Lipids

Question 1

What are the Main Groups of Lipids?

Answer 1

Fatty Acids
Fatty Acid Derivatives
Steroids

Question 2

What are Fatty Acids? Expand on the 2 Types. (how it is at room temperature, how stable, order of chain)

Answer 2

Hydrocarbons with one terminal carboxyl group COOH

Saturated - single bonds only
- solid at room tep - butter, egg, coconut, animal fats
- very stable
- straight chains
- stack tightly

Unsaturated = 1+ double bonds
- mono/polyunsaturated
- liquid at room temperature - plant oils
- bent chains
- two configurations
= cis - carbons are on same side of double bond
= trans - carbons on opposite side of double bond, the shape doesn’t bend much

Question 3

What are the Fatty Acid Deratives? Expand on the 2 Types. (structure and function)
Triglycerides

Answer 3

Triglycerides
- Glycerol + 3FA
- efficient long term storage
- forms in the cytoplasm of adipocytes
- function: protect and cushion organs

Phospholipids
- phosphate + glycerol + 2FA
- functions:
- permeable barrier of cell membrane
- provide supporting matrix
- participate in signal transduction
- provide precursors for processes

Question 4

What is a Steroid, where is it produced, its functions, how does it travel in the blood and 2 types.

Answer 4

hydrophobic molecules characterised by a carbon skeleton of 4 fused rings

75% produced by liver, 25% diet

Functions
- maintain membrane fluidity
- involved in production of hormones and Vitamin D

Transported in Blood via Lipoproteins

LDL - low density (saturated makes up body cholesterol)
HDL - high density
= positive, removes cholesterol

Question 5

What are the Functions of Lipids? (5)

Answer 5

• source of energy
• absorb fat-soluble vitamins
• protect internal organs
• insulate body from heat loss
• support biosynthesis precursors

Question 6

Where are Lipids Digested in the GIT?

Answer 6

• oral cavity
• stomach
• small intestine
• large inestine

Question 7

Role of Oral Cavity in Digestion

Answer 7

saliva contains lingual lipase
- emulsifies fats

Question 8

What 2 Enzymes does the Stomach Contain to bring about Digestion

Answer 8

contain lingual lipase and gastric lipase
- break down fat into diglycerides and FA

Question 9

What gets Stimulated in the Small Intestine During Digestion (3) and what other Enzymes are Present? (3)

Answer 9

chime (digested food) = acidic

mucosal wall stimulated
- secrete cytokinin hormone

gall bladder and pancreas stimulated
- secrete bile salts and pancreatic lipase

Enzymes:
- cholesteryl ester hydrolase
- phospholipase A2
- lysophospholipase

Question 10

What do Bile Salts Do?

Answer 10

hydrophobic side attach to fat droplets
= form micelles

• outside is hydrophilic so allows solubility

Question 11

What is the Role of the Large Intestine in Digestion?

Answer 11

Exretion

Question 12

How are Lipids Absorbed into the Blood Stream? (14)

Answer 12

intestinal lumen
- on the apical border
- micelles transport to the basolateral border via enterocytes
= simple diffusion

in the cells endoplasm’s reticulum
- packed into a chylomicron
- triglycerides combines with protein
- phospholipid and cholesterol also packaged
- chylomicron exits via exocytosis

epithelial cell
- on the basolateral side
- lymph vessels called lacteals
- take up chylomicron
- secrete into bloodstream

Question 13

What Happens Once Chylomicrons Lose their Triglycerides?

Answer 13

left with LDL
= Low density lipoproteins
- back to liver for storage
- secrete when losing fat

Question 14

What are the 2 Types of Lipoproteins and Implications?

Answer 14

LDL
- Low Density Lipoprotiens
- high risk
- large amount of cholesterol and cholesteryl esters
- deliver cholesterol to peripheral tissues

HLD
- High Density Lipoproteins
- less risk
- remove excess cholesterol and take back to liver

Question 15

What Implications does Cholesterol have on Blood Pressure? (5)

Answer 15

• cholesterol forms plaque on interior of blood vessels
• harder and calcified
• narrows lume
• less blood flow
• high blood pressure

Question 16

How is Hyperlipidaemia Treated?

