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
What is the function of the oesophagus?
It is a muscular tube that conencts the mouth and stomach
What is mechanical digestion?
Where teeth bite and chew food, cutting it into smaller pieces that have a large surface area so enzymes can act on food more quickly and stomach muscles
What parts of your body break down foods using enzymes?
The mouth, the stomach and the duodenum.
What are the three classes of enzymes and what do they each break down?
Carbohydrases act on carbohydrates. Proteases act on proteins. Lipases break down lipids.
What enzyme does saliva contain?
Amylase.
What are examples of carbohydrases and what digestive action does it have and where?
Amylase turns starch to maltose, it is produced by the salivary glands to act in the mouth and in the pancreas to act in the small intestine. Maltase turns maltose into glucose, produced in the small intestine and acts in the small intestine.
Examples of proteases and what they do
Pepsin turns proteins into peptides. Tripsin turns proteins into peptides. Peptidases turns peptides into amino acids.
How can pepsin work in the stomach?
Though the stomach is very acidic pepsin has an optimum pH of about 2.
Function of the large intestine?
To absorb most of the remaining water from the contents, leaving a semi solid waste material called faeces.
Why do humans need food?
To supply with fuel and to provide materials for growth and repair.
What should a balanced diet include?
Appopriate portions of carbohydrate, protein, lipids, vitamins, minerals, water an dietary fibre
What are proteins made up of?
Amino acids
What are lipids made up of?
Fatty acids and glycerol
What chemical elements make up carbohydrates?
Carbon, hydrogen and oxygen
What chemical elements make up protein?
Carbon, hydrogen, oxygen and nitrogen
What chemical elements make up lipids?
Carbon, hydrogen and oxygen
What are proteins made up of?
Long chains of amino acids which all contain carbon, hydrogen, nitrogen and oxygen atoms
What are lipids made up of?
Fatty acids and glycerol
Sources of carbohydrates
Pasta, rice, sugar, fruit
Sources of protein
Meat, fish, cheese, milk
Sources of lipids
Butter, oily fish, olive oil, nuts
Sources of the minerals calcium and iron
Calcium - dairy products, fish, vegetables
Iron - red meat, eggs, spinach
Sources of vitamin A, C and D
Vitamin A - carrots, liver, butter
Vitamin C - fresh fruit and vegetables
Vitamin D - found in fish liver oils, also made in skin in sunlight
What is the function of carbohydrates?
Supplying cells with energy
What is the function of proteins?
Needed for growth and repair of tissue, and to provide energy in emergencies
What is the function of lipids?
Essential to cellular structure, provides energy, acts as an energy store, provides insulation
What unit is energy content measured in?
Kilojoules
What is the function of calcium?
Making teeth and bones
What is the function of Vitamin A?
It makes a chemical in the retina and protects the surface of the eye - helps to improve vision
Keeps your skin and hair healthy
What is the function of Vitamin C?
Sticks together cells lining surfaces such as the mouth - prevents scurvy
What is the function of Vitamin D?
Helps bones absorb calcium
What is the function of iron?
Needed to make haemoglobin in the red blood cells, helps carry oxygen
What is the function of water?
Almost every bodily function relies on water - we need a constant supply to replace water lost through urinating, breathing and sweating
Sources of water
food and drink
What is the function of dietary fibre?
Aids the movement of food though the gut (peristalsis)
Source of dietary fibre
wholemeal bread
Why does peristalsis occur?
To squeeze balls of food through the gut otherwise it would get clogged up with food
What is the calcuation for the amount of energy in the food?
1) calculate the amount of energy in joules
energy in food (J) = mass of water (g) x temperature change of water x 4.2
2) calculate the amount of energy in joules per gram:
energy per gram of food (J/g) = energy in food (J) / mass of food (g)
How can the accuracy of the calorimetry experiment be increased?
Quite a bit of energy released from burning is lost to the surroundings - insulating the boiling tube e.g. with foil, would minimise heat loss and keep more energy in the water making your results more accurate
What is ingestion?
Putting food or drink into your mouth
What is chemical digestion?
Enzymes and bile
What is the function of the mouth?
1) Salivary glands in the mouth produce amylase enzyme in the saliva
2) Teeth break down food mechanically
Describe the structure of carbohydrates
Starch and glycogen are large, complex carbohydrates, which are made up of many smaller units from simple sugar (e.g. glucose or maltose molecules) joined together in a long chain
What is the general structure of carbohydrates, proteins and lipids?
large molecules made up from smaller basic units
What is the role of enzymes?
They act as biological catalysts in metabolic reactions
