SAS #8: Carbohydrate Metabolism Flashcards
six metabolic pathways of glucose:
Glucose → 2 molecules pyruvate
Glycolysis
six metabolic pathways of glucose:
glucose →glycogen
Glycogenesis
six metabolic pathways of glucose:
glycogen →glucose
Glycogenolysis
six metabolic pathways of glucose:
formation of glucose from noncarbohydrate sources
Gluconeogenesis
six metabolic pathways of glucose:
glucose produce NADPH, ribose 5 phosphate and other sugar phosphates
Pentose phosphate pathway
glucose (a C6 molecule) is converted into two molecules of pyruvate (a C3 molecule), chemical energy in the form of ATP is produced, and NADH-reduced coenzymes are produced.
GLYCOLYSIS
The conversion of glucose to pyruvate is an oxidation process, no molecular oxygen is utilized.
GLYCOLYSIS
coenzyme NAD+ is the oxidizing agent.
GLYCOLYSIS
Is an anaerobic pathway, means does not required oxygen
GLYCOLYSIS
Takes place in the cytosol.
GLYCOLYSIS
Is an energy consuming stage. The energy release associated with the conversion of two ATP molecules to two ADP molecules is used to transform monosaccharides into monosaccharide phosphates.
Six-carbon stage of Glycolysis (Step 1-3)
Six-carbon stage of Glycolysis (Step 1-3):
Formation of Glucose 6-Phosphate.
Step 1: Phosphorylation Using ATP:
Six-carbon stage of Glycolysis (Step 1-3):
Formation of Fructose 6-Phosphate.
Step 2: Isomerization:
Six-carbon stage of Glycolysis (Step 1-3):
Formation of
Fructose 1,6-Bisphosphate.
Step 3: Phosphorylation Using ATP:
An energy-generating stage. Loss of a phosphate from these high-energy species effects the conversion of ADP molecules to ATP molecules. ese high-energy species effects the conversion of ADP molecules to ATP molecules.
Three-Carbon Stage of Glycolysis (Steps 4–10)
Three-Carbon Stage of Glycolysis (Steps 4–10):
In this step, the reacting C6 species is split into two C3 (triose) species.
Step 4: Cleavage: Formation of Two Triose Phosphates.
Three-Carbon Stage of Glycolysis (Steps 4–10):
Only one of the two trioses produced in Step 4, glyceraldehyde 3-phosphate, is a glycolysis intermediate.
Step 5: Isomerization: Formation of Glyceraldehyde 3-Phosphate.
is a biochemical process by which NADH is oxidized to NAD+ without the need for oxygen. Two fermentation processes—lactate fermentation and ethanol fermentation—are now considered.
Fermentation
is the enzymatic anaerobic reduction of pyruvate to lactate.
Lactate fermentation
is the metabolic pathway by which glycogen is synthesized from glucose 6-phosphate.
Glycogenesis
is the activated carrier of glucose in glycogen synthesis (glycogenesis).
Glucose-UDP
is the metabolic pathway by which glucose 6-phosphate is produced from glycogen.
Glycogenolysis
is the starting material for glycolysis
free glucose
is the metabolic pathway by which glucose is synthesized from noncarbohydrate materials.
Gluconeogenesis
is the metabolic pathway by which glucose is used to produce NADPH, ribose 5-phosphate (a pentose phosphate), and numerous other sugar phosphates.
pentose phosphate pathway
mainly in its reduced form (NADPH), involved in biosynthetic reactions of lipids and nucleic acids.
Phosphorylated coenzymes (NADP+
/NADPH)
mainly in its oxidized form (NAD+), involved in the reactions of the common metabolic pathway (CTC & ETC).
Nonphosphorylated coenzymes NAD+ /NADH
TWO STAGES: Pentose phosphate pathway (PPP)
occurs first, involves three steps through which glucose 6-phosphate is converted to ribulose 5-phosphate and CO2.
Oxidative stage
A second major method for regulating carbohydrate metabolism, besides enzyme inhibition by metabolites, is hormonal control. Among others, three hormones—insulin, glucagon, and epinephrine—affect carbohydrate metabolism.
Hormonal Control of Carbohydrate Metabolism
TYPE 1 OR 2 DIABETES:
Usually during childhood or puberty; symptoms develop rapidly.
Type 1
TYPE 1 OR 2 DIABETES:
Frequently after age 35; symptoms develop gradually
Type 2
TYPE 1 OR 2 DIABETES:
Frequently undernourished
Type 1
TYPE 1 OR 2 DIABETES:
Obesity usually present
Type 2
TYPE 1 OR 2 DIABETES:
10% of diagnosed diabetics
Type 1
TYPE 1 OR 2 DIABETES:
90% of diagnosed diabetics
Type 2
TYPE 1 OR 2 DIABETES:
Genetic predisposition is moderate
Type 1
TYPE 1 OR 2 DIABETES:
Genetic predisposition is very strong
Type 2
TYPE 1 OR 2 DIABETES:
B cells are destroyed, eliminating production of insulin
Type 1
TYPE 1 OR 2 DIABETES:
Insulin resistance combined with inability of B cells to produce appropriate quantities of insulin
Type 2
TYPE 1 OR 2 DIABETES:
Frequency of ketoses: common
Type 1
TYPE 1 OR 2 DIABETES:
Frequency of ketosis: rare
Type 2
TYPE 1 OR 2 DIABETES:
Plasma insulin: low tp absent
Type 1
TYPE 1 OR 2 DIABETES:
plasma insulin: high early in disease; low in disease of long duration
Type 2
TYPE 1 OR 2 DIABETES:
insulin is always necessary
Type 1
TYPE 1 OR 2 DIABETES:
Treatment includes diet, exercise, oral hypoglycemic drugs; insulin may or may not be necessary.
Type 2
involvement occurs in the enzyme pyruvate carboxylate, the enzyme needed to convert pyruvate to oxaloacetate (the new first step in gluconeogenesis).
Biotin
in the form of PLP is involved in glycogenosis.
Vitamin B6
Isoenzyme ALDOLASE produced by different genes:
in most tissue
Aldolase A
Isoenzyme ALDOLASE produced by different genes:
in the liver kidneys, & small intestines
Aldolase B
Isoenzyme ALDOLASE produced by different genes:
in the brain
Aldolase C
