Lipids Flashcards Preview

Science for Medicine > Lipids > Flashcards

Flashcards in Lipids Deck (38):
1

Lipids are

heterogenous organic molecules that exist in a few different forms and have several purposes

2

Give 3 functions of lipids

- a stored form of energy
- a structural component of cell membranes
- needed as enzyme cofactors
- used in hormones
- used for the synthesis of Vitamins A, D, E and K
- used as signalling molecules

3

What are the major lipid classes?

- fatty acids
- triacylglycerides
- phospholipids

4

What are fatty acids?

Hydrocarbon chains with a carboxylic group at one end
- can be saturated or unsaturated
- nomenclature defines which is which

5

What are the four types of fatty acids?

Essential fatty acids - must be obtained from plants

Good fats - high in polyunsaturated fatty acids

Bad fats - high in saturated fatty acids

Really bad fats - trans fatty acids

6

Give an example of an essential fatty acid

- Linoleic acids
- A-Linoleic acids

7

Give an example of a good fat

Plant oils e.g. sunflower oil

8

Give an example of a bad fat

Stearic acid

9

Give an example of a really bad fat

Margarine

10

Essential fatty acids must be obtained via

our diet, since humans cannot introduce double bonds beyond carbon nine

11

What are triacylglycerides?

Esters of fatty acids and glycerol - water insoluble
- coalesce into droplets in water
- major component of adipose tissue
- act as insulation and dietary fuel

12

What are phospholipids?

Glycerol bonded to two fatty acids and a phosphate group
- amphipathic
- form basic structure of the cell membrane

13

What is the main dietary lipid?

Triglycerols

14

Where does most digestion of triglycerols take place? Through the use of what?

Small intestine

pancreatic enzymes, emulsification by bile salts and peristalsis

15

Most triglycerols are digested by ___ into ___

pancreatic lipase

monoacylglycerol and two fatty acids

16

Cholesterol esters are broken down to

cholesterol and a fatty acid

17

Phospholipids are hydrolysed to

a fatty acid and lysophospholipid

18

Mixed micelles release their contents when they

approach the brush border

19

The intestinal cells repackage ___
into ___
which are released ___

TAG, fatty acids and cholesterol esters

chylomicrons

into the blood via the lymphatic system

20

When lipids reach the tissues, TAG is hydrolysed to ___
by ___

fatty acids and glycerol

lipoprotein lipase

21

The resulting free fatty acids are used for ___
or ___

energy

re-esterified into TAG for storage

22

Free fatty acids are transported in lipoproteins in a complex with

serum albumin

23

Fats are also transported in

high and low density lipoproteins

24

LDLs carry

cholesterol from the liver to other tissues

25

HDLs

pick up cholesterol from tissues and bring it back to the liver for elimination

26

The beta-oxidation pathway degrades ___
to form ___

fatty acids two carbons at a time

Acetyl CoA, NADH and FADH2

27

The beta-oxidation pathway occurs in the

mitochondrial matrix

28

What are the three stages of the beta-oxidation pathway?

- activation
- transport
- degradation

29

What happens in the activation stage of the beta-oxidation pathway?

The fatty acids are activated to form fatty acyl CoA in the cytoplasm

30

What happens in the transport stage of the beta-oxidation pathway?

- carnitine shuttle transfers long chain fatty acyl CoA from the cytoplasm to inside the mitochondrion
- carnitine is a non-essential amino acid
- carnitine fatty-acyl transferase is inhibited by malonyl CoA, used in fatty acid synthesis
- therefore synthesis and degradation cannot occur simultaneously

31

What happens in the degradation stage of the beta-oxidation pathway?

- fatty acyl CoA is dehydrogenated to form FADH2 and another intermediate
- this intermediate is then hydrated
- the resulting intermediate is dehydrogenated again to form NADH
- finally, thiolysis occurs to form Acetyl CoA that feeds into the CAC

32

Each beta-oxidation cycle forms

- 1 Acetyl CoA
- 1 NADH
- 1 FADH2
- Carbon species 2 carbons shorter than the original

33

No fatty acid is

gluconeogenic

34

During fasting or starvation, glucose supplies run low and so excess Acetyl CoA from fat metabolism can be made into

ketone bodies

35

What cells can use ketone bodies?

- cardiac muscle cells
- skeletal muscle cells
- brain cells during times of starvation

36

Ketogenesis occurs in the

liver

37

What is also produced in ketogenesis?

Acetone (but is expelled during expiration)

38

What are the main ketone bodies?

Acetoacetate
3-Hydroxybutarate