Macronutrients

Question 1

3 types of lipid

Answer 1

Triglycerides
Sterols
Phospholipids

Question 2

Triglyceride structure

Answer 2

3 fatty acid chains bonded to a glycerol backbone

Question 3

Key features of saturated fats

Answer 3

Solid at room temperature
Saturated carbon structure
Resistant to oxidation due to stabile nature

Question 4

Key features of polyunsaturated fats

Answer 4

Liquid at room temperature
Susceptible to spoilage
Can be hydrogenated to trans fats to protect against oxidation, causing them to behave like saturated fats

Question 5

Sterols

Answer 5

Starting material for bile acids, sex hormones, adrenal hormones and vitamin D
Structural component of cell membranes

Question 6

Endogenous cholesterol

Answer 6

The liver produces 800 - 1500 mg of cholesterol a day

Question 7

Exogenous cholesterol

Answer 7

Cholesterol we take in from dietary animal products

Question 8

Plant sterols importance

Answer 8

Can interfere with cholesterol absorption

Question 9

Fat digestion - mouth

Answer 9

Salivary glands release lingual lipase

Question 10

Fat digestion - stomach

Answer 10

Lingual lipase initiates lipid digestion. Muscle contractions disperse fat into smaller droplets which are then exposed to gastric lipase causing some digestion.

Question 11

Fat digestion - small intestine

Answer 11

Acidic chyme neutralised in duodenum by bicarbonate from pancreatic juice and bile. Bile salts emulsify fat, turning it into small droplets with a large surface area.

Question 12

3 major emulsifying agents

Answer 12

Bile salts
Lecithin
2-monoacylglycerol

Question 13

Lipid digestion in small intestine enzymes

Answer 13

Pancreatic lipase
Pancreatic non-specific esterase
Phospholipase A2

Question 14

Pancreatic lipase

Answer 14

Digests triglycerides to glycerol and free fatty acids

Requires colipase from pancreas to become active

Question 15

Pancreatic non-specific esterase

Answer 15

Removes fatty acids from a variety of non-triglycerides and non-phospholipids

Question 16

Phospholipase A2

Answer 16

Removes fatty acid from 2-position on phospholipid

Question 17

Milk lipase

Answer 17

Important in breast fed human neonate nutrition. Only becomes active in small intestine because it is bile-dependent

Question 18

Lecithin

Answer 18

Phospholipid present in bile and food membranes

Question 19

2-monoacylglycerol

Answer 19

Breakdown product from triglyceride

Question 20

Bile salts are stored in the:

Answer 20

Gallbladder

Question 21

Bile salt movement

Answer 21

Made by liver, stored in gallbladder
CCK stimulates bile release
Reabsorbed in terminal ileum of small intestine
Reused via enterohepatic circulation

Question 22

4 major roles of bile salts in fat digestion

Answer 22

Emulsification
Removal of lipid digestion products from emulsified fat droplets
Cofactors required by lipases for activity
Aids absorption of fat products across enterocyte membrane

Question 23

Chylomicron

Answer 23

Package of lipid digestion, cholesterol, fat soluble vitamins and apolipoproteins. Transport system pass from lacteal in intestinal epithelium to the lymph and eventually the bloodstream.

Question 24

Chylomicron components are removed:

Answer 24

During circulation as a result of TG hydrolysis

Question 25

Chylomicron repackaging

Answer 25

As components are removed from the chylomicron they become smaller and denser Remnants endocytosed by liver Remaining lipid repackaged into lipoprotein complexes to leave liver

Question 26

Types of lipoproteins

Answer 26

``` Chylomicron VLDL IDL LDL HDL ```

Question 27

VLDLs are composed primarily of:

Answer 27

Triglycerides

Question 28

LDLs are composed primarily of:

Answer 28

Cholesterol

Question 29

HDLs are composed primarily of:

Answer 29

Protein

Question 30

Foam cells

Answer 30

Residual fractions of LDL bind low affinity scavenger receptors on macrophages. Macrophages phagocytose LDL forming a fatty aggregate called a foam cell which deposit themselves in atherosclerotic plaques

Question 31

Key roles of proteins

Answer 31

``` Building material Hormones Enzymes Immune function Fluid balance Transporters Antibodies Energy ```

Question 32

9 essential amino acids

Answer 32

``` Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine ```

Question 33

11 non-essential amino acids

Answer 33

``` Alanine Arginine Asparagine Aspartic acid Cysteine Glutamic acid Glutamine Glycine Proline Serine Tyrosine ```

Question 34

2 semi-essential amino acids

Answer 34

Histidine and arginine

Question 35

AMDR

Answer 35

Acceptable macronutrient distribution rate

Question 36

24 specific organic compounds we require for health

Answer 36

9 essential amino acids 2 fatty acids 13 vitamins

Question 37

Two factors that influence protein quality

Answer 37

Protein digestibility | Amino acid composition

Question 38

Protein digestibility

Answer 38

High in animal protein, lower in plant protein Higher digestibility means we can gain more amino acids from it through digestion Can depend on source and also what we eat with the protein

Question 39

Amino acid composition

Answer 39

Essential amino acids are vital for energy and synthesis of other amino acids. A lack of just 1 EAA limits the action of other EAAs even if they are in abundance - it becomes the limiting factor.

