Biochemistry Final Q&A 1-40

Question 1

1- Amino acids: classification of amino acid, structure, general properties, biological function?

Answer 1

• 1-Amino acids: are a group of organic compounds containing two functional groups amino and carboxyl. The amino group (—
  NH2) is basic while the carboxyl group (—COOH) is acidic

——— classification:
–The amino acids are classified according to their structure into: Amino acids with aliphatic side chain : Alanine, valine, leucine,
isoleucine, glycine ).
–Amino acids containing hydroxyl groups: for example: ( serine, threonine )- Sulfur containingamino acids: (cysteine, cystine,
Methionine).
–Acidic Amino acids: ( Aspartic acid, )
–Aromatic amino acids: ( phenylalanine)
–classification of amino acids based on polarity:
– (1) Non-polar amino acids: ( Alanine, Leucine,)
–(2) Polar amino acids with no charge on ‘R’ group: ( Glycine, serine,)
–3-Polar amino acid with positive ‘R’ group: ( Lysine, Arginine,)
.-Polar amino acids with Negative ‘R’ group: ( Aspartic)
-Nutritional classification of amino acids:
*Essential amino acids: ( leucine)
*Semiessential amino acids: ( Arginine)
*Non-essential amino acids: ( Glycine)
-(D)Amino acid classification based on their metabolic fate: (1)Glycogenic amino acids ,(2)Ketogenic amino acids,.(3)Glycogenic & Ketogenic amino acids
——— Structure:
-The amino acid is organic molecule which consists of :amino group (-NH2).carboxyl group (-COOH). (C)radical group (R)or side chain.hydrogen atom
——— property :
1- Solubility , 2- Melting , 3- Taste , 4- Optical properties , -5 Amino acids as ampholytes
——- BIOLOGICAL FUNCTIONS OF AMINO ACIDS
1-Amino acids are building blocks of proteins.
2-They are important in many biological molecules, such as forming part of coenzyme. *or as precursors as biosynthesis of Heme.
3-They have many functions
in metabolism

Question 2

2- structure and function of amino acids with polar or uncharged radical, and chemical modification of amino acid radicals
and the role of these changes in the regulation of the functional activity of proteins?

Answer 2

-These amino acids, carry no charged
on the ‘R’ group. They have groups such as hydroxyl, sulfhydryl and amide and participate in hydrogen bonding of protein
structure.
-(function of polar amino acids with no charge): These side chains can form multiple hydrogen bonds, so they prefer to project into the aqueous phase chemical modification of amino acid radicals): Modified amino acids are derived from a single amino acid.

-(role of these changes in the regulation of the functional activity of proteins): most proteins can be regulated in response to
extracellular signals by either covalent modifications or by association with other molecules.

Question 3

3- structure and functions of non-polar amino acids, the role of these amino acids in the formation of various levels of the
structural organization of proteins?

Answer 3

these amino acids have equal numbers of carboxylic acid groups and amine groups. 2- form the protein surface where it is exposed to the lipid chain region 3-Since proteins have nonpolar side chains their reaction in a
watery environment is similar to that of oil in water. The nonpolar side chains are pushed to the interior of the protein allowing
them to avoid water molecule and giving the protein a globular shape

Question 4

4-structure and functions of polar amino acids (positive charge), and the role of histidine in hemoglobin?

Answer 4

The 3 amino acids
lysine, Arginine, Histidine are included in this group. Functions of polar amino acids (positive charge): it can make hydrogen
bonds with other suitable groups, and the polarity of amino acids can affects on general structures of proteins. Functions of
Histidine in hemoglobin: regulating the oxygen affinity of hemoglobin

Question 5

5-what is the primary and secondary structures of the proteins. And what is the function of protein which is depends on it is
amino acid sequence . Sickle cell anaemia?

Answer 5

1-primary structure: the linear sequence of amino acids forming the backbone of proteins (polypeptides), the amino acids are held together by peptide bond.

