exchange of substances with environment 3.3 Flashcards
aqa as level biology
why is surface area to volume ratio so important?
the relationship between the size of an organism and its surface area to volume ratio play an important role in the type of adaptations it will have
why do small organisms only have single exchange surfaces?
small organisms have very large surface compared to volume so big enough surface for exchange and a small distance to reach middle of it
what is breathing?
movement of air in and out of lungs
what is ventilation?
scientific word for breathing
what is respiration?
chemical reaction to release energy in the form of ATP
what is the structure of human gas exchange system?
alveoli bronchioles bronchi trachea lungs
what are antagonistic muscles mean?
when one muscle relax another contracts
what happens in inspiration? (breath in)
external intercostal muscles contracts and diaphragm contracts + flattens
ribcage pulled upwards and outwards
pressure decreases volume of thorax inceases
atmospheric air greater than pulmonary pressure so air forced in
what happens in expiration? (breath out)
external intercostal muscles relax and diaphragm relaxes
internal intercostal muscles contract
ribcage pulled downwards and inwards
pressure increases volume of thorax decreases
pulmonary pressure greater than atmospheric air so air forced out
what is pulmonary ventilation?
total volume of air that is moved into lungs during one min
what is the equation for pulmonary ventilation?
pulmonary ventilation = tidal volume x ventilation rate
units for pulmonary ventilation?
dm3 min-1
where does gas exchange occur?
alveolar epithelium and blood
what are the adaptations of alveoli?
- large surface area
- epithelium cells very thin so short diffusion distance
- surrounded by network of capillaries so maintains concentration gradient
what is the insect gas exchange system?
spiracles, tracheoles and trachea
what are the three methods of moving gas in the tracheal system (insects)?
- diffusion a concentration gradient between tracheoles and atmosphere
- mass transport insects contract and relax abdominal muscles to move gases
- respire anaerobically to produce lactate this lowers water potential of the cells so water moves from the tracheoles into cells by osmosis decreasing volume of tracheoles so more air drawn in
what are the adaptations for efficient gas exchange in insects?
- high amount of trachea (large surface area)
- walls of tracheoles are thin and short distance between trachea and spiracles
- use of O2 and production of CO2 maintains steep concentration gradient
how are insects adapted to prevent water loss?
- small SA:V ratio
- waterproof exoskeleton
- spiracles can open/close to prevent water loss
what is ficks law?
diffusion is directly proportional to
(surface area x concentration gradient)/length of diffusion
what are adaptations for fish gas exchange?
- large amount of lamellae and gill filaments so large surface area
- short diffusion distance due to capillary network in lamellae
what is the counter current flow?
oxygen and water flow in opposite directions to maintain a concentration gradient (no equilibrium) across the whole length of lamellae
structure of a leaf?
palisade mesophyll
spongy mesophyll
stomata
how does stomata reduce water loss?
closes at night opens in morning
what are xerophytic plants?
plants adapted to survive in limited water environments
what are features of xerophytes?
- curled leaves to trap water to increase local himidity
- hairs to trap moisture
- sunken stomata to trap moisture
- thick cuticles to reduce evaporation
- longer root network to reach more water
what is digestion?
larger insoluble molecules hydrolysed to smaller soluble molecules
what enzymes hydrolyse carbohydrates?
amylase and membrane bound disacchridases
what does amylase do?
hydrolyse carbohydrates into maltose in the pancreas and salivary glands
what does sucrase and lactase do?
hydrolyse sucrose and lactose into monosaccharides
what are endopeptidases?
hydrolyse peptide bonds between amino acids in middle of polymer chain
what are exopeptidases?
hydrolyse peptide bonds between terminal amino acids
what are dipeptidases?
hydrolyse bond between two amino acids
what is lipase?
hydrolyse ester bonds in triglycerides to form monoglycerides and fatty acids - produced in pancreas
what are bile salts?
produced in liver - emulsify lipids to form micelles so larger surface area for lipase to work on
how are micelles formed?
when lipids are digested by lipase and bile salts
how do micelles work?
non polar so can diffuse across cell surface membrane into epithelial cells once in the cells formed back into triglycerides in ER and golgi apparatus
how is ileum adapted to absorption?
