Biochemistry 🧪 Flashcards

Question

what is the site of glycolysis?

Answer 1

Cytoplasm (cytosol) of all cells.

Answer 2

- Glucokinase or hexokinase. - Phosphor-fructo kinase 1 (PFK 1) - Pyruvate kinase. **Irreversible enzymes**

Answer 3

**Fluride:** Inhibit enolase enzyme —> inhibition of glycolysis in bacteria —>↓↓ lactic acid —-> dental caries **Pyruvate Kinase Deficiency:** Inherited deficiency of pyruvate kinase —-> hemolytic anemia because RBCs depend on glycolysis for production of ATP

Answer 4

Conversion of Pyruvic acid into Acetyl CO-A.

Answer 5

Mitochondrial matrix of all tissues except RBC, Severe ms exercise.

Answer 6

- Dehydrogenase Complex (PDH): multi-enzyme complex Formed of : **Enzymes** 1. Pyruvate dehydrogenase (PDH or E1) 2. Dihydro lipoyl transacetylase (E2) 3. Dihydro lipoyl dehydrogenase (E3) **Co-Enzymes** 1. TPP = Thiamine pyro-phosphate = Vit B1 2. FAD = Riboflavin = Vit B2 3. NAD = Niacin = Vit B3 4. CoASH = Pantothenic acid = Vit B5 5. Lipoic acid

Answer 7

2NADH.H = 2X3 ATP = 6ATP

Answer 8

- Cytoplasm —->2/3 ATP - Mitochondria —-> 3 ATP

Answer 9

- Series of reactions which oxidize acetyl Co-A to CO2, H2O & Energy - Hydrogens are transferred to NAD & FAD then to ETC for ATP synthesis

Answer 10

- Tri-carboxylic acid cycle (TCA cycle) - Citric acid cycle

Answer 11

Mitochondria of all cells, Except RBCs (No mitochondria)

Answer 12

Mitochondrial matrix Except Succinate dehydrogenase (attached to inner membrane).

Answer 13

The final common pathway for oxidation of CHO , lipid and protein.

Answer 14

1 ATP 1 FADH2 2 CO2 3 NADH.H

Answer 15

- 4 vitamins of vitamin B complex play role in kreb’s cycle. - They act as cofactors for enzymes: Riboflavin (FAD) Niacin (NAD) vitamin B1 (TPP) Pantothenic acid (part of CoA)

Answer 16

- Alternative pathway for glucose metabolism for formation of pentose phosphate - Multi cyclic process in which 3 molecules of G-6P give rise to: 1. 3 CO2 2. 3 Pentoses 3. 6 NADPH

Answer 17

- phosphor-gluconate pathway - pentose phosphate pathway (PPP)

Answer 18

ATP neither produced nor utilized.

Answer 19

1. 3 CO2 2. 3 Pentoses 3. 6 NADPH

Answer 20

Cytoplasm of Liver, mammary gland, adrenal cortex, adipose tissue, retina, RBCs.

Answer 21

**1. Formation of Ribose 5-P which used in:** - Synthesis of nucleotides & nucleic acids - Synthesis of Co-enzymes as FAD &NAD **2. Formation of F-6P which used in semen nutrition** **3. Formation of NADPH.H which used in:** - F.A synthesis & elongation - Synthesis of cholesterol , steroid & catecholamine. - Detoxication reactions. - Activation of folic acid

Answer 22

1) G6PD: key regulatory enzyme = rate limiting step. 2) Insulin: induce G6PD & 6 phospho gluconate dehydrogenase → leading to stimulation of HMP.

Answer 23

- X-linked inherited deficiency of G6PD (more in male) - It is the most common enzyme deficiency worldwide.

Answer 24

↓ G6PD →↓NADPH production →↓reduced glutathione → ↓integrity of RBCs membranes.

Answer 25

- Most of individual are asymptomatic. **Precipitated by :** 1) Ingestion of fava beans. 2) Certain oxidant drugs: - Antibiotic (Sulfamethazine). - Antimalarial (Primaquine). - Antipyretic (Acetaminophen). 3) Certain infections: Release free radicals which damage RBCs.

Answer 26

- Avoid the predisposing factors - Blood transfusion during the attack.

Answer 27

Synthesis of glucose from non- carbohydrate sources.

Answer 28

- Liver (Mainly) & kidney, Intestine **- It requires both mitochondrial and cytosolic enzymes**

Answer 29

- Supply blood glucose in case of CHO deficiency. (Prolonged fasting, starvation & low CHO diet) - This is of especial important for tissues requiring continuous supply of glucose as a source of energy (eg: Brain, RBCs, Kidney medulla, Lens, Cornea, Testes, exercising muscle muscle...etc)

Answer 30

- It is not simply reversal of glycolysis. - Seven of the reactions of glycolysis are reversible & are shared between glycolysis and gluconeogenesis. - Three of the reactions of glycolysis are irreversible So, bypassed by special reaction which are unique to gluconeogenesis

Answer 31

**Carboxylation of pyruvate to oxaloacetate** - Enzyme: Pyruvate Carboxylase - Coenzyme: Biotin **------------** **Oxaloacetate is reduced and transported out the mitochondria to be converted into Phosphoenol pyruvate** - Enzyme: PEP carboxykinase **------------** **Hydrolysis of Fructose 1,6-diphosphate to F6P** - Enzyme: Fructose 1,6-biphosphatase **------------** **Hydrolysis of glucose-6-phosphate to Glucose** - Enzyme: Glucose 6-phosphatase

Answer 32

- Glycerol - Lactate - Amino Acids - Propionic Acids

Answer 33

- It is released during the hydrolysis of TAG in adipose tissue and released through blood till it reaches the the liver

Answer 34

- Lactate is released into the blood by exercising muscle and by cells that lack mitochondria such as RBC - Lactate is taken up by the liver and converted to glucose which is released back into the circulation. - This cycle is known as Cori cycle.

Answer 35

- Amino acids derived from hydrolysis of tissue proteins, are major source of glucose during a long fast

Answer 36

- Glucogenic amino acid ---> α-Keto acids such as oxaloacetate & α-KG. - These substrate can enter the TCA cycle and form oxaloacetate, a direct precursor of PEP.

Answer 37

- Fatty acids with an odd number of carbons produce propoinyl-CoA. - It enters the main gluconeogenic pathway via TCA after conversion to succinyl CoA.

Answer 38

**- Glycolysis & Gluconeogenesis are reciprocally regulated.** - Fructose 2,6-biphosphate: Inhibits Gluconeogenesis & Stimulates glycolysis - Insulin Inhibits gluconeogenesis - Glucagon stimulates gluconeogenesis

Answer 39

Glycogen is the storage form of glucose in animals

Answer 40

mainly in liver and Skeletal Muscle

Answer 41

**Liver glycogen:** Maintain the blood glucose level (during the early stages of a fast; between meals) **Muscle glycogen:** Serve as a fuel reserve **------** - N.B: Liver glycogen stores are depleted during a fasting

Answer 42

- Glycogen is a branched chain homo polymers of α-D-glucose. - The primary glycosidic bond is α (1→4) linkage - After an average of 8-10 glucose residues, there is a branch containing α (1→6) linkage - Glycogen exist as cytoplasmic granules

Answer 43

The processes of glycogen synthesis

Answer 44

α-D-glucose

Answer 45

Takes place in the cytosol and requires: Uridine triphosphate (UTP) & Energy supplied by ATP

Answer 46

1. Synthesis of UDP-glucose 2. Elongation of glycogen chains 3. Synthesis of a primer 4. Formation of branches

Answer 47

**Enzyme:** UDP-glucose pyrophosphorylase enzyme - The first reaction is between glucose 1-P & uridine triphosphate (UTP) to form UDP- glucose + pyrophosphate - [Glucose 6-phosphate is converted to glucose 1-phosphate by Phosphoglucomutase]