• 2-Secondary structure : the spatial arrangement of protein by twisting of the polypeptide chain, the amino acids are held together by hydrogen bond.
• 3-Structural function of proteins sequences: is used to identify the amino acid sequence and it is conformation.
• 4-Sickle-cell anaemia: is the one of a group of inherited disorders known as sickle-cell anaemia. It affects on the shape of the red blood cells, which carry oxygen to all parts of the body. Treatment : by blood transfusion.

Question 6

6- what is the tertiary and quaternary structures of proteins. Intramolecular interactions ensure their formation. Denaturation
and renaturation?

Answer 6

-Tertiary structures: the overall three-dimensional arrangement of its polypeptide chain in space.
- quaternary structures: some of proteins are composed of 2 or more polypeptide chains referred to as subunits
-Denaturation: is the phenomenon of disorganization of native protein
structure, and denaturation results in loss of secondary, tertiary and quaternary structures of proteins
-Renaturation: is the conversion of denatured protein back into
it is native structure.

Question 7

8- complex proteins: hemoproteins, metalloproteins and glycoproteins?

Answer 7

• Metalloprotein: proteins contains metal ions, such as
  Fe,Co , Cu, Zn, Mg for example, ( ceruloplasmin(Cu),Glycoproteins: the prosthetic group is carbohydrate, which is less than 4% of
  protein. The term mucoprotein is used if the carbohydrate content is more than 4%. for example Mucin(saliva), ovomucoid(egg
  white). Hemoproteins: is a protein that contains a heme prosthetic group.

Question 8

9- classification of proteins: shape, structure and function. Give examples?

Answer 8

–1- Shape of the protein: most of proteins have
globular shaped, which looks like a ball but with irregular shaped.
–2-Structure of the proteins:
(A) Primary structure: it is the arrangement of amino acids in the polypeptide chain. Bonds responsible for primary structure are: peptide bonds.
2-secondary structure: is the spatial relationship of adjacent amino acids residues. Bonds responsible for secondary structure is:
Hydrogen bonds. There are 2 forms of secondary structure Alpha-helix and Beta-pleated sheets.
3-Tertiary structure: is the final
arrangement of a single polypeptide chain resulting from spatial relationship of more distant amino acid residues

–There are 2 forms of tertiary structures: (a) fibrous: which is extended form e.g. keratin, collagen and elastin. (b) Globular: which is a
compact form and results from folding of polypeptide chain e.g. myoglobin.*
— Functions of the protein: 1- enzymes: enzymes are protein. 2- Transport: of small molecules and ions (b) lipids are transported.
3- structural elements: e.g. (a)cell membrane: contains proteins in the form of glycoprotein. (b)skin and bone: contains proteins
in the form of collagen

Question 9

10- The roles of proteins in the human body, classification of proteins by complexity, shape and functions?

Answer 9

1- Proteins have roles in the body. It helps to repair and build your body’s tissues. Allows metabolic reactions to take place. Protein provides your
body with a structural framework, protein also maintain proper PH and fluid balance.
2-classification of proteins by complexity:
are classified into primary structure, secondary structure, tertiary structure and quaternary structure. 3-shape and functions: are
mentioned above.

Question 10

11- chemical modification of amino acid radicles in proteins. Write the reaction of phosphorylation of serine?

Answer 10

1-chemical protein modification methods have been developed and can be categorized into three classes: (i) modification of
proteins using the reactivity of naturally occurring amino acids; (ii) modification by bioorthogonal reactions using unnatural
amino acids, most of which can be site-selectively incorporated into proteins-of-interest using genetic codon expansion
techniques; and (iii) recognition driven chemical modification, which is the only approach that allows modification of
endogenous proteins without any genetic manipulation

Question 11

12-Biologically active peptides: structure and functions?

