Biochemistry Flashcards
Glycogenesis
Converting glucose to glycogen
Glycogenolysis
Breakdown of glycogen to glucose
What is the purpose of liver glycogen?
To be broken down between meals to provide glucose to blood and brain cells
What is the purpose of muscle glycogen?
Provide energy for glycolysis and the TCA cycle
What is the primary source of glucose through the night (i.e. when the body has no food stores?)
Gluconeogenesis
Gluconeogenesis
Production of glucose from non-carbohydrate substrates
Name the 2 bonds in glycogen
a 1-4 glycosidic link
a 1-6 glucosidic link
Which glucosidic link makes branches
1-6
what is the primer in glycogen attached to?
Glycogenin
what are the two options of glucose-6-phosphate?
- Glycolysis
2. Converted to glucose in the liver
Activated form of glucose
UDP-glucose
Activated form of phosphate
ATP
Activated form of acetate
Acetyl-CoA
Name the transporter which gets glucose into the bloodstream
GLUT2
Hexokinase
Converts glucose to glucose-6-phosphate
Phosphoglucomutase
Reversible reaction between Glucose-6-phosphate and glucose 1-phosphate
UDP-glucose phosphorylase
Glucose-1-phosphate to UDP-glucose
Glycogen synthase
UDP glucose to glycogen
Glycogen phosphorylase
Glycogen to glucose-1-phosphate
Glucose-6-phosphatase
glucose-6-phosphate to glucose
Where does energy come from for gluconeogenesis?
Oxidation of fatty acids from adipose tissue
Where does gluconeogenesis occur?
Liver
What are the precursors of gluconeogenesis?
Lactate
Amino acids
Glycerol
What is synthesised to allow gluconeogenesis to continue?
Oxaloacetate
What does glucagon do?
Stimulate gluconeogenesis
Inhibit glycolysis
What does insulin do?
Inhibit gluconeogenesis
Stimulate glycolysis
Why is fat needed in the body (3 roles)?
Energy source
For essential fatty acids
Provides fat soluble vitamins
Name the three types of lipids
Simple lipids
Compound lipids
Steroids
What are triglycerides made of?
Glycerol + three fatty acids
3 main products of fat digestion
Glycerol
Fatty acids
Monoglycerides
What happens to fatty acids in the mucosa of the intestine (both short and long)?
Short - absorbed into blood stream
Long - resynthesises (along with monoglycerides) back to triglycerides
How are resynthesises triglycerides carried?
Via chylomicrons
What are chylomicrons cleaved by and where?
Lipoprotein lipase in the muscle
Lipolysis
Breakdown of lipids
How is ACyl-CoA generated?
CoA + fatty acid
What transports Acyl to the matrix?
Acyl carnitine
Products of B-oxidation in the mitochondria?
1 Acetyl-CoA
1 fatty Acyl-CoA
1 FADH2
1 NADH + H+
Total ATP yield from oxidation of one stearic acid?
120 ATP
What are ketone bodies formed from?
Acetyl-CoA from B-oxidation
Why are ketones produced in uncontrolled diabetes?
There is no oxaloaceteate (being used up in gluconeogenesis) so Acetyl-CoA can’t enter the TCA cycle to be made into energy
Lipogenesis
Fatty acid synthesis
What happens to excess carbohydrate?
Converted to fatty acids and triglycerides in the liver
What transports acetyl groups into the cytoplasm?
Citrate (from TCA cycle)
Which enzyme activates Acetly-CoA into Malony-CoA?
Acetyl CoA carboxylase
When is fatty acid synthesis maximal?
When carbohydrates are abundant
What increases the action of Acetyl-CoA carboxylase?
Insulin and citrate
What does glucagon do to the action of Acetly-CoA carboxylase?
SLOWS action
What is required for the synthesis of triglycerides?
Glycerol-3-phosphate from glycerol (liver) and glucose (fat)
Are amino acids stored?
No - catabolised in liver mainly
What unwanted product does amino acid break down give?
Ammonium ions
How are they mainly excreted?
Via urine (produced in liver)
3 stages of urea synthesis
Transamination
De-amination
Urea cycle
Where does De-amination occur?
In the liver
What is the amino group converted to?
free ammonium ion
3 components of urea
Carbon dioxide
Free ammonium ion
Aspartate
What is the remaining carbon skeleton converted into?
TCA cycle intermediates
