QUESTION 15

Stroma close all day and open all night.

True

False

6.Select the process of cellular respiration in the correct chronological order

7.

____ is where most of the ATP is produced during cellular respiration.

BIOCHEMISTRY

10. Draw structures and write the overall reaction in the citric acid cycle for each step described below:

1. Reaction catalyzed by an enzyme similar to PDH

2. The step in which the reaction product inhibits PFK

3. The step that involves isomerization and an enzyme with Fe-S clusters

4. A reaction that produces substrate level phosphorylation

5. A decarboxylation step coupled to the production of a high energy intermediate

6. A reaction that involves the production of a reduced flavin coenzyme

7. A reaction that is not thermodynamically favored under standard conditions

8. A reaction that involves an enzyme similar to PDH

The enzyme fumarase catalyzes the hydrolysis of fumarate:

Fumarate(aq) + H₂O(liq) → L-maleate(aq)

The turnover number k₂ for this enzyme is 2.5 × 10³ s^-1, and the Michaelis constant is 4.2 × 10^-6 mol / L.

(a) What is the rate of fumarate conversion v if the total concentration of the enzyme is 1.0 × 10^-7 mol / Land the concentration of fumarate is 3.0 × 10^-4 mol / L?

(b) What is the ratio (v/v_max) in the conditions of question (a)?

(c) At what concentration of fumarate is (v/v_max) = 0.28?

An enzyme has a broad pH optimum having high rates of activity between pH 4 and 12. X-ray diffraction studies show that the enzyme has an active site with glutamate and arginine residues in close proximity to the substrate. Explain how these two residues might be able to promote concerted acid-base catalysis (which residue is acting as the acid, which is acting as the base). Finally, explain why enzyme activity drops off sharply below pH 4 and above pH 12.

In a constant volume batch reactor, enzyme E catalyzes the transformation of reactant A to product R as follows:

A -----> R

The rate of consumption of A is given as rA= 200CACE/(2 + CA) (mol/l min). If we introduce enzyme with an initial concentration of 0.001 mol/l and reactant with an initial

concentration of CA0=10 mol/l into a constant volume batch reactor and let the reaction proceed, find the time needed for the concentration of reactant to drop to 0.025 mol/l. Note that the concentration of enzyme remains unchanged during the reaction.

Question 1

What post-translational modification will cause the biggest increase in the size of a protein, immediately when added?

Select one:

a. Phosphorylation

b. Ubiquitination

c. Acetylation

d. Methylation

Question 2

What does HMT do?

Select one:

a. It acts as an epigenator

b. It modifies nitrogenous bases

c. It produces euchromatin

d. It modifies histones

Question 3

Where can an epigenetic maintainer act?

Select one:

a. On the sequence of nucleotides

b. On the sequence of nucleotides and on the nucleotides directly

c. On certain nucleotides and amino acids

d. On certain amino acids

e. On certain nucleotides

Question 4

Which of the following types of protein could be coded by a tumour-suppressor gene?

Select one:

a. A protein that stimulate progression through the cell cycle.

b. A protein that forms part of a growth factor signaling pathway.

c. A protein that codes for a DNA repair enzyme.

d. A protein that helps prevent apoptosis.

e. A protein that repairs lost telomeres

Question 5

Which is NOT a typical mechanism by which a proto-oncogene is converted to an oncogene?

Select one:

a. A point mutation in the proto-oncogene

b. A chromosomal translocation resulting in the up-regulation of the proto-oncogene

c. Duplication of a chromosome region containing a proto-oncogene

d. Complete deletion of the proto-oncogene

e. Amplification of the proto-oncogene

Question 6

Why do you think familial retinoblastoma and Li-Fraumeni are considered to be inherited as autosomal dominant traits when the responsible genes are recessive?

