Biology QCM tset Study Guide

1. An average person requires approximately _______________ Kcal of energy intake per day.
      a) 200      b) 500
      c) 2,000     d) 5,000
      e) 10,000 
2. Which of the following are pluripotent cells capable of self-renewal?
      a) neurons     b) skeletal muscle fibers
      c) stem cells     d) chondrocytes
      e) All of the above 
3. Which of the following statements is correct?
a) The cell membrane is equally permeable to both glucose and water
b) Transport of glucose across the cell membrane requires ATPs
c) Transport of K+ from inside to outside the cell requires ATPs
d) Transport of Na+ from inside to outside the cell requires ATPs
e) None of the above is correct 
4. A protein whose activity has been destroyed by high temperature is said to be
      a) denatured     b) deaminated
      c) phosphorylated    c) buffered
      e) None of the above is correct 
5. Trypsin functions best in a solution containing _____________ H+, which is ________________.
      a) 102 mM; acidic    b) 107 M; neutral
      c) 10-9 mM; basic    d) 10-2 M; acidic
      e) 10-6 mM; basic 
6. Dietary “fibers” are primarily made of
      a) collagen fibers    b) cellulose
      c) protein     d) glycogen
      e) starch 
7. Fish is rich in ____________________________, which are beneficial to our health.
      a) cholesterol     b) saturated fats
      c) mercury     d) omega-3 fatty acids
      e) trans-fatty acids 
8. __________ is a universal energy carrier and is produced in the cell by the _____________.
      a) cAMP; mitochondria   b) cAMP; rER
      c) ATP; mitochondria    d) ATP; Golgi apparatus
      e) cGMP; Golgi apparatus 
                                                Name ________________________
9. Phospholipids are
      a) hydrophobic    b) amphipathic
      c) hydrophilic     d) lipophilic
      e) homophobic 
10. Of these binding forces, which is the weakest?
      a) bonds between neighboring water molecules
      b) bonds between hydrogen atoms in hydrogen molecules
      c) bonds between sodium and chloride ions
      d) bonds between hydrogen and carbon atoms in triglycerides
      e) peptide bonds 
11. Racial differences in skin color are attributed to differences in the
      a) number of keratinocytes   b) number of melanocytes
      c) amount of melanin    d) thickness of epidermis
      e) thickness of dermis 
12. Which of the following is an artificial sweetener often found in diet drinks?
      a) sucrose     b) aspartame
      c) maltose     d) fructose
      e) None of the above is correct 
13. Which of the following is a trace element essential to our health?
      a) oxygen     b) nitrogen
      c) sodium     d) uranium
      e) iodine  
14. Lipolysis involves _______________________, which produces __________ ATPs than glycolysis.
      a) deamination; more    b) free radical formation; more
      c) β-oxidation; fewer     d) transcription; more
      e) None of the above is correct 
15. Acetylcholine receptors are found in the _________ of certain types of cells
      a) cell membrane    b) mitochondria
      c) lysosomes     d) nucleus
      e) Golgi apparatus 
16. A typical cell, such as the red blood cell, in the human body is approximately (in diameter)
      a) 10 μm, and can be seen with the naked eye.
      b) 10 mm, and can be seen with the naked eye.
      c) 10 cm, and can be seen with the naked eye.
      d) 10 μm, and can be seen with electron microscopy.
      e) 10 nm, and can be seen with electron microscopy. 
17.  Which of the following statements about stem cells is NOT correct?
a) It is legal to use private funds to do embryonic stem cell research in the US. 
b) adult stem cells can be found in the hippocampus 
      c) adult stem cells are as versatile as embryonic stem cells
      d) embryonic stem cell lines are generated from cells in the 5-day old blastocyst
      e) somatic cell nuclear transfer is also called therapeutic cloning

18. Lactose intolerance is due to a deficiency in
      a) lactose     b) lactase
      c) galactose     d) fructose
      e) maltase  
19. Normal blood pH is _____, which can be maintained within a narrow range by _________________.
      a) 7.0; buffers     b) 7.4; osmosis
      c) 8.0; unsaturated fats   d) 8.0; saturated fats
      e) 7.4; buffers
Section II. Short Answer (Total 42 points). Each correct answer is worth 6 points.  Please be sure to provide your reasoning for each answer, and limit your answers to the space provided. 
1. Discuss the benefit and the harm, if any, of UV light to human health. 

Benefit: UV converts cholesterol-like molecules in the skin into an inactive form of vitamin D, which can then be converted into an active form of vitamin D in the liver.  Vitamin D is essential for formation of bone and teeth  

Harm: too much exposure to UV may cause skin cancers and damage the retina in the eye.

2. What would happen to those people who are resistant to leptin?  Be sure to explain how leptin works in our body. 
Fat cells secret leptin molecules, which bind leptin receptors in the hypothalamus.  The binding results in the suppression of appetite.  People who cannot respond to leptin (leptin resistant), despite having a normal amount of leptin in their body, would have difficulty in suppressing their appetite and would thus likely become obese.

