer: খ) Diffusion

Explanation: Osmosis is the net movement of solvent molecules, such as water, across a selectively permeable membrane from a region of high solvent concentration (low solute concentration) to a region of low solvent concentration (high solute concentration). This passive process occurs to equalize the solute concentrations on both sides of the membrane and is a type of diffusion.

Correct Answer: ঘ) Made only from strong acid and strong base

Explanation: A buffer solution resists changes in its pH when a small amount of acid or base is added, or when it's diluted. It typically consists of a weak acid and its conjugate base, or a weak base and its conjugate acid. These solutions are vital in maintaining pH stability for various applications, including biological systems like blood, food preservation, and drug delivery.
Buffers are made from a weak acid and its conjugate base or a weak base and its conjugate acid, not strong acids or bases.

Correct Answer: ক) pH = pKa

Explanation:
here the concentration of acid and conjugate base is equal , so their ratio of concentration will be 1.
From Henderson-Hasselbalch:

pH = pKa + log(1)
= pKa + 0
= pKa

Answer: ঘ) C

Explanation:

Ionization energy increases across a period from left to right due to:

o Increased nuclear charge

o Decreased atomic radius
Here, C has highest nuclear charge and smallest atomic radius. so,

Order of first ionization energy in these elements:

Li<B<Be<C

Carbon (C) has the highest among the given options.

Answer: খ) Cu (29) → [Ar] 3d¹⁰ 4s¹

Explanation:

· Expected configuration of Cu: [Ar] 3d⁹ 4s²

· Actual configuration: [Ar] 3d¹⁰ 4s¹

· Reason: A completely filled d-subshell (3d¹⁰) gives extra stability due to symmetrical distribution and exchange energy.

· Hence, Cu shows anomalous behavior.

Explanation(B): Dalton's Law, or the Law of Partial Pressures, states that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual gases. Dalton's Law is based on the assumption that gas molecules in a mixture are far apart (a core tenet of KTG) and therefore do not interact or affect each other's pressure contribution. Each gas exerts pressure as if it were the only gas present.

Correct Answer: গ) Gas molecules exert attractive forces on each other.

Explanation:
Kinetic theory of gases assumes:

Molecules are in constant, random motion.
They do not exert attractive or repulsive forces on each other.
The volume of gas molecules is negligible compared to the container volume.
Collisions are perfectly elastic (no loss of energy).
Hence, intermolecular forces are not considered in the ideal gas model, making option (গ) incorrect.

Answer: c) The average daily intake level sufficient to meet the nutrient requirements of nearly all healthy individuals.

Explanation: The RDA is a scientifically determined value intended to serve as a target for daily intake for the majority of the population. It is designed to prevent deficiency and maintain adequate nutritional status.

Answer: a) Complex carbohydrates and protein.

Explanation: Adolescent athletes have high energy demands and are in a period of rapid growth. Complex carbohydrates (like whole grains) provide sustained energy for performance, while a higher protein intake is essential for muscle repair and growth.

Answer: c) Both undernutrition and overnutrition (obesity).

Explanation: The double burden of malnutrition refers to the coexistence of undernutrition (e.g., stunting, wasting, micronutrient deficiencies) and overnutrition (overweight and obesity) within the same country, community, or even household. This is a growing concern in many developing nations, including Bangladesh.

Answer: b) Potassium (K⁺).

Explanation: Potassium is the principal cation inside cells, while sodium is the principal cation outside cells. This concentration gradient is maintained by the sodium-potassium pump and is vital for nerve impulse transmission and muscle contraction.

Answer: b) The transfer of phosphate groups (phosphorylation).

Explanation: Magnesium is a crucial mineral that acts as a cofactor for over 300 enzymes, particularly those that use ATP. It stabilizes the ATP molecule by binding to its phosphate groups, enabling enzymes like kinases to catalyze phosphorylation reactions.

B) Vitamin C.

Explanation: Vitamin C (ascorbic acid) is a highly water-soluble and heat-sensitive vitamin. It is easily oxidized and destroyed by cooking, boiling, or exposure to light and oxygen, which is why fresh, raw fruits and vegetables are the best sources.

Riboflavin (B2).