Answer 11

-Peptides: are compounds, formed of less than 50 amino acids linked
together by peptide bonds: (1)Dipeptide: ( 2 amino acids and 1 peptide bond). (2)Polypeptide: (10-50 amino acids).
(3)Tripeptide: (3 amino acids and 2 peptide bonds). (4) Oligo peptide: (3-10 amino acids).
-The biological active peptides: peptide
includes many active compounds such as: -Antibiotics: e.g. vancomycin -Antitumour agent -Hormones: 1-insulin and glucagon

Question 12

13- structure and function of nitrogenous bases(nucleases), nucleosides, and nucleotides. Participation in the regulation of
metabolism (secondary messengerscamp, camp), coenzyme function(NAD+,NADP+,FAD,Co)?

Answer 12

1-Function of nitrogenous base: it building blocks of the nucleic acids deoxyribonucleic acids (DNA)& ribonucleic acid (RNA).

2-Structure of nucleosides: nucleosides consists of purine or pyrimidine and ribose or deoxyribonuclease sugar connected by B- glycosidic linkage.

3- Function of nucleosides: it is signalling molecules and as precursors to nucleosides needed for DNA and RNA synthesis.

4- Structure of nucleotides: A nucleotides is made up of 3 parts: phosphate group, 5-carbon sugar, and nitrogenous base.
The 4 nitrogenous base in DNA are: adenine, cytosine, guanine, thymine. RNA contains uracil, instead of thymine.
- Function of the nucleotides: it responsible for replication of DNA and transcription of RNA in rapidly dividing stagesFunction

Question 13

14- structure and function of DNA, secondary structure of DNA. WASTON AND CRICK MODEL. Physical and chemical
properties( melting point, absorption of ultraviolet radiation, septal organization)?

Answer 13

-Structure of DNA: it is made up of 3 parts: -deoxyribonuclease -phosphate group -and nitrogenous base.Function of DNA: DNA
contains constructions needed for an organism to develop, survive and reproduce, and also DNA responsible for storing and
transferring genetic information.

-The secondary structure of DNA: consists of 2 polynucleotide chains wrapped around one another to form a double helix.
Melting point of DNA: melting temperature related to G:C and A:T content. 3-Hydrogen bonds of G:C pair require higher
temperatures to denature than 2-Hydrogen bonds of A:T pair. DNA absorbs the ultraviolet radiation: Due to heterocyclic rings of
the nucleotides

Question 14

15- classification of enzymes, and give examples of reactions from metabolism characteristic of each class?

Answer 14

Classification of Enzymes:
1- oxidoreductases: for example:(Alcohol dehydrogenase, cytochrome oxidase, L-and Damino acid oxidases).

2 - Transferase: for example( hexokinase, transaminase, transmembranes, phosphorylates).

3-Hydrolases: for example( lipase, choline esterase, acid and alkaline phosphatase, pepsin,unease).

4-Lyases: for example(Aldolase, fumarate, histidine).
5-Isomerases: for example( triose phosphate isomerase, retinol isomerase, exosphere isomerase). 6-Ligases: for example(
Glutamine parasyntheta, acetyl-Co carboxylase, succinate hexokinase)

Question 15

17- simple and complex enzymes, zymogens, proenzymes. Give examples?

Answer 15

–Simple enzyme: are polypeptide chains that are
broken down to amino acids by hydrolysis. For example:(enzymes of digestive tract: pepsin, lipase, amylase).
– Complex enzyme:(or holoenzymes): consists of amino acids(Proenzyme) and a nonprotein part(cofactor). For example:(pyruvate dehydrogenase, fatty acid parasyntheta, glutamine parasyntheta).
–Zymogens: is an inactive substance which converted into enzyme when activated by another enzyme.Forexample:(Trypsinogen).
Proenzyme: is the multiple for an enzyme catalysing the same reaction. For example:(Glucosamine).

Question 16

18-structure and function of active and allosteric centres of enzyme. Factors determining the catalytic activity of enzymes?

