Lipids 1

Question 1

What are lipids?

Answer 1

Molecules that contain hydrocarbons and make up the building blocks of structures and function in a living cell

Question 2

When are lipids soluble?

Answer 2

They are hydrophillic but are soluble in organic solution

Question 3

Are lipids hydrophobic or hydrophillic?

Answer 3

Hydrophobic

Question 4

Where can lipids be found?

Answer 4

Cell membranes

Adipose tissue

Blood lipoproteins

Question 5

What are some functions of lipids?

Answer 5

Stored form of energy

Structural element of membreanes

Enzyme cofactors

Hormones

Vitamins A, D, E and K

Signalling molecules

Question 6

What are the 5 lipid classes?

Answer 6

Fatty acids

Triacylglyderol

Phospholipids

Glycolipids

Steroids

Question 7

What are the 2 forms of fatty acids?

Answer 7

Unsaturated (one or more double bonds)

Saturated (no double bonds)

Question 8

How are fatty acids named?

Answer 8

By the number of carbons, number of double bonds and the position of the double bond

Question 9

Give examples of lipid naming?

Answer 9

18: 0 - 18 carbons, no double bonds
18: 3 (9, 12, 15) - 18 carbons, 3 double bonds, double bonds between 9/10, 12/13 and 15/16

Question 10

What are the 4 kinds of fatty acids in our diet?

Answer 10

Essential fatty acids (linoleic eg)

Good fats (high in polyunsaturated fats such as olive oil)

Bad fats (high in saturated fatty acids such as beef)

Very bad fats (trans fatty acids such as hard margarine)

Question 11

What are saturated fats good for?

Answer 11

The nervous system

Question 12

What are essential fatty acids?

Answer 12

Cannot be synthesised, need to be consumed in our diet

Question 13

Why can essential fatty acids not be synthesised?

Answer 13

We cannot introduce double carbon bonds beyond carbon 9

Question 14

What are omega-3 fatty acids derived from?

Answer 14

Linolenic acid (essential fatty acid)

Question 15

What are omega-3 fatty acids good for, and omega-6?

Answer 15

Lowering blood cholesterol

Question 16

What are triacylglycerols?

Answer 16

Esters of fatty acids and glycerol

Question 17

What are triacylglycerols used for?

Answer 17

Storing energy and insulation

Question 18

Are triacylglycerols water soluble?

Answer 18

No

Question 19

What are phospholipids?

Answer 19

A lipid containing a phosphate group

Question 20

How are phospholipids amphipathic?

Answer 20

They contain a hydrophillic head and a hydrophobic tail

Question 21

Why are phospholipids often used in membranes?

Answer 21

They are amphipathic

Question 22

What does amphipathic mean?

Answer 22

Has a hydrophillic and a hydrophobic component

Question 23

What is the main site of lipid digestion?

Answer 23

Small intestine

Question 24

Where does lipid digestion start?

Answer 24

In the mouth

Question 25

What is digestion by pancreatic enzymes (lipases) promoted by?

Answer 25

Emulsification (dispersion) by bile salts and peristalsis (mixing)

Question 26

What pancreatic enzymes digest lipids?

Answer 26

Lipases

Question 27

Where does some lipid digestion occur other than the mouth and the small intestine?

Answer 27

The stomach

Question 28

What are bile salts?

Answer 28

Act as biological detergents to break down fatty acids

Question 29

What are bile salts a derivative of?

Answer 29

Cholesterol

Question 30

How are triacylglycerols digested?

Answer 30

Degraded in small intestine by pancreatic lipases to monoacylglycerol and two fatty acids

Question 31

What are cholesterol esters digested into?

Answer 31

Digested to cholesterol and a free fatty acid?

Question 32

How are phospholipids digested?

Answer 32

Hydrolysed to a fatty acid and lysophospholid

Question 33

What does the digestion of lipids look like?

Answer 33

1. Fat becomes emulsified fat in the duodenum (due to bile) 2. Then broken down into fatty acids and glycerol in the small intestine (due to lipases)

Question 34

What is the process of digested lipid uptake?

