Biochemistry Final Q&A 40-80

Question 1

41-cholesterol: structure, biological role. Biosynthesis of cholesterol in the liver. Hypercholesterolemia: causese and
consequences?

Answer 1

• -Structure -cholesterol is an animal sterol. -it is a solid alcohol having group at C3.
• -Biological role : serves as a building block for synthesizing various steroid hormones, vitamin D, and bile acids. (functions of cholesterol): it is important for:
  (1) it enter in the structure of everybody cell particularly: (a) cell membranes. (b) in nervous tissue. (2)synthesis of steroid
  hormones. (3)synthesis of bile salts. (4)synthesis of vitamin D3

–Biosynthesis of cholesterol in the liver: The synthesis of cholesterol occurs in 5 stages: 1-synthesis of HMG Co-A. 2-formation of
mevalonate (6C). 3-production of isoperinoid units (5C). 4-synthesis of
squalene (30C). 5-conversion of squalene to cholesterol

–Hypercholesterolemia: causes: 1-Diabetes mellitus. 2-Nephrotic syndrome. 3-Hypothyrodism. 4-obstructive jaundice.

Question 2

42-Biosynthesis of fatty acids, Localization, stages of synthesis, citrate shuttle, malonyl-Co-A formation. NADPH sources?

Answer 2

–Localization: -intracellular location: cytosol. -organic location: many tissues including liver, adipose tissue, lung and kidney.
–Stages of synthesis: There are 3 stages of synthesis of the fatty acid: -first stage: production of Acetyl-Co-A and NADPH. -second
stage: conversion of Acetyl-Co-A to malonyl-Co-A. -third stage: reactions of fatty acids synthase complex. Malonyl-Co-A
–formation: Acetyl-Co-A is carboxylated to Malonyl-Co-A by the enzyme Acetyl-Co-A carboxylase. This is an ATP dependent
reaction and requires biotin for Co2 fixation.
–Sources of NADPH: 1- one molecule of NADPH is generated for each molecule of Acetyl-Co-A that is transferred from
mitochondria to the cytosol. 2- NADPH molecules comes from pentose phosphate pathway.

Question 3

43-Triacylglycerols lipolysis in adipocytes: reactions, enzymes, regulation. Ways to use free fatty acids ?

Answer 3

–Enzymes of lipolysis: is carried out by a number of lipase enzyme, which are present in adipose tissue. These are: 1-Hormone
sensitive triacylglycerol lipase. 2-Diacylglycerol lipase. 3-Monoacylglycerol lipase
–Regulation of lipolysis: The key enzyme
controlling lipolysis is Hormone sensitive triacylglycerol lipase. It exists in 2 forms: -Active form (phosphorylated). -Inactive form
(de-phosphorylated).
–Causes of excessive lipolysis: (low insulin and high glucagon): 1-starvation. 2-Diabetes mellitus. 3-low
carbohydrate diet. 4-in certain infectious disease as in tuberculosis (due to high catabolic state).

Question 4

44- Brown adipose tissue: especially metabolism. The mechanism of thermos genesis.

Answer 4

• -Brown adipose tissue: (a) certain areas of adipose tissue appear brown as they contain high content of mitochondria, cytochromes and well developed blood supply
• -Function: production of heat. They contain a protein call Thermogenin. This protein acts as uncoupler of oxidative phosphorylation: decrease production of ATP and increase generating of heat.
• • (c) site: common in animals exposed to cold atmosphere for warmness, and it is little in human.

Question 5

45-Hereditary diseases of lipid metabolism. Familial hypercholesterolemia, Niemann-pick disease, Gaucher,and others?

Answer 5

–Niemann-pick disease: Enzyme deficiency: sphingomyelinase
–Clinical symptoms: Enlarged liver and spleen, mental retardation;
fetal in early life.
–Gaucher disease: Enzyme deficiency: beta-glucosidase.
–Clinical symptoms: Enlarged liver and spleen, erosion of
long bones, mental retardation in infants.
–Familial hypercholesterolemia: Enzyme deficiency: LDL (low density lipoprotein). clinical symptoms: yellowish area around your
eyes, and painful in Achilles tendon.

