Biochem Finals (Batch 2027) Flashcards
Which transporter of lipid is lowest in density but largest in size, containing the highest percentage of lipid and the smallest amount of protein?
A. Chylomicron
B. VLDL
C. LDL
D. HDL
a. Chylomicron
Rationale: Chylomicrons are lipoproteins that transport dietary lipids from the intestines to other locations in the body. They are the largest and least dense of the lipoprotein particles, consisting mostly of triglycerides and having a very small protein content.
A plasmid consisting of its own DNA with foreign DNA inserted into it is called:
A. Junk DNA
B. Recombinant DNA
C. Non-coding DNA
D. None of the above
B. recombinant DNA
Rationale: Recombinant DNA is formed by combining DNA from two different sources, creating new genetic combinations.
Endonucleases, a group of enzymes, cleave DNA:
A. Externally
B. Internally
C. Both A and B
D. Neither A nor B
B. Internally
Rationale: Endonucleases cleave the phosphodiester bond within a polynucleotide chain, acting internally rather than at the ends.
The first human protein produced through recombinant DNA technology is:
A. Somatostatin
B. Erythropoietin
C. Interferon
D. Insulin
A. somatostatin
Rationale: While insulin is one of the most well-known and impactful proteins produced using recombinant DNA technology, the first human protein to be produced in this manner was actually somatostatin. Somatostatin, a smaller peptide hormone that regulates the endocrine system, was successfully synthesized using recombinant DNA techniques in the early 1970s before the production of recombinant insulin.
An example of an autonomously replicating mini chromosome is:
A. Virus
B. Plasmid
C. Phage
D. Lichen
B. plasmid
Rationale: Plasmids are small, circular, double-stranded DNA molecules found in bacteria that replicate independently of the chromosomal DNA.
What is the metabolic fate of the carbon skeleton of amino acids upon degradation?
A. Used for ATP synthesis
B. Used for fatty acid synthesis
C. Used for glucose synthesis
D. All of the above
E. None of the above – it is converted to urea
D. All of the above
Rationale: The carbon skeletons of amino acids can be used for ATP synthesis, fatty acid synthesis, and glucose synthesis, depending on the body’s needs and metabolic state.
Prior to the production of recombinant insulin, insulin obtained from cows and pigs was given to patients. Some problems faced by this treatment were:
A. The insulin was not active
B. In some humans, it induced antibody production
C. It reduced the weight of patients
D. Loss of memory power
B. in some humans it induced antibody production
Rationale: Insulin from cows and pigs sometimes caused allergic reactions or antibody production in humans due to slight differences in the protein structure compared to human insulin.
Electrophoresis, a technique used in DNA fingerprinting, helps to separate:
A. Tissues
B. DNA segments
C. Cells from DNA
D. RNA from DNA
B. DNA segments
Rationale: Electrophoresis is used to separate DNA fragments based on their size and charge, a crucial step in DNA fingerprinting.
A segment of DNA that reads the same forward and backward is called:
A. Plasmid DNA
B. Palindromic DNA
C. Complementary DNA
D. Copy DNA
B. palindromic DNA
Rationale: Palindromic DNA sequences read the same in both directions (5’ to 3’ and 3’ to 5’), and are often recognition sites for restriction enzymes.
cDNA, a term used in recombinant DNA technology, means:
A. Competitive DNA
B. Complementary DNA
C. Chemical DNA
D. Complex DNA
B. complementary DNA
Rationale: Complementary DNA (cDNA) is synthesized from an mRNA template using the enzyme reverse transcriptase, often used in cloning eukaryotic genes in prokaryotes.
What is an important function of fiber?
A. It adds flavor to food
B. It aids in the absorption of fat-soluble vitamins
C. It can bind toxigenic substances
D. It is an important energy source in the absence of lipids
C. It can bind toxigenic substances
Rationale: Dietary fiber can bind to and help eliminate toxins from the body, aiding in digestive health.
How many nitrogen atoms does urea have?
A. One
B. Two
C. Three
D. Four
B. Two
Rationale: Urea has two nitrogen atoms in its structure, which is why it is an efficient way for the body to excrete excess nitrogen.
A defect in the enzyme carbamoyl phosphate synthase I results in:
A. Hyperammonemia
B. Hyperuricemia
C. Hypercitrullinemia
D. Hyperammonuria
A. Hyperammonemia
Rationale: Carbamoyl phosphate synthase I is involved in the urea cycle, which helps to remove ammonia from the body. A defect in this enzyme leads to the accumulation of ammonia, resulting in hyperammonemia.
Amino acid oxidases remove nitrogen from amino acids in the form of:
A. Urea
B. Ammonia
C. Uric acid
D. Glutamate
B. Ammonia
Rationale: Amino acid oxidases catalyze the oxidative deamination of amino acids, producing ammonia as a byproduct.
In amino acid catabolism, the α amino nitrogen is:
A. Used as a substrate for glycogenesis
B. Converted to a less toxic substance in the liver
C. Excreted in the form of uric acid in humans
D. Used as a substrate for fatty acid synthesis
B. converted to a less toxic substance in the liver
Rationale: The α amino nitrogen is converted to urea in the liver, a less toxic substance that can be excreted by the kidneys.