Answer 34

Form mixed micelles with bile salt which approach membrane and release lipid products which enter by diffusion Short and medium chain fatty acids do not require micelles because they are more soluble

Question 35

What is formed from digested lipids and bile salt?

Answer 35

Micelles

Question 36

What could lipid malabsorption be due to?

Answer 36

Defect in bile secretion Defect in pancreatic function Defect in intestinal cells

Question 37

What does lipid malabsorption cause?

Answer 37

A steatorrhea

Question 38

What is a steatorrhea?

Answer 38

Excess fat in faeces

Question 39

What secretes bile salt?

Answer 39

Gallbladder

Question 40

What is the fate of absorbed lipids?

Answer 40

Resynthesised by intestinal cells for export Packaged with apoB-48 into chylomicrons due to being insoluble

Question 41

Why are absorbed lipids packaged with apoB-48 for export?

Answer 41

Because they are insoluble, this packaging makes them soluble

Question 42

What does the packaging of absorbed lipids and apB-48 form?

Answer 42

Chylomicrons

Question 43

How are chylomicrons released?

Answer 43

By exocytosis into the lymph and then the blood

Question 44

What happens once chylomicrons reach the tissue?

Answer 44

1. Hydrolysed to fatty acid and glycerol by lipoprotein lipase 2. Resulting fatty acid is used for energy or resterfication to triacylglycerol for storage

Question 45

What is a chylomicron renment?

Answer 45

Chylomicron depleted of tracylglycerol

Question 46

Where do chylomicron renments go?

Answer 46

The liver where glycerol is used to produce glycerol-3-phosphate

Question 47

Where is lipoprotein lipase normally found?

Answer 47

In capillaries of skeletal muscle and adipose tissue

Question 48

What is the exact process of lipid digestion, absorption and transport summarised?

Answer 48

1. Bile salts emulsify fats in small intenstine, forming micelles 2. Intestinal lipases degrade triacylglycerol 3. Fatty acids are taken up by intestinal mucosa and converted to triacylglycerol 4. Triacylglycerol is incorporated with cholesterol and apolipoprotein into chylimicrons 5. Move through lymphatic system, then blood to tissue 6. Lipoprotein lipase converts tracylglycerol to fatty acid and glycerol 7. Fatty acid enters cells 8. Fatty acid oxidised for fuel or re-esterfied into triacylglycerol for storage

Question 49

Why is triacylglycerol efficient for the storage of fats?

Answer 49

Highly reduced form

Question 50

What is triacylglycerol stored as in adipose tissue?

Answer 50

Droplets

Question 51

What is the process of fatty acids being released from adipose tissue?

Answer 51

1. Hormone sensitive lipase (HSL) activated by phosphorylation in response to noradrenaline 2. Fatty acid released from stored triacylglycerol by HSL

Question 52

What deactivates hormone sensitive lipase (HSL)?

Answer 52

High plasma glucose and insulin by dephosphorylation

Question 53

How is fatty acid transported in the blood?

Answer 53

In a complex with serum albumin, carried in lipoproteins

Question 54

What are lipoproteins that transport fatty acids made of?

Answer 54

Hydrophobic cores (triacylglycerol and cholesterol esters) Hydrophillic surface (unesterfied cholesterol, phospholipids, apolipoproteins)

Question 55

What are the 4 classes of lipoproteins?

Answer 55

Chylamicrons VLDL LDL HDL

Question 56

Does density increase from chylamicrons to HDL or from HDL to chylamicrons?

Answer 56

Chylamicrons to HDL

Question 57

What is the function of chylomicrons?

Answer 57

Transfer triacylglycerol from intestine to tissue, they are triacylglycerol rich

Question 58

What is the function of VLDL?

Answer 58

Transfer triacylglycerol from liver to tissue, triacylglycerol rich

Question 59

What is the function of LDL?

Answer 59

Transfer cholesterol to tissue, cholesterol rich

Question 60

What is the function of HDL?

Answer 60

Transfer cholesterol from tissue to the liver for elimination, protein/cholesterol rich

Question 61

What is a disease that too much LDL leads to?

Answer 61

Atherosclerosis