Gasexchange And Digestion Flashcards
2 features of unicellular organisms
Have large SA:V
Short diffusion distance
2 features on multicellular organisms
Have a small SA:V
Diffusion distance is large
Why do smaller animals have a lower metabolic rate?
Because they have a greater SA:V but they lose heat more easily
Explain why oxygen uptake is a measure of metabolic rate in organisms
Oxygen used in respiration which provides energy/ ATP
What do the salivary glands produce and help to digest
Produces amylase in saliva
Breaks glycosidic bonds in starch to form maltose
What does the pancreas produce and help to digest
Produces pancreatic amylase which is released into the small intestine
And it helps to break down glycosidic bonds to hydrolyse starch to form maltose
What does the small intestine produce and help to break down
Produces membrane bound disaccharides in the cell membrane of epithelial cells
Breaks glycosidic bonds or hydrolyse disaccharides into monosaccharides
Describe the role of enzymes of the digestive system in the complete breakdown of starch
Amylase, in pancreas, hydrolyses starch into maltose
Maltose is then hydrolysed into glucose by the enzyme maltase
Amylase is secreted by the salivary gland in the mouth which hydrolyses starch into maltose
Pancreas secretes amylase to further hydrolyse starch into maltose
Alpha glucose is co-transported into epithelial cells and into the blood
Describe the processes involved in the absorption of the products of starch digestion
Glucose move in with sodium into epithelial cells
Ions and glucose molecules are co-transported into the epithelial cell via facilitated diffusion
Glucose molecules diffuse across the epithelial cell & enter the capillary at the other end of the cell via facilitated diffusion
The low concentration of sodium ions is maintained by actively transporting sodium out of the epithelial cells and into the blood.
What are peptidases/ proteases
Enzymes which breakdown proteins in a series of hydrolysis reactions
Role of an endopeptidase
Hydrolyse peptide bonds within a protein to create smaller polypeptide chains
Create for terminal ends for exopeptidases to work on
Role of exopeptidases
Hydrolyse terminal peptide bonds to remove individual amino acids and create smaller polypeptide chains
Role of dipeptidases
(Type of exopeptidase)
Located on the membrane of epithelial cells lining small intestine
- work on dipeptides to hydrolyse the peptide bond holding them together
Describe the roles of micelles in the absorption of fats into the cells lining the ileum
Micelles include bile salts and fatty acids
Makes the fatty acids more soluble in water
Releases fatty acids into the lining of the ileum
Maintains a higher concentration of fatty acids to the lining of the ileum
Fatty acids are absorbed by diffusion
How are sodium ions involves in the absorption of amino acids
Used in co-transport
What are lipases
Enzymes which hydrolyse the ester bonds in triglycerides to form fatty acids and monoglycerides
Where are bile salts stored and produced and released
Produced by the liver and stored in the gall bladder which releases them into the small intestine
Role of bile salts
Help to break down large fat globules by emulsifying them into smaller droplets, helping to speed up the action of lipases by increasing the SA of lipids that can be exposed to the enzyme
What happens once the lipid is broken down by lipase
The monoglycerides and fatty acids stay attached to the bile salts & form micelles
What are the steps in absorption of lipids (5 points)
1 micelles hit epithelial cells and breakdown allowing monoglycerides and fatty acids to diffuse across the membrane because they re lipid soluble
2 monoglycerides and fatty acids are transported to the ER where they recombine to form triglycerides again
3 inside the Golgi they bind with cholesterol and proteins and are packages to form chylomicrons
4 chylomicrons travel in a vesicle to the cell membrane and are exocytosed from epithelial cell
5- chylomicrons enter lacteals transporting them away from the small intestine to muscle tissue
Suggest how chylomicrons leave the epithelial cell
Travel in a vesicle to the cell membrane then are exocytosised out of the cell as the size is too large to leave by other methods
Explain the advantages of lipid droplet and micelle formation