Explanation: Riboflavin, also known as vitamin B₂, is a vitamin found in food and sold as a dietary supplement. It is essential to the formation of two major coenzymes, flavin mononucleotide and flavin adenine dinucleotide.
Riboflavin deficiency is also known as ariboflavinosis. Its symptoms include inflammation of the lips, mouth, and tongue (glossitis), and cracks at the corners of the mouth (cheilosis).

Answer: c) Iron.

Explanation: Women of reproductive age have higher iron requirements due to blood loss during menstruation. The RDA for iron is 18 mg/day for women aged 19-50, compared to 8 mg/day for men. Menstruating women generally require more dietary iron, with the US Food and Drug Administration's Recommended Dietary Allowance (RDA) for adult women aged 19-50 being 18 mg per day, while teenaged women require 15 mg per day. These requirements account for increased loss of iron through menstrual blood, particularly in women with heavy periods, which can also necessitate higher iron intake or supplementation to prevent deficiency and maintain health.

Answer: c) Copper.

Explanation: Menkes syndrome, also known as Menkes kinky hair syndrome, is a rare, inherited genetic disorder that impairs the body's ability to absorb and distribute copper, leading to severe neurological problems and other issues. Symptoms typically appear in infancy and can include developmental delays, seizures, distinctive kinky hair, sagging facial features, and weakened bones. The disorder is caused by mutations in the ATP7A gene, which encodes a copper-transporting protein, and is inherited in an X-linked recessive pattern. While there is no cure, early treatment with copper injections, or other treatments, can improve outcomes and increase life expectancy

Answer: c) Blood clotting and muscle contraction.

Explanation: Calcium is a vital signaling ion. In muscle cells, a rise in intracellular calcium triggers muscle contraction. It is also an essential cofactor for several enzymes in the coagulation cascade that leads to blood clotting.

Answer: B) Glucose

Explanation: Glucose in urine (glucosuria) can be a normal finding in very small amounts, but high levels typically indicate either high blood sugar due to diabetes or a rare kidney problem, known as renal glucosuria, where the kidneys don't reabsorb enough glucose even with normal blood sugar levels. Common causes include uncontrolled diabetes, gestational diabetes (during pregnancy), certain medications, and conditions like Fanconi syndrome. If you have glucose in your urine, a blood glucose test is usually recommended to determine the cause and guide further treatment.
Glucose is normally reabsorbed completely. Its presence in urine indicates a condition like diabetes mellitus.

Answer: C) Bicarbonate ions
Explanation: Carbon dioxide is primarily transported in the blood as bicarbonate ions (HCO₃⁻), with about 70-85% of CO₂ carried in this form. Other forms of transport include carbaminohemoglobin (CO₂ bound to hemoglobin) and dissolved CO₂ in plasma.
How CO₂ is transported:
As Bicarbonate Ions (70-85%):CO₂ diffuses into red blood cells.
It then reacts with water to form carbonic acid (H₂CO₃), a reaction catalyzed by the enzyme carbonic anhydrase.
Carbonic acid then dissociates into hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻).
The bicarbonate ions are then transported in the plasma.

Answer: B) Medulla oblongata
Explanation: The medulla oblongata controls the basic rhythm of respiration by generating a central pattern generator (CPG) that establishes the breathing rate. It is part of the brainstem and coordinates vital functions, receiving input from various receptors to maintain a stable and rhythmic pattern of breathing for gas exchange.
The Brainstem's Role
The brainstem, which includes the medulla and the pons, houses the respiratory control centers.
The medulla contains the dorsal respiratory group (DRG) and the ventral respiratory group (VRG), which work together to create the fundamental rhythm of breathing.

Answer: B) Type II alveolar cells
Explanation: Type II alveolar cells, also known as granular pneumocytes or great alveolar cells, are cuboidal cells in the lung that produce and secrete pulmonary surfactant, a substance that reduces surface tension and prevents the alveoli from collapsing. They also contribute to host defense by secreting immune-modulating proteins, regulate alveolar fluid balance, and act as progenitor cells that regenerate the alveolar epithelium after injury.

