Food and Digestion Flashcards
What does the process of breaking down food involve?
Ingestion, digestion, absorption, assimilation and egestion
What is the role of bile? Where is it produced and stored?
It neutralises stomach acid and emulsifies fats
Produced by the liver and stored in the gall bladder
How does the structure of the villus help absorption of the products of difestion in the small intestine?
There’s a really big surface area for absorption, because the walls of the small intestine are covered in millions and millions of tiny projections called villi
Each cell on the surface of a villus also has its own microvilli - little projections that increase the surface area even more
Villi have a single permeable layer of surface cells (one cell thick) and a very good blood supply (network of capillaries) to assist quick absorption
What is digestion?
The breakdown of large insoluble molecules to smaller soluble ones
What is the alimentary canal?
A muscular tube which runs from your mouth to your anus and all the organs
How does food move through your gut?
By peristalsis - waves of muscular contraction
What is the function of the stomach?
It pummels the food with its muscular walls
It produces the protease enzymes, pepsin
It produces hydrochloric acid to kill bacteria and to give the right pH for pepsin (pH2 - acidic)
What is the function of the small intestine?
It produces proteases, amylase, maltase and lipase enzymes for digestion
This is where nutrients are absorbed out of the alimentary canal into the body
What is the function of the pancreas?
Produces protease, amylase and lipase enzymes for digestion
How would you test for glucose?
Add Benedict’s reagent (which is blue) to a sample and heat it.
Make sure the solution doesn’t boil.
If the test’s positive it will form a coloured precipitate
The colour of precipitate goes from blue to green to yellow to orange to brick red
The higher the concentration of glucose, the further the colour change goes - you can use this to compare the amount of glucose in different solutions
How would you test for starch?
Iodine solution will turn from orange brown to blue-black if starch is present
Test for protein?
Biuret reagent will turn from light blue to lilac
What is assimilation?
When digested molecules have been absorbed, they’re moved into body cells and are used to build new parts of cells
What are faeces?
Semi solid waste material stored in the rectum and ejected from the anus
What is the difference between excretions and egestion?
Egestion is the process of getting rid of unused waste materials
Excretion is the removal of metabolic chemical waste
What are the breakdown products of carbohydrase?
Glucose
What are the breakdown products in protease?
Amino acids
What are the breakdown products of lipase?
Fatty acids and glycerol
What is absorption?
The products of digestion (food molecules) are absorbed into your bloodstream in the small intestine.
What is egestion?
All of the undigested food forms faeces which then leaves the body through the anus
How is the ileum adapted to absorb digested food?
The surface area is covered in vlili, which in turn are covered in microvilli. This increases the surface area. Small intestine is folded to increase surface area. Outer surface is just one cell thick. Each villus has a capillary so a good blood supply. Each villus has a lacteal to transport fatty acids and glycerol.
What does amylase do? Where is this enzyme produced? where does it act?
Turn starch to maltose.
This is excreted by the salivary glands and acts in the mouth OR is produced by the panreas and acts in the small intestine.
What does maltase do? Where is this enzyme produced? where does it act?
Turns maltose to glucose.
Produced in the walls of the small intestine and acts in the small intestine.
What do proteases do? Where is this enzyme produced? where does it act?
Turn proteins to amino acids. Pepsin is produced in the stomach wall and acts in the stomach.
Others are produced in the pancreas and work in the small intestine.
What does lipase do? Where is this enzyme produced? Where does it act?
Turns lipids into fatty acids and glycerol.
It is produced in the pancreas and acts in the small intestine.
Describe an experiement to measure the energy content of food (calorimetry)
Food can be burnt to see how much energy it contains
1) weigh a small amount of dry food (peanuts/crisps) and put it on a needle
2) add 25cm3 to a boiling tube held with a clamp
3) measure the temperature of the water and using a Bunsen burner set fire to the food
4) hold the burning food under the boiling tube until it goes out
5) continue to relight the food and burn it until it will no longer relight
Then measure the temperature of the water again
How do energy requirements vary in different people?
The amount of energy each person needs is different. There are 3 things it depends on:
ACTIVITY LEVEL: Active people need more energy than people who sit around all day
AGE:children and teenagers need more energy than older people. They need energy to grow
PREGNANCY: pregnant women need more energy than other women as they’ve got to provide the energy their babies need to develop
Name four types of sugars
fructose
sucrose
glucose
lactose
Name a protein deficiency disease
kwashiorkor
