Lipid Oxidation / Metabolism

Question 1

What are fats stored as for energy source

Answer 1

Triglycerides- glycerol and 3 fatty acids

Question 2

Where are triglycerides/ fat stores found

Answer 2

In adipose fat tissues under the skin eg in bum

Question 3

What are the adipose tissues made from

Answer 3

Lipocytes/ adipocytes which have a nuclei and mitochondria and triglycerides

Question 4

How is energy generated from triglycerides

Answer 4

Energy generated from the oxidation (removal of H and E) from carbon

Question 5

Why is fat a better storage molecule than glycogen

Answer 5

Because less oxygen is present in fatty acids (only on carboxylic acid) , this means they remain reduced longer

Question 6

What are the 3 functions/ advantages of triglycerides storage for energy in adipose tissues

Answer 6

1- FA weigh less than glucose = concentrated storage

2- end result is h20 due to hydrolysis = provides h20 storage in eg camels which store fats for water

3- insulation- under skin and electrical as myelin sheath

Question 7

Why lipid is not used for energy storage and why

Answer 7

Cholesterol - needs combustion to break down

Question 8

How is glycerol linked to fatty acids

Answer 8

An ester O bond (loss of water when condensation occurs)

Question 9

Where are fatty acids condensed

Answer 9

When they are saturated due to hydrophobic interaction and no kinks

Question 10

Explain the difference between unsaturated Cis and trans bonds

Answer 10

Trans = double bond occurs diagonally (c are further apart) = causes straight chain

CIs = carbons are on same side so close to each other— try to repel eachother causing a bend in the fatty acid

Question 11

Why are unsaturated fats termed healthier than the saturated fatty acids

Answer 11

Easier to metabolise (not stored often)

Question 12

What is glycerol

Answer 12

An alcohol

Question 13

What is it called when lipids/triglycerides are broken down for energy

Answer 13

Lipolysis

Question 14

Which enzyme activated by hormones such as epinephrine and glucagon causes lipolysis

Answer 14

Lipase enzyme - when body is in starvation mode or exercising (low BGC)

Question 15

What does lipase do in lipolysis

Answer 15

Hydrolyses the ester bond in triglycerides forming free glycerol and fatty acids

Question 16

Where is glycerol transported to after lipolysis by lipase

Answer 16

The liver

Question 17

Explain the first step of how glycerol is converted to glycerol 3 phosphate

Answer 17

Glycerol kinase first uses atp hydrolysis to phosphorylate glycerol

Forming glycerol 3 phosphate

Question 18

How is glycerol 3 phosphate then converted to dihydroxyacetone phosphate

Answer 18

Glycerol phosphate dehydrogenase which reduced NAD to form NADH and oxidised glycerol 3 phosphate

Forming dihydroxyacetone phosphate

Question 19

How is dihydroxyacetone phosphate then converted to glyceraldehyde 3 phosphate in catabolism of glycerol (oxidation)

Answer 19

Using triose phosphate isomerase

Question 20

What can happen with the glycerol oxidation into glyceraldehyde 3 phosphate

Answer 20

Gluconeogenesis (converted back)

or go to pyruvate for glycolysis

Question 21

How does fatty acid oxidation differ to glycerol

Answer 21

It can’t be used for gluconeogenesis

Question 22

What needs to happen to fatty acids before they can be oxidised

Answer 22

Activation by the addition of coA to form fatty acyl coA

Question 23

How is fatty acid converted into fatty acyl coA in activation

Answer 23

Acyl coA synthetase catalyses the thioester bond forming between coA and fatty acid

ATP is fist hydrolysed by pyrophosphorylase which adds 2 phosphates providing energy for the formation of fatty acyl coA

Question 24

Where does formation of acyl coA from fatty acids occur

Answer 24

In cytoplasm near the mitochondria

Question 25

Where does oxidation of fatty acids occur

Answer 25

In the mitochondrial matrix

Question 26

What is acyl coA converted to to be able to cross the mitochondrial membrane

Answer 26

Acyl carnitine

Question 27

How is acyl coa converted to acyl carnitine

Answer 27

Loss of coA and addition of acyl to carnitine By carnitine acyl transferase 1

Question 28

How can acyl carnitine pass the mitochondrial membrane

Answer 28

Because it is recognised by a membrane protein

Question 29

How is acyl carnitine when in the matrix converted back to acyl coa and carnitine is recycled

Answer 29

Carnitine acyl transferase 2 | will add coA from the citric cycle to the free acyl when is is removed from carnitine

Question 30

What is the first step of B oxidation of fatty acids (fatty acyl coA)

Answer 30

Fatty acid is oxidised (removal of 2 H) to reduce fad into FADH2 This creates a c=c double bond

