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Biochemistry notes ( basics of metabolism), Study notes of Biology

Biochemistry notes , basics of metabolism

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2024/2025

Uploaded on 04/14/2025

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Carbohydrate Metabolism
: Definition of Metabolism
The chemical processes occurring within a living cell or organism that are necessary for the
maintenance of life. All these are called anabolism and catabolism.
Metabolism
Anabolic reaction catabolic reaction
1. synthesis of complex molecules 1.break down of large molecules
from simple compound. Such as polysaccharides, proteins
2. energy is needed for synthesis Into small molecules like, CO2,
( endergonic reaction) NH3, H2O.
2. liberated energy.
( exergonic reaction)
:absorption Digestion and
Digestion of CHO is accomplished by the enzymes of digestive fluids, saliva, pancreatic juice and
intestinal juice.
salivary glands secrete saliva mouth: 1.
(ptyalin), water 99.5% and glycoprotein as food lubricant. Saliva contains: α- amylase
α- amylase, hydrolysis starch to dextrin and maltose.
PH of α- amylase = 5.8 7.1 less than 4.0 is in active
2. stomach --------------------- no digestion is seen in stomach , amylase is in active
Because the PH of stomach (1 - 2 ) very acidic.
3. small intestine: it is the major site of digestion of CHO, pancreatic amylase hydrolyze dextrin into
PH of amylase = 7.1. The optimum maltose
4. intestinal mucosal : mucosal cell membrane bound enzymes , the site where disaccharides hydrolyze.
Maltose maltase glucose + glucose
Sucrose sucrase glucose + fructose
Lactose lactase glucose + galactose
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Carbohydrate Metabolism Definition of Metabolism : The chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. All these are called anabolism and catabolism. Metabolism Anabolic reaction catabolic reaction

  1. synthesis of complex molecules 1.break down of large molecules from simple compound. Such as polysaccharides, proteins
  2. energy is needed for synthesis Into small molecules like, CO2, ( endergonic reaction) NH3, H2O.
  3. liberated energy. ( exergonic reaction) Digestion andabsorption : Digestion of CHO is accomplished by the enzymes of digestive fluids, saliva, pancreatic juice and intestinal juice. 1 .mouth: salivary glands secrete saliva Saliva contains: α- amylase (ptyalin), water 99.5% and glycoprotein as food lubricant. α- amylase, hydrolysis starch to dextrin and maltose. PH of α- amylase = 5.8 – 7 .1 less than 4.0 is in active 2. stomach --------------------- no digestion is seen in stomach , amylase is in active Because the PH of stomach (1 - 2 ) very acidic. 3. small intestine: it is the major site of digestion of CHO, pancreatic amylase hydrolyze dextrin into maltose. The optimum PH of amylase = 7. 4. intestinal mucosal : mucosal cell membrane – bound enzymes , the site where disaccharides hydrolyze. Maltose maltase glucose + glucose Sucrose sucrase glucose + fructose Lactose lactase glucose + galactose

Absorption of Carbohydrates

Intestine

The overall process of glycolysis is: Glucose + 2 NAD+^ + 2 ADP + 2 Pi → 2 Pyruvate + 2 NADH + 2 H+^ + 2 ATP + 2 H 2 O

Isocitric acid to α-ketoglutarate 1NADH =3ATP

α – ketoglutarare to succinyl COA 1NADH =3ATP

Succinyl COA to succinic acid 1GTP =1ATP

Succinic acid to fumeric acid 1FAD =2 ATP

Malic acid to oxaloacitic acid 1NADH =3ATP

total 15 ATP

Net ATP produced per glucose molecule = 15 × 2= 30 ATP

Total ATP per glucose (aerobic oxidation + anaerobic ) 30 + 8= 38 ATP

Glycogenesis (glycogen synthesis) :formation ofglycogenfromglucose. 1. Glycogen is serves as an energy store primarily in muscle and liver, when glucose and ATP are present in relatively high amounts. 2 .theexcess of insulin promotes the glucose conversion into glycogen for storage in liverand muscle cells. 3. It is stored in the form of granules cytoplasm in the cell. 4. The concentration of glycogen in muscle is low (1- 2 % fresh weight) compared tothelevels stored in the liver (up to 8% fresh weight)^. 5 .Glycogen is an energy reserve that can be quickly mobilized to meet a sudden needfor glucose.

Glycogenolysis: biochemical breakdown of glycogen to glucose.

1 .take place in the cells of muscle and liver tissues in response to hormonal and

neural signals.

- from diet (intestinal absorption).

- glycogenolysis (liver).

- gluconeogenesis.

- lipolysis

- conversion of fructose and galactose into glucose

b. factors remove glucose from blood (decrease blood glucose level).

- glycogen formation in liver and muscle (glycogenesis).

- glycolysis in liver(oxidation of glucose).

- convertion of glucose to fat in adipose tissue( lipogenesis).

- B-oxidation (supply energy).

- synthesis of glycoprotein.

- excretion in urine (diabetes)

Hormones decrease blood glucose level

1 .insulin secreate from β-cells of pancreas.

causes the liver to convert more glucose into glycogen (this process is calledglycogenesis ).

2. about 2/3 of body cells(primarilymuscleand fat tissue cells) take up glucose from

the blood, thus decreasing blood sugar..

Hormonesin crease blood glucose level

1. glucagon

invery heavy exercise or lack of food for extended periods, theAlpha cells of the

pancreas releaseglucagon, ahormone act to increase blood glucose levels. They

convert glycogen into glucose (this process is calledglycogenolysis).

2 .Epinephrine , also known as adrenalin or noradrenaline , is a hormone, neurotransmitter and

medication

a. Enhances release of glucose from glycogen (glycogenolysis ).

b. Enhances release of fatty acids from adipose tissue (lipolysis).

3 .Cortisol, Enhances (gluconeogenesis) ; Antagonizes Insulin.

4 .Thyroxine, Enhances release of glucose from glycogen; Enhances absorption of sugars

from intestine

5 .ACTH , Enhances release of fatty acids from adipose tissue (Lipolysis).

Abnormalities in blood glucose level:

 1.Hyperglycemia: Hyperglycemia is an abnormally high blood glucose (blood sugar) level.

 Hyperglycemia is a hallmark sign of diabetes (both type 1 diabetes and type 2 diabetes) and

prediabetes.

 Diabetes is the most common cause of hyperglycemia.

A. Normal blood sugar level= 70 – 100 mg/ dl or 80 – 110 mg/dl

B. Conditions in which blood sugar level is raised.

1 .diabetes melletus 2.hyperthyrodism. 3.hyperadrenalism 4.thyrotoxicosis

C. Conditions in which blood sugar level is low.

1. Overdose of insulin treatment of diabetes melletus.

2. hypothyrodism

D. Kidney threshold of glucose equal = 180 mg/dl

E. Hormones regulate blood glucose level (insulin).

F. The functions of insulin are :

1. excess glucose in the bloodstream, known as hyperglycemia, insulin encourages

the storage of glucose as glycogen in the liver, muscle (glycogenesis).

2. in fat cells(adipose tissues) synthesis of triglycerides (lipogenesis).

3. Build muscle following sickness or injury.

4. Enhance learning and memory of the brain functions.

Disorders in CHOs metabolism 1.Lactose intolerance :It is a condition in which people have symptoms due to the decreased ability to digest lactose, a sugar found in milk products. Symptoms: Abdominal pain, bloating, diarrhea, gas, and nausea. These typically start between half and two hours after drinking milk. Severity depends on the amount a person eats or drinks. It does not cause damage to the gastrointestinal tract