Week 10 - Gastrointestinal System

Question 1

What are the daily recommendations for macronutrient consumption ? (Eat well plate)

Answer 1

1/3 carbohydrates (bread, pasta, rice etc)
1/3 fruit and vegetables
1/3 oils+spread, proteins and dairy

Question 2

Functions for the following:

a. Carbohydrates
b. Proteins
c. Fat
d. Vitamins
e. Minerals
f. Fibres
g. Water

Answer 2

A. Energy source 
B. Repair and growth 
C. Long tern energy store; insulation 
D: A: Vision
    C: antioxidant 
    D: Ca absorption 
E: Ca: bone mineralisation
    Fe: oxygen transport 
F. Effective bowel function 
G.Hydration

Question 3

What is the structure of fats and give examples of other dietary fats? (3)

Answer 3

Fats:
Triglycerides = glycerol and 3 fatty acids
Cholesterol: base of bile salts and plasma membrane
Phospholipids: 2 fatty acid chain added to glycerol and phosphate group

Question 4

What are the sources of dietary fats? Saturated, unsaturated, cholesterol

Answer 4

Saturated: mainly animal foods eg. Meat, fat, butter, cream

Unsaturated: mainly plants eg. Olive and rape seed

Cholesterol:
Plants and animals eg. Dairy products, palm chess and coconut oil

Question 5

What are the issues of too much fat?

Answer 5

Issues:

Atherosclerosis
Obesity

Question 6

What are the 9 essential amino acids ?

Answer 6

Phenylalanine
Valine 
Tryptophan
Threonine 
Isoleucine 
Methionine 
Histidine 
Leucine 
Lysine

Question 7

Examples of monosaccharides

Answer 7

Glucose
Fructose
Galactose

Question 8

Examples of disaccharides

Answer 8

Sucrose: glucose + fructose

Maltose: glucose + glucose

Lactose:
Glucose + galactose

Question 9

Examples of polysaccharides

Answer 9

Starch

• amylose linear -alpha (1-4) glycosidic bond)
• amylopectin branched - alpha (1-4 )glycosidic bond )

Question 10

What are the effects of fibre in the body ?

Answer 10

Cellulose from plants can’t be digested as the body doesn’t have the enzyme to digest the beta- 1-4 glycosidic bond, so therefore it is used to aid bowel digestion

Question 11

What are the effects of too much carbohydrates?

Answer 11

Too much can cause weight gain which occurs when dietary energy intake exceeds energy expenditure

Negatively effects general health and physiology = obesity

Typically men eat 2500kcal/day and women eat 2000kcal/day

Question 12

What do the macromolecules break down to ?

Answer 12

Carbohydrates- monosaccharides

Protein - amino acids

Fat - fatty acids

Question 13

What is digestion?

Answer 13

It is the process in which food is broken down into components simple enough to be absorbed in the intestine.

And this is carried out by secretions in the mouth, stomach, pancreas and enterocytes

Question 14

Where are saliva secreted from. And what is it’s function ?

Answer 14

Produced by parotid, submandibular and sublingual salivary glands

Function:
Moisten food
Start digestion of carbohydrates with alpha-amylase. And minor digestion of proteins with lingual lipase.

Question 15

What does an down of carbohydrates in the mouth produce ?

Answer 15

Maltotriose
Maltose
Glucose
Alpha-limit dextrin

Question 16

What occurs in the stomach ?

Answer 16

Start of protein digestion which chief cells which secrete pepsinogen and
Parietal cells that secrete hydrochloride acid

This activates pepsin and denatures proteins.

Question 17

What is endopeptidase?

Answer 17

It is pepsin which cleaves peptide bonds within the polypeptide chain to produce smaller oligopeptide .

Question 18

What are zymogens ?

Answer 18

These are inactive precursors which can become activated by cleaving of or a few specific peptide bonds.

Eg.
Pepsinogen to pepsin

Question 19

What is the function of the pancreas?

Answer 19

The pancreas had two functions:

Exocrine:
Pancreatic juices and alkali secretions (accessory organ)

Endocrine: secretions of insulin and glucagon

Question 20

What pancreatic secretions are released as zymogens ?