Answer 48

**Enzyme:** Glycogen synthase enzyme - Transfer Glucose from UDP-glucose to the non-reducing end of glycogen primer. - Makes α (1→4) linkages. - Cann′t initiate chain synthesis, require glycogen primer (already existing glycogen molecule)

Answer 49

- If glycogen is depleted a protein, called Glycogenin, gets glycosylated forming short α(1→4) glucosyl chain that serves as a primer (The reaction is catalyzed by glycogenin itself via autoglucosylation)

Answer 50

**Branching enzyme:** amylo-α(1→4) → α(1→6) transglucosidase - Transfer a chain of 6-8 glucosyl residues from the end of the glycogen chain To nearby non-terminal glucosyl residue by an α(1→6) linkage

Answer 51

The processes of glycogen degradation

Answer 52

1. Shortening of chains 2. Removal of branches 3. Conversion of glucose 1-phosphate to glucose 6-phosphate 4. Lysosomal degradation of glycogen

Answer 53

**Enzyme:** Glycogen phosphorylase enzyme **Coenzyme:** Pyridoxal phosphate (PLP) covalently bound to the enzyme - Cleaves the terminal α (1→4) glycosidic bond - By simple phosphorolysis producing glucose 1- P - Until last four glucosyl units before a branch point

Answer 54

**Debranching enzyme (single protein with two enzymatic activities):** Oligo-α(1→4)→α(1→4)-glucan transferase - Remove the outer three of the four glucosyl residues and transfers them to the Non-reducing end of another chain - Amylo-α(1→6)-glucosidase activity Remove the remaining single glucose residue (attached in an α (1→6) linkage) By hydrolysis releasing free glucose

Answer 55

**Enzyme:** Phosphoglucomutase enzyme - Liver: G-6P is transported into the ER by glucose 6-phosphate translocase. Then, Converted to glucose by glucose 6-phosphatase - Muscle: G-6 P enters glycolysis (muscle lacks glucose 6-phosphatase enzyme)

Answer 56

Small amount (1–3%) of glycogen is continuously degraded by the lysosomal enzyme, α(1→4)-glucosidase (acid maltase).

Answer 57

Glycogen synthase & Glycogen phosphorylase

Answer 58

* Hormonally regulated to meet the needs of the body as a whole * Allosterically controlled to meet the needs of a particular tissue.

Answer 59

**Liver** * In well fed state, Glycogen synthase is activated by G-6-phosphate * Glycogen phosphorylase is inhibited by G-6-phosphate, ATP and glucose itself **Muscle** * In the muscle; Ca++ and AMP activates glycogen phosphorylase

Answer 60

* **Insulin:** Stimulate glycogen synthesis (glycogenesis) and inhibits its breakdown * **Glucagon (liver) and Epinephrine (muscle and liver):** Stimulate glycogenolysis and Inhibit glycogenesis (cAMP mediated)

Answer 61

Group of inherited disorders characterized by deficient mobilization of glycogen or deposition of abnormal forms of glycogen (GSD)

Answer 62

Result from a defect in an enzyme required for glycogen synthesis or degradation

Answer 63

The severity ranges from mild to severe and fatal

Answer 64

May affect single tissue: liver (hypoglycemia) or muscle (muscle weakness), or may be more generalized.

Answer 65

- Type Ia (Von Gierke's disease) - Type II (Pompe's disease) - Type IIIa Limit Dextrinosis (Cori's disease) - Type IV (Amylopectinosis) (Andersen’s disease) - Type V (Mc Ardle’s syndrome) - Type VI (Her’s disease)

Answer 66

Glycogenoses

Answer 67

Glucose 6-phosphatase

Answer 68

Affects liver and kidney (high glycogen in liver & renal tubules)

Answer 69

Hypoglycemia, lactic acidemia , Ketosis, hyperlipemia

Answer 70

Glucose 6-phosphate translocase

Answer 71

Lysosomal α-(1-4) & α-(1-6)- glucosidase (acid maltase)

Answer 72

Accumulation of glycogen in lysosome

Answer 73

**Juvenile onset:** Muscle hypotonia & death from heart failure by age 2 **Adult onset:** Muscle dystonia

Answer 74

Debranching enzyme (liver & Muscle)

Answer 75

Accumulation of characteristic branched polysaccharide (Limit Dextrin)

Answer 76

Fasting hypoglycemia, muscle weakness

Answer 77

as Type IIIa but Deficiency of: Liver debranching enzyme. So, no muscle affection )

Answer 78

Branching enzyme

Answer 79

- Accumulation of polysaccharide with few branches - Early death from heart or liver failure

Answer 80

Muscle Phosphorylase

Answer 81

High glycogen in muscle & Poor exercise tolerance

Answer 82

Liver phosphorylase

Answer 83

- Hepatomegaly, accumulation of glycogen in liver - Mild hypoglycemia

Answer 84

generaly, Good prognosis

Answer 85

- Cholesterol is synthesized by the cytosol and endoplasmic reticulum of all tissues containing nucleated cells. - Most of the biosynthesis of cholesterol occurs within liver cells.

Answer 86

1. Carbon atoms by acetyl-CoA 2. Energy where the pathway is endergonic, ATP provides energy 3. Coenzymes: NADPH provides the reducing equivalents

Answer 87

HMG CoA reductase

Answer 88

**Sterol-dependent regulation of gene expression of HMG CoA reductase:** - When sufficient cholesterol is present, transcription of this gene is suppressed and vice versa. **Sterol-accelerated enzyme degradation:** - When sterol levels in the cell are high, it increases the degradation of the HMG CoA reductase enzyme. **Hormonal regulation by covalent modification:** - Insulin and thyroxine activate the enzyme by dephosphorylation - Glucagon deactivate the enzyme by phosphorylation **Inhibition by drugs:** - The statin drugs are structural analogs of HMG CoA and are competitive inhibitors of HMG CoA reductase. (Statins are used to decrease cholesterol levels in patients with hypercholesterolemia)

Answer 89

Ketogenesis is the formation of ketone bodies (acetoacetic acid, β- hydroxyl butyric acid and acetone) from acetyl-CoA.

Answer 90

ketone bodies are synthesized exclusively by the liver mitochondria.

Answer 91

- The source of acetyl CoA is B-oxidation of fatty acids in excess of optimal function of Krebs cycle. - The acetyl CoA formed from fatty acids can enter and get oxidized to Co2 and water in TCA cycle only when carbohydrates are available. - During starvation and diabetes mellitus, the acetyl CoA takes the alternate fate of formation of ketone bodies.

Answer 92

- Ketone bodies go via blood to extrahepatic tissues where they become oxidized to CO2 and water (ketolysis). - Most tissues can more easily oxidize ketone bodies than FAs. - Ketogenesis may be considered as a preparatory step performed in the liver to facilitate the oxidation of FA by extrahepatic tissues. - Ketogenesis becomes of great significance during starvation (when carbohydrate stores are depleted) and high fat diet when oxidation of fats becomes a major source of energy to the body.

Answer 93

- Acetoacetate is the primary ketone body while beta-hydroxy butyrate and acetone are secondary ketone bodies. 1. Condensation 2. Production of HMG CoA 3. Lysis 4. Reduction 5. Spontaneous decarboxylation

Answer 94

Two molecules of acetyl CoA are condensed to form aceto-acetyl CoA.

