3B: Exchange of Substances Flashcards
What is Digestion?
The process in which large molecules are hydrolysed by enzymes into small molecules which can be absorbed and assimilated
What is Physical Breakdown?
breaking up large pieces of food into small making the food ingestible (larger SA)
What is Chemical Breakdown?
hydrolyses large insoluble molecules into smaller ones carries out by enzymes
How many enzymes are needed to hydrolyse a large molecule?
> 1
What are Carbohydrases?
Enzymes that hydrolyse carbohydrates into monosaccharides
What are Lipases?
Enzymes that hydrolyse Lipids (fats and oils) into glycerol and fatty acids
What are Proteases?
Enzymes that hydrolyse Proteins into Amino Acids
Where is Amylase produced?
in the mouth and pancreas
What does amylase do?
Hydrolyse alternate glyosidic bonds of starch to produce disaccharides of maltose
What does Maltase do?
Hydrolyse maltose
Where is maltase produced?
Ileum Lining, membrane-bound
Why is saliva slightly alkaline?
to counteract any acid produced by bacteria and food to maintain a neutral pH for amylase
What does Sucrase do?
Hydrolyse sucrose into glucose and fructose
What does lactase do?
Hydrolyse lactose into glucose and galactose
Where are lipases produced?
Pancreas
What is a monoglyceride?
a glycerol molecule with a fatty acid attached
What are micelles?
tiny droplets of lipids that are water soluble
What emulsifies lipids and where is it produced?
Bile salts produced by the liver
What is emulsification?
the process where bile salts break up lipids into micelles
Why are bile salts needed to emulsify lipids?
to increase their surface area to speed up the hydrolysis reaction
What are endopeptidases?
enzymes that hydrolyse peptide bonds between amino acids in the central region
Where are endopeptidases produced?
the ileum
What are exopeptidases?
enzymes that hydrolyse pepide bonds on terminal amino acids
What are dipeptidases?
enzymes that hydrolyse peptide bonds in dipeptides
How is the Ileum structure adapted for absoption?
thin walls lined with epithelial cells
a rich network of capillaries
villi and microvilli to increase surface area
constant muscle contraction to maintain concentration gradient
How are amino acids and monosaccharides absorbed?
facilitated diffusion and co transport
How are Lipids absorbed?
- emulsified into micelles by bile salts
- micelles release fatty acids, glycerol, and monoglycerides to diffuse into the epithelial cells lining the ileum
- the ER processes and packages the products into triglycerides
- the golgi apparatis packages these into chylomicrons
- chylomicrons enter blood stream via lacteals (exocytosis)
Give examples of mechanical digestion
emulsification, chewing, oesophagus/small intestine contractions
Give examples of chemical digestion
hydrolysis catalysed by enzymes
What do micelles do?
Deliver fatty acids, glycerol and monoglycerides to the epithelial cells of the ileum by releasing them
What is the Lymphatic System?
the system chich the lymph (excess tissue fluid) travels through after exiting th capillary, before rejoining the blood
What is Transpiration?
the movement of water through the xylem vessels from evaporation of water from the leaves
Describe the process of transpiration
- water evaporates from mesophyll cells due to the heat from the sun
- water molecules for hydrogen bonds causing cohesion
- water forms continuous unbroken columns across mesophyll cells + down xylem
- water evaporated from the mesophyll layers cause more water molecules to be drawn up
Give evidence for cohestion theory
- trunk diameter changes due to rate of transpiration
- broken xylem vessels- air enters and flower droops
- broken xylem vessels- water doesn’t leak out (although root pressure)
Describe the structure pf Xylem
dead, hollow lignin tubes with no wall ends
What is the purpose of the Lymphatic System?
Drain excess tissue fluid that doesn’t get reabsorbed into the blood
Describe the process of tissue fluid production in relation to capillaries, venules, and the lymphatic system
‘Tissue fluid’ leaks out of the gaps between the cells lining the capillaries due to the hydrostatic pressure from the heart
The water potential of the ‘blood’ decreases as water is the main component that leaks out
It fills the gaps around cells
The hydrostatic pressure in the venules is lower than the capillaries
Water moves via osmosis back into the venules down the water potential gradient, as well as other substances moving via diffusion
Excess tissue fluid is taken in by the lymphatic capillary, which is closed ended so it can only move forward.
Lymphatic capillaries have valvues to maintain unidirectional flow
The lymph moves through the lymphqtic system and reenters the blood flow near where the cardinal veins enter the heart