3. Define isotopes and discuss the benefit and the harm, if any, of isotopes to human health. 
Definition:  atoms of the same element that differs in mass become they contain different numbers of neutrons. 
Benefit: Because isotopes are often radioactive, they could be used as a diagnostic tool, for example, to detect thyroid cancers; could also be used for radiation therapy to kill cancer cells. 
Harm:  Because of their radioactivity, isotopes could also kill normal cells as well as causemutation.

4. Explain why we need anti-oxidants and how they work.

During metabolism, free radicals are sometimes generated in our body.  Free radicals are oxygen-containing molecules that have an unpaired electron in their outer shell, and are unstable and highly reactive.  They show strong tendency to remove electrons from another molecules, and the destructive cascade of events results in damage of cells and tissues.  For example, free radicals may cause motoneuron degeneration in Amyotrophic Lateral Sclerosis.  We thus need anti-oxidants, such as vitamin C, K, β-carotene, selenium, which can inactivate free radicals or prevent their formation.
5. Why is it important to understand the tertiary structure of protein molecules?  Be sure to use a disease as an example to illustrate your point. 
The tertiary structure describes how folding and bending of a chain of amino acids result in the three-dimensional shape of a protein.  Misfolding of protein structure could render proteins useless or harmful.  For example, in sickle cell anemia, misfolding of hemoglobin due to amutation of just one amino acid (glutamic acid at position 6 becomes valine) alters the shape of hemoglobin and the red blood cells.  The sickle-shaped red blood cells cannot pass through small blood vessels resulting in anemia.  Other examples are cystic fibrosis due to a defect in chloride channels, and Alzheimer’s disease related to an accumulation of abnormal protein aggregates.
6. Why is cyanide so deadly? 
O2 is required for aerobic respiration, which generates a great of energy for our cellular functions.  Following the electron transport system in the mitochondria, high-energy electrons would be accepted by O2.  Cyanide blocks the acceptance of these electrons by O2 and would thus inhibit energy production by the aerobic respiration.  Without energy production, our cells would not be able to function and would die. 
7. Which pathway of carbohydrate metabolism does an athlete use primarily during (a) a 100m dash, and (b) during a marathon?  Explain the advantages and disadvantages of these two pathways.   
a) 100m dash: anaerobic respiration.
b) marathon: aerobic respiration
                        Advantage     Disadvantage
    Fast action
Not efficient in energy production as it produces only 2 ATPs
    Much more efficient as it produces about 36 ATPs (38 OK)
Slow action

Section III. Essay Questions (Total 20 points).
1. (10 pts) (a) Define “double-blind” experiments and discuss why it is important to perform “double-blind” experiments to test the effectiveness of a new drug (5 pts).  
Due to the power of suggestion, patients may feel better by an otherwise ineffective treatment such as sugar pills, this is the so-called “placebo effect.”  In single-blind experiments, patients are not told whether they will receive the drug or the placebo (sugar pills).  In double-blindexperiments, both experimental subjects and experimenters do not know which subjects receive the drug or placebo.  Only after the completion of the trials, do the researchers know which subjects had received the drug treatment or placebo.  This would lessen the placebo effect and the possible bias in experimental observations and data interpretations.  

 b) Describe the clinical trials required for FDA approval before you can market any new drug in the US (5 pts).         
    1. Phase I:  test the drug in a small group (20-80 people) of healthy human subjects.  The major goal of this phase is to make sure that the drug is safe to use.  First, do no harms!

    1. Phase II: test the drug in a large group, several hundreds (100-300) of subjects with similar degree of hypertension.  The design of this experiment is similar to that described above in (A).  The major goal is to test both safety and effectiveness of a new drug.  It may take up to two years for this phase.

    1. Phase III: test the drug in an even larger group, 1,000-4,000, of patients.  The goal is tolook for any uncommon adverse reactions and continue testing both safety and effectiveness of the drug for a widespread use.

On average, it may take 12-15 years and costs 500 million to complete these three phases of clinical trials.  Only after FDA approves all three phases, can a new drug then be on the market.  Even after the approval, a new drug could be recalled by FDA if adverse effects are found (Phase IV).

2. (10 pts).  A patient needs an intravenous (i.v.) injection of saline solution to stay alive.  Is it safe to give this patient an i.v. injection of a solution containing 90 mg/mL of NaCl?  Is this solution isotonic, hypotonic or hypertonic relative to the intracellular fluid of red blood cells?  Please be sure to provide your reasoning in your answers.  (Hint: The physiological saline solution contains 0.9 % sodium chloride) 

It would NOT be safe to give this patient an i.v. injection of 90mg/mL of NaCl.
Physiological saline solution contains 0.9% NaCl, or 0.9 g/100 ml solution (1 ml of water weights about 1 g), which is the same as 900 mg/100 ml or 9 mg/mL.  Because physiological saline solution is isotonic, any solution containing NaCl greater than 9 mg/mL, as in this solution (90 mg/mL), must be hypertonic relative to the intracellular fluid.  
When red blood cells are bathed in a hypertonic solution, water would flow from inside the cells to outside through osmosis.  As a result, the volume of these red blood cells decreases, and the cells would shrink and die when placed in this solution.

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