CARBOHYDRATE METABOLISM

46問 • 1年前

問題一覧

• Transforming small molecules into big molecules constituting the body structures and machinery. • It is energy requiring, e.g., glycogenesis and lactose synthesis

ANABOLIC PATHWAYS

• Breakdown of large molecules into smaller molecules to produce energy or smaller molecules or reducing equivalents

CATABOLIC PATHWAYS

• They are utilized for both anabolic and catabolic purposes • e.g., glycolysis and Krebs' cycle.

AMPHIBOLIC PATHWAYS

Biochemical process by which food molecules are broken down into simpler chemical units that can be used by cells for their metabolic needs

DIGESTION

starch, glycogen, maltose, sucrose, and lactose (oligosaccharides and polysaccharides).

Digestible carbohydrates

• Which do not need digestion and are absorbed • e.g., monosaccharides: glucose, mannose, galactose, fructose and pentoses.

Ready-to-absorb carbohydrate

• Which are called dietary fibers. • These include cellulose, gums and pectins. • They are very important for stools excretion and are anticancer and intestinal bacteria feed on it to release certain vitamins.

Non-digestible carbohydrates

• salivary amylase (PTYALIN) is produced by the salivary glands. • Its optimum pH is 6.7 - 6.8 and is activated by chloride ions • specific for hydrolysis of -1,4 glucosidic linkage present in cooked starch and glycogen from meat to produce smaller disaccharides and maltose • Salivary amylase cannot digest -1,4 glucosidic linkage in cellulose.

MOUTH

CARBOHYDRATE DIGESTION IN _____ Salivary amylase continues to act on starch, glycogen or dextrins for 2-3 minutes only in the stomach

BUCCAL CAVITY

CARBOHYDRATE DIGESTION IN _____ • Saliva is 99% water and small amounts of inorganic and organic molecules • Triggered by taste, smell, sight and thought of food • 1.5L saliva/day

STOMACH

CARBOHYDRATE DIGESTION IN _____ • In the _____, there are two juices that digest carbohydrates: • The pancreatic juice: • pancreatic amylase • an -glycosidase • has an optimum pH 7.1 • also activated by chloride ion • It acts exactly as salivary amylase • digesting cooked and uncooked starch • glycogen and starch dextrins which escaped digestion by salivary amylase in the mouth

SMALL INTESTINE

___ SALIVA PER DAY

1.5L

SALIVA IS ___% WATER

two juices that digest carbohydrates

PANCREATIC JUICE AND PANCREATIC AMYLASE

The final digestion of carbohydrates occurs in the small intestine by the action of the following disaccharidases: ______, ______, _____ .

SUCRASE, MALTASE, LACTASE

_____ hydrolyzes lactose into glucose and galactose.

LACTASE

3 major breakdown products

GLUCOSE, FRUCTOSE, GALACTOSE

GLUCOSE, FRUCTOSE, GALACTOSE These monosaccharides are absorbed through the ______

INTESTINAL WALL

In the bloodstream, they are transported to the _____

LIVER

_____ and ______ rapidly converted to compounds that are metabolized by the same pathway as glucose

FRUCTOSE, GALACTOSE

Central focus of carbohydrates metabolism is a pathway called as

GLYCOLYSIS

Glucose is converted into ______________

2 MOLECULES OF PYRUVATE

Intracellular site and tissue distribution: • It occurs in the _____ of all tissues in the body

CELL CYTOSOL

• are devoid of mitochondria and depend on glycolysis as the main source of energy. • Mammalian erythrocyte is unique in that about 90% of its total energy requirement is provided by glycolysis.

RBC

due to occlusion of blood vessels by the muscular contraction that decreases oxygen

Contracting muscles

which have a limited blood supply and lack mitochondria which if present would absorb and scatter light interfering with transparency.

Cornea, lens and some parts of retina

where there are relatively few mitochondria.

Kidney (medulla), testicles, leukocytes and white muscle fibers

due to dissociation of the high rate of glycolysis from Krebs', i.e., aerobic production of lactate.

Cancer Cells

also normally derive most of their energy from glycolysis

Brain and gastrointestinal tract

• Glucose oxidation producing ATP. • It is the major source of energy in certain tissues e.g.,RBCsandskeletalmuscles. • It provides pyruvic acid needed for Krebs' cycle. • It is a link with fat metabolism, e.g., dihydroxyacetone phosphate into glycerol 3- phosphate in adipose tissue. • It a link with amino acid metabolism, e.g., 3- phopshoglycerate into serine and pyruvate into alanine and vice versa. • Production of 2,3-DPG that is important in tissue oxygenation.

GLYCOLYSIS

7. It is the major source of ______ that is gluconeogenic.

LACTIC ACID

8. Reversal of _____ is ________, an important source of glucose

GLYCOLYSIS, GLUCONEOGENESIS

Main pathway of metabolism of ____ from the diet.

FRUCTOSE

A small number of genetic diseases occur due to deficiency in activity of enzymes of glycolysis, are manifested mainly as ______

HEMOLYTIC ANEMIAS

_______ are glycolytic producing large amount of lactate, favoring a relatively acidic local pH in the tumor, a situation that was utilized to develop therapy for cancer that could be locally activated by this acidic pH.

CANCER CELLS

• Stimulates synthesis of glucokinase, phosphofructokinase and pyruvate kinase, so it stimulates glycolysis. • It also induces glucose transporters to provide cells with glucose for glycolysis

INSULIN

______ and ______ are inhibitory by inhibiting pyruvate kinase

ADRENALINE, GLUCAGON

are those enzymes that catalyze the irreversible steps of glycolysis

Phosphofructokinase, Hexokinase, Pyruvate kinase

• Pyruvate • Produced from glucose via glycolysis • End product of glycolysis

FATES OF PYRUVATE

The metabolic pathway by which glycogen is synthesized from glucose 6-phosphate

GLYCOGENESIS

• Metabolic pathway by which glucose 6- phosphate is produced from glycogen • In muscles and brain cells,an immediate need for energy is the stimulus that initiates ______ • Needs the enzyme glucose 6-phosphatase to convert G6P to glucose before it can enter the bloodstream

GLYCOGENOLYSIS

Muscle and brain cells lacks ____

G6 PHOSPHATASE

- Synthesis of glucose from noncarbohydrate materials • Pyruvate • Lactate (muscles and RBC) • Glycerol (triacylglycerol hydrolysis) • Amino acids ( muscle protein during starvation) - 90% in the liver - Helps maintain blood sugar level in times of inadequate dietary CHO intake

GLUCONEOGENESIS

________ occurs during replenishing depleted liver, converting lactase back to glucose, maintain blood glucose levek when glucogen stores has beed depleted

GLUCONEOGENESIS

LACTATE formed from glucose under anaerobic conditions in muscle cells is transferred to the liver, where it is reconverted to glucose which is then transferred back to the muscle cells

CORI CYCLE

- Metabolic pathway by which G6P is used to produced NADPH and other sugar phosphates - Significant in cells that produce lipids • Fatty tissues • Liver • Mammary glands • Adrenal cortex

PENTOSE PHOSPHATE PATHWAY

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JHAYS · 5問 · 1年前

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