Question 6

46-structure and function of biological membranes. The role of lipids and proteins in the maintaining the function of the
membranes. Transport of substances through cell membranes, modes of transport ?

Answer 6

— Structures :it composed of phospholipid
bilayer, which have 2 parts: hydrophilic part and hydrophobic part.
–Functions of the biological membranes: 1-to separate the
interior and exterior of the cell. 2-to maintain concentration of the gradients of the various ions
–The role of lipids and proteins in the maintaining the function of the membranes: to formation the permeability barrier of cells and subcellular organelles in the form of a lipid bilayer.
–Modes of transport: there are 3 mechanisms of transport: passive, facilitated, active transport

Question 7

48- Digestion of proteins in the gastrointestinal tract, biosynthesis of hydrochloric acid and pepsinogen in the stomach,
proteases of the pancreas and intestines. Activation of zymogens in the gastrointestinal tract, the specifics of the action of
each of the proteases ?

Answer 7

—Digestion of proteins proteolytic enzymes of the GIT by attack peptide bonds of a number of amino acids, but they exhibit the
preference for particular types of peptide bonds: proteinases: -pepsin: aromatic (Phe, Try) and acidic amino acids(GLU, ASP). -
Trypsin: basic amino acids (Arg, Lys) -chymotrypsin: hydrophobic (phe,Tyr, Trp, Leu) and acidic AA (Glu, Asp).
–Elastase: an amino acid with a small side chain (Gly, Ala, Ser)
–Peptidases: Carboxypeptidase A: all amino acids (not Arg and Lys). Carboxypeptidase B: basic amino acids (Arg, Lys)
–Leucine aminopeptidase: all amino acids. Prolidase: proline. Dipeptidase: splits only dipeptides.
–Digestion in the gastrointestinal tract:1- in the mouth: chewing starts the mechanical breakdown of protein. 2- in the stomach:
the chemical digestion of protein begins from hydrochloric acid (HCL), and the enzyme pepsin. 3- in the small intestine:
polypeptides are broken doen into amino acids, dipeptides, and tripepetides by protein digesting enzymes secreted from the
pancreas. 4- A variety of different transport proteins move the products from protein digestion into the mucosal cell. 5-Dipeptides and tripeptides can enter the mucosal cell, they are broken down into single amino acids. 6- Amino acids pass from
the mucosal cell into the blood and travel to the liver. The liver regulates the distribution of amino acids to the rest of the body.
7- small amounts of dietary protein is lost in the feces.
–Biosynthesis of HCL: in the stomach HCL are secreted by parietal cells (or oxyntic cells) of gastric gland.
– Biosynthesis of proteases :of the pancreas and intestines Several proteases are synthesized in the pancreas and secreted into
the lumen of the small intestine.

Question 8

50- common ways of amino acid conversion. Examples of reactions. Gives the name of enzymes and the role of these
transformations ?

Answer 8

– Common ways of amino acid conversion
1-Transamination: is the transfer of amino group from Alpha-amino acid to Alphaketoacid to form a new Alpha-amino acid and new Alpha-ketoacid.
-2-Deamination: is the removal of amino group from amino acid in the form of ammonia (NH3). Site: mostly in the liver and
kidney. Steps: oxidative, non-oxidative, hydrolytic deamination.
-3-Trans-deamination: it is a transamination of most amino acids with Alpha-ketoglutarate to form glutamate, then glutamate
de-aminated to give ammonia
-Functions: -some amines have important biological function: (a) Histamine (from histidine) is vasodilator. (b) gamma amino
butyric acid (from glutamate) is neurotransmitter. 1-Deamination: glutamate dehydrogenase. 2-Decarboxylation: decarboxylase.

Question 9

51- Transamination of amino acids. Give examples of reactions. Name the reaction enzymes and the role of transamination of
amino acids ?