Answer: B) Portal vein and hepatic artery
Explanation: the liver receives blood from the hepatic portal vein, which carries nutrient-rich blood from the digestive system, and the hepatic artery, which provides oxygenated blood from the heart. This dual blood supply is a unique feature of the liver, with the portal vein supplying about 75% of the blood and the hepatic artery providing the remaining 25%.
Hepatic Portal Vein
Function: Delivers nutrient-rich but deoxygenated blood from the digestive organs (stomach, intestines, pancreas, spleen) and other abdominal organs to the liver for processing.

Answer: B) Facilitated diffusion and active transport
Explanation: Most nutrients require either facilitated diffusion or active transport for absorption into enterocytes. The absorption of most nutrients occurs through the small intestine, with over 90% of nutrient absorption taking place there. The small intestine features structures like villi and microvilli, which vastly increase its surface area for absorption into the bloodstream and the lymph system.

Answer: D) Lipase
Explanation: Lipase, secreted by the pancreas, breaks down triglycerides into fatty acids and glycerol. Lipase is an enzyme that breaks down fats (lipids) into fatty acids and glycerol to aid in their digestion and absorption. Produced by the pancreas and other tissues, lipase is essential for processing dietary fats and also plays roles in lipid transport and storage within the body. High levels of lipase in the blood often indicate pancreatic damage, such as acute pancreatitis, and a lipase blood test is used to help diagnose these conditions.

Answer: B) Fat absorption
Explanation: Micelles are important for fat digestion and absorption, where they solubilize and transport lipids and fat-soluble vitamins (like A, D, E, and K) in the watery environment of the intestine, and also have important applications in medicine for drug delivery, encapsulating hydrophobic drugs to improve their solubility, stability, and targeting.

Answer: B) Vitamin B12
Explanation: Vitamin B12 is the vitamin absorbed in the ileum with the help of intrinsic factor. Intrinsic factor, a glycoprotein produced in the stomach, binds to vitamin B12 in the stomach and then binds to receptor sites on the ileal mucosal cell for absorption into the bloodstream.

Answer: B) Streptokinase
Explanation: Streptokinase is used to dissolve blood clots that have formed in the blood vessels. It is used immediately after symptoms of a heart attack occur to improve patient survival. This medicine may also be used to treat blood clots in the lungs (pulmonary embolism) and in the legs (deep venous thrombosis)

Answer: B) Interleukin-1
Explanation: Interleukin-1 (IL-1) is a group of cytokines, primarily IL-1α and IL-1β, that are central to the body's innate immune response, mediating inflammation and defending against infections. It acts as a potent pro-inflammatory cytokine, stimulating immune cells, increasing inflammation, and causing fever.
Interleukin-1 is an Autocrine hormones act on the same cell that secreted them, such as interleukins in immune signaling.

Answer: A) Calcium ions
Explanation: Calmodulin is a highly conserved, ubiquitous calcium-binding protein found in all eukaryotic cells that functions as a calcium sensor and messenger protein, converting calcium signals into various biological processes by interacting with and regulating numerous target proteins like kinases, phosphatases, and ion channels.
Calmodulin binds calcium ions, leading to activation of calcium-dependent enzymes.

Answer: B) Hypothalamus
Explanation: The gonadotropin-releasing hormone (GnRH) is secreted by the hypothalamus, a region of the brain that acts as the primary control center for the pituitary gland, thereby regulating the entire reproductive system. GnRH travels from the hypothalamus to the anterior pituitary, where it stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which then act on the gonads.

Answer: B) Autoimmune destruction of beta cells
Explanation: Autoimmune destruction of beta cells is the underlying mechanism of Type 1 diabetes (T1D), where the body's immune system mistakenly attacks and destroys the insulin-producing beta cells in the pancreas. This process involves various immune cells, including T lymphocytes, macrophages, and dendritic cells, recognizing beta cell autoantigens and leading to beta cell dysfunction and eventual insulin deficiency. The development of this autoimmune response is linked to a combination of genetic predisposition, environmental triggers (like viral infections), and complex immune system interactions.