- covered in villi
- villi covered in mircovilli
- thin walls surrounded by network of capillaries
what are the steps of cotransport in the ileum
- Sodium ions (Na⁺) actively transported out of epithelial cells into the blood using the sodium-potassium pump (requires ATP).
- This creates a low Na⁺ concentration inside the epithelial cells.
- Sodium ions diffuse into the cell from the small intestine down their concentration gradient through a co-transport protein.
- Glucose is carried into the cell with Na⁺, moving against its own concentration gradient.
- Glucose then diffuses into the blood via facilitated diffusion through another carrier protein.
what is cooperative binding of haemoglobin?
haemoglobin changes shape when binding to its first oxygen making it easier to bind to other oxygens
what is the bohr effect?
when a high CO2 concentration causes oxyhaemoglobin curve to shift to the right reducing oxygen affinity as haemoglobin structure changes a little
where does fetal haemoglobin come from?
the mother it has high affinity for oxygen
why does blood flow at lower pressures in the lungs?
prevents damage to capillaries + allows more time for gas exchange
what are the properties of cardiac muscle?
- myogenic
- never fatigues (with constant supply of oxygen)
- branch off from aorta
what are the features of atria?
- thinner muscle walls
- elastic walls to stretch
what are features of ventricles?
- thicker muscle walls
- left ventricles thicker than right
what does vena cava do?
carry deoxygenated blood from body to heart
what does pulmonary veins do?
carries oxygenated blood from lungs to heart
what does pulomary artery do?
carry deoxygenated blood from heart to lungs
what does aorta do?
carry oxygenated blood from heart to body
where are the semi lunar valves located?
in aorta and pulomary artery
where are atrioventricular valves located?
between atria and ventricles
what do valves do?
prevent backflow of blood only open when pressure of blood high infront than in back
structure of arteries?
- thicker muscle layer
- thicker elastic layer
- thicker wall
- no valves
structure of veins?
- thinner muscle layer
- thinner elastic layer
- thin walls
- valves
structure of arterioles?
- thicker muscle layer than artery
- thinner elastic layer
- thinner wall than artery
structure of capillaries?
one cell thick
what happens in diastole?
- atria and ventricle muscles are relaxed
- blood enters atria via vena cava and pulmonary vein
- increasing pressure of atria
what happens in atrial systole?
- atria muscle contracts increasing pressure further
- causes atrioventricular valves to open
- blood flows into ventricles
what happens in ventricular systole?
- short delay
- ventricle muslces contract increasing pressure
- causes atrioventricular valves to close and semilunar to open
- blood pushed out into arteries
what is cardiac output?
the volume of blood that leaves one ventricle in one minute
how to calculate cardiac output?
cardiac output = heart rate x stroke volume
what is tissue fluid?
fluid containing ions water glucose etc
how is tissue fluid formed?
- blood enters capillaries causing high hydrostatic pressure
- so water glucose amino acids etc are forced out
- large proteins remain in capillary
- lowered water potential
- due to proteins
- water enters by osmosis at venule end
- rest of liquid reabsorbed by lymphatic system and drains back into bloodstream
what factors affect transpiration?
light
temperature
wind
humidity
what is the cohesion tension theory?
- water evaporates out of stomata lowering water potential
- more water pulled up by xylem to replace it
- due to hydrogen bonds in water its cohesive creating a continuous column of water
- water molecules adhere to the xylem walls helping it move up
- creating tension pulling water up xylem
describe translocation
Sucrose moves from companion cells into sieve tube elements by active transport.
This reduces the water potential
Water moves into the phloem by osmosis, which increases the hydrostatic pressure.
This forms a pressure gradient
Solutes move down the pressure gradient towards the sink end of the phloem.
Solutes move into sink cells used for respiration
