Macronutrients

Question 1

What are Fats?

Answer 1

Insoluble/poorly soluble in water but soluble in organic solvents

Question 2

What is the basic structure of lipids?

Answer 2

Over 90% dietary fats are triacylglycerols

Triacylglycerols = glycerol + 3 fatty acids

Fatty acid chains can be:

• Saturated (no double bonds)
• Monounsaturated (1 double bond)
• Polyunsaturated (> 1 double bond)

Question 3

What are fats when they are in RT?

Answer 3

Liquid = OILS

Question 4

Which type of fatty acids are high in the following oils:

• vegetable oil
• fish oil

Answer 4

Veg. oil = high in PUFAs (low in SFAs)

Omega6 PUFAs predominate

Fish oil = high in SFAs (low in PUFAs)

Omega3 PUFAs predominate

Question 5

What is the difference between omega6 + omega3?

Answer 5

Omega6 = 1^st double bond 6 carbons from methyl terminal

Omega3 = 1^st double bond 3 carbons from methyl terminal

Question 6

Fat is one type of lipid in diet.

What are the other types?

Answer 6

Phospholipids

• e.g. phosphatidylcholine
• structural lipids (in membranes)

Sterols

• e.g. cholesterol
• membranes
• precursor to bile salts
• precursor to steroid hormones
• only found in animal fats
• Plants have instead phytosterols than cholesterol*
• Which inhibit cholesterol uptake from GIT*

Question 7

Why do we need essential fatty acids?

Answer 7

They are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them

Humans cannot insert a double bond between any of the the first 7 carbons of FAs

Required for e.g. prostaglandins, leukotrienes

Question 8

What is cholesterol?

Answer 8

Primary component of cell membrane

Substrated for bile acid synthesis, steroid hormones + vitamin D

Dietary cholesterol has little influence on blood cholesterol

The more dietary cholesterol we eat, the less bile reabsorbed from GIT

Question 9

How are cholesterol + fats (TAGs) transported around the body?

Answer 9

Via lipoproteins

Types:

• VLDL = (TAG rich) transport TAG to adipose/muscles
• LDL = (cholesterol rich) transport cholesterol from liver to cells
• HDL = removal of excess cholesterol from peripheral tissues to the liver

Question 10

What happens when we have a raised LDL-cholesterol?

Answer 10

Taken up by macrophages to from foam cells

Foam cells accumulate in blood vessel walls

Blood vessel walls harden to cause atherosclerosis

Question 11

How much protein do we require?

Answer 11

Reference nutrient intake says 0.75g/kg body weight per day

a 60kg women would need 45kg body weight

Increased requirements during growth, for repair (post-surgery), preganancy, lactation etc

If obese, using body weight overestimate protein needs

a BMI of more than 40 need 65% of RNI protein value

Question 12

What is high biological value proteins? (HBV)

Answer 12

Proteins that contain all the essential amino acids in sufficient amounts of protein synthesis

e.g. animal proteins

Question 13

What is low biological value proteins? (LBV)

Answer 13

Lack some essential amino acids

e. g. plants
* Good plant protein sources include beans, nuts + seeds*

Question 14

What are carbohydrates?

Answer 14

Main energy source

Surplus stored as glycogen in liver + skeletal muscle

Question 15

What are the different type of carbohydrates?

Answer 15

Sugars

Polysaccharide (starch)

Fibre (non-starch polysaccharide)

Insoluble NSP (wholegrains + nuts)

Soluble NSP