B3 Organisation and the digestive system Flashcards
Enzymes that break down substances are…
Catabolic
Enzymes that build substances from substrates are…
Anabolic
Explain what we mean by the ‘lock and key theory’
The ‘lock and key theory’ is an idea we use to explain the way enzymes work.
It suggests that the 3D shape of the active site of the enzyme is like a lock and can breakdown only one type of substrate just like the lock can only be opened by one shape of key.
Give another example of a food rich in fat.
There are many foods rich in food. Ice cream is obviously one but also;
butter, oil, lard, ghee, margarine, avacado, oily fish, nuts, peanut butter, sausages, chocolate, cream, greek yoghurt, flaky pastry and any fried food.
Give an example of a food which is a good source of carbohydrate.
There are lots of examples of a foods which are good sources of carbohydrates. You are correct if you suggested one of bread, rice, potatoes, crisps, chips, cakes, biscuits, sweets, pasta, fruits, fizzy drinks, syrup and honey.
How is the small intestine adapted for fast absorption of food?
The small intestine is adapted for fast absorption of food in 4 ways
- large surface area (villi)
- good blood supply
- wet
- thin wall
What is an organ system?
Organ systems are a collection of different organs which do a particular job in the body.
e.g. cadiovascular/ circulatory system (heart and blood)
digestive system (food breakdown and absorption)
the respiratory system (gaseous exchange)
Name a food rich in protein.
There are lots of great foods rich in protein. You are right if you said one of meat, fish, eggs, milk, cheese, yoghurt, nuts, beans, lentils, chickpeas, quinoa, whey protein, tofu, soya or quorn.
What are organs?
Organs are collections of different types of tissues with a special job to do
e.g. heart pumps blood, stomach digests food, liver breakes down chemicals
What do carbohydrases do?
Carbohydrases are digestive enzymes which break down carbohydrates to simple sugars.
What do lipases do?
Lipases break down lipids (fats) to glycerol and fatty acids.
What do our bodies use carbohydrates for?
Our bodies use carbohydrates for fuel for respiration.
Starch is a slow release fuel and and sugars such as glucose give us fuel quickly.
What do our bodies use fats for?
Our bodies use fats in many ways. You are right if you suggested one of
- as slow release energy,
- to store extra energy,
- to build cell membranes,
- to make hormones
- for insulation.
What do our bodies use proteins for?
Our bodies use proteins for growth and repair.
What do proteases do?
Proteases break down proteins to amino acids.
What does glandular tissue do?
Glandular tissue is made of lots of secretory cells. They release enzymes and hormones.
What happens in the digestive sytem?
The digestive system is an organ system in which food is digested and absorbed.
What 3 things happen in your small intestine?
3 things happen in your small intestine,
- bile is added to the food to help break fats into smaller droplets
- more enzymes (protease and lipase) are added to finish breaking down food
- the tiny food particles made cross the gut wall into the blood stream
What is a tissue?
(Not something you blow your nose on!)
A tissue is a group of cells with a similar structure and function.
What is amylase, what does it do and where does it do it?
Amylase is a carbohydrase enzyme which breaks down starch in the mouth and small intestine.
What is an enzyme?
Enzymes are biological catalysts. They are proteins which speed up specific reactions in living organisms.
What is an optimum pH or temperature of an enzyme?
An optimum pH or temperature of an enzyme is the pH or temp at which it works best/fastest.
What is the acid secreted by the stomach?
The acid secreted by the stomach is hydrochloric (HCl).
It makes about 3 litres of it every day!
What is the job of digestive enzymes?
Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream.
What is the optimum pH for the activity of amylase?
The optimum pH for the activity of amylase is pH7
What is the pH of bile?
Bile has an alkaline pH of about 8 to neutralise hydrochloric acid from the stomach.
What is the test for lipids?
Ethanol goes from colourless to cloudy white
What is the test for protein?
If protein is present the Biuret reagent goes from light blue to purple.
What is the test for starch?
If starch is present yellow iodine turns blue black.
What is the test for sugars?
If sugars are present the Benedict’s test turns from light blue to orange (via yellow and green) on heating
What is the name of the 2 processes which move digested food from the small intestine into the blood?
- Active transport (which uses up energy) e.g Glucose
- Diffusion (slower but needs no energy)
Where is bile made and stored?
Bile is made in the liver and stored in the gall bladder.
What type of food group do lipase enzymes break down?
(Where do they do this?)
Lipase enzymes break down lipids to fatty acids & glycerol.
(They do this in the pancreas and small intestine.)
What type of food group do amylase enzymes break down (and where do they do it) ?
Amylase enzymes break down starch to sugars.
They are made in the salivary glands, pancreas and small intestine.
What type of food group do protease enzymes break down?
Where are they made?
Protease enzymes break down proteins to amino acids.
They are made in the stomach, pancreas and small intestine.
Which part of an enzyme molecule is involved in chemical reactions?
The active site is the part of an enzyme molecule involved in chemical reactions
Why do we call enzymes biological catalysts?
We call enzymes biological catalysts because they are made of protein and speed up reactions.
Why do we have to digest our food?
Food is made up of large insoluble molecules which need breaking down before we can absorb and use them.
Why does the optimum (best) pH of digestive enzymes vary?
The optimum pH of digestive enzymes depends on the part of the digestive system where each enzyme works. Enzymes which work in the stomach have to work at a very low pH because the stomach is very acidic. The enzymes in the small intestine have to work at an alkaline pH.
Why don’t enzymes work above 40OC?
Enzymes stop working above 40OC because they are proteins and protein denatures (changes shape) above this temperature. This changes the shape of the active site so they cannot speed up reactions any more.
Why is bile very important in the digestion of fat?
Bile emulsifies fat to form small droplets which increases the surface area. The large surface area allows the lipase enzyme to breakdown fat quickly.
