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Problem 1
Fill in the following concept map to review the processes by which molecules move across membranes.
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Problem 2
Label the parts of the following diagram illustrating the catalytic cycle of an enzyme.
Problem 3
Which best describes the structure of a cell membrane?
a. Proteins between two bilayers of phospholipids
b. Proteins embedded in a bilayer of phospholipids
c. A bilayer of protein coating a layer of phospholipids
d. Cholesterol embedded in a bilayer of phospholipids
Problem 4
A plant cell placed in distilled water will ______________; an animal cell placed in distilled water will ______________.
a. Burst … burst
b. Become flaccid … shrivel
c. Become turgid … be normal in shape
d. Become turgid … burst
Problem 5
The sodium concentration in a cell is 10 times less than the concentration in the surrounding fluid. How can the cell move sodium out of the cell? (Explain your answer.)
a. Passive transport
b. Receptor-mediated endocytosis
c. Active transport
d. Facilitated diffusion
Problem 6
The synthesis of ATP from ADP and
a. Stores energy in a form that can drive cellular work
b. Involves the hydrolysis of a phosphate bond
c. Transfers a phosphate, priming a protein to do work
d. Is an exergonic process
Problem 7
Facilitated diffusion across a membrane requires ______________ and moves a solute ______________ its concentration gradient.
a. transport proteins . . . up (against)
b. transport proteins . . . down
c. energy and transport proteins . . . up
d. energy and transport proteins . . . down
- What are the main types of cellular work? How does ATP provide the energy for this work?
Problem 8
- Why is the barrier of the activation energy beneficial for cells? Explain how enzymes lower activation energy.
Problem 9
- Relate the laws of thermodynamics to living organisms.
Problem 10
Problem 11
How do the components and structure of cell membranes relate to the functions of membranes?
- Sometimes inhibitors can be harmful to a cell; often they are beneficial. Explain.
Problem 12
Problem 13
Cells lining kidney tubules function in the reabsorption of water from urine. In response to chemical signals, they reversibly insert additional aquaporins into their plasma membranes. In which of these situations would your tubule cells have the most aquaporins: after a long run on a hot day, right after a large meal, or after drinking a large bottle of water? Explain.
Problem 14
Mercury is known to inhibit the permeability of water channels. To help establish that the protein isolated by Agre's group was a water channel, the researchers incubated groups of RNA-injected oocytes (which thus made aquaporin proteins) in four different solutions: plain buffer, low concentration and high concentration of a mercury chloride (HgCl₂) solution, and low concentration of a mercury solution followed by an agent (ME) known to reverse the effects of mercury. The water permeability of the cells was determined by the rate of their osmotic swelling. Interpret the results of this experiment, which are presented in the graph below. Control oocytes not injected with aquaporin RNA were also incubated with buffer and the two concentrations of mercury. Predict what the results of these treatments would be.
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Problem 15a
A biologist performed two series of experiments on lactase, the enzyme that hydrolyzes lactose to glucose and galactose. First, she made up 10% lactose solutions containing different concentrations of enzyme and measured the rate at which galactose was produced (grams of galactose per minute). Results of these experiments are shown in Table A below. In the second series of experiments (Table B), she prepared 2% enzyme solutions containing different concentrations of lactose and again measured the rate of galactose production.
Graph and explain the relationship between the reaction rate and the enzyme concentration.
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Problem 15b
A biologist performed two series of experiments on lactase, the enzyme that hydrolyzes lactose to glucose and galactose. First, she made up 10% lactose solutions containing different concentrations of enzyme and measured the rate at which galactose was produced (grams of galactose per minute). Results of these experiments are shown in Table A below. In the second series of experiments (Table B), she prepared 2% enzyme solutions containing different concentrations of lactose and again measured the rate of galactose production.
Graph and explain the relationship between the reaction rate and the substrate concentration. How and why did the results of the two experiments differ?.
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- Organophosphates (organic compounds containing phosphate groups) are commonly used as insecticides to improve crop yield. Organophosphates typically interfere with nerve signal transmission by inhibiting the enzymes that degrade transmitter molecules. They affect humans and other vertebrates as well as insects. Thus, the use of organophosphate pesticides poses some health risks. On the other hand, these molecules break down rapidly upon exposure to air and sunlight. As a consumer, what level of risk are you willing to accept in exchange for an abundant and affordable food supply?
Problem 16