Digestive system Flashcards
What is digestion?
The breakdown of large, insoluble food molecules into smaller soluble molecules to be absorbed into the bloodstream
Function of the mouth/salivary glands
Where food enters and is broken down mechanically by teeth or chemically by amylase produced in salivary glands
Function of the oesophagus
Moves food to the stomach
Function of the stomach
Where digestion continues, churns the food mechanically as it is a muscular organ = turn into a liquid to increase surface area digestion
produces enzymes for digestion of proteins
Produces HCl to aid enzyme digestion
Pancreas
Produces enzymes that are taken to the duodenum (top of small intestine)
CONTINUE digestion of starch and protein and START the digestion of lipids
Function of the liver
Produces bile
Function of the gallbladder
Stores bile before releasing it into the duodenum (top of small intestine)
Function of the duodenum
Where food is mixed with enzymes + bile and neutralised to be broken down even further
Function of the small intestine
Where nutrients are absorbed into the blood via villi
Continue digestion of protein and lipids
Function of the large intestine
Where water is reabsorbed
Function of the rectum
Where faeces is stored
Function of the anus
Where faeces leaves the body
Adaptations of the stomach
Secretes HCl to kill off any harmful bacteria
Produces enzymes to speed up digestion, also they work best in acidic conditions
Stomach muscles tissues that can contract rapidly to churn food, contain lots of mitochondria to get energy
Adaptations of the small intestine
Contains microvilli for a larger surface area so more diffusion happens at the same time
Thin walls with capillaries on the outside so a shorter diffusion distance into the bloodstream
Good blood supply for higher diffusion gradient
Adaptations of oesophagus
Can expand and contract (muscular) to let food and liquid pass to the stomach
What are digestive enzymes?
Biological catalysts that speed up the rate of digestion of large molecules into smaller ones without changing the reaction
How do enzymes work in digestion?
Through the catabolic lock and key method
An enzyme’s active site and food molecule are complementary in shape: only works on that specific molecule.
Attached together then large molecule broken down
Then repeat
Amylase
Produced in salivary glands and pancreas
Breaks down starch to simple sugars
Needs slightly acidic to neutral
Protease
Produced in stomach, pancreas and small intestine
Breaks down protein to amino acids
Both acidic and alkali proteases
Lipase
Produced in pancreas
Breaks fats into fatty acids and glycerol
Pepsin
Produced in stomach but works in duodenum
Breaks protein into peptides
A more neutral-alkali optimum pH so bile works alongside it
Denaturing
When an enzymes active side changes and can’t work on that substrate anymore
Due to the temperature or pH getting too high
Factors effecting how effective the enzyme is
Temperature
pH levels
Pressure
Surface area
Enzyme and substrate concentration
Optimum
All enzymes have an exact pH and temperature where its activity is highest
If it goes above the enzyme denatures
How does Bile help digestion?
Enzymes in the duodenum’s optimum pH is alkali
After being in the stomach the food molecules are acidic
Bile neutralises the small intestine to be less acidic to help the enzymes
How does bile help lipase?
Emulsifies (breaks down) fat globules into fat droplets to give a larger surface area for lipase to work on.
Enzyme rate of reaction
Amount of product formed / reactant used
———————————————————————
Time
What are enzymes made out of?
Proteins that are made up of chains of amino acids
Where is amylase produced?
Salivary glands
Pancreas
Where is protease produced?
Pancreas
Stomach
Small intestine
Where is lipase produced?
Pancreas
What are the main nutrients in foods?
Carbohydrates (starch)
Protein
Lipids (fats)
Where are digested molecules absorbed into the bloodstream?
In the small intestine via diffusion and active transport
How does the small intestine have a large surface area?
Is 5m long
Contains villi (many shapes) that are divided into microvilli
How does the small intestine having a good blood supply help?
It can rapidly remove away the products of digestion
To increase the concentration gradient
How does the small intestine having a thin membrane help digestion?
Shortens the diffusion path
If molecules aren’t absorbed by diffusion how are they absorbed in the small intestine?
Via active transport
How are enzymes structured?
Made out of proteins (amino acids)
Have a groove (cut) called active site where substrate attaches to
Where is protease produced?
Stomach
Pancras
Small intestine
How does digestion of proteins work?
Proteins = chains of amino acids
Protease breaks it into singular amino acids to be absorbed into bloodstream
Once absorbed in cells = chains again then formed into human proteins
How does digestion of starch work?
Starch = chain of glucose
Amylase breaks it into simple sugars (no chain)
Where is amylase found?
Salivary glands
Pancreas
How does digestion of lipids work?
Lipid = glycerol + 3 fatty acids
Lipase breaks it down into glycerol and fatty acids (no longer attached)
With help of bile
Where is lipase found?
Pancreas
Small intestine
How does bile work?
Emulsifies lipid globule into smaller lipid droplets
Increases the surface area
Increases rate of breakdown helping lipase
Also neutralises stomach acid as it is alkaline to increase rate of lipid digestion as lipase works best in neutral conditions
How does temperature effect enzyme activity?
Increasing temp = enzyme moves faster so more collisions per second between substrate and active site
At certain temp it acts at fastest possible rate (optimum)
Beyond that activity falls to 0
Because the shape of active site has changed = no longer fits substrate = denatured = no activity
How does pH effect enzyme activity?
Has the optimum at a more specific pH, any above or below that and it will begin to denature
Much less gradual than temperature
If the temperature of an enzyme is too low, has it denatured?
No
In terms of temperature it only denatures if it exceeds ABOVE the optimum not below
Unlike pH, denatures above or below
What are the products of digestion used for?
Build new carbohydrates, lipids and proteins
Some of the glucose for respiration
What is the optimum temperature for most human enzymes?
37°C
Because it’s our average body temperature