Droplets increase surface area for enzyme action so there’s faster hydrolysis of lipids
Micelles carry fatty acids and glycerol
How are amino acids transported from the lumen of the ileum into the blood
Majority of amino acids move from the lumen to epithelial cells via co transport using sodium ions
When the concentration of amino acids is greater in the lumen than the epithelial cells, they can move via facilitated diffusion
Facilitated diffusion into the blood
3 products of the digestion of lipids by lipase
Monoglycerides, fatty acids and glycerol
What do chylomicrons enter rather than capillaries
Lacteals- found alongside the capillaries
Why do Tracheoles have thin walls
Shorter DD of gases into cells
Why are Tracheoles highly branched
Increases SA for gas exchange
Why is there fluid in the ends of the trachea where it joins tissue
- gas exchange from air to liquid occurs in the Tracheole which allows gases to diffuse to tissue quicker
- tracheal fluid can be withdrawn into the body fluid to increase the SA of the Tracheole exposed to air
Benefit of muscles pumping body and forcing air in/out
Maintains concentration gradient for gases
Benefit of having spiracles closed / not open all the time
Prevents water loss and keeps organism waterproof
What does pumping of the insects body muscles do
Raises pressure in the body and forces air our of the spiracles down the concentration gradient
What are the folds on the gill filaments called and what do they do
Lamellae - further increase the SA of the gills and have lots of capillaries and a thin layer of cells
What occurs at the lamella
Gas exchange - counter-current flow
What is countercurrent flow
Water and blood flow over and through the lamellae in opposite directions to each other
Blood always flows next to water that has a higher oxygen concentration so diffusion happens along the full length of the lamellae
The blood absorbs more and more oxygen as it moves along
Why do fish have thin epithelium / walls of lamellae
Shortened DD of gases from water to blood
Why do fish have ventilation by operculum
Ensures constant fresh water flow over gills to replace lost oxygen and maintains a steep concentration gradient
Ventilation in fish
Mouth opens, operculum shuts
Water enters cavity due to decreased pressure
Mouth closes, operculum opens
Increased pressure
Forces water over gills
Role of pleural fluid
Lubricates the lungs and allows lungs to expand with the chest during inhalation
Function of cartilage in trachea and bronchi
Provides stranger by holding the airway open
Prevents collapse of airway when air pressure falls
Function of surfactant that coats the surface of the lungs
Phospholipid layer which maintains moisture but reduces surface tension to stop alveoli collapsing when air pressure falls
Function of smooth muscle lining trachea and bronchioles
Can contract to constrict airways
Function of goblet cells
Secrete mucus which traps particles of dust and bacteria which are breathed into the lungs
Function of ciliated epithelial cells
Beat regularly to move mucus up the airway towards the mouth to be removed
Helps keep airways clear and prevent infections
Contains lots of mitochondria to provide energy requires to move cilia
Role of elastin lining airways and alveoli
Allows lung tissue to stretch when breathing in and filling up the lungs
Allows alveoli to return to original shape after exhaling
Role of squamous epithelium
Gives a short DD pathway for oxygen and carbon dioxide in the alveoli
What happens to guard cells when plants are hydrated
The guard cells become turgid keeping pores open
What happens to hard cells when plants are dehydrated
Guard cells become flaccid causing hole to close
What are xerophytes
Plants adapted to a dry habitat
Why do xerophystes have sunken stomata in pits
Creates local humidity and decreases exposure to air currents
What does the presence of hairs in xerophytes create
Local humidity and decreases exposure to air currents by reducing flow around stomata
What does a think waxy cuticle of xerophytes allow
Makes plant more impermeable to water as water cant pass through or leave
What does a small sa of a leaf allow
Reduced SA for evaporation
What does stomata on inside of rolled leaf create
Local humidity and decreases exposure to air currents because water vapour evaporates into air spaces rather than in the atmosphere