Answer 16

–The allosteric centre: is located in the alternative site of an enzyme molecule. Such as enzyme have quaternary structure
–function of allosteric centre: it serves for binding low molecular substances-(allosteric effectors).
–Structure of active site: it consists of (binding site)- which form temporary bonds with the substrate, and (catalytic site)- which catalyse the reaction of
substrate.
– Function of active site: it binds with the substrate and orients it for catalysis.
–Factors influencing enzyme activity: 1-temperature. 2-PH 3-substrate concentration 4-presence of inhibitors
–enzymatic reaction: rate This effect is determined by several factors: (1)enzyme denaturation under extremely high and low PH
values (2)changing of charge value of substrate or enzyme

Question 17

19- structure and function of fat-soluble vitamins: A,D,E,K ?

Answer 17

—vitamin A(retinoids): structure: 1- carotenes are provitamin A. 2- retinol, retinal and retinoic acid are the forms (vi tamers) used
by the body. Functions: 1-vision: retinal is essential for night vision. 2-reproduction: retinol is essential for reproduction. It
—Vitamin D (calciferous): structure: Active vitamin D: is a steroid hormone. Functions: 1- Normalization of serum calcium:
recalcitrant maintains serum calcium level through it is effects on intestines, bones and kidneys
—Vitamin E ( Tocopherols): structure: there are 4 types of tocopherols: Alpha , Beta , Gamma , sigma. -All contain tool ring. -the
most active member is Alpha-tocopherol. -Gamma and sigma differ from alpha tocopherol in number and position of CH3 group
attached to the tool ring. Functions: 1-Antioxidant: vitamin E prevents non enzymatic oxidation of cell components 2- vitamin E
removes peroxide formation in polyunsaturated fatty acids.

Question 18

20- structure and functions of water soluble vitamins: B1, B2, B3, B5, B6 ?

Answer 18

—VITAMIN B1 (Thiamin ) structure: -Thiamin consists of pyrimidine ring connected to thiazide ring through a methylene bridge
(CH2). -Active form of vitamin B1 is Thiamin diphosphate (TPP): (a) it is also called Thiamin pyrophosphate. (b) formation of
TPP needs Thiamin kinase enzyme which is present in the liver
—VITAMIN B2 ( RIBOFLAVIN ) structure: 1-it is formed of flavin ring attached to ribitol (alcohol of ribose sugar). 2- active forms of
riboflavin is: (a) riboflavin enters the structure of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). (b) FMN
is formed by phosphorylation of riboflavin by ATP
—VITAMIN B3 ( nicotinic acid ) structure: 1- nicotinic acid is a pyridine derivative. 2- it is non toxic substance present in a toxic
alkaloid nicotine of tobacco. 3- Active forms: (a) nicotinic acid is converted into active form nicotinamide that enter the
structure of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP).
—VITAMIN B5 ( PANTOTHENIC ACID) structures: -pantothenic acid is formed of panto acid connected to beta alanine
Functions: 1-coenzyme A(Co Ash): -Co-A acts in the transfer of acyl groups. 1- Acetyl Co-A: it is an important intermediate in the
metabolism of carbohydrate, lipids and protein metabolism

Question 19

21- structure and function of water soluble vitamins: B9,B12,H,C,P?

Answer 19

—-VITAMIN B9 ( folic acid ) structure: folic acid consists of 3 components: piperidine ring, p-amino benzoic acid (PABA) and
glutamic acid. The active form: of folic acid is tetrahydrocannabinol (THF OR FH4). It is synthesized from folic acid
functions: (1)essential for the formation of red blood cells. (2)essential for fetal development. (3)important for production of
DNA and RNA.

—VITAMIN B12 ( COPALAMINE ) structure: vitamin B12 consists of corrie ring with a central cobalt atom. The corrie ring has 4
pyrrole units, just like a porphyrin. 2 of the pyrrole units (A&D) are directly bond to each other, while the 2 pyrroles units (B&C)
are held by methylene bridge. Functions: 1- synthesis of methionine from homocysteine. 2- Oligomerisation of monomethyl Co
to succinate Co. 3- maintenance of the central nervous system. 4- it essential for production of RACs.

