Membrane Transport

Explanations:
In the usual Na+ gradient, the [Na+] is higher in extracellular than in intracellular fluid (maintained by the Na+–K+ pump). Two forms of transport are energized by this Na+ gradient cotransport and countertransport. Because glucose is moving in the same direction as Na+, one can conclude that it is cotransport.

Inhibition of Na+,K+-adenosine triphosphatase (ATPase) leads to an increase in intracellular Na+ concentration. Increased intracellular Na+ concentration decreases the Na+ gradient across the cell membrane, thereby inhibiting Na+–Ca2+ exchange and causing an increase in intracellular Ca2+ concentration. Increased intracellular Na+ concentration also inhibits Na+–glucose cotransport.

Explanations:
Cells contain a variety of organelles that perform specialized cell functions. The nucleus is an organelle that contains DNA and is the site of gene transcription. The endoplasmic reticulum and the Golgi apparatus are important in protein processing and the targeting of proteins to correct compartments within the cell. Lysosomes and peroxisomes are membranebound organelles that contribute to protein and lipid processing. Mitochondria are organelles that allow for oxidative phosphorylation in eukaryotic cells and also are important in specialized cellular signaling.

Explanations:
The cell and the intracellular organelles are surrounded by semipermeable membranes. Biological membranes have a lipid bilayer core that is populated by structural and functional proteins. These proteins contribute greatly to the semipermeable properties of biological membrane.

Explanations:
The cell and the intracellular organelles are surrounded by semipermeable membranes. Biological membranes have a lipid bilayer core that is populated by structural and functional proteins. These proteins contribute greatly to the semipermeable properties of biological membrane.

Explanations:
The cell and the intracellular organelles are surrounded by semipermeable membranes. Biological membranes have a lipid bilayer core that is populated by structural and functional proteins. These proteins contribute greatly to the semipermeable properties of biological membrane.

Golgi apparatus sorts and packages proteins within a cell

[Ganong 24th p-48]

Membrane must be present.

The acetylcholine-gated channel has a diameter of about 0.65 nanometer, which is large enough to allow the important positive ions-sodium (Na+), potassium (K+), and calcium (Ca2+)-to move easily through the opening. Patch clamp studies have shown that one of these channels, when opened by acetylcholine, can transmit 15,000 to 30,000 sodium ions in 1 millisecond. Conversely, negative ions, such as chloride ions, do not pass through because of strong negative charges in the mouth of the channel that repel these negative ions.

The H+/monocarboxylate cotransporter (MCT) recognizes monocarboxylates such as lactate, pyruvate, acetoacetate, and β-hydroxybutyrate. It is a proton-driven transporter with a coupling stoichiometry of 1 H+ : 1 monocarboxylate and, thus, MCT is an electroneutral transporter (Fig. 4). The direction of transport is governed by the prevailing proton gradient.

Explanations:
The centrosomes are microtubule-organizing centers (MTOCs) that contain γ-tubulin. The microtubules grow out of this γ-tubulin in the pericentriolar material. When a cell divides, the centrosomes duplicate themselves, and thepairs move apart to the poles of the mitotic spindle, where they monitor the steps in cell division.