6.Exchange Flashcards
What is tissue fluid
The environment around the cells of multicellular organisms
What common things are interchanged between organism and its environment?
Respiratory gases
Nutrients
Excretory products
Heat
For exchange to be effective what must exchange surfaces be?
Large compared to volume
How do you work out ratio of surface area to volume?
Surface area➗volume
What are features of specialised exchange surfaces
- large SA relative to volume which increases rate of exchange
- very thin short diffusion distance rapid diffusion
- selectively permeable to allow selected materials across
- movement of environmental median to maintain diffusion grad
- transport system for internal median to maintain diffusion grad
Gas exchange in single called organisms
Small
Large surface to volume
Oxygen absorbed by diffusion across body surface
Carbon dioxide diffuses out across body surface
What are spiracles
Tiny pores on body surface
Gases enter and leave through
When open water vapour can evaporate
What is the exchange system in insects made of
Internal network of trachea-supported by strengthened rings to prevent collapsing
Tracheoles-branch off trachea, extended through out bodytissue, gas brought directly to respiring tissues
In insects what does the diffusion gradient do
- When respiring cells use up oxygen, creates diffusion grad, draws gaseous oxygen from atmosphere along trachea and tracheoles
- carbon dioxide is created so creates diff grad in opposite direction
What is mass transports role in respiration of insects
Interaction of muscles in insects squeezes trachea, enabinling mass movements of air in n out
Speeds up exchange
What is the function of end of tracheoles being filled worth water
During periods of major activity, muscle cells carry out anaerobic
Produces lactate, it’s soluble and lowers w.p of cells
Water moves into cells by osmosis
Water in tracheoles decreases in volume so further draws air in
Final diffusion is in gas phase which is more rapid than in liquid
Structure of gills
- Gill bar
- Branching of gill bar are Gill filaments
- At right angle to filament are gill lamellae
- Flow of water over gills is opposite to flow of blood within them (countercurrent flow)
What’s the countercurrent exchange principle
- Opposite flow direction of blood and water
- Blood is well loaded with oxygen when meets water, meets water with max conc of oxygen so diffusion of oxygen from water to blood occurs
- blood with little oxygen meets water with little oxygen left, diffusion oxygen from water to blood occurs
- diffusion grad maintained whole width of gill lamellae
Structure of plant gas exchange
Stomata-allow gaseous diffusion
Interconnecting air spaces-allowgases readily contact with mesophyll cells
Large surface area of mesophyll cells-rapid diffusion
How is water loss limited in insects
- Small surface are to volume ratio-minimise area over which water is lost
- waterproofing coverings-rigid outer skin eg chitin that’s cover d with waxy cuticle
- spiracles-can be closed to reduce water loss
What are xerophytes
Plants adapted to living in areas where water is in short supply
What adaptations do xerophytes have
- Thick cuticle-thicker the waxy cuticle the less water loss
- Rolling up of leaves-protects lower epidermis, region gets saturated with water vapour, no w.p gradient no water loss
- hairy leaves-thick layer traps still moist air, water potential between inside and outside cell reduced less water loss
- stomata in pits of grooves-trap still moist air
- reduces SA to volume-smaller SA slower diffusion
Why is the volume of oxygen absorbed and volume of carbon dioxide removed so large in mammals?