—VITAMIN C ( L-Ascorbic acid ) structure: -Animal tissues contains 90% of L-ascorbic acid and 10% dehydro L-Ascorbic acid. Both
forms are active. -further oxidation gives inactive form called Logie-Coldstone acid converted into oxalic acid. Functions: 1-formation of collagen protein. 2- Absorption and mobilization of iron. 3- act as coenzyme for many hydroxylate enzymes. 4-
Antioxidant action.

—VITAMIN H ( BIOTIN ) structure: it is formed by fusion of imidazole and Ethiopian rings with valeric acid side chain.
Functions: -The biotin serves as a coenzyme for several metabolic reactions: 1- Nucleogenesis and citric acid cycle. 2- Fatty acid
synthesis. 3- propionyl Co-A. 4- in the metabolism of leucine.

—VITAMIN P ( FLAVONOIDS ) structure: it consists of 2 phenyl rings (A and B) and a heterocyclic ring -Functions: 1- regulating
plant development. 2- and regulating pigmentation. 3- reduction of blood pressure. 4- Antioxidant function.

Question 20

22- structure of the respiratory chain. Mitchell’s chemosynthetic hypothesis?

Answer 20

-1- The respiratory chain is located on the inner membrane of the mitochondria. 2- The components of respiratory chain are arranged in order of increasing their standard redox potential: NAD, FMN, FAD, Semiquinone
-Electron transport chain: is a series of protein complexes that transfer electron from electron donor to electron acceptors
-Function: accepts electron from NADH and transfers them to coenzyme Q .Transfers 4H+ ions to the outer surface of the inner mitochondrial membrane
–Mitchell’s chemosynthetic hypothesis: Mitchell’s realised that the movement of ions across an electrochemical potential
difference could provide the energy needed to produce ATP

Question 21

23- pathology of enzymes (hereditary, acquired ) and methods of their correction, enzyme diagnostics, enzyme therapy ?

Answer 21

-1-Enzyme pathology: is the study of enzymes activity in normal and pathological states including the diagnostics of hereditary
diseases associated with genes defects.
-2-Enzyme therapy: means the usage of enzymes and regulators of enzymes activity as
drugs. Proteolytic enzymes inhibitors normally produced by the pancreatic gland inactive state are used for pancreas autolysis
prevention in case of acute pancreatitis.
-3-Enzyme diagnostics: is developed in the following directions:(1)use of enzymes for
analysis in biological fluids for diagnostic purposes. This method is characterized by high specificity and sensitivity.
—2)determination of the activity of the of enzymes in blood when organs and tissues are damaged. The change in the level of
enzymes it is a result, but not causes pathological process.

Question 22

24- Electron transport chain: structure and biological role. Mitchell’s chemosynthetic hypothesis?1

Answer 22

–Electron transport chain: is a series of protein complexes that transfer electron from electron donor to electron acceptors
–Function: accepts electron from coenzyme Q and transfers them to cytochrome C. Transfers 2H+ ions to the outer surface of the
inner mitochondrial membrane. Complex 4 cytochrome c-oxygen oxidoreductase. Function: accepts electrons from cytochrome
C and transfers them to oxygen to form water.
–Mitchell’s chemosynthetic hypothesis: Mitchell’s realised that the movement of ions across an electrochemical potential
difference could provide the energy needed to produce ATP.

–biological role of electron transport chain: it generate an electrochemical gradient that leads to
creation of ATP in a complete system called oxidative phosphorylation.

Question 23

25- Krebs cycle: localization, enzymes and coenzymes, regulation, bioenergetics of the process. The relationship between the
Krebs cycle and the electron transport chain

Answer 23

–1-Localization: the Krebs cycle takes place in the matrix of mitochondria.
–Enzymes of the Krebs cycle: there are 8 enzymes 1- citrate synthase.2- Aconitine.3- Isocrates dehydrogenase.4- Alpha glutaraldehyde dehydrogenase.5- succinate hexokinase.6- succinate dehydrogenase.7- Fumarate.8- Malate dehydrogenase.
–Coenzymes of the Krebs cycle:1-NADH,2- GHP and 3-FADH2.
–Regulation of the Krebs cycle: The Krebs cycle are regulated by the
following steps:1- citrate synthase.2- Isocrates dehydrogenase.3- alpha-glutaraldehyde dehydrogenase.
–Bioenergetics of the Krebs cycle: there are 3 NADH, one FADH2 and one GTP. The relationship between the Krebs cycle and
transport chain: 1- Both Krebs cycle and electron transport chains occurs inside the mitochondria.2- electron carriers such asNADH produced during glycolysis and the Krebs cycle passes . their electrons to the electron transport chain, which results in
synthesis a lot of ATP.

