Carbohydrate and Lipids Flashcards
How body deals with excess glucose?
Glycogen structure?
- Glycogen synthesis, Pentose Phosphate pathway (PPP), FA synthesis
- Highly branched polysaccharide anchored by Glycogenin
Glycogen formation
Characteristics of glycogen
- In liver, G6P→G1P→UDP-glucose
- GLYCOGENIN reacts with UDP-glucose to branch glycogen
- Affects osmolarity
- Glucose store
Glycogen breakdown
- Phosphorylase, Transferase, and Debranching 1-6 glucosidase break all the links
- Phosphoglucomutase and G6 Phosphatase do G1P→G6P→Glucose
Pentose Phosphate Pathway (PPP)
How Gluconeogenesis maintains blood glucose?
- G6P from glycolysis can go into the PPP - makes a Ribose 5 phosphate precursor for nucleotide synthesis
- Pyruvate is converted back into glucose. Other substrates used are AAs, lactate, glycerol
- Blood glucose is maintained as its the main fuel for the brain and RBCs.
Lipids as an energy source?
Fate of excess carbs?
- Contain lots of energy
- Stored as fat, which cardiac muscle prefers to use for energy. Most fat is made in the liver and is stored in adipose tissue
FA synthesis
Excess Acetyl CoA = excess Citrate, which leaves the mitochondrion to become FA’s
- Active conversion of Acetyl CoA→Malonyl-CoA - uses Acetyl-CoA carboxylase and ATP
- Elongation of malonyl-CoA
- Acetyl/Malonyl-CoA are linked to ACP - the enzymes used to form FA synthase complex
FA degradation
The release of energy from fat stores in 3 steps:
- Mobilisation - in adipose during starvation
- Activation - in hepatocyte cytosol
- Degradation - in hepatocyte mitochondria
Ketogenesis and its importance
Give an example of a ketone body present in the body?
Made in liver: Acetyl CoA → Ketone bodies
Acetyl CoA→Acetoacetate, which is an energy source for the heart and kidney. During starvation, the brain used it.
- Acetoacetate
Types of Lipoproteins
Chylomicrons
VLDL, LDL, IDL, HDL
Role of Chylomicrons in transport of lipids
- Made in GUT, and are low density. Carry lipids from the bowel. Secreted into lymph vessels to reach non-hepatic tissue.
Structure of Lipoprotein
Function of apoproteins
- Made of cholesterol, cholesterol esters, phospholipids, triglycerides, and APOPROTEINS
- Role in structure, solubilising lipids, enzymes/cofactors, tissue targeting
Composition and role of:
VLDL
LDL
HDL
- Made in liver, and has an LDL receptor ligand.
- Made from VLDL, and has an LDL receptor ligand. Main carrier of cholesterol
- Made in liver/gut, and has 2 apoproteins and LCAT. Transports cholesterol to liver and steroid-producing cells
How are LDL taken up and regulated?
↓Cholesterol = ↑LDL receptor expression so more LDL will be taken up.
Uptake is regulated by the hormones and nutritional status
