Week 10 - Gastrointestinal System Flashcards
What are the daily recommendations for macronutrient consumption ? (Eat well plate)
1/3 carbohydrates (bread, pasta, rice etc)
1/3 fruit and vegetables
1/3 oils+spread, proteins and dairy
Functions for the following:
a. Carbohydrates
b. Proteins
c. Fat
d. Vitamins
e. Minerals
f. Fibres
g. Water
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.HydrationWhat is the structure of fats and give examples of other dietary fats? (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
What are the sources of dietary fats? Saturated, unsaturated, cholesterol
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
What are the issues of too much fat?
Issues:
Atherosclerosis
Obesity
What are the 9 essential amino acids ?
Phenylalanine Valine Tryptophan Threonine Isoleucine Methionine Histidine Leucine Lysine
Examples of monosaccharides
Glucose
Fructose
Galactose
Examples of disaccharides
Sucrose: glucose + fructose
Maltose: glucose + glucose
Lactose:
Glucose + galactose
Examples of polysaccharides
Starch
- amylose linear -alpha (1-4) glycosidic bond)
- amylopectin branched - alpha (1-4 )glycosidic bond )
What are the effects of fibre in the body ?
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
What are the effects of too much carbohydrates?
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
What do the macromolecules break down to ?
Carbohydrates- monosaccharides
Protein - amino acids
Fat - fatty acids
What is digestion?
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
Where are saliva secreted from. And what is it’s function ?
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.
What does an down of carbohydrates in the mouth produce ?
Maltotriose
Maltose
Glucose
Alpha-limit dextrin
What occurs in the stomach ?
Start of protein digestion which chief cells which secrete pepsinogen and
Parietal cells that secrete hydrochloride acid
This activates pepsin and denatures proteins.
What is endopeptidase?
It is pepsin which cleaves peptide bonds within the polypeptide chain to produce smaller oligopeptide .
What are zymogens ?
These are inactive precursors which can become activated by cleaving of or a few specific peptide bonds.
Eg.
Pepsinogen to pepsin
What is the function of the pancreas?
The pancreas had two functions:
Exocrine:
Pancreatic juices and alkali secretions (accessory organ)
Endocrine: secretions of insulin and glucagon
What pancreatic secretions are released as zymogens ?
Trypsin Chymotrysin Caboxypeptidase Elastase Phospholipasse
What pancreatic secretions are released in their active form ?
Alpha-amylase
Lipase
Ribonuclease
Deoxyribonuclease
What is the function of the liver ?
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
What is bile synthesised from and it’s function ?
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
What are the parts of the small intestines and their functions ?
Duodenum
- mixes secretion from pancreas, and liver to food
- neutralise acid
- further digestion
- absorption
Jejunum
- complete breakdown
- nutrient absorption
Ileum
-nutrient absorption
What enzyme is used to activated pancreatic zymogens ?
Enterokinase activated tryinogen to trypsin and then releases a cascades of other enzymes to be released
What enzymes are int he small intestines?
The small intestines have brush border enzymes which is an integral part of the membrane
- peptidases
- lactase
- sucrose
- maltase
What digestion occurs in the mouth ?
For carbs, proteins and fats
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
What occurs in the stomach to regards of carbs, fats and proteins ?
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
What occurs in the duodenum to carbs, fats and proteins ?
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
What are the different forms of absorption ?
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
What is the structure of a micelle ?
Polar head group on the outside (hydrophilic)
And non polar hydrocarbons chain (hydrophobic)
Hydrophobic core( fatty acids, and 2-monoacylglycerol)
What is chylomicrons ?
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.
How does absorption take place for carbs?
Glucose and galactose - secondary active transport with sodium - then falciliated diffusion to blood
Fructose - facilitated diffusion to blood
How does absorption take place for proteins ?
Amino acids- active transport with sodium - diffusion to blood
Di and tripeptides - active transport which H+ - diffusion to blood
How does absorption take place for fats ?
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