Glutamate dehydrogenase catalyzes what type of reaction?
A. Reductive biosynthesis
B. Transketolation
C. Methyl group transfer
D. Oxidative deamination
D. Oxidative deamination
Rationale: Glutamate dehydrogenase catalyzes the oxidative deamination of glutamate, producing α-ketoglutarate and ammonia.
A patient was said to be gaining nitrogen and is in a state of positive nitrogen balance. Which condition fulfills this criteria?
A. An elderly patient in a cachectic state
B. Child undergoing a growth spurt
C. Infant with protein energy malnutrition
D. A post-partum mother
B. Child undergoing a growth spurt
Rationale: A positive nitrogen balance occurs when nitrogen intake exceeds nitrogen loss, which is typical during periods of growth, such as in a child undergoing a growth spurt.
Absence of this enzyme causes dietary cellulose to remain undigested.
A. Glucoamylase
B. Lactase B-glycosidase
C. Sucroamylase
D. Trehalase
b. lactase B-glycosidase
Rationale: Lactase β-glycosidase is not involved in the digestion of cellulose. In fact, none of the listed enzymes (glucoamylase, lactase β-glycosidase, sucroamylase, or trehalase) are responsible for breaking down cellulose. Humans lack the enzyme cellulase, which is necessary to digest cellulose. Therefore, the absence of cellulase is the reason dietary cellulose remains undigested in humans. However, since cellulase is not listed as an option, the question might be misleading as none of the provided enzymes can digest cellulose.
Procarcinogens need to be activated by an enzyme to become which of the following?
A. True carcinogens
B. Pre-carcinogens
C. Ultimate carcinogens
D. All of the above
C. Ultimate carcinogens
Rationale: Procarcinogens are converted to active carcinogens, known as ultimate carcinogens, through metabolic activation by enzymes.
A mechanism of oncogene activation where a piece of one chromosome is split off and joined to another, as seen in Burkitt’s lymphoma.
A. Promoter insertion
B. Enhancer insertion
C. Gene amplification
D. Chromosomal translocation
D. Chromosomal translocation
Rationale: Burkitt’s lymphoma is characterized by a chromosomal translocation, where a part of chromosome 8 is transferred to chromosome 14, leading to the activation of the MYC oncogene.
Calcitonin is a tumor biomarker that is associated with:
A. Medullary carcinoma of the thyroid
B. Myeloma
C. Hepatocellular carcinoma
D. Germ cell tumor
A. Medullary carcinoma of thyroid
Rationale: Calcitonin is produced by the parafollicular C cells of the thyroid gland and is a specific marker for medullary thyroid carcinoma.
Imatinib, a tyrosine kinase inhibitor, belongs to which of the following classes of drugs?
A. Inhibitors of hormone receptors
B. Monoclonal antibodies
C. Inhibitors of signal transduction
D. Anti-angiogenesis agents
C. Inhibitors of signal transduction
Rationale: Imatinib (Gleevec) is a tyrosine kinase inhibitor that specifically inhibits the BCR-ABL tyrosine kinase, which is involved in signal transduction pathways that lead to cancer cell proliferation.
Loss of tumor suppression in a cell usually results from:
A. A deletion of a tumor suppressor gene
B. A translocation of a tumor suppressor gene
C. An inversion involving a tumor suppressor gene
D. Cytokine activation of a tumor suppressor gene
A. A deletion of a tumor suppressor gene
Rationale: Loss of function in tumor suppressor genes often occurs due to deletions or mutations, leading to uncontrolled cell growth and cancer development.
Growth of new blood vessels in and around tumors is called:
A. Invasiveness
B. Dedifferentiation
C. Metastasis
D. Angiogenesis
D. Angiogenesis
Rationale: Angiogenesis is the process by which new blood vessels form from pre-existing vessels, providing tumors with the necessary oxygen and nutrients to grow.
Which hormone/s will be released upon stimulation of Thyroid Stimulating Hormone (TSH)?
A. Thyroxine
B. Triiodothyronine
C. Thyrotropin-releasing hormone
D. Only A and B
D. Only A and B
Rationale: Thyroid-stimulating hormone (TSH) stimulates the thyroid gland to produce and release thyroxine (T4) and triiodothyronine (T3).
The following are true of steroid hormone action, EXCEPT:
A. Hydrophobic steroid hormones bound to plasma protein carriers diffuse into the target cell
B. Steroid hormone receptors are in the cytoplasm or nucleus
C. The receptor-hormone complex binds to DNA and affects the genes
D. Activated genes produce new mRNA that moves back into the cytoplasm
a. Hydrophobic steroid hormones bound to plasma protein carriers diffuse into the target cell
Rationale: Hydrophobic steroid hormones do not diffuse into target cells while bound to plasma protein carriers. They must first dissociate from these carriers to enter the cell.