Answer 95

- One more acetyl CoA is added to aceto-acetyl CoA to form HMG CoA (beta hydroxy beta methyl glutaryl CoA). - The enzyme is HMG CoA synthase. Mitochondrial HMG CoA is used for ketogenesis, while cytosolic fraction is used for cholesterol synthesis.

Answer 96

- HMG CoA is lysed to form acetoacetate (AAA). - HMG CoA lyase is present only in liver.

Answer 97

Beta-hydroxy butyrate is formed by reduction of acetoacetate.

Answer 98

Acetone is formed (a side product excreted from lungs)

Answer 99

the complete oxidation of ketone bodies to energy, CO2 and water.

Answer 100

- Mitochondria of extrahepatic tissues due to high activity of the enzymes: acetoacetate thiokinase and thiophorase, but not in the liver due to deficiency of these enzymes. - Tissues like brain can also utilize the ketone bodies as alternate sources of energy, if glucose is not available.

Answer 101

- Ketolysis completes the oxidation of FA, which started in the liver. - It is a major source of energy to extrahepatic tissues during starvation.

Answer 102

1. Β-hydroxy butyrate is oxidized to acetoacetic acid 2. Acetoacetate is activated to aceto-acetyl CoA by thiophorase or thiokinase 3. Acetoacetyl CoA is lysed to 2 acetyl CoA which enter Krebs cycle.

Answer 103

- the condition characterized by increased production and circulating of excessive amounts of ketone bodies in blood (ketonemia) and in urine (ketonuria).

Answer 104

- Normally the rate of synthesis of ketone bodies by the liver is such that they can be metabolized by the extrahepatic tissues. Hence, the blood level of ketone bodies is less than 1 mg/dl and only traces are excreted in urine (not detectable by usual tests). - When the rate of synthesis exceeds the ability of extrahepatic tissues to utilize them, there will be accumulation of ketone bodies in blood. - This leads to ketonemia, excretion in urine (ketonuria) and smell of acetone in breath (fruity odor). All these three together constitute the condition known as ketosis.

Answer 105

- **Metabolic acidosis:** Acetoacetate and beta-hydroxy butyrate are acids. When they accumulate, metabolic acidosis results. - **Reduced buffers:** The plasma bicarbonate is used up for buffering of these acids. - **Kussmaul's respiration:** Rapid deep breathing. - **Smell of acetone** in patient's breath. - **Osmotic diuresis** induced by ketonuria may lead to dehydration. - **Coma:** due to dehydration and acidosis contribute to the lethal effect of ketosis.

Answer 106

- The presence of ketosis can be established by the detection of ketone bodies in urine by Rothera's test. - Urine strip tests based on the same principle are also available.

Answer 107

- Lipogenesis is the biosynthesis of triacylglycerol (TG) principally from excess glucose to be stored after a carbohydrate rich meal.

Answer 108

It occurs in most tissues especially adipose tissue, liver, lactating mammary gland and brain.

Answer 109

The substrates needed for lipogenesis are: Fatty acid (Acyl-CoA) and Glycerol (Glycerol-3-P), both are derived from glucose.

Answer 110

Lipogenesis can be divided into 3 processes: 1. Biosynthesis of fatty acids. 2. Biosynthesis of glycerol. 3. Biosynthesis of the triacylglycerol.

Answer 111

Acetyl CoA

Answer 112

1. Oxidative decarboxylation of pyruvate from glycolysis 2. Oxidation of long-chain fatty acids 3. Oxidative degradation of certain amino acids

Answer 113

1. The acetyl CoA in the mitochondria may be oxidized in Krebs cycle 2. ketogenesis: synthesize the substances called ketone bodies. 3. F.A synthesis 4. Cholesterol synthesis 5. Synthesis of acetyl choline (neurotramsmitter)

Answer 114

Fatty acids synthesis may be: 1. Cytoplasmic (Extra-mitochondrial) FA Synthesis. 2. Mitochondrial FA Synthesis. 3. Microsomal FA Synthesis.

Answer 115

This is the only system responsible for de novo synthesis of FA from active acetate (acetyl CoA).

Answer 116

Free palmitate (C16) is the main product.

Answer 117

The excess acetyl-CoA (from carbohydrate source or less commonly proteins) through the oxidation of pyruvic within mitochondria.

Answer 118

1. Via Citrate 2. Via Carnitine

Answer 119

- Acetyl-CoA molecules are used for palmitic acid synthesis. - Oxaloacetate is converted by malate dehydrogenase to malate, Malate then may be converted into pyruvate by malic enzyme, NADPH+H+ is produced, which is essential for FA synthesis.

Answer 120

- Translocation of Acetyl-CoA involves condensation with oxaloacetate to form citrate, which can pass out mitochondrial membrane. * In cytoplasm citrate splits again by ATP citrate lyase enzyme into Acetyl-CoA and oxaloacetate. * Acetyl-CoA molecules are used for palmitic acid synthesis. * Oxaloacetate is converted by malate dehydrogenase to malate. * Malate then may be converted into pyruvate by malic enzyme. * NADPH+H+ is produced, which is essential for FA synthesis.

Answer 121

Acetyl-CoA may also pass out through the mitochondrial membrane in the form of acetyl-carnitine. This requires the enzyme carnitine-acetyl transferase.

Answer 122

1. Acetyl-CoA carboxylase 2. fatty acid synthase complex (multi-enzyme complex)

Answer 123

* This complex is a dimer (2 subunits). * Each monomer contains all 7 enzymes of FA synthase. * The acyl radical will combine acyl carrier protein (ACP). * ACP contains pantothenic acid (Vit B5) containing SH group. * In close proximity is another SH group of β-ketoacyl synthase (condensing enzyme) of other monomer. * The 2 monomers lie in head to tail configuration. * Since both SH group participate in the synthase activity, only the dimer is active.

Answer 124

1. Synthesis of malonyl-CoA (3C) by acetyl-CoA carboxylase 2. Synthesis of palmitate by the fatty acid synthase complex

Answer 125

It is synthesized from acetyl-CoA in presence of ATP, biotin and bicarbonate as a source of CO2.

Answer 126

The first 3 steps involves 3 enzyme actions: * 1st step is addition of an acetyl CoA to SH group at position 1 * 2nd step is addition of a malonyl CoA to SH group at position 2 * 3rd step is condensation of the acetyl CoA in position 1 with the malonyl CoA in position 2 with the release of one CO2 **--------** Next 4 steps process involves 3 enzyme actions: 1. Reduction in the presence of NADPH+. 2. Dehydration release of one H2O. 3. Reduction in the presence of NADPH+. 4. Transfer from position 2 to 1. **-------** Now position 2 is free to accept a new malonyl CoA. **-------** This sequence of reactions is repeated six more Times by addition of a new malonyl CoA at position 2 each time until 16 carbon acyl radical (palmitic) is formed. **-------** Palmitic acid is released from the enzyme complex by the enzyme thioesterase (deacylase)

Answer 127

acetyl-CoA carboxylase step (i.e. synthesis of Malonyl CoA).

Answer 128

Acetyl-CoA carboxylase is an allosteric enzyme: - activated by citrate - inhibited by long chain FA.

Answer 129

* Insulin activates acetyl-CoA carboxylase by dephosphorylation. * Glucagon and epinephrine inhibit acetyl-CoA carboxylase by increasing cAMP (phosphorylation).