Answer 9

-Transamination of amino acids: it is the transfer of amino group from alpha-amino acid to alpha-keto acid to form
a new alpha-amino acid and new alpha-keto acid
-Name of the enzyme: transaminase. Role of transamination of amino acids: to generate the amino acid version of keto-acids and
keto-acids version of the original amino acid

Question 10

52- Amino acid decarboxylation. Biologically active amines derived from amino acids. Structures and functions ?

Answer 10

–Biogenic amines: is the product of decarboxylation of amino acids ,they consist of :an aliphatic, aromatic, or heterocyclic
structure with attached of one or more amino groups.
–functions: some amine have biological functions. e.g. 1-Histamine: (from
Histidine) is vasodilator. 2-Gamma- amino butyric acid: (from glutamate) is neurotransmitter.

Question 11

53- Metabolism of phenylalanine and tyrosine. Synthesis of hormones and neurotransmitters (catecholamines, thyroxine,
triiodothyronine). Phenyl ketonuria, albinism, alkaptonuria ?

Answer 11

–phenylalanine is a ketogenic and glycogenic essential amino acids.
-Function: phenylalanine is a precursors of tyrosine in the liver as the following:
-This reaction needs phenylalanine hydroxylase enzyme and tetrahydrobiopterin as coenzyme. This result in the formation of
Dihydrobiopterin
-Metabolism of tyrosine:Tyrosine is a ketogenic and glycogenic non-essential amino acids. –it becomes essential in case of
deficiency of phenylalanine hydroxylase
-Synthesis of catecholamines: They are synthesized from tyrosine at storage sites: adrenergic neurons and adrenal medulla.
-Biosynthesis of Thyroid hormones Thyroid hormones: Thyroxine ( tetraiodothyronine and triidothyronine- are synthesized from
tyrosine residues of the protein thyroglobulin and activated iodine.
–Phenylketonuria Definition: it is inherited deficiency of phenylalanine hydroxylase enzyme (hepatic enzyme).
Symptoms: (1)mental retardation. (2)increased blood phenylalanine. (3)Failure to walk and talk.
-Prevention of phenylketonuria: -Any infant proved to have abnormal high level of phenylalanine, should feed milk containing
very low amount of phenylalanine.
–Albinism definition: hereditary deficiency of tyrosine hydroxylase enzyme in melanocytes.
Effects: defective synthesis of melanin pigments. Eye, skin and hair are affected. Types of Albinism: according to the site
affected (a)eye: ocular albinism. (b)skin: cutaneous albinism. (c)eye and skin

Question 12

54- Alanine metabolism. Synthesis of alpha-alanine from pyruvate and aspartate. Catabolism of alpha-alanine to the final
products. Role of Alanine in transport of ammonia from skeletal muscles ?

Answer 12

–Alanine is produced by the transamination of one
molecule of pyruvate by 2 different steps: (1) conversion of glutamate to alpha-ketoglutarate using a glutamate-alanine
transaminase. (2) conversion of valine to alpha-ketoisovalerate by transaminase C.
–synthesis of Alanine from Aspartate :Aspartate is non-essential amino acid and glycogenic. Aspartate is formed from
oxaloacetate by transamination. Aspartate transaminase is important for the interconversion of aspartate and glutamate
–Role of Alanine in transport of ammonia from skeletal muscles: Alanine undergoes a transamination reaction with free alphaketoglutarate, which is then deaminated to form pyruvate and free ammonium ion. Catabolism of alpha-alanine to the final
products

Question 13

57-synthesis of ammonia in the body. Toxicity of ammonia to brain cells. Temporary and final neutralization of ammonia in
the body. Urea cycle ?

