Digestion Flashcards
What is the function (job) of carbohydrates in the body?
Act as a source of energy
Which foods are major sources of carbohydrates?
Potatoes, rice, pasta, cereals
What is the function (job) of proteins in the body?
Used for growth and repair
Which foods are major sources of proteins?
Meat, eggs, cheese, beans, nuts and seeds
What is the main function (job) of lipids?
- Used as a source of energy
- Make up the cell membranes
Which foods are major sources of lipids?
Butter, meat, plant oils, oily fish, nuts and seeds
Name three polymers of glucose.
- Starch
- Cellulose
- Glycogen
What happens to glucose molecules once absorbed by the body?
- Used for respiration
- Reassembled into glycogen and stored in the liver
What are proteins made up of?
Amino acids
What happens to excess amino acids?
They are broken down in the liver
What are lipids made up of?
Fatty acids and glycerol
Describe a positive food test result for sugars.
Benedict’s solution turns from blue to orange-brown when heated
Describe a positive food test result for starch.
Iodine turns from yellow to blue-black
Describe a positive food test result for proteins.
Biuret solution turns from blue to purple.
Describe a positive emulsion test result for lipids.
Ethanol turns cloudy.
What is the function (job) of the small intestine?
Absorption of simple sugars, amino acids, fatty acids and glycerol
What is the function (job) of the large intestine?
Absorption of water
What are villi?
Folds in the wall of the small intestine that provide a large surface area for absorption
What are microvillli?
Smaller folds on the surface of villi, which are folds found on the surface of the instestinal lining
How is the small intestine adapted for absorption?
- Very large surface area due to villi and microvilli
- Large blood supply
What are enzymes?
Biological catalysts that speed up chemical reactions
What is an active site?
The part of an enzyme that a specific substrate can fit into
What is a substrate?
A substance that fits into an enzyme
Describe the 3 steps to enzyme action.
- Substrate attaches to the active site of the enzyme.
- The enzyme catalyses and breaks down the substrate.
- The products are released from the active site.
How does temperature affect enzyme action?
- At low temperatures, few collisions with enzymes and substrate
- 37C optimum temperature for enzymes, work best
- Higher temperatures can denature enzymes
What two things can denature enzymes?
- Extreme temperatures
- Extreme pH
What is the optimum pH of amylase?
6.8
What is the optimum pH of the stomach protease pepsin?
1.5 - 2.0
What is the optimum pH of the pancreatic protease trypsin?
7.5 - 8.0
What is the function of carbohydrases?
To break down carbohydrates into simple sugars
What is the function of amylase?
To break down starch into maltose or glucose
What is the function of proteases?
To break down proteins into amino acids
What is the function of lipases?
To break down lipids into fatty acids and glycerol
Where is bile produced?
In the liver
What role does bile play in digestion of lipids?
Bile emulsifies lipids, breaking them up into tiny droplets and giving them a larger surface area over which lipase can work.
How does bile help to produce an optimum pH for pancreatic enzymes?
It contains sodium hydrogencarbonate, which is an alkali. This neutralises the stomach acid, creating an optimum pH for pancreatic enzymes.
Where is bile stored and concentrated?
In the gallbladder
Where is bile stored and concentrated?
In the gallbladder
