What is :
digestion ?
Digestion is the process where large (insoluble) molecules are broken down into smaller (soluble) molecules to be absorbed into the bloodstream
-digestion involves mechanical and chemical digestion
What is :
a) what is mechanical digestion also known as?
b) what is Mechanical Digestion ?
c) + example
-a) also known as physical digestion
-b) breaks food into smaller pieces without changing the substance itself
c) e.g.
- chewing with teeth ,
-churning in the stomach ,
-bile breaking fat into droplets
what is :
a) what is Chemical digestion ?
b) + example
a) uses ENZYMES to change food into smaller soluble molecules
e.g. amylase —-> starch to sugars
Define: (memorise!)
- mechanical digestion
-chemical digestion
MECHANICAL: breaks food into smaller pieces without changing the substance itself
CHEMICAL: uses ENZYMES to change food into smaller soluble molecules
which of the following involve mechanical or chemical digestion or both ?
-mouth
-stomach
-small intestine
-mouth B
-stomach B
-small intestine B (muscular movements)
Give 3 reasons why villi are useful :
1 . villi provide the small intestine with a LARGE SURFACE AREA so more digested food can be absorbed into the bloodstream
2.villi also have a GOOD BLOOD SUPPLY(maintains steep conc. gradient )
- their linings are ONE CELL THICK (short diffusion pathway –> increases the rate of diffusion)
NOTE: all of these increase the rate of diffusion
-probably just go back to the diffusion adaptation flashcards as they are better
Give the enzyme that is found in the mouth
-name
-breaks down…..
-into……
Name : Amylase /Carbohydrase
Beaks down : starch /carbohydrate
Into : sugar (glucose)
Give the enzyme that is found in the stomach
-name
-breaks down…..
-into……
Name : protease (pepsin)
Beaks down : proteins
Into : amino acids
Give the enzymes that are found in the small intestine
-name
-breaks down…..
-into……
Name : protease (trypsin)
Beaks down : proteins
Into : amino acids
- Name : carbohydrase
Beaks down : starch /carbohydrates
Into : sugars (glucose)
3.
Name : lipase
Beaks down : lipids
Into : fatty acids + glycerol
How does digestion occur in the :
MOUTH
-food is chewed by the teeth
- food is chopped into smaller pieces which increase the surface area
- this means that the enzymes ,amylase can react with food and break it down more quickly
-saliva also mixes with food ,making it easier to swallow
How does digestion occur in the :
OESOPHAGUS
food moves down the oesophagus by muscular contractions by a process called peristalsis
How does digestion occur in the :
STOMACH
- Food enters the stomach where it is churned and mixed with hydrochloric acid
-The acidic conditions kill microorganisms and provide the optimum pH for enzymes
-Protease enzymes break down proteins into amino acids
How does digestion occur in the :
small intestine
- the food now enters the small intestine where bile from the liver ( stored in the gall bladder) is added to emulsify fats into droplets
- pancreatic enzymes also enter the small intestine to continue breaking down carbohydrates , proteins and lipids (fats) into molecules small enough to be absorbed into the bloodstream
(include what they break it down to)
-the wall of the small intestine is lined with villi which absorb the nutrients into the bloodstream
How does digestion occur in the :
large intestine
the remaining undigested material passes into the large intestine where water is absorbed and waste is formed into faeces
How does digestion occur in the :
rectum and anus
finally the faeces are stored in the rectum and expelled through the anus
why is acid released in the stomach?
hydrochloric acid provides optimum pH (2) so that the enzyme, protease can work effectively and break down protein into amino acids + kills microorganisms
why is it important food is broken down into the smallest size chunks possible?
-provides a larger SURFACE AREA so enzymes can work faster
(for enzymes to react with and break down food , so enzymes can work faster )
-so the NUTRIENTS can be absorbed through the wall of the small intestine
(through the small intestine wall and pass into the bloodstream)
what is meant by the term ‘emulsification’
the process where bile breaks large fat globules into smaller droplets to provide larger surface area for enzymes to work on
What is the roll of this tissue in the stomach:
MUSCULAR TISSUE
to churn and mix the food and digestive juices of the stomach together
What is the roll of this tissue in the stomach:
GLANDULAR TISSUE
produce digestive juices /enzymes to break down food
What is the roll of this tissue in the stomach:
EPITHELIAL TISSUE
covers the inside and outside of the stomach and forms a barrier of mucus so the strong acid does not digest the stomach wall
