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Midterm II: Chapters 22-24
Section I: Chapter 22: Enzymes (65 pts)
1. a) What is an enzyme? (4pts)?
A BIOLOGICAL CATALYST
b) Name two factors that influence enzyme activity nonspecifically. What happens to the
enzyme at the extremes of these factors (6pts)?
TEMPERATURE AND PH. AT THE EXTREMES OF BOTH, ENZYME BECOME
DENATURED AND LOOSE ACTIVITY
c) Name two ways to increase enzyme activity, specifically (draw graphs to illustrate your
answer) (6pts).
INCREASE ENZYME
OR SUBSTRATE
CONCENTRATION
CONCENTRATION
2. Name the types of enzymes that catalyze the below reactions (9pts).
a)
c)
OXIDOREDUCTASE
b)
ISOMERASE
TRANSFERASE
O
O
NH3-CH-COO + C-COOCH2
CH2
CH2
COO-
COO-
O
O
C-COO + NH3-CH-COOCH2
CH2
CH2
COO-
COO-
3. Give the relationship between cofactor and protein and what is formed, indicate activity for
each and the name of each species (I am not asking about product formation) (6pts).
APOENZYME
COFACTOR
HOLOENZYME
PROTEIN
NON-PROTEIN
PROTEIN + COFACTOR
(INACTIVE)
(INACTIVE)
(ACTIVE)
4. Describe how zymogens (proenzymes) are activated (5pts)?
ZYMOGENS ARE ACTIVATED BY CLIPPING AWAY THE INHIBITORY PORTION
OF THE PROTEIN, WHICH WILL IN TURN EXPOSE THE ACTIVE SITE.
5. a) How do poisons act as enzyme inhibitors (5pts)?
POISONS BIND COVALENTLY TO ENZYMES AT THEIR ACTIVE SITE, WHICH
RESULT IN THEIR INHIBITION.
b) What kind of inhibition is this called (3pts)?
IRREVERSIBLE INHIBITION
6. Name the two types of reversible inhibition and the main difference between them (6pts)?
COMPETITIVE AND NONCOMPETIVE. IN COMPETITVE INHIBITION THE
SUBSTRATE AND INHBITOR COMPETE FOR THE ACTIVE SITE. IN
NONCOMPETIVE INHIBITION THE INHIBITOR BINDS IN A SITE DIFFERENT
THAN THE ACITIVE SITE, BUT BY BINDING INDUCES A CONFORMATIONAL
CHANGE IN THE ENZYME, PREVENTING PRODUCT FROM FORMING.
7. a) Name the two categories vitamins can be divided into (4pts).
WATER SOLUBLE AND FAT SOLUBLE
b) What are the complex B vitamins precursors of? Name an example of a Vitamin in this
group and what the product would be (6pts)?
COFACTORS (OR COENZYMES). EXAMPLE, NIACIN IS THE PRECURSOR FOR
NAD
c) What symptoms would a person with Vitamin K deficiency exhibit (5pts)?
A DEFICIENCY INCREASES THE AMOUNT OF TIME REQUIRED FOR BLOOD TO
CLOT. SYMPTOMS INCLUDE BLEEDING UNDER THE SKIN AND IN MUSCLES
LEADING TO UGLY BRUISES FROM SMALL BLOWS.
Section II: Chapter 23: Nucleic Acids and Protein Synthesis (70 pts)
8. a) Define what a gene is (4pts)?
GENES ARE THE BASIC UNIT OF HEREDITY. A GENE ENCODES ONE
POLYPEPTIDE.
b) What large structures are genes a component of and how many of these structures do
humans have (4pts)?
CHROMOSOMES. THERE ARE 23 PAIRS IN HUMANS.
9. a) What is the purpose of DNA replication and where in the cell does it occur (6pts)?
THE PURPOSE OF DNA REPLICATION IS TO DUPLICATE ALL THE DNA IN THE
NUCLEUS TO PASS ON TO DAUGHTER CELLS. IT OCCURS IN THE NUCLEUS.
b) What is the purpose of transcription and where in the cell does it occur and where does the
message get sent (6pts)?
THE PURPOSE OF TRANSCRIPTION IS TO COPY A SPECIFIC GENE TO THEN
TRANSLATE INTO PROTEIN. IT OCCURS IN THE NUCLEUS.
c) What is the purpose of translation and where in the cell does it occur (6pts)?
THE PURPOSE OF TRANSLATION IS TO MANUFACTURE PROTEIN FROM AN
RNA MESSAGE. IT OCCURS IN THE CYTOPLASM.
10. What is the main difference between the structure of DNA and mRNA (4pts)?
DNA IS A DOUBLE STRANDED HELIX. mRNA IS A SINGLE STRAND THAT IS
MAINLY UNSTRUCTURED.
11. List the three types of RNA and what the role of each one is in the cell(6pts).
mRNA IS MESSENGER RNA THAT CARRIES THE MESSAGE TO THE
TRANSLATIONAL MACHINERY TO MAKE PROTEIN.
tRNA IS TRANSFER RNA THAT IS RESPONSIBLE FOR BRINGING THE AA TO
THE GROWING PROTIEN CHAIN.
rRNA IS RIBOSMAL RNA AND IS THE CATALYTIC UNIT OF THE RIBOSOME.
12. a) What would be the complimentary DNA strand to the following strand (5pts):
5’ d-AGTACTACGACCAAACAT-3’
3’ d-TCATGATGCTGGTTTGTA-5’
b) What would be the transcriptional product of the DNA strand, in a
(5pts)?