Answer 13

–The production of ammonia occurs from the amino acids ( transamination and deamination ), biogenic
amines, amino group of purines and pyrimidines and by the action of the intestinal bacteria (urease) on urea
–Toxicity of ammonia to brain cells Definition: it is the elevation in the blood ammonia concentration is harmful to the
brain.
Symptoms: (A)Flapping tremors, slurring speech, blurring vision. (B)High concentration of ammonia may cause coma and
death
–Types and causes of hyper ammonemia: Hyperammonemia: elevation in blood NH3 level. Types: may be genetic or
acquired. Impairment in urea synthesis due to a defect in any one of the 5 enzymes which are described in urea synthesis. All
these disorders leads to hyperammonemia and cause hepatic coma and mental retardation.
—Temporary and final neutralization of ammonia in the body:
(A) Ammoniotelic
(B) uricotelic
C ) ureotelic:

Question 14

59- protein biosynthesis: activation, initiation, elongation, termination, post-translation ,modification.

Answer 14

–protein biosynthesis :is a core biological process, occurring inside cells, balancing the loss of cellular proteins (via degradation or
export) through the production of new proteins.
–The phosphorylation of a protein can make it active or inactive.
Phosphorylation can either activate a protein (orange) or inactivate it (green).
–The initiation of protein
synthesis: is the process that results in bringing together an 80S ribosome with a messenger RNA (mRNA) and initiator
methionyl-transfer RNA (Met-tRNAi)
–Elongation: is the phase of the protein-synthesis pathway that is responsible for the growth of nascent polypeptide chains.
–termination :once a stop codon has been encountered. The new polypeptide chain is released with the help of termination sequences
– post-translation :covalent processing events that change the properties of a protein by proteolytic cleavage and adding a modifying group, such as acetyl
–modification: Changes in tertiary structure of proteins brought about by specific chemical conjugation affect key cellular processes

Question 15

60- Nucleoprotein exchange: purine breakdown. Violation of Nucleoprotein metabolism ?

Answer 15

–Metabolism of purine: The end product of purine metabolism in the human is uric acid. The sequence of reactions in the
metabolism of purine:
1- the nucleotide mono-phosphates are converted to their respective nucleosides forms (adenosine, inosine and guanosine ) by the action of nucleotidase.
2- The amino group, either from AMP or adenosine, can
be removed to produce IMP or inosine.
3- Inosine and guanosine are converted to hypoxanthine and guanine by purine nucleoside phosphorylase. Adenosine is not degraded by this enzyme, hence it has to be converted to inosine.
4- Guanine undergoes deamination by guanase to form xanthine. 5- Xanthine oxidase: is an important enzyme that converts hypo-xanthine
to xanthine, and xanthine to uric acid.
–Violation of Nucleoprotein metabolism (disorders):
1- Hyperuricemia and gout: refers to elevation in the serum of the uric acid
2- Gout: is the metabolic disease associated with overproduction of uric acid.

Question 16

61- Chromoprotein metabolism: heme synthesis, porphyria ?

Answer 16

–1-Heme: is the most important porphyrin containing compound. It
is synthesised in the liver and the erythrocyte-producing cells of the bone marrow
–The biosynthesis of heme
occurs in the following stages: 1- Formation of gamma- aminolevulinate. 2- synthesis of porphobilinogen. 3- Formation of
porphyrin ring. 4- conversion of uroporphyrinogen III to protoporphyrin IX.
–2- porphyrias: are the metabolic disorders of heme synthesis, characterized by the increased excretion of porphyrins or
porphyrin precursors

Question 17

62- Chromoprotein metabolism: heme destruction, obturation, parenchymal and hemolytic jaundice ?

Answer 17

–Heme destruction (catabolism): The first reaction is cleavage of the heme ring by the hemeoxygenases.
– In the second reaction, biliveridin reductases reduces the central methene bridge of biliveridin, producing bilirubin. Bilirubin is the end product of heme
–Parenchymal (hepatic) jaundice causes: This type of
jaundice is caused by dysfunction of the liver due to damage to the parenchymal cells
–Haemolytic jaundice: This condition is associated with increased
hemolysis of erythrocytes

Question 18

63-Lipophilic hormones: chemical nature, nature of interaction with target cells, features of cellular response to interaction
with certain hormones?

