MHS Module 3 - lipid metabolism, synthesis p3

define lipolysis

breaks down lipids into pieces that can be:

• converted to pyruvate

• channelled directly into citric acid cycle

how is a triglyceride split

by hydrolysis into 1 molecule of glycerol and 3 fatty acids

what occurs to glycerol in the cytosol

enzymes convert glycerol into pyruvate, then into acetyl CoA to enter the citric acid cycle

explain beta-oxidation

series of reactions in mitochondria

breaks fatty acid molecules into 2-carbon fragments producing

FAD + NAD+ —> FADH2 + NADH

explain the steps of beta-oxidation

generates molecules of acetyl CoA, NADH, and FADH2

leaves a shorter carbon chain bound to CoA

explain the breakdown of fatty acid

produces 120 ATP from 1 18-carbon fatty acid molecule

what is used in lipid synthesis

any organic substrate because lipids, amino acids and carbohydrates can convert into Acetyl CoA

how is glycerol synthesised

synthesised from dihydroxyacetone phosphate- intermediate product of glycolysis and gluconeogenesis

how are nonessential fatty acids and steroids synthesised

synthesised from Acetyl CoA

how are essential fatty acids synthesised

cannot be synthesised in the body, must be consumed ig linoleic acid

explain lipid storage

important energy reserves, difficult for water soluble enzymes to reach

why is the transport of lipids important

lipids needed to maintain plasma membrane

steroid hormones must reach target cells in other tissues

how are lipids distributed in the body

because they are not soluble in water, special transport mechanisms carry lipids from one region to another

what form do lipids transport in

lipoproteins

explain free fatty acids (FFAs)

diffuse easily across plasma membrane

generally bound to albumin (plasma protein) in blood

how are FFA’s sourced in blood

when not used in the synthesis of triglycerides that diffuse from intestinal epithelium

those that diffuse out of lipid reserves when triglycerides are broken

how are FFA’s energy sources and how?

when glucose supplies are limited

liver cells, cardiac muscle cells, skeletal muscle cells can metabolise FFA’s