Answer 130

**1) Hexose Monophosphate Shunt (pentose shunt) (the chief source)** - The tissues which possess an active HMP are specific for lipogenesis. Both metabolic pathways are found in the cytoplasm of the cell. So there is no membrane or permeability barrier for the transfer of NADPH+H/NADP. **2) Malic enzyme.** **3) Cytoplasmic isocitrate dehydrogenase (of minor importance).**

Answer 131

Free palmitate must be activated to palmityl CoA before it can be used or proceeds via any other pathway as: 1. Esterification with glycerol (to form TG) or with cholesterol (to form cholesterol esters) 2. Chain elongation: For synthesis of longer chain F.A. 3. Desaturation→Synthesis of unsaturated FA. 4. Sphingosine formation: Palmityl CoA + amino acid serine

Answer 132

1. Glycerol-3-P is formed from glycerol by the enzyme glycerol-kinase in presence o ATP. - Glycerokinase enzyme is absent or very low in activity in muscle and adipose tissue. **------------** 2. Alternative source is derived from intermediates of the glycolysis: - Glucose is oxidized to DHAP which is reduced to glycerol-3-P by the enzyme glycerol-3 phosphate dehydrogenase.

Answer 133

The lipids in the body physiologically exist in two forms: 1- structural lipids. 2- stored lipids (Depot fats; adipose tissue) =The stored calories in the form of triglycerides.

Answer 134

The TG of adipose tissue are continually undergoing hydrolysis (Lipolysis) and re- esterification.

Answer 135

The results of these two processes (Lipolysis & esterificattion) determines the amount of FFA released from adipose tissue into blood.

Answer 136

When the rate of lipolysis > the rate of re-esterification

Answer 137

Many of the nutritional, metabolic and hormonal factors

Answer 138

hormone-sensitive triacyl-glycerol lipase

Answer 139

**Hormone sensitive triacylglycerol lipase: Key regulating enzyme.** **The two non-hormone-sensitive lipases:** * Diacylglycerol lipase * Monoacylglycerol lipase. **lipoprotein lipase:** present in the capillary wall (that catalyses hydrolysis of the TG present in chylomicrons and VLDL).

Answer 140

- An active form (lipase a) which is phosphorylated by protein kinase. (Protein kinase is cAMP dependent) - An inactive form (lipase b) which is dephosphorylated by phosphatase.

Answer 141

- The bulk of free fatty acids formed by (lipolysis) can be reconverted in the tissue to acyl-CoA by Acyl-CoA synthase then re-esterified with Glycerol-3- P. - Some of hydrolyzed FA return to circulation being carried by albumin (FFA Pool).

Answer 142

- Adipose tissue (and muscles) lacks Glycerol kinase enzyme, so the glycerol passes into the blood and is taken by the liver, kidney and other tissues which possess glycerokinase and to be utilized for gluconeogenesis.

Answer 143

- On adequate nutritional intake, glucose utilization by adipose tissue is ↑ with ↑ Glycerol-3-P production. - So, re-esterification > lipolysis and↓ plasma FFA levels.

Answer 144

- In both conditions, ↓ glucose availability in the adipose tissue resulting in ↓ Glycerol-3-P. - So, re-esterification < Lipolysis and ↑ plasma FFA levels.

Answer 145

**(Insulin is the principal hormone)** - Insulin with a diet rich in carbohydrates ↑ both the re-esterification of FAA and lipogenesis (with ↓ FFA release into blood). Insulin acts by: 1. Increase transport of glucose into the fat cell. 2. Stimulation of glycolysis (Glycerol-3-P) 3. simulation of HMP shunt (NADPH+H+) 4. Increase activity of: pyruvate dehydrogenase (↑ acetyl CoA), acetyl-CoA carboxylase (↑ FA synthesis), glycerol-phosphate acyl transferase (↑ TG synthesis). - Insulin ↓ lipolysis (↓ the release of FFA from adipose tissue) by inhibiting the activity of hormone- sensitive triglyceride lipase through ↓ cAMP ↓ release of FFA and glycerol.

Answer 146

- Catecholamines (epinephrine and norepinephrine) are the principal hormones. - Glucagon, GH, Glucocorticoids, Most of them act by activating adenyl cyclase, thus ↑ cAMP to activate hormone-sensitive triacylglycerol lipase. - Glucocorticoids stimulate the synthesis of the triacylglycerol lipase enzyme.

Answer 147

**Major Pathway**: β-oxidation Energy Production **Minor Pathway**: alpha & Omega oxidation

Answer 148

major pathway for catabolism of fatty acids and in which two carbon fragments are successively removed from the carboxyl end of the fatty acyl CoA, producing acetyl CoA, NADH & FADH2

Answer 149

- Mitochondria of many tissues (Mainly liver, kidney & heart) - Doesn't occur in brain (FA cannot be taken up by brain or RBCs)

Answer 150

1. Fatty acid activation (In Cytoplasm) 2. Transport of active FA from cytoplasm to mitochondria

Answer 151

1- Carnitine can be obtained from the diet (meat products). 2- Carnitine can also be synthesized from the amino acids lysine and methionine by an enzymatic pathway found in the liver and kidney but not inskeletal or heart muscle

Answer 152

cAMP formation (by adenyl cyclase enzyme) is: - inhibited by insulin. - activated by adrenaline, noradrenaline, glucagon, ACTH, TSH, MSH.

Answer 153

spherical, macromolecule complexes of lipids and specific protein called apo-protein (apo-lipoprotein)

Answer 154

**Lipid transport in the blood** - Lipids are insoluble in water, Lipids bind to protein to make lipoproteins water-soluble to be transported in the blood). So, provide an efficient mechanism for transporting their lipid contents to and from the tissues.

Answer 155

- Lipoproteins are complex particles that have a central hydrophobic core of non-polar lipids, primarily cholesterol esters and triglycerides. - This hydrophobic core is surrounded by a hydrophilic membrane consisting of phospholipids, free cholesterol, and apolipoproteins.

Answer 156

1) Chylomicrons 2) Very low density lipoproteins (VLDL) 3) low density lipoproteins (LDL) 4) High density lipoproteins (HDL)

Answer 157

intestinal mucosa

Answer 158

* lipid core (non polar triglyceride 85% and cholesterol ester 3% ) - surrounded by single layer of phospholipids 8% & cholesterol * Outer protein layer called apolipoprotein B-48 (1-2%)

Answer 159

transport exogenous (dietary) triglycerides, cholesterol ester & phospholipids from the intestine to peripheral tissues (liver, muscle, adipose tissue)

Answer 160

- Synthesis of nascent chylomicrons - conversion of nascent chylomicrons to mature chylomicrons - Degradation of chylomicrons - Formation of chylomicron remnants - Fate of chylomicron remnants

Answer 161

- Nascent chylomicrons are formed in the intestinal mucosa and pass to lymphatic to then to general circulation through the thoracic duct.

Answer 162

- After entering the bloodstream, the chylomicron particles receive apo E (which is recognized by hepatic receptors) and C Apolipoproteins (apo C-II) from circulating HDL converted to mature CM

Answer 163

- Apo-CII activates lipoprotein lipase (LPL= clearing factor) - Lipoprotein lipase (LPL) (clearing factor) is an extracellular enzyme that is bound to the endothelial surface of capillary walls of most peripheral tissues (adipose tissue, cardiac and skeletal muscle). - LPL Hydrolyze triglyceride (TG) in the core of CM to free fatty acids and glycerol. - The fatty acids are stores (by the adipose) or used for energy (by the muscle) - Glycerol is used by the liver for example in lipid synthesis, glycolysis or gluconeogenesis.

Answer 164

As the of TG in the core is degraded by lipoprotein lipase, a- the particle decreases in size and increase in density. b- the C apoproteins (but not apo E) are returned to HDLs, the remaining particle, called chylomicron remnants

Answer 165

- CM remnants is rapidly removed from the circulation by the liver via Lipoprotein receptors that recognize apo E. - They interact with receptors on liver cells and are taken by endocytosis, then catabolized within the hepatic lysosomes releasing (amino acids, fatty acids, cholesterol) into the cytosol and reutilized by the hepatic cells.

