Unit 6b - Carbohydrate Metabolism Flashcards
Where does carbohydrate metabolism occur? What are the processes involved?
It occurs in the cytoplasm, involves catabolic and anabolic processes
What are the sources of carbohydrates?
From the diet
Breakdown of glycogen or glycerol
propionate stored in the liver (in ruminants)
Give a brief explaination of the carbohydrate pathway. Arrow to arrow
From the intestines + H20 + polysaccharides (glycogen) -> Hydrolysis -> Monosacc (glucose) -> EITHER = 2 ATP for Cytoplasm OR glycolysis to = 2 pyruvate to EITHER make lactic acid (if o2 not abundant) -> Acetyl CoA (if o2 abundant) -> krebs cycle to make 2 ATP, or electron trans system to make 34 ATP and H20
What is the primary carb found in the blood?
Glucose
What carb is absorbed by all cells? How?
Glucose - Facilitated diffusion or active transport
Where do RBC and brain cells derive energy from?
Glucose, cannot derive energy anywhere else
Where do skeletal muscles derive energy from
Ketones + Fatty acids
What is diabetes mellitus?
Caused by insufficient insulin lvls or decreased insulin receptor proteins
body cells are starved of energy bc they cannot absorb and use glucose
Which organ is vital in regulating blood glucose lvl? When does it regulate it and how?
The liver, removes glucose from blood after meals and converts it to glycogen or triglycerides for storage
What happens when blood glucose lvls are low?
Liver convertes stored glycogen to glucose
can make new glucose from non-carb material
Explain carbohydrate metabolism. What is the chain of events?
Glucose enters cell -> broken down to pyruvate thru glycolysis -> either aerobic process or anerobic to make lactic acid
Occurs in cytoplasm where glucose is broken down to form pyruvate. Net prod. of energy is 2 NADH and 2 ATP
What three enzymes regulate glycolysis? What are the inhibited or activated by?
Hexokinase - inhib by glucose-6-phosphate + feedback inhibition
Phoshpfructokinase - inhib by ATP and citrate + activated by ADP and AMP
Pyruvate Kinase - inhib by ATP
Where does Aerobic respiration occur? How many stages are there?
In mutochondria
2 stages - krebs + E trans chain
enzymes + cofactors found in cristae
How is carb metabolism related to the Kreb’s cycle? What is the chain of events?
Pyruvate enters mitochondria thru outer + inner membrane
b4 enters krebs cycle -> acetyl group
Acetyl group binds to coenzyme A -> acetyl CoA
Acetly CoA enters krebs -> oxaloacetate to form citric acid
Coverted back to oxaloacetate.
CO2 is a byproduct
Each turn = 1 ATP, 1 FADH2, 3 NADH
How is the krebs cycle regulated?
Adjusts its rate to meet cellular needs for ATP
Entry of Acetyl-CoA into cycle and rate at which the cycle operates are reduced by high ATP levels
when ATP is low, cycle is stimulated
Explain the relation betwen Carb metab and e trans system
Produces majority of ATP for cell
NADH and FADH2 donate high energy electrons to chain of e carrier molecules called cytochrome
each step is used to pump protons from mitochondrial matrix into intermembrane space
Last e acceptor is oxygen to = h20
What is the summary of energy production from one glucose molecule? What makes what and where?
Cytoplasm (glycolysis) = 2 ATP
Mitochrondria
From glycolysis = 2 NADH + 6 ATP
From Cellular Respire
Pyrivic acid-acetyl CoA = 2 NADH + 6 ATP
Krebs = 6 NADH + 2 FADH + 24 ATP
Total 38 ATP
What energy carrier molecules are produced by the Krebs cycle
Does glycolysis require oxygen?
What is the product of glycolysis
What is glycogen synthesis?
Glucose consumed in excess of immediate body needs is converted to glycogen which is stored in the liver and muscle
What is glycogenesis?
The synthesis of glycogen from glucose.
Occurs in all cells but important in liver + muscle
Glygocen synthase forms bonces btw glucose using UTP as energy source
What is Glycogenolysis
Breakdown of glycogen to glucose, occurs when muscles need energy and when liver is restoring low blood sugar level to normal
occurs in liver, kidney and intestinal cells (not in muscle bc enzyme for las step is missing)
muscle cels cannot form free glucose but can prod glucose-6-phosphate for glycolysis pathway
What is gluconeogenesis?
The synthesis of glucose from noncarb molecules
synthesizes glucose from lactate, some amino acids and glycerol
occurs in like (~90%)
(lactate, some amino acids, glycerol) -> pyruvate -> Glucose
What is the cori cycle? What happens during active exercise?
Anaerobic conditions, lactate prod by muscles recoverted to glucose by liver via cori cycle
Lactate lvls inc. in muscle tissue
lactate diffuses into blood
lactate -> liver -> pyruvate
pyruvate -> glucose via gluconeogenesis (synthesis of noncarb molecules like lactate)
glucose enters blood and returns to muscles
What 3 main hormons control carbohydrate metabolism?
Insulin, glucagon, epinephrine
Explain how insulin works with carb metab?
dec blood glucose lvls
inc absorption of glucose by cells
inc synthesis of glycogen, fatty acids and proteins
stimulates glycolysis
Explain how glucagon works with carb metab?
Inc blood glucose lvls
activates glycogen breakdown in liver
explain how epinephrine works with carb metab?
Inc blood glucose lvls
stims glycogen breakdown in muscle