Question 40

Process of protein digestion

Answer 40

1) Mastication - involves moistening protein rich foods into a bolus 2) HCl denatures food proteins and stimulates pepsinogen ---> pepsin cleavage 3) Pepsin catalyses hydrolysis of proteins into smaller polypeptides and amino acids 4) Pancreatic endopeptidases secreted as inactive precursors in small intestine. When activated by enteropeptidase they break polypeptides down into tripeptides, dipeptides and amino acids 5) Remaining peptides break down further into amino acids

Question 41

Enzyme mediated protein digestion in small intestine

Answer 41

Pancreatic endopeptidases secreted as inactive precursors which are activated by enteropeptidase (which activates trypsinogen first, followed by the other proteases) Activated endopeptidases cleave polypeptides into peptides and amino acids which are further cleaved into single amino acids by tripeptidases, dipeptidases and aminopeptidases Pancreatic juice contains procarboxypeptidases which are activated into carboxypeptidases (A and B) which break down the carbon ends of peptides once activated in the lumen of the small intestine

Question 42

3 pancreatic endopeptidases and their inactive precursors

Answer 42

Trypsin - trypsinogen Chymotrypsin - chymotrypsinogen Elastase - pancreatic elastase

Question 43

Protein absorption

Answer 43

Sodium linked amino acid transporters and sodium linked peptide transporters on enterocyte in the small intestine which are pulled across by the diffusion of Na+. At the same time, Na+/K+ antiporters are moving ions across the enterocyte/blood border to power the Na+ linked symporters

Question 44

3 key hormones in the protein digestion process

Answer 44

Gastrin (regulates acid secretion in stomach) | Secretin and CCK (regulate pancreatic secretions)

Question 45

Nitrogen balance

Answer 45

A state of equilibrium where the rate of nitrogen intake is equal to the rate of nitrogen expenditure

Question 46

Factors causing negative nitrogen balance (degradation > synthesis)

Answer 46

``` Decreased short term protein intake Starvation Injury, trauma and surgery Illness, infection and burns Cancers Lactation ```

Question 47

Factors causing positive nitrogen balance (synthesis > degradation)

Answer 47

Increased short term protein intake Growth Pregnancy Recovery from illness or trauma

Question 48

Protein Energy Malnutrition

Answer 48

A condition often seen in poor communities characterised by wasted limbs but protruding bellies due to fluid retention around the liver as a result of low protein

Question 49

3 types of nitrogen excretion

Answer 49

Urea Uric acid Creatinine

Question 50

Types of carbohydrate

Answer 50

Complex (starch and dietary fibre) | Simple (sugars)

Question 51

Energy that we use most readily

Answer 51

Carbohydrate

Question 52

Energy that we store the most

Answer 52

Fat

Question 53

Carbohydrate that makes up plant cell walls

Answer 53

Cellulose

Question 54

2 basic compounds that make up a carbohydrate

Answer 54

Ketone and aldehyde

Question 55

3 key monosaccharides

Answer 55

Glucose Galactose Fructose

Question 56

3 key disaccharides

Answer 56

Lactose Maltose Sucrose

Question 57

Sucrose is made of:

Answer 57

Glucose and fructose

Question 58

Lactose is made of:

Answer 58

Glucose and galactose

Question 59

Maltose is made of:

Answer 59

Glucose and glucose

Question 60

Storage polysaccharide in plants

Answer 60

Starch (amylose and amylopectin)

Question 61

Non-starch polysaccharides

Answer 61

Glucose links can't be broken so they aren't digested | Dietary fibre - can be soluble or insoluble

Question 62

Glycogen

Answer 62

Storage carbohydrate in animals. Stored in liver and muscles, broken down when energy required for rapid glucose release

Question 63

Soluble fibre

Answer 63

Dissolves in water to form a gel like substance and is easily digested by bacteria in the colon Commonly found in legumes, psyllium and fruits and vegetables

Question 64

Insoluble fibre

Answer 64

Not dissolvable in water and is not broken down as easily by bacteria Responsible for bulking feces for easy passage Commonly found in whole grains and vegetables

Question 65

Carbohydrate digestion

Answer 65

1) Salivary alpha amylase hydrolyses starch 2) Breakdown of oligosaccharides to monosaccharides at brush border 3) Monosaccharides absorbed at enterocyte brush border. Non-degraded disaccharides continue into colon where bacteria feed and can cause inflammation 4) Glucose and galactose absorbed by active transport 5) Fructose and galactose isomerised to glucose

Question 66

High glycaemic index

Answer 66

Blood sugar peaks when lots of simple sugars are consumed. Insulin also peaks to force blood sugar down. Feel hungry due to low blood sugar, eat more sugar causing another spike and so on.

Question 67

Low glycaemic index

Answer 67

Lower insulin response means you feel full for longer and don't need to eat as often so less blood sugar and insulin spikes. Increased exercise increase glucose utilisation so not as much insulin needed to push sugar spikes down.