TRUE of primary hypersecretion due to a problem with the adrenal cortex:
A. Low CRH levels
B. Low ACTH levels
C. High cortisol levels
D. All of the above
d. All of the above
Rationale: In primary hypersecretion due to an adrenal cortex problem, cortisol levels are high, which leads to feedback inhibition resulting in low levels of CRH (corticotropin-releasing hormone) and ACTH (adrenocorticotropic hormone).
After an overnight fast, a diabetic woman feels nauseous and skips breakfast but takes her insulin shot. This results in:
A. Increased glycogenolysis
B. Hypoglycemia
C. Increased lipolysis
D. Glycosuria
b. Hypoglycemia
Rationale: Taking insulin without eating can lead to a significant drop in blood glucose levels, resulting in hypoglycemia.
Hormonal stimulation of the formation of the second messenger IP3 leads to the release of which other intracellular messenger?
A. Cyclic AMP
B. Prostaglandin
C. Calcium
D. Leukotriene
c. Calcium
Rationale: Inositol triphosphate (IP3) stimulates the release of calcium ions from the endoplasmic reticulum, acting as a second messenger in various signaling pathways.
The following hormones use cAMP as a second messenger, EXCEPT:
A. FSH
B. LH
C. Glucagon
D. Estrogen
d. Estrogen
Rationale: Estrogen primarily acts through intracellular receptors that directly influence gene transcription, rather than using cAMP as a second messenger.
Hormones that act on cells near the secreting cell are classified as:
A. Endocrine
B. Paracrine
C. Autocrine
D. Neurocrine
b. Paracrine
Rationale: Paracrine signaling involves the release of hormones that act on nearby cells, unlike endocrine signaling which involves hormones traveling through the bloodstream to distant cells.
Biotin is involved in which of the following types of reactions?
A. Hydroxylations
B. Dehydrations
C. Decarboxylations
D. Carboxylations
D. Carboxylations
Rationale: Biotin acts as a coenzyme for carboxylase enzymes, which are involved in carboxylation reactions.
If there is a dysfunction in the oxidase enzyme system (like cytochrome oxidase, ascorbic acid oxidase), which mineral is most likely affected?
A. Zinc
B. Copper
C. Chloride
D. Selenium
B. Copper
Rationale: Copper is a key component of many oxidase enzymes, including cytochrome oxidase and ascorbic acid oxidase.
A deficiency of vitamin B12 causes:
A. Cheilosis
B. Pernicious anemia
C. Beriberi
D. Scurvy
B. Pernicious anemia
Rationale: Vitamin B12 deficiency can lead to pernicious anemia, a condition in which the body can’t make enough healthy red blood cells.
All the following vitamins give rise to cofactors that are phosphorylated in the active form, except:
A. Pyridoxine
B. Niacin
C. Lipoamide
D. Riboflavin
C. lipoamide
Rationale: Lipoamide is not a vitamin that gives rise to a phosphorylated cofactor; it is derived from lipoic acid and acts as a cofactor in its own right.
All the following statements describing vitamin K are true, except that:
A. It is synthesized by intestinal bacteria
B. It prevents thrombosis
C. It is obtained by eating spinach and cabbage
D. It is required for liver synthesis of prothrombin
B. it prevents thrombosis
Rationale: Vitamin K is essential for blood clotting and helps in the synthesis of clotting factors; it does not prevent thrombosis but rather supports the clotting process.
All the following statements are true of vitamin A, except:
A. It is synthesized in the skin
B. It promotes maintenance of epithelial tissue
C. It is used to treat severe acne
D. It promotes maintenance of vision
A. it is synthesized in skin
Rationale: Vitamin A is not synthesized in the skin; this statement is true for vitamin D. Vitamin A is obtained from the diet and is essential for vision, epithelial maintenance, and treatment of severe acne.
This is a toxic protein aggregate that is the hallmark of diseases such as Parkinson’s and Alzheimer’s Disease:
A. Amyloid
B. Schiff base
C. Amylopectin
D. Amadori intermediate
A. Amyloid
Rationale: Amyloid proteins aggregate to form plaques, which are associated with neurodegenerative diseases such as Parkinson’s and Alzheimer’s.
What is the role of telomeres in the aging process?
A. Telomeres cause a progressive slowing down of an individual’s heart rate when they accumulate with age
B. In theory, telomeres generate protein aggregates which when expressed will cause DNA damage
C. Telomeres generate Okazaki fragments, which are not detected by DNA polymerases during cell replication of DNA
D. Telomeres shorten after every cell division until senescence sets in
D. Telomeres shorten after every cell division until senescence sets in
Rationale: Telomeres protect chromosome ends but shorten with each cell division, leading to cellular aging and eventual senescence.
Which of the following is an important cofactor for vitamins C, E, and Glutathione Peroxidase in the neutralization of free radicals?
A. Copper
B. NADPH
C. Selenium
D. Bioflavonoids
C. Selenium
Rationale: Selenium is an essential cofactor for the enzyme glutathione peroxidase, which plays a critical role in protecting cells from oxidative damage by neutralizing free radicals. While NADPH is important for the regeneration of glutathione, it is not a cofactor for vitamins C, E, and glutathione peroxidase in the same direct sense as selenium.