Answer 18

–Lipophilic hormones (chemical nature): it is the hormones that aren’t soluble in aqueous medium, but soluble in lipid. For
example, Thyroid hormones and steroid hormones.
–Nature of interaction with target cells: they can enter target cells and bind to intracellular receptors to carry out their action. They can easily cross the cell membranes

Question 19

64-Hydrophilic hormones: chemical nature, nature of interaction with target cells, features of cellular response to interaction
with certain hormones?

Answer 19

–Hydrophilic hormones (chemical nature): They can not pass through the cell membranes; bind to cells
membrane receptors. For example, peptide hormones, amines and prostaglandin.
–Nature of interaction with the target cells:
they can not enter to the target cells; Because fatty acid tails of cell membrane are hydrophobic
–Features of cellular response to interaction with hormones: The hydrophilic hormones are able to diffuse through the membrane and interact with an intracellular receptors

Question 20

65-Thyroid hormones: effect on metabolism. Hypothyroidism and hyperthyroidism, mechanisms of occurrence and
consequences ?

Answer 20

–1- influence on the metabolism rate: Thyroid hormones stimulate the metabolic activities & increase the O2
consumption in the most of the tissues of the body (exception brain, lungs, testes, and retina)
–2- Effect on protein synthesis: Thyroid hormones acts like steroid hormones in promoting protein synthesis by acting at the
activate DNA to produce RNA
–3- influence on the carbohydrate metabolism: Thyroid hormones promote intestinal absorption of glucose and it is utilization. These hormones increase gluconeogenesis & glycogenolysis
–4- Effect on lipid metabolism: lipid turnover and utilization are stimulated by thyroid hormones.
–Hyperthyrodism : is This also known as (Thyrotoxicosis) and is associated with overproduction of thyroid hormones.
–Hypothyroidism: This is due to an impairment in the function of the thyroid gland that causes decreased circulatory levels of T3&T4. Disorders of pituitary or hypothalamus can be also causes hypothyroidism

Question 21

66-Adrenaline : synthesis, effect on the metabolism, utilization ?

Answer 21

–Adrenaline is synthesised in the chromffin cells of the adrenal gland and small number of neurons of the medulla oblongata in
the brain through a metabolic pathway that converts the amino acids phenylalanine and tyrosine into a series metabolic
intermediate and adrenaline
–Utilization of Adrenaline (functions or uses): It increase the cardiac output, blood pressure and oxygen consumption. They
cause smooth muscle relaxation in bronchi, gastrointestinal tract
–Effect on the metabolism: 1- Effects on carbohydrate metabolism: Epinephrine and nor-epinephrine in general increase the
degradation of glycogen (glycogenolysis), synthesis of glucose
–2- Effects on lipid metabolism: both epinephrine and nor-epinephrine enhance
the breakdown of triacylglycerols (Lipolysis) in the adipose tissue

Question 22

67-pancreatic hormones (insulin, glucagon): formation, effect on metabolism, utilization ?

Answer 22

–Biosynthesis of insulin: insulin is produced by beta-cells of the iselts of Langerhans of pancreas. The synthesis of insulin involves
2 precursors, preproinsulin with 108 amino acids and proinsulin with 86 amino acids. They are degraded to form the active
hormone insulin.
–Utilization of insulin: 1- promote glucose uptake. 2- promote glycogenesis. 3- promote lipogenesis.
–Biosynthesis of Glucagon: Glucagon is synthesised by alpha-cells of the pancreas, opposes the actions of insulin. It is a
polypeptide hormone composed of 29 amino acids in a single chain.
–Effect of Glucagon on the metabolism: 1- Effects on carbohydrate metabolism: it increase the blood glucose level causes
(Hyperglycemic). Glucagon acts on the liver to caused increased synthesis of glucose
–3- Effects on protein metabolism: Glucagon increases the amino acid uptake by the liver, which promote gluconeogenesis.
Glucagon causes decrease of plasma amino acids. Utilization of Glucagon it helps to treatment the decrease of blood sugar level.