5’ d-AGTACTACGACCAAACAT-3’
3’-UCAUGAUGCUGGUUUGUA-5’
BUT THEN FLIP 5’-AUGUUUGGUCGUAGUACU-3’
c) What would be the sequence produced after translation (5pts)?
5’-AUG-UUU-GGU-CGU-AGU-ACU-3’
N’ MET-PHE-GLY-ARG-SER-THR C’
13. Match the following (10pts):
A
Write the letter next to name:
Cytodine
___D__
Uridine triphosphate
____B__
Guanosine
____C___
Thymidine
____E__
B
C
D
E
Adenosine triphosphate ____A__
14. Why are DNA mutations potentially harmful to organisms (5pts)?
THEY CREATE CHANGES IN THE DNA THAT IS USED AS A TEMPLATE, FOR
EITHER DNA REPLICATION OR TRANSCRIPTION. THESE CHANGES MAY
RESULT IN A DISEASE.
15. Name one benefit of recombinant DNA technology (4pts)?
DNA TECHNOLOGY CAN BE USED TO SYNTHESIZE HUMAN PROTEIN. THIS
PROTEIN CAN THEN BE PROVIDED TO PEOPLE WITH DISEASES THAT ARE A
RESULT OF MISSING THIS ESSENTIAL PROTEIN.
Section III: Chapter 24: Metabolism and Energy (65 pts)
16. How do organisms obtain energy? Compare only photosynthetic organisms and animals
(6pts).
ANIMALS OBTAIN ENERGY FROM EATING CARBOHYDRATE, LIPID OR
PROTEIN. (OR THEY MUST EAT PLANTS AND PLANT EATING ANIMALS)
PHOTOSYNTHETIC ORGANISMS OBTAIN ENERGY FROM THE SUN.
17. Why do organisms obtain energy through cellular respiration and not combustion (4pts)?
CELLULAR RESPIRATION RELEASES ENERGY FROM ORGANIC MOLECULES
SLOWLY, PRODUCING LESS HEAT IN THE PROCESS, WHILE COMBUSTION
RELEASES ENERGY VERY RAPIDLY, PRODUCING TO MUCH HEAT FOR THE
CELL.
18. What is the main driving force for the hydrolysis of ATP (4pts)?
THE HIGH ELECTRON DENSITY IN THE ADJACENT PHOSPHATE GROUPS,
DRIVES THE HYDROLYSIS OF ATP. THE PHOSPHATE GROUPS REPEL EACH
OTHER.
19. Name the main enzymes responsible for the breakdown of the following nutrient molecules
and where the digestion of each begins (9pts).
Carbohydrates- AMYLASES, DIGESTION BEGINS IN THE MOUTH
Protein- PEPTIDASES (OR PROTESASES), DIGESTION BEGINS IN THE STOMACH
Fats- LIPASES, DIGESTION BEGINS IN THE SMALL INTESTINE
20. What are the two main functions of bile salts (6pts)?
BILE SALTS ARE IMPORTANT BREAKING DOWN LARGE FAT GLOBULES,
PRODUCING SMALLER GLOBULES AND THEY ARE IMPORTANT IN MAINTING
THE FAT GLOBULES SOLUBLE (DISSOLVED) IN THE AQUEOUS ENVIRONMENT.
21. a) What is the purpose of catabolism (4pts)?
THE PURPOSE OF CATABOLISM IS TO BREAKDOWN NUTRIENT MOLECULES
TO RELEASE ENERGY.
b) What are the main products at the end of Stage I of catabolism (3pts)?
AMINO ACIDS, MONOSACCHARIDES, AND GLYCEROL & FATTY ACIDS
22. a) What is the main role of Acetyl-CoA in catabolism (4pts)?
THE MAIN ROLE OF ACETYL-COA IS TO BE THE MAIN MOLECULE THAT
AFTER STAGE II, FEEDS INTO THE KREBS CYCLE TO PRODUCE ENERGY
b) What are the main products formed from the breakdown Acetyl-CoA at the end of the
Krebs Cycle (4pts)?
1 GTP, 3 NADH, 2 CO2, 1 FADH2
23. Why is O2 needed in the electron transport chain (4pts)?
O2 IS THE TERMINAL ELECTRON ACCEPTOR, (OR IS NEEDED FOR THE
REOXIDATION OF THE COENZYMES PRODUCED IN THE KREBS CYCLE)
24. a) What is the main purpose of the complexes in the electron transport chain (4pts)?
THEIR MAIN PURPOSE IS TO HELP TRANSFER ELECTRONS TO O2.
b)Name the two pathways by which the electron transport chain can be accessed and the two
coenzymes that access these pathways (4pts).
NADH ACCESSES THE ELECTRON TRANSPORT CHAIN THROUGH COMPLEX I
FADH2 ACCESSES THE ELECTRON TRANSPORT CHAIN THROUGH COMPLEX II
25. What drives ATP synthesis in the mitochondria (5pts)?
ATP SYNTHESIS IS DRIVEN BY THE H+ GRADIENT FORMED IN THE
INTERMEMBRANE SPACE.
26. Compare what is occurring when a person is exercising moderately versus someone doing
strenuous exercise (4pts).
A PERSON EXCERCISING MODERATELY IS BREAKING DOWN NUTRIENT
MOLECULES AEROBICALLY, WHILE A PERSON EXCERSING STRENOUSLY IS
OBTAINING ENERGY ANAEROBICALLY.