lipid metabolism and ketones

Question 1

what does increased fat intake without appropriate energy expenditure lead to

Answer 1

> increase in number of adipocytes
more fat in adipocytes
ie obesity

Question 2

what does energy balance depend on

Answer 2

genetically linked factors ie protein messengers regulating appetite
environmental factors ie food abundance, fashionable foods

Question 3

why is fat required

Answer 3

> an energy source
for essential fatty acids
fat soluble vitamins ie A D E and K

Question 4

what are lipids

Answer 4

they are collections of different compounds
>they are predominantly hydrocarbon
>usually contain long chain fatty acids
>insoluble in water
>important for their biological functions

Question 5

simple lipids

Answer 5

fatty acids, triglycerides, waxes

Question 6

compound lipids

Answer 6

phospho- ,glyco-lipids , lipoproteins

Question 7

steroids

Answer 7

cholesterol and steroid hormones

Question 8

triglycerides

Answer 8

the same as triglycerols
>main energy source form in adipose tissue 
>compact
>hydrophobic
>high energy yield per gram 
>consist of glycerol and 3 fatty acids

Question 9

fatty acids

Answer 9

> mainly straight chains
aliphatic
usually contain an even number of carbons
branched chains and odd numbers of carbons are rare
they can be saturated, unsaturated and polyunsaturated
double bonds usually cis

Question 10

the three main natural fatty acids

Answer 10

palmitic acid
stearic acid
oleic acid

Question 11

polyunsaturated fatty acids

Answer 11

occur only in small amounts

>cannot be synthesised in the body

Question 12

fatty acid nomenclature

Answer 12

pls just look at the slides i can’t explain this

Question 13

fatty acid - melting point variation

Answer 13

> fatty acids with up to 8 carbons are liquid at room temp.
double bonds lower the melting point
plant fats contain large proportions of unsaturated fatty acids ie liquids
animal fats contain mostly palmitic and stearic ie solid

Question 14

what are the main products of fat digestion

Answer 14

glycerol
fatty acids
monoglycerides

Question 15

how is fat absorbed into mucosal cells of intestine

Answer 15

> short and medium length fatty acids enter portal blood

>longer chain FAs and monoglycerides are re-synthesised to triglycerides

Question 16

what are chylomicrons

Answer 16

fat that is coated with a layer of protein, phospholipid and cholesterol

Question 17

chylomicrons

Answer 17

enter the lymph and then the blood stream
>at muscle and adipose tissue, chylomicrons are attacked and cleaved by lipoprotein lipases

**there, free fatty acids are
resynthesised into triacylglycerols, oxidised to provide energy, and this all depends on amount available

Question 18

lipolysis of stored fat

Answer 18

= the breakdown of lipids 
>fat is stored in adipose tissue 
>initial cleavage by hormone sensitive lipases (eg adrenaline sensitive) 
-releases free fatty acids and glycerol 
-occurs when energy is needed

Question 19

fatty acid oxidation - activation

Answer 19

> before fatty acids can be oxidised to generate energy, they have to be converted to CoA derivatives
occurs in the cytoplasm
requires energy ie 2ATP
further oxidation of fatty acids occurs in the mitochondrial matrix
need to be transported into mitochondria by special carrier mechanism

Question 20

function of the carnitine shuffle

Answer 20

**in the cytoplasm, fatty acids are transferred from acyl-CoA to carnitine
>Acyl-carnitine transport in inner membrane - facilitates antiprotons of acyl-carnitine into the mitochondrion and carnitine out
>ie acyl-CoA located is the mitochondrial matrix

Question 21

beta oxidation (fatty acids)

Answer 21

cycle of reactions occurs in the mitochondrial matrix
>four steps in each cycle
>products of each cycle = acetyl-CoA
=FADH2
=NADH + H
=fatty acyl-CoA shortened by 2 carbon atoms

Question 22

beta oxidation and unsaturated fatty acids…

Answer 22

???
requires two additional enzymes:
enoyl-CoA Isomerase
2,4 Dienoyl CoA reductase

Question 23

yield of beta oxidation

Answer 23

cycle is repeated 8 times creates: 
>>8 FADH + 8NADH + 8H
>used for ATP generation in oxidative phosphorylation 
>>9 acetyl-CoA
>oxidised in citrate cycle to CO2, yield 9 FADH, 27NADH + 27 H , 9 GTP 
>>P/O ratio:
FADH NADH + H
total yield = 120 ATP

Question 24

additional pathways include …

Answer 24

unsaturated fatty acids
odd chain fatty acids
branched chain fatty acids
»requires several enzymes

Question 25

breakdown of glycerol

Answer 25

> > activated to glycerol-3-phosphate by glycerol kinase
present in liver and kidney but absent from adipose tissue, skeletal and heart muscle
dehydrogenated to dihydroxyacetone phosphate
normal intermediate of carbohydrate metabolism

Question 26

ketone bodies

Answer 26

> they are formed in the liver mitochondria (from acetyl-CoA from B oxidation)
diffuse into the blood stream and to peripheral tissues
important molecules of energy metabolism for heart muscle and renal cortex (converted back to acetyl-CoA which enters the TCA cycle)

Question 27

ketosis in starvation and diabetes

Answer 27

> oxaloacetate is consumed for gluconeogenesis
fatty acids are oxidised to provide energy
acetyl-CoA is converted to ketone bodies
high levels in blood
too much for extrahepatic tissue (i.e. heart, brain, etc.)
ketone bodies are moderate acids
accumulation leads to severe acidosis (blood can’t buffer any more)
impairs tissue function, particularly central nervous system
smell of acetone can be detected in breath

**normally
fatty acid oxidation yields acetyl-CoA, it enters citrate cycle if fat and carbohydrate degradation are balanced
>depends on oxaloacetate for formation of citrate
>oxaloacetate can be provided as a side-product of glycolysis

Question 28

lipid catabolism

Answer 28

!! idk bro study