Answer: C) Bones and kidneys
Explanation: PTH (Parathyroid Hormone) acts primarily on the bone and kidneys to regulate calcium and phosphate levels in the blood. In the kidneys, PTH increases calcium reabsorption and increases phosphate excretion, while also activating vitamin D. In the bones, PTH promotes calcium and phosphate release by stimulating osteoclasts for bone resorption.

Answer: C) Gluconeogenesis and lipolysis
Explanation:
Thyroid hormones stimulate energy mobilization, including gluconeogenesis and breakdown of fats. Thyroid hormones regulate the body's metabolic rate, controlling energy production and expenditure. They are essential for growth and development, particularly of the brain, and affect almost every organ in the body by influencing heart rate, body temperature, digestion, and mood. Too little hormone slows bodily functions, while too much speeds them up

Answer: A) Estrogen and progesterone
Explanation: During menopause, ovarian function declines, leading to low estrogen and progesterone. Menopause is a hormonal process caused by the ovaries stopping the production of sufficient estrogen and progesterone and no longer releasing eggs each month. This decline in estrogen, a key female sex hormone, leads to the cessation of ovulation and menstruation, bringing on the symptoms and physical changes of menopause. While a natural decrease in ovarian function is the most common hormonal cause, early or premature menopause can also result from medically induced factors like surgery or certain cancer treatments.

Answer: B) Hypocalcemia and tetany

Explanation: Hypoparathyroidism is a rare disorder characterized by the parathyroid glands underproducing parathyroid hormone (PTH), leading to low blood calcium (hypocalcemia) and high blood phosphate (hyperphosphatemia). Common symptoms include muscle cramps and twitching, tingling in the fingers and toes, and dry skin, though more severe complications like seizures, abnormal heart rhythms, and kidney issues can occur. Treatment typically involves lifelong calcium and active vitamin D supplementation.

Answer: A) Oxytocin
Explanation: Oxytocin is a naturally occurring hormone produced in the hypothalamus and released by the pituitary gland that plays a key role in reproduction, childbirth, and social bonding. In medicine, it is used to induce or continue labor and control postpartum bleeding, while in behavior, it's associated with social recognition, trust, and attachment. Its effects are complex, influencing mood, stress levels, and pair bonding, and research continues to explore its potential in treating conditions like autism and social phobia.

Answer: B) Adenylate cyclase
Explanation: Adenylate cyclase converts ATP to cAMP upon activation by G-proteins. Adenylate cyclase (Adenylyl cyclase) is an enzyme that converts adenosine triphosphate (ATP) into cyclic adenosine monophosphate (cAMP) and pyrophosphate. This reaction produces cAMP, a crucial second messenger inside cells that plays a key role in various cell signaling pathways, including those regulated by G-protein-coupled receptors. The enzyme's activity can be stimulated or inhibited, allowing for precise regulation of cellular responses, such as those involved in cardiac function and other cellular processes.

Answer: c
Explanation: Thyroid hormones are aromatic amino-acid (tyrosine) derivatives with iodine — thus they are amine hormones (more specifically iodinated tyrosine derivatives). They are unusual in that although they are amine-derived, they act intracellularly like steroids.

Answer: B) Drinking boiled or treated water
Explanation: Safe drinking water prevents infections that cause diarrhea.

Answer: B) Poor absorption of solutes like lactose
Explanation: Undigested solutes draw water into the intestines, causing osmotic diarrhea. Osmotic diarrhea is caused by the presence of osmotically active, poorly absorbed substances in the bowel lumen, which draw water into the intestine. This can be due to malabsorption of certain foods, such as in lactose intolerance, or the consumption of poorly absorbed sugar alcohols found in some foods and artificial sweeteners like sorbitol and xylitol. Certain laxatives, like lactulose, also induce this type of diarrhea by the same mechanism.

Answer: B) Defective conjugation of bilirubin
Explanation: A mild genetic defect in bilirubin conjugation leads to slightly elevated unconjugated bilirubin.
Gilbert's syndrome involves a mild genetic liver disorder that causes a buildup of bilirubin, a yellowish pigment, in the blood, leading to recurrent, mild episodes of jaundice (yellow skin and eyes) and other symptoms like fatigue and abdominal discomfort.