Select one:

a. They are expressed in a dominant fashion in males, but recessive in females.       

b. People with this mutation are always homozygous for this allele.

c. If you are born with one allele mutated in every cell, the chance that the other allele will be mutated in one of the retinal cells is extremely high.

d. This recessive gene needs only one copy to express this phenotype.

e. Retinoblastoma was mischaracterized originally when it was called an autosomal dominant trait.

Question 7

Question text

In a normal cell, pRB binds to __________, which inhibits cell division. In the presence of __________ pRB becomes __________, which leads to cell division.

Select one:

a. cyclin+Cdk; oncogenes; dephosphorylated

b. transcription factors; cyclin+Cdk; phosphorylated

c. tumor suppressor; p53; phosphorylated

d. p21; p53; dephosphorylated

e. tumor suppressor; p21; hyperactive

Question 8

The following information relates to the next three questions:

A few decades ago, Knudsen and colleagues proposed a theory that, for a normal cell to become a cancer cell, a minimum of two genetic changes had to occur in that cell. Knudsen was studying retinoblastoma, a childhood cancer of the eye.

Two children are born from the same parents. Child one inherits a predisposition to retinoblastoma (one of the mutations) and child two does not. However, both children develop the retinoblastoma. Which of the following would you expect?

Select one:

a. a history of exposure to mutagens in child one but not in child two

b. increased levels of apoptosis in both children

c. an earlier age of onset in child one

d. decreased levels of DNA repair in child one

e. a more severe cancer in child one

Question 9

In colorectal cancer, several genes must be mutated in order to make a cell a cancer cell, supporting Knudsen’s hypothesis. Which of the following kinds of genes would you expect to be mutated?

Select one:

a. genes that are especially susceptible to mutation

b. the same genes that Knudsen identified as associated with retinoblastoma

c. genes coding for enzymes that act in the colon

d. the genes of the bacteria that are abundant in the colon

e. genes encoding transcription factors that regulate cyclin production

Question 10

Knudsen and colleagues also noted that persons with hereditary retinoblastoma that had been treated successfully lived on but then had a higher frequency of developing osteosarcomas (bone cancers) later in life. This provided further evidence of their theory because:

Select one:

a. osteosarcoma cells express the same genes as retinal cells.

b. one of the mutations involved in retinoblastoma is also one of the changes involved in osteosarcoma.

c. p53 gene mutations are common to both tumours.

d. retinoblastoma is a prerequisite for the formation of osteosarcoma later in life.

e. both kinds of cancer involve uncontrolled proliferation of cells.

Fill in the blanks

1. the ____ atoms of the ____ groups and the hydrogen atoms attached to the ____ atoms form ____.

(answer choices; nitrogen, carbon, a-helices or b-pleated sheets, carbonyl, globular of firbrous structures, oxygen, amino, random coil, thiol)

2. In the a helix, hydrogen bonds form between the ____ oxygen atom and the ____ hydrogen atom of a peptide bond in _____. In the B-pleasted sheet, hydrogen bonds form between the ____ oxygen atom and the ____ hydrogen atom of a peptide bond in ____.

(answer choices; parallell sections of a long polypeptide chain, the next amino acid unit, carboxyl, the next turn of the helical chain, thiol, amino, carbonyl)

1. Explain how lipids are digested and absorbed.

2. Differentiate among saturated, monounsaturated, and polyunsaturated fatty acids in terms of structure and food sources.

3. List four classes of lipids and the role of each in nutritional health. Distinguish between fatty acids and triglycerides.

90.LDL is involved in the transport of endogenous cholesterol from tissue to the liver.

89.The synthesis of fatty acids is a reductive process. NADH provides the reducing equivalent for fat production.

88.In the biosynthesis of fatty acid, the acyl group carrier for the biosynthetic reaction is acyl carrier protein.

87.The breakdown of the fatty acid CH3CH2CH2CH2CH2CH2CH2CH2COOH via the β-oxidation pathway would yield three moles acetyl units and one mole propionyl unit.

86.In the oxidation of fatty acids, transportation of activated fatty acids into mitochondria requires the reaction with carnitine.