Question 23

68-Hormones of the adrenal cortical layer: Mineralocorticoids, glucocorticoids. Synthesis, mechanism of interaction with the
target cell, effect on metabolism ?

Answer 23

–Mineralocorticoids :There are also 21 carbon containing steroids produced by zona glomerulosa. They are regulate water and
electrolyte balance.
-(Aldosterone): is the most prominent mineralocorticoid
- (Glucocorticoids): these are 21 carbon steroids, produced mostly zona fasciculata. They affect glucose
- (Cortisol): also known as hydrocortisone is the most important glucocorticoid in humans. Corticosterone is predominantly found in rats.

Question 24

69-Biochemistry of Diabetes mellitus ?

Answer 24

–Diabetes mellitus is associated with insulin deficiency. This is result in impaired carbohydrate metabolism and increased lipolysis, both of them leading to the accumulation of acetyl-co-A and it is conversion to
ketone bodies. In severe diabetes, the ketone body concentration in blood plasma may reach 100 mg/dl and the urinary
excretion may be reaches to 500 mg/day

Question 25

71-pathological components of urine, detection and causes ?

Answer 25

– The pathological components of the urine: are proteins, sugar,
blood, bile pigments and ketone bodies .
–Causes: – Diabetes mellitus and Diabetes insipidus. – Addison’s disease. – Chronic progressive renal failure. – Excess water intake. – Intake of Diuretics, like alcohol and caffeine.
– Detection( diagnosis): by the analysis of the urine in the laboratory: 1- red blood cell urine test. 2- Glucose urine test. 3- urine pH level test. 4- Ketones urine test. 5- Bilirubin urine test.

Question 26

72-Buffer systems of blood, violations of acid-base balance, causes, correction.

Answer 26

–The blood contains 3 buffer systems:
1- Bicarbonate buffer. 2- phosphate buffer. 3- protein buffer. Violations of acid-base
- balance (Disorders): they are classified according to their causes and the direction of pH change into: -respiratory acidosis: Due
to increase in carbonic acid. -Metabolic acidosis: Due to decrease in bicarbonate. -respiratory alkalosis: Due to decrease in
carbonic acid. - Metabolic alkalosis: Due to increase in bicarbonate
–Correction of acid-base disorders (treatment) 1-oral or
intravenous sodium bicarbonate to raise blood pH. 2-sodium citrate to treat metabolic acidosis

Question 27

74-pathological changes in the composition of the blood, methods of detection. Usage of blood test in diagnostic purposes ?

Answer 27

—The blood disorder includes: • Anemia. • Hemophilia. • Leukocytes. • Polycythemia vera. • Sickle cell disease. • Thalassemia. •
Von Willebrand disease. Methods of detection of blood disorders These include the prothrombin (PT) test and the partial
thromboplastin time (PTT) test. These tests can help diagnose clotting disorders such as hemophilia
–Hemoglobin electrophoresis checks for the amounts and types of hemoglobin in the blood. Usage of blood test in diagnostic
purposes Find out how well organs such as your kidneys, liver, heart, or thyroid are working. Help diagnose diseases such as
cancer, diabetes, coronary heart disease, and HIV/AIDS.

Question 28

75-Blood: composition, functions, features of metabolism in erythrocytes and leukocytes?

Answer 28

—The blood is composed of: -red blood cells (erythrocytes). -wight blood cells ( leukocytes). -platelets (Thrombocytes). - plasma.
–Functions of the blood: 1- Respiration: transport of O2 from the lungs to the tissues and transport of Co2 from tissues to the
lungs. 2- Nutrition: transport of absorbed food materials. 3- Excretion: transport of metabolic waste to the kidneys,
–features of metabolism in leukocytes: 1- active synthesis of protein and nucleic acid. 2- synthesis and storage of glycogene. 3-
active glycolysis.
–features of metabolism in erythrocytes :1- RBC is highly dependent upon glucose ads it is energy source, and it is not dependent
upon insulin. 2- RBC has variety of transports that maintain ionic and water balance.

Question 29

76-Blood: composition, functions,structure. Plasma proteins and function ?