Answer: A) Bound to albumin in plasma
Explanation: Unconjugated bilirubin is lipid-soluble and travels bound to albumin in the blood. Unconjugated bilirubin binds to albumin in the bloodstream because it is water-insoluble and cannot be transported alone; this albumin-bilirubin complex then travels to the liver, where the unconjugated bilirubin is released to be processed and made water-soluble. This binding prevents the fat-soluble bilirubin from accumulating in tissues, causing damage, and allows it to be carried safely through the circulatory system.

Answer: C) Enhancing glucose uptake by tissues
Explanation: Insulin stimulates glucose transport into cells, especially muscle and fat. Insulin primarily lowers blood glucose by allowing it to leave the bloodstream and enter cells for energy or storage. It does this by increasing glucose uptake in tissues like muscle and fat, stimulating the storage of glucose as glycogen in the liver and muscles, and reducing the production of glucose by the liver (gluconeogenesis and glycogenolysis).

Answer: C) ≥126 mg/dL
Explanation: Fasting glucose ≥126 mg/dL confirms a diagnosis of diabetes mellitus.

Answer: B) Mutation in beta-globin gene
Explanation: Sickle cell anemia is caused by a genetic mutation that leads to the production of abnormal hemoglobin, a protein in red blood cells. This inherited gene is passed from both parents, resulting in red blood cells that become rigid, sticky, and sickle-shaped. These misshapen cells can block blood flow, leading to chronic pain, anemia, and other serious complications.

Answer: B) Excess uric acid deposition
Explanation: High uric acid leads to formation of sharp crystals in your joints (usually your big toe). Flare-ups of symptoms like pain and swelling come and go in periods called gout attacks.

Answer: A) Phenylalanine → Tyrosine
Explanation:
PKU prevents phenylalanine from being converted to tyrosine. This metabolic error leads to a buildup of toxic levels of phenylalanine in the blood and brain, which can cause severe intellectual disability and other neurological problems.

Answer: B) Heart attack
Explanation: CK-MB is specific to cardiac muscle damage. An elevated CK-MB level suggests potential heart muscle damage, such as from a heart attack, myocarditis, cardiac trauma, or recent cardiac surgery. It can also indicate skeletal muscle damage from conditions like rhabdomyolysis or certain medications, though this is typically indicated by a low CK-MB index relative to total CK.

Answer: D) 60S
Explanation: Eukaryotic ribosomes are 80S, with 40S (small) and 60S (large) subunits.

Answer: B) Exit of uncharged tRNA
Explanation: The E site releases empty tRNA after amino acid transfer.

Answer: B) Elongation and translocation
Explanation: GTP hydrolysis provides energy for ribosome movement during translation.

Answer: A) Chain termination method
Explanation: It uses chain-terminating dideoxynucleotides to sequence DNA. Sanger sequencing is a DNA sequencing method, also known as the "chain termination method," that determines the precise order of nucleotide bases in a DNA segment. Developed by Frederick Sanger in the 1970s, it involves using dideoxynucleotides (ddNTPs) that randomly terminate DNA strand replication, creating DNA fragments of varying lengths. These fragments are then separated by size using capillary electrophoresis, and the sequence is read by detecting the fluorescently labeled ddNTPs at the end of each fragment, resulting in a chromatogram that shows the DNA sequence. It is a highly accurate method still used for validating results from other sequencing technologies, testing known variants, and sequencing small, targeted regions of the genome.

Answer: C) Phosphate backbone
Explanation: DNA is negatively charged because of the phosphate groups in its sugar-phosphate backbone. Each phosphate group has a negative charge, and because DNA molecules are composed of many such groups, they carry an overall negative charge. The phosphate groups carry negative charges, allowing movement in electrophoresis.

Answer: A) Antibodies
Explanation: Western blotting detects proteins using specific antibodies. Western blotting is a lab technique that identifies a specific protein in a complex sample by first separating all proteins by size using gel electrophoresis, transferring them to a membrane, and then using specific antibodies to detect and visualize the target protein.

Answer: B) Cancer
Explanation: Tumor suppressor genes are genes that slow or stop cell growth and division, and promote DNA repair or programmed cell death (apoptosis). When these genes are mutated or their function is lost, it can lead to uncontrolled cell proliferation and the development of cancer. Famous examples of tumor suppressor genes include TP53 (p53) and BRCA1/BRCA2 Loss of tumor suppressor function allows uncontrolled cell growth.