Answer 166

apo E (which is recognized by hepatic receptors) and C Apolipoproteins (apo C-II) from circulating HDL converted to mature CM

Answer 167

through the thoracic duct

Answer 168

(clearing factor) is an extracellular enzyme that is bound to the endothelial surface of capillary walls of most peripheral tissues (adipose tissue, cardiac and skeletal muscle).

Answer 169

Hydrolyze triglyceride (TG) in the core of CM to free fatty acids and glycerol.

Answer 170

- The fatty acids are stores (by the adipose) or used for energy (by the muscle - Glycerol is used by the liver for example in lipid synthesis, glycolysis or gluconeogenesis.

Answer 171

- triglycerides 55% - phospholipids 20% - cholesterol ester 15% - cholesterol 8%, - protein 7-10% mainly B 100

Answer 172

Transport triglycerides from liver to extrahepatic tissues

Answer 173

- VLDLs are secreted directly into the blood by the liver as nascent VLDL particles containing Apolipoprotein B-100. - They obtain apo CII and apo E from circulating HDL and become mature VLDL, apo CII is required for activation of lipoprotein lipase. - AS VLDLs pass through the circulation TG is degraded by lipoprotein lipase, causing the VLDL to decrease in size and become denser. - Surface components including apo CII lipoproteins are returned to HDL → forming intermediate-density lipoprotein (IDL) or VLDL remnant . - Then mention the fate of IDL

Answer 174

- A small amount of IDL is taken up by liver through receptor-mediated endocytosis that uses apo E as the ligand. **___________________** - Most of IDL converted to LDL by 1- losing their apo-E 2- Transferring cholesterol ester from HDL to IDL in an exchange with phospholipids or TG [this exchange is carried out by cholesterol ester transfer protein (CETP) (apo D) a component of HDL).

Answer 175

- 13% triglycerides - 28% phospholipids - 48% cholesterol ester - 10% free cholesterol - 20% protein mainly apo B100

Answer 176

Carry cholesterol from liver to extrahepatic tissue

Answer 177

- LDL is not synthesized / or secreted by the liver or intestine. It is formed principally by degradation of circulating VLDL which initially forms IDL. - Most IDL particles change into LDL particles, by losing their apo-E also triacylglycerol is transferred to HDL in exchange with cholesterol esters, this is catalyzed by cholesterol ester transfer protein (apo D). - The most core lipid in LDL is cholesterol ester and ApoB100 is the only apolipoprotein on the surface. - This makes LDL richer in cholesterol esters and free cholesterol and poorer in TG.

Answer 178

- LDL bind to specific apo-B-100 receptors in both extrahepatic tissues (30%) and liver (70%) where they are endocytosed and their contents are metabolized. - LDLs are an important source of cholesterol to extrahepatic tissues.

Answer 179

LDL receptors are named apo B-100 / apo E receptors because of their ability to recognize particles containing both apo B-100 and E.

Answer 180

- increase the risk of atherosclerosis - Atherosclerosis is the buildup of LDL bad cholesterol which causes hardening of the arteries and blockage to flow.

Answer 181

synthesized mainly in liver & to lesser extent in the intestine

Answer 182

- Triglycerides 3%. - Free cholesterol 5%. - Cholesterol esters 15%. - Phospholipids 25% - Proteins 50% mainly apo A

Answer 183

1. Reservoir of apolipoproteins 2. uptake of unesterified cholesterol 3. Estrifications of cholesterol 4. Reverse cholesterol transport

Answer 184

- HDL particles serve as a circulating reservoir of apo C II (the apoprotein that is transferred to VLDL & chylomicron & is activator of lipoprotein lipase) & and apo E (apolipoprotein requiring for the receptor mediated endocytosis of IDLs and chylomicron remnants)

Answer 185

Nascent HDL are disk-shaped particles containing primarily phospholipid (largely phosphatidylcholine) and apolipoproteins A, C, and E. They take up cholesterol from peripheral tissues and return it to the liver as cholesteryl esters this phenomenon is termed (reverse cholesterol transport)

Answer 186

They take up cholesterol from peripheral tissues and return it to the liver as cholesteryl esters

Answer 187

by a membrane transporter designated ATP binding cassette transporter (ABCA 1), also transfer phospholipids along with free cholesterol to nascent HDL

Answer 188

- When cholesterol is taken up by HDL it is immediately esterified by plasma enzyme LCAT which is synthesized by liver. - LCAT binds to nascent HDL and is activated by apo A1. - LCAT transfers the FA from carbon 2 of lecithin to cholesterol this produces a hydrophobic CE which is sequestred in the core of the HDL & lysophosphatidylcholine which bind to albumin - As the nascent HDL accumulates cholesterol esters it first becomes classified as HDL3 and further addition of CE to HDL3 produce HDL2. - CE generated transferred to VLDL & IDL by CETP associated with HDL particles.

Answer 189

The selective transfer of cholesterol from peripheral cells to HDL, and from HDL to the liver for bile acid synthesis or disposal via the bile, and to steroidogenic cells for hormone synthesis. This is the basis for the inverse relationship seen between plasma HDL concentration and atherosclerosis, and for HDL’s designation as the “good” cholesterol carrier

Answer 190

**Takes place in the liver by:** 1. selection uptake of CE mediated by called scavenger receptor B1 (SR-B1). 2. cell surface hepatic lipase that hydrolyses TG of HDL particles. 3. The apoA1 from the degradation of HDL is recycled for new HDL formation.

Answer 191

The amount of free amino acids distributed throughout the body Plasma level: 4-8 mg / dl

Answer 192

1. Dietary protein. 2. Breakdown of tissue proteins. 3. Biosynthesis of nonessential amino acids.

Answer 193

- Transamination - Deamination - Decarboxylation Reaction (Amines Formation)

Answer 194

Transamination means transfer of amino group from α-amino acid to α-keto acid with formation of a new α-amino acid and a new α-keto acid

Answer 195

The liver is the main site for transamination.

Answer 196

All amino acids can be transaminated except lysine, threonine, proline, hydroxyproline

Answer 197

pyridoxal phosphate

Answer 198

reversible and catalyzed by transaminases.

Answer 199

- Alanine transaminase (ALT) or glutamic pyruvic transaminase (GPT) - Aspartate transaminase(AST) or glutamic oxaloacetic transaminase

Answer 200

- Transaminases are intracellular enzymes, Their levels in blood plasma are low under normal conditions. - ALT (GPT) is present mainly in the cytoplasm of liver cells. - AST (GOT) is present in both cytoplasm and mitochondria in liver, heart, and skeletal muscles. **_________________________** - Any damage to these organs will increase the level of transaminases in blood 1. In liver diseases, there is an increase in both serums ALT (SGPT) and AST (SGOT) levels. 2. In acute liver diseases, e.g. acute viral hepatitis, the increase is more in SGPT. 3. In chronic liver diseases, e.g. liver cirrhosis the increase is more in SGOT. 4. In heart diseases, e.g. myocardial infarction, there is an increase in SGOT only.

Answer 201

removal of amino group from α-amino acid in the form of ammonia with formation of α-keto acid.

Answer 202

liver and kidney are the main sites for deamination.

Answer 203

Oxidative & Non-oxidative

Answer 204

removal of the carboxylic group in the form of CO2 from amino acid with formation of corresponding amines.

Answer 205

decarboxylase enzyme.

Answer 206

pyridoxal phosphate

Answer 207

10-60 **u**g/dl

Answer 208

Ammonia is toxic to the central nervous system and its accumulation in the body is fatal.

Answer 209

- The liver converts ammonia to urea by urea cycle **(Kerbs Hensleit cycle)** , which is less toxic, water soluble and easily excreted in urine.

