Digestion Flashcards
What is the name of the tube that passes through all humans and mammals for absorbing energy from food?
The alimentary canal.
What is ingestion?
Taking food in through the mouth and swallowing.
What is digestion?
Breaking down large insoluble molecules in food into smaller pieces (physical digestion) and smaller, soluble molecules (chemical digestion).
What is absorption?
The movement of small soluble molecules out of the gut and into the blood by diffusion and active transport.
What is egestion?
Passing out undigested food through the anus.
What is assimilation?
Building larger biological molecules from the small soluble molecules, in all cells.
What is the first structure in the alimentary canal?
The mouth.
Where does ingestion take place?
The mouth.
What two types of digestion happen in the mouth?
Mechanical and chemical.
How is food mechanically digested in the mouth and what 2 things does this help with?
Food is broken up into smaller pieces by chewing. This increases the surface area for enzymes and also prevents discomfort when swallowing.
How is food chemically digested in the mouth?
Saliva is released into the mouth by the salivary glands. It makes the food easier to swallow and also contains the enzyme amylase. Amylase breaks down the starch to maltose.
What happens to the amylase in the mouth when it reaches the stomach? Why?
It denatures and stops working because it works best at neutral pH.
What happens to food before it is swallowed?
It is shaped into a ball by the tongue and moved towards the back of the mouth.
What is the ball of food called just before swallowing?
A bolus.
What is the epiglottis?
A flap which blocks the food from entering the trachea.
What process pushes food down from the mouth to the stomach?
Peristalsis.
What 2 sets of muscles work when during peristalsis?
Circular and longitudinal muscles.
How do the circular and longitudinal muscles work during peristalsis?
The circular muscles contract behind the bolus, pushing it along. When the longitudinal muscles contract they make the oesophagus wider.
What is the end product of the digestion of carbohydrates?
Smaller carbohydrate molecules ie glucose.
What is the end product of the digestion of proteins?
Amino acids.
What is the end product of the digestion of lipids?
Glycerol + 3 fatty acids.
Where is amylase found?
The mouth and the duodenum.
Where is pepsin found?
The stomach.
Where is lipase found?
The duodenum.
Where is trypsin found?
The duodenum.
Where is maltase found?
The duodenum.
Where is peptidase found?
The duodenum.
What secretes the enzyme amylase?
The salivary glands and pancreas and ileum
What secretes the enzyme pepsin?
Gastric glands in the stomach wall.
What secretes the enzyme lipase?
The pancreas.
What secretes the enzyme trypsin?
The pancreas.
What secretes the enzyme maltase?
The lining of the duodenum.
What secretes the enzyme peptidase?
The lining of the duodenum.
What does amylase do?
Converts starch to maltose.
What does pepsin do?
Converts proteins to peptides.
What does lipase do?
Converts lipids to fatty acids + glycerol.
What does trypsin do?
Converts proteins to peptides.
What does maltase do?
Converts maltose to glucose.
What does peptidase do?
Converts peptides to amino acids.
Why does the stomach wall contract?
To mix the contents of the stomach, maximising contact between enzymes and food.
Where is hydrochloric acid released from?
Gastric glands.
What prevents the hydrochloric acid in our stomachs from burning through?
A mucus lining.
What are 2 functions of the hydrochloric acid in our stomachs?
-Help the enzyme pepsin work at its optimum condition (acidic pH)
-Kills many bacteria and fungi which may be present in the food we eat.
What 2 processes take place in the duodenum?
Digestion and absorption.
Where is the final site of chemical digestion?
The duodenum.
What organ makes several enzymes and secretes them into the duodenum?
The pancreas.
What does the large intestine consist of?
The colon and rectum.
What is the function of the colon?
It is the site for all reabsorption of water.
What is the function of the rectum?
Stores faeces.
What are the 3 digestive enzyme groups?
1) Carbohydrases - carbohydrates to smaller molecules like glucose
2) Proteases - proteins to amino acids
3) Lipases - lipids to glycerol and 3 fatty acids
The duodenum wall contains gland which secretes which enzymes?
Maltase and peptidase.
Where is bile produced and stored?
Produced by the liver and stored in the gall bladder.
What are the 2 functions of bile?
- Neutralises stomach acid as enzymes in duodenum work best at pH7-8
- Emulsifies lipids - breaks large droplets into smaller droplets, increasing surface area for lipase to digest the fats
What 2 processes take place in the small intestine?
Digestion and absorption.
Where is the final site of chemical digestion?
The duodenum.
Which 3 enzymes are secreted into the duodenum by the pancreas?
-Trypsin
-Amylase
-Lipase
What is the ileum covered with?
Finger like projections called villi.
What 2 ways are small soluble molecules absorbed by the vili?
By diffusion and active transport.
Give 3 ways the rate of diffusion is increased in the villi:
1) Large surface area - folding of ileum, villi and microvilli all increase this
2) Short diffusion distance - the villi walls are one cell thick
3) High concentration gradient - provided by capillary network and lacteals removing absorbed molecules