Answer 20

Trypsin 
Chymotrysin 
Caboxypeptidase
Elastase 
Phospholipasse

Question 21

What pancreatic secretions are released in their active form ?

Answer 21

Alpha-amylase
Lipase
Ribonuclease
Deoxyribonuclease

Question 22

What is the function of the liver ?

Answer 22

It produces a s secretes bile, which is stored in TPS concentrate form in the gallbladder, and released in the duodenum after a meal.
Emulsification of fats occur. It also aids in absorption of fats by forming micelles

Question 23

What is bile synthesised from and it’s function ?

Answer 23

It is synthesised from cholesterol, chalice acid and chenideoxycholic acid

It is conjugated to an amino acid, and is amphipathic which means it’s both hydrophilic and hydrophobic

Functions:
Emulsification of lipids
Solubilisation and transport of lipids in aqueous environment

Question 24

What are the parts of the small intestines and their functions ?

Answer 24

Duodenum

• mixes secretion from pancreas, and liver to food
• neutralise acid
• further digestion
• absorption

Jejunum

• complete breakdown
• nutrient absorption

Ileum
-nutrient absorption

Question 25

What enzyme is used to activated pancreatic zymogens ?

Answer 25

Enterokinase activated tryinogen to trypsin and then releases a cascades of other enzymes to be released

Question 26

What enzymes are int he small intestines?

Answer 26

The small intestines have brush border enzymes which is an integral part of the membrane

• peptidases
• lactase
• sucrose
• maltase

Question 27

What digestion occurs in the mouth ?

For carbs, proteins and fats

Answer 27

The mouth turns the food to a bolus by mastication.

Carbohydrates: Starch broken down by a-amylase to maltotriose, maltose and a-limit dextrin

Proteins:
Nothing

Lipids:
Lingual lipase, but minor contribution

Question 28

What occurs in the stomach to regards of carbs, fats and proteins ?

Answer 28

Churning in the stomach occurs to turn the food into chyme

Carbohydrates: nothing

Proteins: HCl denatures proteins and activates pepsin (endopeptidase that cleaves proteins to smaller peptides)

Lipids: gastric lipase present but minor contribution

Question 29

What occurs in the duodenum to carbs, fats and proteins ?

Answer 29

Chyme mixes which pancreatic juices and bile, making it slight alkaline

Carbohydrates:
Alpha-amylas further digestion, and brushborder disaccharides turn to monosaccharides

Proteins:
Cleaved by trypsin and other enzymes to produce smaller peptides and dipeptides, brush border peptides produce amino acids

Lipids:
Pancreatic lipase digest lipid to monoglycerides and fatty acids. Phospholipase digest phospholipids to lysolecithin and fatty acids

Question 30

What are the different forms of absorption ?

Answer 30

Passive diffusion : slow and goes down concentration gradient

facilitated transport: slight faster, involves membrane carrier and it is controllable

Active transport: uses energy, it is fast, uses the membrane carrier and is controllable

Question 31

What is the structure of a micelle ?

Answer 31

Polar head group on the outside (hydrophilic)

And non polar hydrocarbons chain (hydrophobic)

Hydrophobic core( fatty acids, and 2-monoacylglycerol)

Question 32

What is chylomicrons ?

Answer 32

If fatty acids are smaller than 12 carbons they go straight to portal blood.

If larger, the triglycerides reform to produce a structure called a chylomicrons.

These are 76-100nm in diameter and are secreted into lymphatics via lacteals.

Question 33

How does absorption take place for carbs?

Answer 33

Glucose and galactose - secondary active transport with sodium - then falciliated diffusion to blood

Fructose - facilitated diffusion to blood

Question 34

How does absorption take place for proteins ?

Answer 34

Amino acids- active transport with sodium - diffusion to blood

Di and tripeptides - active transport which H+ - diffusion to blood

Question 35

How does absorption take place for fats ?

Answer 35

Small short chain fatty acids- simple diffusion - diffusion to blood

Micelle - splits into 2 - large chain fatty acid and monoglycerides- simple diffusion - triglyceride reform to chylomicron - goes to lacteal - thoracic duct and enter junction of left internal jugular and left subclavian vein