Answer 16

Statins
- inhibit HMG-CoA Reductase
- mimics the natural substrate and bind to enzyme
- inhibit cholesterol synthesis in the liver

Question 17

Define Atheroma

Answer 17

the accumulation of intracellular and extracellular lipid in the initma of large and medium sized arteries

Question 18

Is Atheroma Common? When does it Begin? It is Reversible? What can Reduce it?

Answer 18

very common
early lesions begin 20/3s
not reversible but drugs can stabilise
- calcium antagonists can reduce foam cell production

Question 19

Define Atherosclerosis

Answer 19

• thickening and hardening of arterial walls
• increases blood pressure
• consequence of atheroma
• in response chronic endothelial cell damage

Question 20

How does Atheroma lead to Atherosclerosis, then Lead to Thrombus

Answer 20

• atheroma ruptures
• chronic endothelial cell injury
• endothelial dysfunction
• LDL’s enter intima
• intimal macrophages engulf lipids
• fatty streaks = early lesion
• continued accumulation of lipid on smooth muscle wall
• raised yellow lipid plaque
• fibrous cap forms over lipid core - calcifies
• ulceration - surface breaks
• predisposition of thrombus formation

Question 21

What are Risk Factors for Atherosclerosis (6)

Answer 21

diet
hypertension
diabetes
obesity
smoking
sedentary lifestyle

Question 22

What is the Primary and Secondary Prevention for Atherosclerosis

Answer 22

primary - risk factor modification
- delaying formation in those who have never suffered a serious complication

secondary - regular medication
- prevent reccurent events in high risk patients

Question 23

How Does Atheroma Affect Different Parts of the Body? - aorta, coronary arteries, internal carotid arteries, iliac and popliteal artery

Answer 23

aorta
- weaken wall
- dilation = aortic aneurysm
- risk of rupture

corny artery
- narrow arterial lumen
- reduced blood flow
- angina - myocardial ischemia
- thrombus formation over plaque
- lumen occlusion
- myocardial infarction

internal carotid artery
- reduced blood flow
- embolism builds up and travels to the brain
- blocks blood flow
- if transient = ischemia, if stroke = infarction

iliac and popliteal artery
- arterial lumen narrows
- reduced blood flow
- ischaemia - intermittent claudication and gangrene

Question 24

Draw out Fatty Acid Synthesis

Question 25

State 4 Essential Fatty Acids

Answer 25

a-linolenic acid
linoleic acid
y-linoleic acid
arachidonic acid

Question 26

Why is arachidonic acid important?

Answer 26

derivatives: prostaglandins, thromboxanes in inflammation etc

Question 27

How Is arachidonic acid found?

Answer 27

20:4 = 20C with 4 Double bonds

Question 28

Where are Double Bonds Only Formed in Fatty Acids

Answer 28

Δ4,5,6,9

• can’t go past 9th carbon

Question 29

Draw Lipolysis

Question 30

Draw Beta-Oxidation

Answer 30

aceyl-CoA into Acetyl CoA

Question 31

How is Lipase Activated and Inactivated?

Answer 31

activate
- protein kinase phosphorylates ATP to ADP, activates cAMP

inactivate
- dephosphorylated by phosphatase

Question 32

How can you Transport Liver Acetly CoA in the blood?

Answer 32

ketone bodies

Question 33

Define Ketosis

Answer 33

normal physiological response to fasting or low carb diet

Question 34

Define Ketoacidosis

Answer 34

abnormal high levels of ketone bodies in the blood

Question 35

How are Ketone Bodies used?

Answer 35

if in fasting or uncontrolled type 1 diabetes, as an alternative source of energy

• uses oxaloacetate to produce glucose
• TCA slows down
• Acetyl CoA increases
• fatty acids use it making more ketone bodes

Question 36

What is the Effect of Diabetic Ketoacidosis?

Answer 36

excess glucose - large osmotic loss, dehydrated kidney

excess ketone bodies - reduces pH, coma and death

Question 37

How does Diabetic Ketoacidosis Work?

Answer 37

BGC is high, cant take up no glucose
- no insulin
- liver thinks its fasting
- gluconeogenesis
- more glucose in the blood
- b-oxidation - more ketone bodies