biochemistry COPY Flashcards
what is glycogenesis
synthesis of glycogen from glucose
what is glycogenolysis
breakdown of glycogen to form glucose
what is gluconeogenesis
de novo synthesis of glucose from metabolic precursors
where is glycogen stored
liver and muscle cells
how is liver glycogen broken down
broken down between meals and released to maintain blood glucose levels for red blood cells and the brain
how does muscle glycogen provide energy
Provides energy via glycolysis and the TCA during bursts of physical activity
what is the primary source of glucose over night when hepatic glycogen is depleted
gluconeogenisis
what is the structure if glycogen
- polymer consisting of glucose molecules
- joined by alpha 1-4 glycosidic links
- branches are introduced by alpha 1-6 glycosidic links
- glycogenin is an enzyme involved in converting glucose to glycogen. It acts as a primer, by polymerizing the first few glucose molecules
what is a glycogenic protein
A primer of straight chain polymer. Contains at least 4 glucose residues
what is the function of hexokinase in glycogen synthesis
Primer for glucose phosphorylation
what is the function of phosphoglucomutase in glycogen synthesis
targets glucose away from glycolysis and towards glycogen synthesis by changing the position of the phosphate from group 6 to group 1
what is the function of UDP-glucose pyrophosphorylase in glycogen synthesis
Binds UDP to the glucose
what is the function of the glycogen synthase
Attaches UDP-glucose as a primed molecule to form glycogen. It adds one glucose molecule to glycogen at a time. It can only extend the glycogen chains and it cannot start new molecules
what is UDP-glucose
An activated form of glucose
- UDP-glucose is used in nucleotide sugar metabolism as an activated form of glucose
- precursor of glycogen
- precursor of sucrose, lipopolysaccharides and glycosphingolipids
what are the steps of glycogenolysis
Steps of glycogenolysis (glycogen breakdown)
- glycogen is broken down Inyo glucose-1-phosphate by the enzyme glycogen phosphorylase
- glucose-1-phosphate is broken down into glucose-6-phosphate by the enzyme phosphoglucomutase
3a. liver = glucose-6-phosphate is converted to glucose by the enzyme glucose-6-phosphatase which will travel into the blood via GLUT2 transporter
3b. muscle cells = glycolysis
where does glycogenolysis occur
the muscles and the liver
when is glycogenolysis important
- In starved state
- When ATP is low
what is the difference between glycogenolysis in the liver and in the (skeletal) muscle
in the liver the glucose-6-phosphate can be de-phosphorylated and the resulting glucose released into the blood stream
in muscle glucose-6-phosphate cannot be de-phosporylated by instead is used to provide energy via glycolysis and the TCA cycle
when does gluconeogenesis occur
- During prolonged starvation, new glucose has to be synthesised
- Proceeds via the synthesis of oxaloacetate in mitochondria
what are precursors for the synthesis of glucose in gluconeogenesis
lactate, amino acids, glycerol
what are the 4 enzymes that gluconeogenesis requires
- glucose-6-phosphate
- fructose-1,6-bisphosphate
- PEP carboxykinase
- pyruvate carboxylase
what is the cori cycle
metabolic pathway in which lactate produced by anaerobic glycolysis in muscles is transported to the liver and converted to glucose, which then returns to the muscles and is cyclically metabolized back to lactate.
what does increased fat intake without appropriate energy expenditure leads to
- increase in number of adipocytes
- more fat in adipocytes
- obesity
what are features of lipids
- collection of different compounds
- predominantly hydrocarbon
- usually contain long chain fatty acids
- insoluble in water
what are the features of triglycerides
- main energy storage form in adipose tissue
- compact
- hydrophobic
- high energy yield per gram
what is the structure of triglycerides
- 3 fatty acids
- glycerol
how do double bonds affect melting point
lower melting point
what are the main products of fat digestion
- glycerol
- fatty acids
- monoglycerides
where is fat absorbed
The mucosal cells of the intestine. Short and medium length fatty acids enter the portal blood. Longer chains fatty acids and monoglycerides are resynthesises to triglycerides
what are chylomicrons
fat is coated with a layer of protein, phospholipid, cholesterol called chylomicron. Formed in the intestinal epithelium to transport long-chain triglycerides to the tissues
What is lipolysis
the breakdown of lipids
where is fat stored
adipose tissue
what initially cleaves fat, releasing free fatty acids and glycerol
hormone sensitive lipases
what needs to be done to fatty acids for them to generate energy
converted to CoA derivatives and then oxidised
what is the carnitine shuttle
Carnitine transports long-chain fatty acids into mitochondria to be oxidized for energy production, and also participates in removing products of metabolism from cells.
In the cytoplasm, fatty acids are transferred from acyl-CoA to carnitine. Acyl-carnitine transporter in inner membrane: facilitates anti port of acyl-carnitine into the mitochondrion and carnitine out
Net result = acyl-CoA located in mitochondrial matrix
what is beta oxidation of fat
beta oxidation consists in breaking down long fatty acids that have been converted to acyl-CoA chains into progressively smaller fatty acyl-CoA chains
how is glycerol broken down
Activated to glycerol-3-phosphate by glycerol kinase. Dehydrogenated to dihydroxyacetone phosphate
How are ketone bodies formed
Formed in the liver mitochondria from acetyl-CoA from beta oxidation
why are ketone bodies important
Important molecules of energy metabolism for heart muscle and renal cortex. Its converted back to acetyl-CoA, which enters the TCA cycle
what is ketosis
Ketosis is a process that happens when your body doesn’t have enough carbohydrates to burn for energy. Instead, it burns fat and makes things called ketones, which it can use for fuel.
what are ketones
Ketones are a type of chemical that your liver produces when it breaks down fats.
what are the enzymes in glycolysis
hexokinase, phosphofructokinase, and pyruvate kinase
what are the enzymes in glycogenesis
hexokinase, phosphofructokinase, and pyruvate kinase
what are the enzymes in glycogenolysis
phosphorylase kinase and glycogen phosphorylase.