Question 31

What happens when fatty acid is oxidised by reduction of fad into FADH2

Answer 31

water is added to provide the oxygen for full b oxidation

Question 32

What happens next to the water added in b oxidation

Answer 32

It is dehydrogenated by the reduction of nad to NADH2

Question 33

Which carbon is oxidised by the oxygen in b oxidation

Answer 33

The beta carbon c=c turned into c = o

Question 34

What happens when beta carbon is oxidised

Answer 34

Acetyl coA forms which is then released when a new coA is present to restart the b oxidation process with another carbon down the fatty acid

Question 35

What can happen to the acetyl coA formed in b oxidation of fatty acids

Answer 35

Can be used in the citric cycle for glucose catabolism

Question 36

Which source is preferred for energy, glycogen or lipids

Answer 36

Lipid oxidation - glycogen only used by brain or red blood cells

Question 37

Why is acetyl coA converted into ketones

Answer 37

When there is low glucose in cells (diabetes or starvation) this means not enough intermediates produced from glycolysis, acetyl coA is in high supply due to lipid oxidation and builds up to produce ketones

Question 38

What hormone suppresses fatty acid oxidation into acetyl coA which isn’t present in diabetes = build up

Answer 38

Insulin

Question 39

Where does Ketogenesis occur

Answer 39

In the liver

Question 40

How are 2 acetyl coA used to produce ketone bodies explain the first step

Answer 40

2 acetyl coa firsf have 1 coA released Forms acetoacetyl coA

Question 41

Explain second step of ketogenesis

Answer 41

Acetoacetyl coA has another acetyl coA added and H2O Releases 1 coa Forming hydroxy - 3 - methyl- glutaryl coA

Question 42

What happens to hydroxy 3 methyl glutaryl coA

Answer 42

Loses 1 acetyl coA forming acetoacetate

Question 43

Which 2 ketone bodies are produced from acetoacetate

Answer 43

Acetone and 3 hydroxy butyrate

Question 44

How is acetone produce from acetoacetate

Answer 44

H+ is added to remove a co2

Question 45

How is 3 hydroxyl butyrate produced from aceto acetate

Answer 45

NADH 2 is oxidated and reduces acetoacetate into 3 hydroxy butyrate

Question 46

What is fatty acid synthesis promoted by

Answer 46

Insulin (which inhibits lipolysis)

Question 47

Is fatty acid synthesis favoured or not

Answer 47

No , it is endergonic

Question 48

How does Lipo genesis differ to fatty acid synthesis

Answer 48

Acetyl coA is converted to fatty acids instead of fatty acids being coursed into acetyl coA for energy

Question 49

What is needed for lipogenesis to occur

Answer 49

The acyl group and also addition of Malonyl coA group

Question 50

How is acetyl coa converted to malonyl coA for lipogenesis

Answer 50

Acetyl coA and co2 is converted into malonyl coA By acetyl coA carboxylase (uses ATP hydrolysis for energy)

Question 51

Which enzyme is controlled to control lipogenesis

Answer 51

Acetyl coA carboxylase

Question 52

What are the positive modulators and negative modulators for acetyl coA carboxylase

Answer 52

+ = acetyl coA and citrate build up - = glycogen AMP Adrenaline Excess fat They indicate that glucose breakdown is needed which is helped by lipolysis

Question 53

What happens in lipogenesis which is different to lipolysis

Answer 53

Acyl + malonyl Condensation Reduction Dehydration (instead of addition of h20) Reduction (instead of b oxidation) Forming acyl group + 2c = growing fatty acid

Question 54

What is ACP and why is it needed for lipogenesis

Answer 54

Acyl carrier protein which is an enzyme complex which stops the loss of fatty acids in lipogenesis

Question 55

How is it thought that excess fatty build up in the liver due to Lipogenesis can cause type 2 diabetes

Answer 55

B cells in the pancreas hide from the lipids and therefore causes B cell de differentiation which causes increase BGC

Question 56

Where does synthesis of lipogenesis occur

Answer 56

In the matrix

Question 57

What are the activation carrier proteins in lipogenesis vs lipolysis

Answer 57

Lipolysis = coA which activates fatty acids oxidation Lipogenesis = acyl carrier proteins (ACP)

Question 58

What are the electron carriers in Lipogenesis (when they are oxidised to reduce acyl and malonyl into fatty acids) vs lipolysis (oxidation occurs via reduction of electron carrier)

Answer 58

Lipogenesis = NADPH which is oxidised Lipolysis = nad and fad in b oxidation which are reduced

Question 59

Why is ketogenesis important in some cases if not in high amounts like diabetics

Answer 59

Because it generates atp from acetyl coA which is emergency for the brain and rbcs