Answer: A) DNA ligase
Explanation: DNA ligase is an enzyme that repairs breaks and joins fragments of DNA by forming phosphodiester bonds, which are crucial for DNA replication, repair, and genetic engineering. In living organisms, it seals gaps in the DNA backbone and joins fragments on the lagging strand during replication. DNA ligase joins DNA fragments during cloning.

Answer: C) 2003
Explanation: Completion was announced in 2003, mapping all human genes.

Answer: B) Host DNA
Explanation: A host restriction-modification (R-M) system is a bacterial defense mechanism that protects against foreign DNA, such as bacteriophages, by recognizing specific DNA sequences. The system includes a restriction enzyme, which cuts unmethylated foreign DNA, and a modification enzyme (methyltransferase), which adds methyl groups to the host cell's DNA at the same recognition sequences, making it resistant to cleavage by the restriction enzyme. Methylation of host DNA prevents restriction enzymes from cutting it.

Answer: A) Retroviruses
Explanation: Reverse transcriptase was first discovered in 1970 by Howard Temin and David Baltimore, who independently isolated the enzyme from RNA tumor viruses, specifically the Rous sarcoma virus (RSV) and a mouse leukemia virus (MLV). Retroviruses replicate via reverse transcription of RNA to DNA.

Answer: D) Large eukaryotic DNA
Explanation: YAC vectors are used for cloning and propagating very large DNA fragments, often up to one million base pairs in length, into yeast cells. They facilitate the creation of physical maps for genomes, enable the study of complex genes, and serve as a tool for modeling genetic diseases by introducing them into mammalian cells for expression.

Answer: A) Two different species
Explanation: Shuttle vectors in biotechnology are engineered plasmids designed to replicate and function in at least two different host organisms, most commonly prokaryotic (like E. coli) and eukaryotic (like yeast or mammalian cells) systems. They contain multiple origins of replication and selectable markers, one set for each host, allowing researchers to easily transfer, manipulate, and amplify genetic material in a simpler host, and then express and test it in a more complex host. Shuttle vectors contain origins of replication for two host organisms.

Answer: D) They cut at specific recognition sites
Explanation: Type II restriction endonucleases always cleave at or near their recognition sites. They produce small, well-defined fragments of DNA that help to characterize genes and genomes and that produce recombinant DNAs.
This precision is why Type II enzymes are widely used in genetic engineering.

Answer: C) Gamma (γ)
Explanation: The Eukaryotic DNA polymerase responsible for mitochondrial DNA (mtDNA) replication is DNA polymerase gamma (pol γ). It is the sole DNA polymerase found in animal cell mitochondria, meaning it is solely responsible for all DNA synthesis, repair, and replication processes within the mitochondria.

Answer: C) Anemia
Explanation: Anemia is a condition characterized by reduced RBC count or hemoglobin level, leading to decreased oxygen transport. Anemia is a condition where your blood doesn't have enough healthy red blood cells or hemoglobin to carry sufficient oxygen to your body's tissues, leading to symptoms like fatigue, weakness, and shortness of breath. It can be caused by a lack of iron, vitamin deficiencies (like B12 or folate), blood loss, or conditions that destroy red blood cells.

Correct Answer: গ) Cellulose
Explanation:
Cellulose is a linear polymer of β(1→4)-linked glucose units, which cannot be hydrolyzed by human enzymes. Cellulose is the most abundant organic polymer on Earth, forming the strong, structural cell walls of plants and is a type of dietary fiber. Humans cannot digest it, but it aids digestion by moving waste through the gut. Cellulose is a key material for industries like paper and textiles and is used as a food additive for its thickening and stabilizing properties.

Explanation: (a) Palmitate (C16) is a saturated, even-chain fatty acid. It undergoes 7 cycles of beta-oxidation, each producing one acetyl-CoA. The 7th cycle cleaves the last 4-carbon unit into two acetyl-CoA molecules, making a total of 8 acetyl-CoA from the complete oxidation of one palmitate.