Question 24

27- Digestion in the gastrointestinal tract, absorption of hydrolysis products?

Answer 24

1-Mouth: production of saliva containing alpha
amylase, partial digestion of polysaccharide.
2-Stomach: Elaboration of gastric juice with HCL and proteases, partial digestion of
proteins.
3-Pancreas: release of NaHCO3 and many enzymes required for intestinal digestion.
4- Liver: synthesis of bile acids.
5- Gall bladder: storage of bile.
6- Small intestines: final digestion of foodstuffs, absorption of digested products.
7-Large intestines: mostly absorption of electrolytes, bacterial utilization of certain nondigested or unabsorbed food

Question 25

28- Glycolysis in conditions of normal oxygen content: localization, stages, reactions, enzymes and coenzymes, bioenergetics,
significance for the body?

Answer 25

– (localization): cytosol of all tissue cells. Stages of Glycolysis:
1- stage one (the energy requiring stage): (a) one molecule of glucose is converted into two molecules of glycolaldehyde-3- phosphatase. (b) this step requires 2 molecules of ATP(energy loss). 2- stage two ( the energy producing stage): (a) the 2 molecules of glycolaldehyde-3-phosphate
are converted into pyruvate ( aerobic glycolysis ) or lactate ( anaerobic glycolysis). Reactions of glycolysis
–coenzyme of glycolysis:nicotinamide adenine dinucleotide (NAD+). Bioenergetics of glycolysis= 2 ATP. Functions of glycolysis pathway: -glycolysis is a
major pathway for ATP synthesis.

Question 26

29- Nucleogenesis: substrates, cellular localization, reactions, enzymes and coenzymes, regulation, significance for the body
(considered the reaction of nucleogenesis from lactate)?

Answer 26

– It is the formation of glucose from non-carbohydrate sources. sources
include: – lactate - pyruvate - glycerol – some amino acids - propionate (in ruminants only) 2- Cellular localization: in cytosol and
mitochondria.
–Regulation of Nucleogenesis: (A) Hormonal regulation:
1-increase of Glucagon: -secreted in response to hypoglycaemia. -
increased synthesis of glycogenesis enzyme. -inhibit glycolysis. -stimulate insulin secretion.
2-increased cortisol: -increase
synthesis of glycogenesis enzyme. -increased protein catabolism. -increased glycogenic amino acids. -inhibit glycolysis. -
3-Decreased of insulin: -secreted in response to hyperglycaemia.
–substrate regulation: Acetyl Co-A and ATP 1- stimulate nucleogenesis by inhibiting glycolysis and stimulate nucleogenesis. 2-
Acetyl Co-A also stimulate pyruvate carboxylase
–the body (function of nucleogenesis):
1- maintenance of blood glucose: the main function of nucleogenesis is the maintaining
of blood glucose when the carbohydrate is non available in sufficient amount,
2- Removal of lactic acid: produced by red blood cells and contracting muscles
3- Removal of glycerol: produced by lipolysis in
the adipose tissue

Question 27

30- Glycogenesis in the liver: reactions, enzymes, regulation, significance for the body. The role of the liver in maintaining
normal blood glucose level?