Answer 210

1- Deamination of amino acid with formation of α-keto acids and ammonia. **------------** 2- Transamination of most amino acids with α-ketoglutaric acid to form glutamic acid, which in turn is deaminated by glutamate dehydrogenase to form α-ketoglutarate and ammonia. **------------** 3-Glutamine in the kidney by glutaminase enzyme gives glutamic acid and ammonia, which is used by kidney to regulate the acid base balance. **-----------** 4- Ammonia produced by the action of intestinal bacteria on the non-absorbed dietary amino acids. **-----------** 5- Ammonia is released from monoamines (e.g. epinephrine, norepinephrine, and dopamine) by the action of monoamine oxidase enzyme. **-------------** 6- Ammonia is released during purine & pyrimindine catabolism.

Answer 211

1- Biosynthesis of glutamic acid from ammonia and α-ketoglutaric acid by the action of glutamate dehydrogenase enzyme. **-----------** 2- Biosynthesis of non-essential amino acids through transdeamination reaction (transamination with ketoglutaric acid by transaminases followed by deamination of the produced glutamic acid by glutamate dehydrogenase enzyme). **-----------** 3- Biosynthesis of glutamine by glutamine synthetase enzyme. **----------** 4- Small amounts of ammonia are excreted in urine in the form of ammonium ions. **-------------** 5- Urea biosynthesis.

Answer 212

The first 2 steps occur in the mitochondria & the last 3 steps occur in cytoplasm.

Answer 213

It utilizes 3 ATP and 4 high energy bonds.

Answer 214

1. Biosynthesis of carbamyl phosphate 2. Formation of citrulline 3. Formation of argininosuccinate 4. Cleavage of argininosuccinate 5. Cleavage of arginine

Answer 215

- This step occurs in mitochondria and needs CO2, ammonia and phosphate and energy. - CO2 is a product of citric acid cycle. - Ammonia is derived from glutamate by deamination. - The phosphate and energy are derived from ATP. - It is catalyzed by carbamoyl phosphate synthetase-I.

Answer 216

- This step occurs in mitochondria. - It is catalyzed by ornithine transcarbamylase.

Answer 217

- This step occurs in cytoplasm. - It is catalyzed by argininosuccinate synthetase. - It utilizes one ATP and 2 high energy bonds

Answer 218

- It is catalyzed by argininosuccinase enzyme. - Argininosuccinate is cleaved into arginine and fumarate. - Fumarate produced is used to regenerate aspartic acid again.

Answer 219

- It is catalyzed by arginase enzyme. - Arginine is cleaved to urea and ornithine.

Answer 220

- Short-term regulation - Long-term regulation

Answer 221

carbamoyl phosphate synthetase-I.

Answer 222

- N-acetyl glutamate is allosteric activator of carbamoyl phosphate synthetase-I - N-acetyl glutamate is synthesized from acetyl CoA and glutamate by N-acetyl glutamate synthetase enzyme, which is allosterically activated by arginine.

Answer 223

- Enzymes of the urea cycle are controlled at the gene level with long-term changes in the quanitity of dietary protein. - Long-term increase in the quantity of dietary proteins leads to a significant increase in the concentration of the enzymes of urea cycle

Answer 224

**Acquired hyperammonemia:** Liver diseases **Inherited hyperammonemia:** Genetic deficiencies of any of the 5 enzymes of urea cycle

Answer 225

1) Detoxication of Benzoic acid. 2) Conjugation with bile acids to form bile salts . 3) Synthesis of : - Purine bases: C4, C5, N7. - Heme. - Glucose. - Glutathione (detoxify H2O2 by converting it to 2 molecules of H2o). - Creatine and creatinine. - Serine.

Answer 226

- 1 gm/day in female. - 1.5 gm/day in males.

Answer 227

Glycine, Arginine and methionine (GAM).

Answer 228

creatinine is the excretory product in urine

Answer 229

α-Alanine & β-Alanine

Answer 230

Synthesis of: - Protein. - Pyruvic acid. - glucose.

Answer 231

**1) Forms di-peptides with histidine** as anserine , carnosine in brain & Skeletal ms which used for : - Activate myosin ATPase enzyme. - Have antioxidant activity. **2) Formation of pantothenic acid & COASH**

Answer 232

1. Phosphoprotein. 2. Formation of ethanolamine. 3. Biosynthesis of choline. 4. Biosynthesis of sphingosine. 5. Formation of glycine & cysteine. 6. Glucogenic.

Answer 233

1. Sulphur containing Hormones as insulin 2. Some enzymes 3. Taurine which enters in formation of Bile salts 4. Detoxication reactions 5. Glutathione (y-glutamyl-cysteinylglycine). 6. COASH. 7. Glucogenic.

Answer 234

1) Protein structure 2) Synthesis of glucose 3) Synthesis of ketone bodies 4) Biosynthesis of tyrosine

Answer 235

1) Protein structure 2) Synthesis of glucose 3) Synthesis of ketone bodies 4) Biosynthesis of melanin pigment 5) Biosynthesis of thyroid hormones 6) Biosynthesis of catecholamines

Answer 236

1) Protein structure 2) Synthesis of glucose 3) Synthesis of ketone bodies 4) Biosynthesis of melatonin → antioxidants. 5) Biosynthesis of serotonin → neurotransmitter. 6) Biosynthesis of Niacin (vitamin B3)

Answer 237

- Phenylalanine - Tyrosine - Tryptophan

Answer 238

- Congenital deficiency of phenylalanine hydroxylase enzyme. - Phenylalanine is converted to phenyl-pyruvic, phenyl- lactic, and phenyl-acetic.

Answer 239

- Mental retardation. - Neyrologic manifestations. - Mousy odour of urine.

Answer 240

Diet poor in phenylalanine and rich in tyrosine.

Answer 241

Inherited deficiency of tyrosinase enzyme in melanocytes (no synthesis of melanin pigment).

Answer 242

- Skin, and hair are whitish. - Iris is colorless, but, appears red due to presence of blood vessels.

Answer 243

- It is a hereditary disease in tryptophan metabolism, where there is an impairment in intestinal absorption, renal tubular reabsorption of tryptophan .

Answer 244

Defect in niacin (vit B) leads to pellagra (diarrhea, dermatitis, dementia).

Answer 245

Glutamic & Aspartic acid

Answer 246

- Glutamine formation (remove excess NH3 in brain). - Glutathione formation. - GABA formation (inhibitory neurotransmitter). - Formation of N-acetyl glutamic (allosteric activator of carbamyl phosphate synthetase 1 in urea cycle) - Folic acid (vit B10) synthesis. - Proline, ornithine formation. - Glucogenic.

Answer 247

- Sources of N1 of purine. - Sources of N1, C4,5,6 of pyrimidine. - Asparagine formation. - B-alanine formation. - Urea formation. - Glucogenic.

Answer 248

- Histidine, Arginine & Lysine

Answer 249

1. Histamine formation by decarboxylation. - VD. - Neurotransmitter 2. Histidine with β-alanine form dipeptide carnosine & anserine in ms. 3. Ergothionine (antioxidant) 4. Glucogenic.

Answer 250

- Urea formation. - Creatine, creatinine formation. - Nitric oxide (VD and ↓ BP and neurotransmitter) by nitrous oxide synthetase.

Answer 251

- Combine with biotin to form biocytin which act as co-enzyme for carboxylase . - CO2 fixation - Collagen synthesis - Glucogenic and ketogenic

Answer 252

Cysteine & Methionine

Answer 253

- Protein synthesis. - Convert to active form which is S-adenosyl methionine (SAM) which act as methyl donor.

