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Features of Specialised Exchange ?
Large SA:Vol ratio → increases diffusion rate
Thin walls → shortens diffusion pathway
Extensive blood supply → maintains concentration gradient
Selectively Permeable → controls what is exchanged
How does gas exchange occur in insects
Air enters the tracheal system through open spiracles in the exoskeleton.
Air moves into tracheae and diffuses into tracheoles.
Oxygen dissolves in water in tracheal fluid and diffuses from tracheoles into body cells.
Carbon dioxide diffuses out of body cells into the tracheoles.
Air is then carried back to the spiracles via the tracheae and released from the body.
Components of digestion
Salivary Glands → Contain amylase → (Starch to maltose)
Oesophagus
Stomach → digests foods (esp proteins), produces acid to destroy pathogens & has muscular walls
Liver → produces bile salts → help digest lipids
Pancreas → contains enzymes (lipase, exo & endopeptidase, amylase)
Small Intestine (ileum) → villi increase SA & are thin to shorten diffusion pathway
Large Intestine → absorbs water
Rectum & Anus → Store and release faeces
Describe Inhalation
External intercostal muscles contract and ribcage is pulled up and out
Diaphragm contracts and flattens
Thorax volume increases and pressure decreases so air is drawn in down pressure gradient
Describe Exhalation
External intercostal muscles relax and ribcage moves down and out
Diaphragm relaxes and becomes dome shaped
Thorax volume decreases and pressure increases so air is forced out by elastic recoil in lungs
How do insects limit water loss?
Exoskeleton is covered in waxy cuticle to prevent water loss
Spiracles can close
small sa:vol ratio where water can evaporate from
What are the adaptations for gills?
Lamellae increase surface area
Lamellae are thin → decrease diffusion pathway
Gills have good blood supply → maintains conc. gradient
Describe counter-current flow system
Blood and oxygen flow in opposite directions
So concentration gradient is maintained across whole length of lamellae
As there is always more oxygen in water than in blood
How can plants limit water loss ?
guard cells that open and close stomata (close at night when photosynthesis isnt occuring)
waxy cuticle
How do xerophytes limit water loss ?
thick waxy cuticle → reduces water loss
rolled leaves → maintain humid air around stomata so shallower concentration gradient
hairy leaves → maintain humid air around stomata so shallower concentration gradient
stomata in sunken pits → maintain humid air around stomata so shallower concentration gradient
small leaf SA:Vol → reduces SA for evaporation
State the adaptations of the human gas exchange system
Trachea → rings of cartilage to prevent collapsing, muscle can contract to control airflow & elastic fibres can stretch out and spring back
Bronchi → produces mucus to trap dirt and cilia moves dirty mucus to throat
Bronchioles → elastic fibres so can stretch out and spring back
Describe the role of micelles in the absorption of fats into the cells lining the ileum
Micelles include bile salts and fatty acids
They make the fatty acids more soluble
They carry fatty acids to epithelial cell lining
They maintain higher concentration of fatty acids than in cell
How is alveoli adapted for gas exchange?
(CO2 diffuses out of blood in capillaries to alveoli and O2 diffuses into blood from alveoli)
alveoli have large SA, thin walls and is surrounded by a network of capillaries which maintains conc. gradient
what is digestion
physical → large food molecules are broken down into smaller molecules which increases SA for chemical digestion
chemical → large insoluble molecules are hydrolysed into small soluble molecules by enzymes
how are carbohydrates digested
amylase (pancreas + salivary glands) hydrolyses starch into maltose
maltase (small intestine) hydrolyses maltose into glucose
(glucose passes into cytoplasm from lumen of gut via facilitated diffusion)
how are proteins digested
endopeptidase hydrolyses peptide bonds between amino acids in the middle of polypeptide
exopeptidase hydrolyses peptide bond between amino acids at the end of polypeptide
dipeptidase hydrolyses peptide bond between two amino acids
how are lipids digested
Lipids are emulsified by bile salts (produced in pancreas, stored in gall bladder)
Many droplets of lipids increase SA and allow fast hydrolysis by lipase
Lipase hydrolyses emulsified lipids into fatty acids and glycerol
describe the process of lipid absorption
lipids are digested into monoglycerides and fatty acids by bile salts and lipase which form micelles
micelles are non-polar so they easily diffuse across cell surface membrane into epithelial cell
triglycerides reform in golgi and are packaged into chylomicrons for transport
chylomicrons exit epithelial cell via exocytosis and enter bloodstream via lacteals
define tidal, vital, residual and total lung capacity
how do you calculate pulmonary ventilation rate (PVR)
tidal volume → resting breathing rate
vital capacity → the max volume you can inhale or exhale
residual volume → the minimum volume in the lungs
total lung capacity → max. volume of air u can fit in lungs
PVR = breathing rate x tidal volume
there is positive correlation between lung cancer deaths and cigarettes smoked per year
however correlation doesnt mean causation
data overlaps from 2500 to 3500 cigarettes smoked per year as lung cancer deaths doesnt increase