Answer 27

Glycogenesis: Breaking down of glycogen into glucose (in the liver) and lactate (in the muscles).
Site: cytoplasm of the liver and muscles. Regulation of Glycogenesis :1-Hormonal regulation -low blood glucose level (fasting)
releases these 2 hormones: Glucagon and Epinephrine. -Glycogen phosphorylate exists in 2 forms: 1- An active ‘‘a’’ form. 2-
inactive ‘‘b’’ form -Glucagon and Epinephrine both stimulate intracellular pathway by increasing levels of camp. Significance of
the Glycogenesis for the body: is the maintaining blood glucose concentration. Role of the liver in maintaining blood glucose
level: is supplies sugar or glucose by turning glycogen into glucose by a process called glycogenesis

Question 28

31- Anaerobic glycolysis: localization, stages, reactions, enzymes and coenzymes, bioenergetics of the process, significance for
the body, Features of glycolysis in erythrocytes?

Answer 28

– (Anaerobic glycolysis): Breakdown of glucose into 2 molecules of lactate.
Localization: cytosol of all tissue cells. Stages of glycolysis: 1- stage one (The energy requiring stage): (a)one molecule of glucose
is converted into 2 molecules of glycolaldehyde-3-phosphates. (b)This step requires 2 molecules of ATP. 2- stage two (The
energy producing stage): -The 2 molecules of glycolaldehyde-3-phosphate are converted into lactate (anaerobic glycolysis).
Bioenergetics of Anaerobic glycolysis: 2 ATP ( 4 ATP produced – 2 ATP utilized)

–significance of Anaerobic glycolysis for the body:
1- production of ATP. 2- oxygenation of tissues. 3- very important: -in tissue with no mitochondria: e.g. mature RBC, cornea and
lens. -in tissues with few mitochondria: e.g. tests and leukocytes. -tissues undergo frequent oxygen lack: e.g. skeletal muscles.
Functions of glycolysis in RBC: 1- mature RACs contain no mitochondria thus: (a) they only depend upon glycolysis for energy
production (=2ATP). (b) lactate is always the end product. 2- Glucose uptake by RACs is insulin independent. 3- reduction of Methaemoglobin: Met-haemoglobin binds oxygen irreversibly.

Question 29

33- The pentose phosphate pathway: localization of the process, reactions, enzymes and coenzymes, regulation, and
significance for the body, features in different organs?

Answer 29

-Localization:1-intracellular location: cytosol
-2-organ location:(a) it is active in tissues: where NADPH+H is needed for fatty acids synthesis:1-Adipose tissue and liver 2-
Adrenal cortex and gonads.3-red blood cells 4-Retina
(b) in many tissues: it supplies pentoses for synthesis of nucleotides.
-reactions(step) of pentose phosphate pathway:-two phases: oxidative and non-oxidative:
1-oxidative (irreversibly) phase : where 3 molecules of ‘‘glucose-6-phosphate’’ are converted into 3 molecules of ‘‘ribose-5-
phosphate’’ with production of NADPH+H and CO2.

2-Non-oxidative (reversible) phase: where the 3 molecules of ‘‘ribose-6-phosphate’’ are interacted and converted into 2
molecules of ‘‘glucose-6-phosphate’’ and one molecules of ‘‘glucose-3-phosphate’’.

–Significance for the body: The pentose phosphate pathway is important for generating 2 products: pentoses and NADPH, which
is needed for biosynthetic reactions and other functions.
–Features of pentose phosphate pathway in different organs: The 2 most important products from this process are the ribose-5-
phosphate sugar used to make DNA and RNA, and the NADPH molecules which help with building other molecules

Question 30

34- Hereditary pathologies of carbohydrate metabolism: glycogenesis, fructose, galactosidase, lactose intolerance, tec ?

Answer 30

–Galactosidase: is due to the deficiency of enzyme galactose-1-phosphate pentosyltransferase. 1- Galactose metabolism is
impaired leading to increased in the galactose levels in the circulation (galactosidase) and in the urine
–Fructose: is due to the deficiency of the enzyme hepatic enterokinase, and fructose is not converted into fructose-1-phosphate.
Lactose intolerance: people with lactose intolerance unable to fully digest the sugar (lactose) in milk.
–Symptoms of lactose intolerance: weakness, Diarrhoea, vomiting

Question 31

35- lipids: classification, structure, physio-chemical properties, biological role, Digestion of lipids in the Gastrointestinal tract
and the role of bile acids in this process ?

