Enzymes and Digestion Flashcards
Basic steps in the digestion of food
Ingestion Digestion Absorption Assimilation Egestion
Ingestion
Food is taken into the alimentary canal/Buccal cavity
Digestion
Large, insoluble molecules are broken down to small molecules
Absorption
The small molecules are absorbed into the blood
Egestion
Food, which could not be digested or absorbed is removed from the body via the rectum
Molecules that can enter the blood
Vitamins
Minerals
Simple sugars/glucose
Molecules that need to be broken down
Starch
Protein
Fats
Humans can not digest cellulose and passes through the system relatively unchanged
Mechanical digestion
This is breaking food down without the aid of any chemicals
There are two major sites:
-The mouth
-Bile
In the mouth the teeth break down food into small chunks
The action of bile emulsifies fats creating a greater surface area for enzymes to work on
Chemical digestion
This method results in the breakage of bonds holding large molecules together. This results in smaller more soluble compounds that can enter the blood.
Enzymes are responsible for this
The mouth/ Buccal cavity
Food is broken down mechanical by teeth
Starch is chemically digested into maltose via the action of salivary amylase
The salvia moistens the food to allow is to pass easily down the oesophagus
Oesophagus
A muscular tube leading from the mouth to the stomach. The muscles help move chewed food along by a process of peristalsis.
This is how food is moved throughout the alimentary canal
Stomach
J shape muscular bag
The inner lining of stomach is lined with gastric pits
Gastric pits produce gastric juice
Types,of digestion in the stomach
Chemical digestion through the use of enzymes PEPSIN
Mechanical digestion via churning of the muscular walls
This ensures food and gastric juice is mixed
The small intestine
Has two major roles:
- digestion
- absorption
Digestion takes place in the duodenum
Absorption takes place in large intestine
Bile
Produced in the liver and stored in the gall bladder
Contains mineral salts and bile salts and no enzymes
Mineral salts in bile
These have an alkaline pH and are involved in neutralising the acid chyme
The enzymes of the small intestine can only work efficiently at a neutral pH
Bile salts in bile
These emulsify lipids, this involves breaking large fat globules into much smaller droplets with an increased surface area
Intestinal juice
Includes:
Mineral salts
Mucus
Enzymes
Mucus in intestinal juice
Lubricates intestinal walls allowing easier movement and also protects the intestinal wall from self digestion
Enzymes found in intestinal juice
Protease Amylase Maltese Lactase Sucrose
Pancreatic juice
Leaf shape organ situated below stomach
Includes: Mineral salts Protease enzymes Pancreatic amylase Lipase enzyme
Protease enzyme in pancreatic juice
Breaks down proteins onto polypeptides
Breaks down polypeptides into amino acids
Pancreatic amylase in pancreatic juice
This completes the digestion of starch begun in the mouth
Lipase enzyme in pancreatic juice
This involves the chemical break down of the lips droplets produced by the action of bile
Food in the ileum
Food molecules have been completely digested into simple molecules that can gross the gut wall and enter the bloodstream
Features of the ileum for efficient absorption
Long: food will spend a long time passing through (6m)
Highly folded: increases surface area
Villi: increase surface area and thin permeable walls
Blood supply: maintain concentration gradients in blood stream
How molecules are absorbed through villi
Substances enter through capillaries
Includes:
Fatty acids
Glycerol enters lacteals which carry lymph
These fatty substances enter the blood in the vein. They are carried to the liver where they will either be stored or used
Enzyme definition
Protein molecules that act as biological catalysts increasing the rate of biological reactions
Lock and key model
Each enzyme is specific to one molecule called the substrate. This will only react to the uniquely shaped pocket on the surface of the enzyme known as the active site.
Factors that can affect the rate of the enzyme
Temperature
pH
Enzyme concentration
The affect of temperature on an enzyme
Low/optimum/high
Low temperature:
The reacting molecules move more slowly and less likely to collide and react less often. Rates of reaction are low at low temperatures
Optimum temperature:
As temperature increases so does the movement of molecules. They collide more often and so the rate increases. (30-40)
High temperatures:
Above optimum level the rate of the enzyme drops suddenly. This is because the active sure has be denatured and doesn’t recognise its substrate. This is an irreversible change. (60)
Affects of pH on an enzyme
It can also affect the shape of an enzymes active site
Pepsin acts in acidic conditions in the stomach
Amylase acts in neutral slightly alkaline conditions
Affects of enzyme concentration on an enzyme
As a enzyme concentration increases so does the rate of reaction. This is because there is a greater chance of collision between the enzyme and the substrate. Eventually the rate will level off as the substrate gets used up. If no more substrate is available the rate will drop as the enzyme has nothing to react with.
Commercial uses of enzyme
One of the biggest uses of enzymes is in the manufacture of biological washing powders
Reabsorption in the colon
All digestive juices contain high levels of water
Much of the the water passes into the colon with the in digested food and fibre.
This changes the liquid food into semi solid faeces.
Colon has a large surface area
Without this process we would become rapidly dehydrated
The content of faeces
Indigestible food
Dead cells from the lining of the intestine
Bile pigments