Answer 254

Maple syrup urine disease

Answer 255

- Inborn error of branched chain AA metabolism. - Deficiency in α keto acid decarboxylase with accumulation of valine, leucine and isoleucine in blood and increase in urine.

Answer 256

- Characteristic odor of urine (maple syrup or burnt sugar). - Extensive brain damage. - Without treatment, death with in one year.

Answer 257

- Valine --> Glucogenic - Leucine --> Ketogenic - Isoleucine --> Mixed

Answer 258

polymers of nucleotides.

Answer 259

**There are two types of nucleic acids:** (a) Ribonucleic acid (RNA) (b) Deoxyribonucleic acid (DNA)

Answer 260

Storage and expression of genetic information.

Answer 261

planar, aromatic, heterocyclic molecules that are structural derivatives of Purine or Pyrimidine

Answer 262

- The most common Purine ( Adenine and Guanine) - The most common Pyrimidine (Cytosine, Thymine (DNA) & Uracil (RNA))

Answer 263

ribose-5-phosphate molecule

Answer 264

multienzyme complex in eukaryotic cells.

Answer 265

- Synthesis of 5' phospho-ribosyl-1- pyrophosphate (PRPP) **(Step 0 "Preparatory Step")** - Synthesis of 5' phospho-ribosylamine: by PRPP glutamyl amido-transferase **(Step 1)** - Synthesis of Inosine mono-phosphate (IMP) **(Steps 2-10)**

Answer 266

- Ribose-5-phosphate is the donor of PRPP for de novo synthesis. PRPP is also used for the salvage pathway. - The synthesis of PRPP is not considered as a step in the de novo synthesis of purine nucleotides; it is called a preliminary or preparatory step. - Ribose-5-P is derived from pentose shunt.

Answer 267

Synthesis of 5' phospho-ribosylamine: by PRPP glutamyl amido-transferase **(Step 1)**

Answer 268

- 5'phosphoribosylamine is converted to IMP by sequence of 9 linear reactions - energetically expensive process - IMP is parent purine nucleotides - Conversion of IMP to AMP (adenosine mono- phosphate), and GMP (guanosine mono-phosphate)

Answer 269

- it ensures the recycling of purines resulting from degradation of nucleotides - It is of special importance in tissues like RBCs and brain. Where the de novo pathway is not operating. - economizes intracellular energy expenditure

Answer 270

PRPP, it is also a substrate for de novo synthesis, hence these two pathways are closely interrelated

Answer 271

**Phosphoribosylation of purine bases:** - The free purines are salvaged by two different enzymes; adenine phospho ribosyl transferase (APRTase) and hypoxanthine guanine phosphoribosyl transferase (HGPRTase) by addition of PRPP. **Direct Phosphorylation of purine nucleosides**

Answer 272

Uric acid Normal blood level: in man (4-7 mg/dl), In women (3-6mg/dl)

Answer 273

serum uric acid concentration exceeding 7 mg/dl in male and 6 mg/dl in female.

Answer 274

Serum uric acid is less than 2mg/dl

Answer 275

**Xanthine Oxidase deficiency:** Increased execretion of xanthine and hypoxanthine

Answer 276

Mono articular, usually affecting the first meta-tarsophalengeal joint of the big toe, in male mainly

Answer 277

**Defective HGPRT** - in this condition, purine bases cannot be salvaged. - Instead, they are degraded, forming excessive amounts of uric acid leading to gout.

Answer 278

- developmental delays and intellectual disabilities - they are also prone to chewing of their fingers and performing other acts of self-mutilation

Answer 279

- N1, C4, C5 & C6...... Aspartate - C2...... Co2 - N3..... Amide group of glutamine

Answer 280

- De novo synthesis of pyrimidine nucleotides - Salvage pathway of pyrimidine nucleotides

Answer 281

pyrimidine

Answer 282

- pyrimidines are synthesized as bases and ribose is added later on

Answer 283

- The pyrimidine ring can be completely degraded in humans. - The products include: NH3, CO2, β-alanine, and β-aminoisobutyrate. - Both β -alanine, and β -aminoisobutyrate can be further converted into acetyl-CoA and succinyl-CoA, respectively, or are excreted in the urine.

Answer 284

- Orotic aciduria - Deficiency of Urea cycle enzyme

Answer 285

Type I & Type II

Answer 286

- Deficiency of both Orotate phospho-ribosyl transferase (OPRT) and orotidylate decarboxylase - orotate and OMP cannot be converted to UMP, CMP, TMP ----> Orotate & OMP accumlate -----> Inhibition of DNA and RNA synthesis

Answer 287

- Deficiency of only orotidylate decarboxylase - OMP cannot be converted into UMP ----> inhibition of DNA / RNA synthesis

Answer 288

- Patients typically present with excessive orotic acid in the urine, - Failure to thrive, developmental delay - Megaloblastic anemia which cannot be cured by administration of vitamin B12 or folic acid

Answer 289

- deficiency of ornithine trans carbamoylase - Carbamoyl-phosphate cannot enter urea cycle - Exits into cytosol & simulates pyrimidine synthesis - Leads to increased execretion of precursors of pyrimidines like orotic acid, uracil & orotidine

Answer 290

A. Hyper-lipoprofeinemia. B. Hypo-lipoprofeinaemias.

Answer 291

Group of disorders characterized by increased plasma lipoproteins.

Answer 292

According to Fredrickson : 1- Type 1: Familial lipoprotein lipase deficiency 2- Type Il: familial hyper-cholesterolaemia (FHC) 3- Type III: Familial Dys-Beta lipoproteinemias. 4-Type IV: Hyper-pre-beta-lipoprotenemia 5- Type V: combined hyper-lipidemia

Answer 293

Familial lipoprotein lipase deficiency

Answer 294

Familial hyper-cholesterolacmia (FHC)

Answer 295

Familial Dys-Beta lipoproteinaemias = Broad Beta disease = Remnant removal disease

Answer 296

Hyper-pre-beta-lipoproteinemia

Answer 297

Combined hyper-lipidaemia

Answer 298

- Inc. TG & chylomicron. - Inc. VLDL (pre-B lipoproteins) so inc. carbohydrate intake. - Dec. HDL & LDL.

Answer 299

- Hyper B lipoproteinaemia (LDL inc.) - inc total cholesterol.

Answer 300

a. Familial type is due to defect in LDL receptors in liver & other tissues. b. Acquired type occur in hypothyroidism. - The thyroid hormone, T3 has a positive effect on the binding of LDL to its receptor.

Answer 301

- Inc remnants of VLDL (IDL) & chylomicron. - Hyper-cholesterolemia and Hyper-triglycerodemia

Answer 302

- Familial type is caused by defective apo E necessary for uptake and metabolism of VLDL and chylomicron remenants by the liver.

Answer 303

- inc plasma VLDL and TGs and some increase in plasma cholesterol.

Answer 304

- Familial type: due to inc formation of TGs from carbohydrates. - Acquired type: occurs in severe type II diabetes mellitus, obesity and alcoholism.

Answer 305

- Inc chylomicrons & VLDL - Inc TG and cholesterol - Usually associated with obesity.

Answer 306

The cause of disease in unknown but may be due to increase formation of аро В.

Answer 307

* Usually associated with obesity.

Answer 308

- Abeta lipoproteinaemia - Hypo-Beta Lipoproteinemia - Familial alpha lipoprotein deficiency (Tangiers disease) - Familial LCAT deficiency

Answer 309

- caused by failure of the liver and intestine to synthesis apo-B

Answer 310

- Absences of chylomicron, VLDL and LDL from blood - The intestine fails to absorb TGs (fatty diarrhea). - The liver fail to mobilize fats to blood leading to fatty liver.