Answer 29

–Plasma proteins: Plasma contains many proteins broadly classified into • albumin and •globulins (predominantly
immunoglobulins). Albumin is a: •major transport protein - trace metals, hormones, bilirubin, and free fatt acids; •protein
reserve in nutritonal depleton; •osmotic regulator
–structure and five classes of immunoglobulin exist with diferent protectve functions. Immunoglobulins are produced in
response to foreign substances (antigens).
–Functions of plasma proteins :1- blood clotting & fibrinolysis function. 2- transport function. 3- Defence function body. 4- Buffer action. 5- source of amino acids for the tissues. 6- regulation of capillary
permeability

Question 30

77-Kidney biochemistry: urine formation in nephrons (ultrafiltration, reabsorption and secretion ), urine composition in
normal and pathological conditions ?

Answer 30

–1- kidneys have ametabolic rate more than 400 kcal/kg per day which is as heart and twice liver and brain –kidneys metabolism is related to carbohydrates –proteins -peptides and other nutrients and also aerobic
–metabolism : its mainly determined by tubular transport activity)occurs to determine oxygen consumption
–In medulla:oxidative metabolism occurs and it produces energy for active transport of sodium nad there by facilitating the
process The first step in urine formation begins with a passive process of ultrafiltration at the glomerulus
- 2- reabsorption:When the filtrate exits the glomerulus, it flows into a duct in the nephron called the renal tubule.
As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries
–3-secretion :The filtrate absorbed in the
glomerulus flows through the renal tubule, where nutrients and water are reabsorbed into capillaries.
–Normal Chemical and Constituents: are urea, creatinine, organic acids, electrolytes, uric acid etc.
–Abnormal chemical constituents are: sugar, proteins, blood, bile salts, bile pigments and ketone bodies.

Question 31

78-Metabolism of proteins, carbohydrates and lipids in the kidney?

Answer 31

–1-Large proteins and polypeptide molecules filtered by the glomerulus, are absorbed from proximal tubular fluid by luminal
endocytosis into apical vacuoles which fuse with primary lysosomes where hydrolysis occurs followed by diffusion of metabolites
out of the cells and into the blood
–2- In addition to their important role in gluconeogenesis, the kidneys contribute to glucose homeostasis by filtering and
reabsorbing glucose.
— Renal filtration and receptor-mediated uptake of lipid-binding and lipid-regulating proteins may therefore influence overall
lipid metabolism.

Question 32

79-Biological function of macro and micro-elements: Na, K, Ca, Mg, Co, Fe, Zn, P, Cl, F ?

Answer 32

–sodium (Na):, sodium regulates the body’s acid-base balance
–Potassium (K+): 1- potassium maintaining intracellular osmotic pressure.
–Calcium (Ca+2): 1- Development of bone and teeth. 2- Muscle contraction. 3- Blood coagulation
–Magnesium (Mg+): 1- Magnesium is required for the formation of bones and teeth. 2- Magnesium serve as a cofactor for several
enzymes requiring ATP
–Cobalt (Co): Cobalt is a necessary component of vitamin B12 and a fundamental coenzyme of
cell mitosis
–Iron (Fe): 1- Haemoglobin and myoglobin are required for the transport of Co2 and O2.
–Zinc (Zn): 1- Zinc is essential component of several enzymes
–Phosphorus (P): 1- is essential for the development of
bones and teeth
–Chloride (Cl): 1- chlorine is involved in the regulation of acid-base balance
–Fluorine (F): 1- Fluoride prevents the development of caries
–

Question 33

80-sources of pyruvate and ways of using pyruvate in the cell ?

Answer 33

1-In most cells, the major source of pyruvate is the last step of glycolysis, where pyruvate kinase
converts phosphoenolpyruvate to pyruvate

2- Pyruvate is a key intersection in the network of metabolic pathways. Pyruvate can be
converted into carbohydrates via gluconeogenesis, to fatty acids or energy through acetyl-CoA,
to the amino acid alanine, and to ethanol.