Exchange (all based on kerboodle i think)

why do larger animals have a lower surface area to volume ratio?

their volume increases at a faster rate than their SA meaning that simple diffusion of substances across the outer surface can ony meet the needs of inactive organisms

features of specialised exchange surfaces?

• large surface area to volume ratio - increases rate of exchange

• very thin - short diffusion distance

• selectively permeable - allows selected materials to cross

• movement of the environmental medium - maintains a diffusion gradient

• transport system - ensures movement of internal medium to maintain diffusion gradient

Fick’s law

rate of diffusion is directly proportional to SA X concentration difference divided by thickness of membrane

what are the pores on a insects surface called?

spiracles

how do the spiracles minimise water loss?

may be guarded by valves and surrounded by hairs

what are the air pipes and subdivided ones called?

tracheae (strengthened by rings of chitin) and tracheoles

how do tracheoles aid diffusion?

they have thin permeable walls that extend all through the tissues

how does oxygen enter the insect?

down a concentration gradient formed through the use of oxygen for respiration, CO2 does the opposite

how can the entry of oxygen be helped?

by the contraction of muscles and abdominal pumping

how does water in the tracheoles assist in periods of high activity?

• muscles around the tracheoles respire anaerobically producing lactate and lowering water potential of muscle cells

• water moves into those cells by osmosis causing water in tracheoles to decrease in volume and draw more air in

how is the insect adapted to be efficient? ms

• tracheoles have thin walls so short diffusion distance to cells

• high branched large no of tracheoles so short diffusion distance to cells

• high branched large no of tracheoles so large SA for gas exchange

• tracheae provide tubes full of air so fast diffusion into tissues

• fluid in end of tracheoles moves out during exercise so faster diffusion through air to exchange surface and larger surface area

• body can be moved by muscles to move air so maintains conc grad for o2

what are the thin plates in gills?

gill filaments

what are the tiny structures that cover the gill filaments?

lamellae

what is the counter current system?

blood flows through the lamellae in one direction and water flows over them in the opposite direction

what does the counter current system mean?

water with a relatively high oxygen conc always flows next to blood with a lower conc of oxygen so steep conc maintained

how are fish adapted for gas exchange?

• thin gill filaments and small lamellae increase surface area for diffusion

• lamellae have lots of blood capillaries and a thin surface of cells to speed up diffusion between water and blood

• counter current system maintains concentration gradient

what is a xerophyte?

plants that are specially adapted for life in warm, dry or windy habitats where water loss is a problem

examples of xerophyte adaptations?

• stomata sunk in pits to trap water vapour reducing conc grad between leaf and air, reduces evaporation

• hairs on epidermis to trap water vapour round the stomata

• curled leaves with stomata inside protecting from wind

• reduced number of stomata

• thick waterproof waxy cuticle to reduce evaporation

what is the main surface for gas exchange in a leaf?

mesophyll cells

route of air in humans?

mouth, trachea, bronchus, bronchioles, alveoli

trachea

flexible airway

inspiration

• external intercostal and diaphragm muscles contract

• ribcage moves upwards and outwards and diaphragm flattens increasing volume of thoracic cavity

• lung pressure decreases to below atmospheric

• air flows from an area of higher pressure to lower pressure down trachea and into lungs

is inspiration an active or passive process?

active, it requires energy

expiration

• external intercostal and diaphragm muscles relax

• ribcage moves downwards and inwards and diaphragm curves upwards again

• volume of thoracic cavity decreases so air pressure increases to above atmospheric pressure

• air forced down pressure gradient out of lungs

is expiration a passive process?

yes, but can have forced expiration where external intercostal muscles relax and internal intercostal muscles contract pulling ribcage further down and in

what’s the alveolar epithelium?

the wall of the alveolus made from a single layer of thin, flat cells

how does oxygen move through the gas exchange system?

down a pressure gradient until the alveoli then down a diffusion gradient

factors affecting rate of diffusion?

• thin exchange surface

• large surface area

tidal volume

the volume of air in each breath

ventilation rate

the number of breaths per minute

forced expiratory volume

maximum volume of air that can be breathed out in one second

forced vital capacity

maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in

risk factors for lung disease?

smoking, air pollution, genetic makeup, infections, occupation

major parts of the digestive system?

oesophagus, stomach, ileum, large intestine, rectum, salivary glands, pancreas

digestion includes…

physical breakdown and chemical breakdown - enzymes and hydrolysis

what does amylase do?

catalyses conversion of starch into smaller sugar maltose by hydrolysis of the glycosidic bonds

where’s amylase produced?

salivary glands and pancreas

what are membrane bound disaccharidases?

enzymes attached to the cell membranes of epithelial cells lining ileum that break down disaccharides eg maltose into monosaccharides eg glucose

what does lipase do?

catalyse breakdown of lipids into monoglycerides and fatty acids by hydrolysis of ester bonds

where is lipase made?

pancreas and works in the small intestine

bile salts

produced by liver and emulsify lipids and once lipid broken down, monoglycerides and fatty acids stick with the bile salts to form tiny structures called micelles

whats involved in protein digestion?

peptidases (proteases)

endopeptidases

hydrolyse the peptide bonds between amino acids in central region of a protein molecules forming a series of peptide molecules

exopeptidases

hydrolyse the peptide bonds on terminal amino acids of peptide molecules formed by endopeptidases, progressively release dipeptides and single amino acids

dipeptidases

hydrolyse the bond between two amino acids of a dipeptide, these are membrane bound being part of cell surface membrane of epithelial cells lining ileum

how are monosaccharides absorbed?

• by active transport with sodium ions via a co-transporter protein for glucose and galactose

• via facilitated diffusion for fructose

how are monoglycerides and fatty acids absorbed?

micelles help to move monoglycerides and fatty acids towards epithelium and then they ‘release’ them to diffuse across membrane

how are amino acids absorbed?

via co-transport

how do villi on the ileum increase efficiency of absorption?

• increase surface area for diffusion

• thin walled reducing distance

• contain muscle so can move maintaining diffusion gradient because movement mixes content of ileum so providing new rich material once old is absorbed

• well supplied with blood vessels so can carry molecules away maintaining gradient

• posses microvilli further increasing surface area