Answer 311

- Caused by dec. formation of apo-Bioo by liver.

Answer 312

decreased formation of VLDL and LDL.

Answer 313

- Absence of ATP-binding cassette transporter - Reduction in apo-A

Answer 314

- deficiency of a lipoprotein (HDL J. - Leading to accumulation of cholesterol esters in different tissues.

Answer 315

- Abscent of phosphatidyl choline cholesterol acyl transferase (PCAT) or LCAT.

Answer 316

- marked decrease in HDL.

Answer 317

**Glucose to lipid:** Through: - Acetyl CoA - DHAP - NADPH **Lipid to glucose:** Through: - Glycerol - Fatty acids

Answer 318

Carbohydrate in excess is converted to triacylglycerol in both adipose tissue and liver

Answer 319

- Glucose by glycolysis is converted to pyruvic acid, then pyruvic by oxidative decarboxylation is converted into acetyle COA. - Acetyl COA can be used in cholesterol and triglycerides synthesis.

Answer 320

- Glucose by glycolysis is converted into DHAP then DHAP is converted into glycerol 3 phosphate. - Glycerol-3-p (active glycerol) used in tri-acyl-glycerol biosynthesis.

Answer 321

- NADPH originated from HMP pathway can be used for fatty acid biosynthesis.

Answer 322

Can be phosphorylated to glycerol-3-phosphate then converted to dihydroxyacetone phosphate, which continues through glycolysis.

Answer 323

- Beta-oxidation will form acetyl CoA that proceeds into the citric acid cycle. - The fatty acids with an odd number of carbon atoms yield propionyl COA as the product of the final cycle of beta oxidation and this can be a substrate for gluconeogenesis (relatively rare).

Answer 324

**Protein to glucose:** Through: - Glucogenic amino acids - Mixed amino acids

Answer 325

- Excess amino acids by deamination will form alpha keto acids and ammonia: a) the liver synthesizes urea from two ammonia molecules and a carbon dioxide molecule. b) Alpha keto acid is called the carbon skeleton and can be re-used in biosynthesis of non-essential amino acids.

Answer 326

- The liver synthesizes urea from two ammonia molecules and a carbon dioxide molecule.

Answer 327

tryptophan, phenylalanine, tyrosine, isoleucine, and threonine.

Answer 328

Glycine, serine, aspartic acid, glutamic acid, glutamine, valine, methionine, histidine, and arginine

Answer 329

**protein to Lipid:** Through: - Ketogenic amino acids

Answer 330

1. Produce energy. 2. Produce substance that are the building block of body. 3. Produce glucose.

Answer 331

1. The availability of substrates. 2. Regulation through the action of allosteric enzymes, which increase or decrease the activity under the influence of effector molecules. 3. Hormonal regulation. 4. Regulation at DNA level: the concentration of the enzyme is changed by regulation at the level of synthesis of the enzyme.

Answer 332

- Fed or anabolic state - Fasting or catabolic state

Answer 333

Amino acids which give Pyruvic acid (which gives glucose) or one of the intermediates of the Kreb’s cycle are Glucogenic

Answer 334

- Amino acids which give Acetyl CoA and Pyruvic acid or one of the intermediates of Kreb’s cycle are both Glucogenic and Ketogenic

Answer 335

Pyruvate can be carboxylated to oxaloacetate, which is the primary substrate for gluconeogenesis, and other intermediates of the cycle.

Answer 336

1. **↑ Increased glycogen degradation (glycogenolysis):** - By activation of glycogen phosphoreylase and inhibition of glycogen synthase **-------------** 2. **↑ gluconeogenesis** by activation of its key enzymes: - Fructose 1,6 bisphosphatase - Pyruvate carboxylase.

Answer 337

1. **↑glycogenolysis** - Muscles can't form glucose due to lack the enzyme glucose-6- phosphatase. 2. **↓ Glucose uptake by the muscles** - leads to decrease glucose metabolism in muscles

Answer 338

**↓ Glucose uptake by the adipocytes** - leads to decrease glucose metabolism in adipose tissue → **↓ TG synthesis** in adipose tissue

Answer 339

The 1st few days of fasting: brain use glucose exclusively as a source of energy as it is produced via liver gluconeogenesis

Answer 340

1. **↑ Fatty acids oxidation** - by activation of CAT 1 2. **↑ Ketone bodies (KB) synthesis** - to supply KB for use as fuel by the peripheral tissues including the brain.

Answer 341

1st week of fasting: **muscle uses FA and KB (Ketolysis)** as sources of energy

Answer 342

1. **↓ Uptake of FAs** - because the activity of Lipoprotein lipase of adipose tissue is low 2. **↑ TAG degradation (lipolysis):** - By activation of hormone sensitive TG lipase ,to form: ^FA that will be transported to tissues for use as a fuel. ^odd number FA and Glycerol that will be used as a gluconeogenic substrate by the liver.

Answer 343

**↑ protein catabolism** to supply glucogenic amino acids for gluconeogenes

Answer 344

1st few days of fasting: **Increased protein catabolism** of muscle protein to supply AA for gluconeogenesis.

Answer 345

1. **++glucose phosphorylation** By activation of glucokinase. 2. **++glycolysis** 3. **++glycogenesis** by activation of glycogen synthase . 4. **++pentose** shunt to supply NADPH+H for hepatic lipogenesis **-----------------** 5. **-- gluconeogenesis**

Answer 346

1. insulin increase **glucose uptake** by muscles through GLUT 4 2. **++glycogenenesis** by activation of glycogen synthase

Answer 347

1. insulin increase **glucose uptake** through GLUT 4. 2. **++glycolysis** to increase supply glycerol 3P & acetyl CoA for **lipogenesis.** 3. **++ pentose shunt** to supply NADPH + H for lipogenesis

Answer 348

Glucose is the only source of energy for brain in fed state

Answer 349

1. **↑ fatty acid synthesis** by activation of acetyle COA carboxylase 2. **↑ triglycerides synthesis**

Answer 350

- **↑ Fatty acid supply** to muscles by insulin which ++ lipoprotein lipase which break TGs which are presented in chylomicrons

Answer 351

1. **TAG synthesis (lipogenesis).** 2. **↓TAG degradation (lipolysis)** by inhibition of Hormone sensitive lipase enzyme

Answer 352

- The brain has no stores of TAG. - Fatty acids can’t cross BBB.

Answer 353

**↑protein synthesis** in liver : to replace of any protein that may have been degraded , the liver can't store protein like CHO and lipid.

Answer 354

**↑ protein synthesis:** Amino acids are used for protein synthesis to replace the degraded protein.

Answer 355

Complete deprivation of foods, salts and water.

Answer 356

Starvation is associated with decrease in insulin level and an increase in glucagon.

Answer 357

- At the starved state after the first week of fasting , changes occur in the utilization of fuel stores as the following : 1. **In prolonged fasting (2-3weeks):** plasma **KB** become the **primary source of energy for the brain** **_________** 2. **Muscle decreases its use of ketone bodies and increase fatty acid oxidation** as its primary energy sources leading to increase ketone bodies conc. in blood ,so brain can take up ketone bodies as a source of energy. **____________** 3. **Liver gluconeogenesis is decreased.** **__________** 4. **Several weeks of fasting:** the rate of muscle catabolism ↓. **Muscle protein is spared**, so **less muscle protein degraded** to provide amino acids **for gluconeogenesis**. **______________** 5. Because of decrease conversion of amino acids to glucose , **less urea is produced** from amino acid nitrogen in starvation than overnight fasting. **____________** 6. The **body uses its fat stores** as its primary sources of energy **during late starvation** to **conserve the functional proteins.**