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Biology questions

In the absence of specific carrier proteins, which of the following can diffuse readily across the plasma membrane of a cell? ATP, glucose, amino acids, fatty acids, water, gases, proteins, ions, polysaccharides, glycerol, hemoglobin, ethanol.

Using artificial liposomes researchers showed that phospholipid bilayer membranes containing different amounts of cholesterol have different permeability to glycerol. What was the observed relationship between cholesterol content and glycerol permeability? How can the effect of cholesterol be explained? What other experimental variable used in these experiments affected membrane permeability (and membrane fluidity) in a consistent way?

What was the effect observed in this case and what is a reasonable explanation for the observed effect?

Cells of fish that live in the near-freezing waters off Alaska are likely to have bilayer membranes that contain phospholipids with what kinds of tails? How much cholesterol are their membranes likely to contain (only a little, a moderate amount, or a lot?)?

How does "active transport" of material across membranes differ from the movement of material across membranes via channel proteins and transport proteins? How can dissolved materials be moved from the outside to the inside of a cell when the inside concentration of the material is already high? What, if any, is the difference between facilitated diffusion and passive transport?

The components of the cytoskeleton consist of microfilaments, intermediate filaments and microtubules. Which component is involved in movement of organelles (transport vesicles), chromosome movement and cell motility involving flagella or cilia? Is vesicle transport an energy-dependent process? How did researchers find the answer to this question? Will transport along microtubules occur in a mixture of purified microtubules, purified vesicles
and ATP? What protein component was ultimately isolated from the soluble fraction of cell extracts that acts as the "motor" for vesicle transport? How does it work?

Assume a cell is respiring aerobically and is using glucose as an energy source. What is the ultimate fate of each of the 6 carbon atoms in a glucose molecule that begins the aerobic pathway (i.e., what happens to each of the carbons and where does it happen)?

List all of the products of glycolysis in decreasing order of the amount of chemical energy they contain as single molecules. [Note: Intermediate compounds are not products.]

Can proteins be used by your cells as a source of chemical energy to make ATP? Explain.

Many plant cells, such as root cells, lack chloroplasts. How do plant cells that lack chloroplasts produce the ATP they need? (Hint: they don't do it by photosynthesis). Do plant cells that contain chloroplasts also contain mitochondria? Why or why not?

How would poisoning the electron transport system associated with the light-dependent reactions of photosynthesis affect the light-independent reactions?

What is MPF? Is it different in different species of eukaryotes? MPF protein kinase is relatively constant across the cell cycle. How, then, can it be a trigger for initiating M-Phase? What is the relationship of cyclin to MPF? What "activates" MPF and when does this activation occur? What causes the MPF concentration to decline sharply during M-Phase?

In what way are the structures of mitochondria and chloroplasts similar and different? What molecules or systems function in both types of organelles? Which enzymes or processes are unique to each organelle?

A photosynthesizing plant is exposed to CO2 molecules containing radioactively labeled carbon atoms (14C02).

What stable intermediate in the light-independent pathway (the Calvin Cycle) is the one in which the labeled carbon will first appear?

What are the overall inputs (substrates and energy sources) and outputs (products and by products) for the light-dependent reactions of photosynthesis and the light-independent reactions of photosynthesis? How are the light-dependent and light-independent parts of photosynthesis coupled? Where do the reactions of the light-dependent part of photosynthesis take place? the light-independent reactions?

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Solution Summary

Movement of organelles,chromosomal movement and cell motility is carried out by microtubules. Microtubules are cylindrical tubes, 20-25 nm in diameter. Microtubule-based vesicle transport driven is by kinesin and cytoplasmic dynein motor proteins which facilitates several membrane-trafficking steps including elements of endocytosis and exocytosis in many different cell types.