Answer 31

Lipid are classified into 3 groups: (a)

• -simple lipids: which includes fats (acyl glycerol)
• -waxes. (b) compound lipids: which include glycolipid, phospholipids, glycolipid
• -(c)Derived lipid: which include fatty acids, steroids, fat-soluble vitamins

— Structure of the lipids :Lipids are composed of elements such as: carbon, hydrogen and oxygen.
Lipids are insoluble in water. Physio-chemical properties of lipids: 1- insoluble in water. 2- soluble in in non-polar organic
solvents e.g. acetone. 3- contain carbon, hydrogen and oxygen, sometimes contains nitrogen and phosphorus. 4- on hydrolysis
they gives fatty acids. 5- take part in part in plant and animal metabolism.

–Biological role of lipids: -lipids have variety functions: 1-Energy formation: Triglyceride breakdown to give more energy. 2-
Hormone production: many hormones are lipid-derived, and it is called steroid hormones

Question 32

36- Transport forms of lipids: formation, structure, classification, role and their subsequent disposal .

Answer 32

– The main plasma lipid transport forms are free fatty acid, triglyceride and cholesteryl ester.

Question 33

37- beta-oxidation of saturated fatty acids with an even number of carbon atoms( on the example of palmitate oxidation)?

Answer 33

—Beta-oxidation of saturated fatty acids it occurs in the mitochondrial matrix, acyl-Co-A of fatty acid breaks down by 4 reactions:

1-Dehydrogenation with FAD dehydrogenase.
2-Hydration reaction with water.
3-second dehydrogenation with NAD dehydrogenase.
4-cleavage (Thrombolysis).
–The combination of these 4 reactions make up one cycle of the beta-oxidation of fatty acid. At the end acetyl-Co-A is produced
and it is oxidized in the Krebs cycle.

Question 34

38- Beta-oxidation of unsaturated fatty acids with an odd number of carbon atoms( on the example of oleic acid)?

Answer 34

–Fatty acid
with an odd number of carbon atoms are oxidized in the same way like oxidized fatty acids with an even number number of
carbon atoms. But in the last stage of the betaoxidation of unsaturated fatty acids with an odd number of carbon atoms, are
produced one propionyl-Co-A molecule and one acetyl-Co-A molecule

Question 35

39- Synthesis of triacylglycerols and glycerophospholipids. Features in synthesis in white adipose tissue and liver?

Answer 35

–Synthesis of triglyceride in adipose tissue Triglycerides are synthesized in adipocytes from glucose. The synthesis of triglycerides from glycerol
in adipocytes is impossible, since the activity of the enzyme glycerol kinase involved in the formation of glycerol-3-phosphate
from glycerol is very low. Triglycerides synthesized in adipocytes and accumulate and remain as energy reverse.

–Glycerophospholipids phospholipids: are molecules are made of phosphate head and a lipid tail. The head is hydrophilic and the
tail is hydrophobic. Synthesis of phospholipids occur in the endoplasmic reteculum.

Question 36

40- Ketone bodies: structure, ketogenesis, utilization. Regulation of ketogenesis. Ketonemia, kitoacidosis?

Answer 36

–Structure :these are
3 compounds are formed in the liver from acetyl-co-A acetoacetate, acetone, beta-hydoxybutyrate. Ketogenesis: location: liver
–Steps: 1-formation of acetoacetyl-Co-A. 2-formation of HMG-Co-A. 3-formation of acetoacetate by HMG-Co-A
lyase. 4-Acetoacetate is : (a) spontaneously decarboxylated into acetone
–Ketonemia: is the increase of blood ketone bodies above the normal concentration. It occurs when the rate of ketogenesis is
greater than the rate of ketolysis.
–Kitoacidosis: definition: is a condition of metabolic acidosis result from ketonemia.