- large organisms with large volume of living cells
- maintain high body temperature which is related to high metabolic and respiratory rates
What features make up the respiratory system in mammals
Rib cage Lungs Trachea Bronchi Bronchioles Alveoli
What is the structure and function of the lungs
Pair of lobed structures
Made up of highly branched tubules (bronchioles)
End up as tiny air sacs called alveoli
What is the structure and function of the trachea
- Flexible airway supported by rings of cartilage
- Cartilage prevents collapsing as pressure inside falls when breathing in
- tracheal walls made of muscle, lined with ciliates epithelium and goblet cells
What is the structure and function of the bronchi
Two divisions of trachea
Lead to lung
Similar in structure to trachea produce mucus to trap dirt and use cilia to move trapped particles towards throat
Amount of cartilage reduced as bronchi get smaller
What is the structure and function of bronchioles
- Series of branching subdivisions of bronchi
- Walls made of muscle lined with epithelial cells
- Muscle allows them to construct so can control flow of air in n out of alveoli
What is the structure and function of the alveoli
- minute air sacs at end of bronchioles
- between alveoli is collagen and elastic fibres
- lined with epithelium
- Elastic fibres allow the alveoli to stretch and spring back during breathing
- gas exchange surface
What is inspiration
When air pressure of atmosphere is greater than air pressure inside of the lungs, so air is forced in
What’s expiration
When air pressure is greater inside of lungs than the air pressure of atmosphere, air is forced out of lungs
What’s the process of inspiration
1-external intercostal muscles contract, while the internal intercostal muscles relax
2-ribs pulled upwards and outwards increasing volume of thorax
3-diaphragm muscles contract, it flattens,further increases thorax volume
4-increased volume results in reduction of pressure in lungs
5-atmospheric pressure greater,air forced in
What’s the process of expiration
1-internal intercostal muscles contract, external intercostal muscles relax
2-ribs move downwards and inwards, decreasing volume of thorax
3-diaphragm muscles relax causing it to dome, pushed up by contents of abdomen, volume of throws further decreased
4-decreased volume means pressure increased in lungs
5-greater pressure in lungs than atmosphere so air forced out lungs
Why is diffusion across alveoli rapid
- one cell thick wall for short diffusion pathway
- large capillary network, narrow capillaries so red blood cells flattened against wall reduces diffusion pathway
- red blood cells slowed as pass through pulmonary cappliaries allowing more time for diffusion
- breathing movements constantly ventilate lungs, heart constantly circulates blood around alveoli so steep con grad maintained
What are the major parts of the digestive system
Oesophagus Stomach Ileum Large intestine Rectum Salivary glands Pancreas
What’s the role of the stomach
Muscular sac with an inner layer that produces enzymes
Role is to store and digest food eg protein
Has glands that produce enzymes which digest protein
What’s the role of ileum
- Long muscular tube
- Food further digested by enzymes produced by its walls and by glands that our secretions into it
- inner walls of ileum are folded into villi =large SA
- microvilli further increases SA
- adapts for the absorption of products of digestion into bloodstream
What’s the role of large intestine
Absorbs water
Most of water absorbed is water from the secretions of many of the digestive glands
What’s the role of the rectum
Faeces are stored befor periodically being removed via the anus in process called egestion
What’s the role of salivary glands
Situated near mouth
Pass their secretion via a duct into mouth
Contain amylase which hydrolyse starch into maltose
What’s the role of pancreas
Large gland situated below stomach
Produces pancreatic juice
Secretion contains proteases, lipase, and amylase
What is the physical breakdown in digestion
Large molecules broken down into smaller molecules by teeth
Creates larger SA for chemical disgestion
Food is churned by stomach walls which further breaks it down
What is chemical digestion
Hydrolyse large insolubk molecules into smaller soluble ones
Carried out by enzymes
3 main types of enzyme
Carbohydrases-carbs into monosaccharides
Lipases-lipids into glycerol and fatty acids
Proteases-proteins into amino acids
What is the process of carb digestion in humanse
1-saliva in mouth, from salivary glands, mixed with food in chewing
2-salivary amylase, hydrolyse starch into maltose, mineral salts maintain pH around neutral
3-food swallowed, enter stomach, acid denatures amylase
4-moves into small intestine, pancreatic juices from pancreas mix with food
5-pancreatic amylase hydrolyse remaining starch, alkaline salts neutralise acidic conditions from stomach
6-muscles in intestine walls push food along ileum, Maltase is membrane bound enzyme turning maltose to a-glucose
What are the other two common disaccharides in the diet that are hydrolysed
Sucrose - sucrase hydrolysed it onto glucose and fructose
Lactose - lactase hydrolysed it into glucose galactose
What happens in lipid digestion
- Lipases produced by pancreas and hydrolyse Ester bond in triglycerides
- firstly emulsification occurs to form micelles increases surface area so action of lipases speed up
What’s the process of protein digestion
3 types of peptidases
1-endopeptidases hydrolyse peptide bonds in central region forming series of peptide molecules
2-exopeptidases hydrolyse peptide bonds on terminal amino acids forming dipeptides and single amino acids
3-dipeptidases hydrolyse dipeptides into amino acids (membrane bound in ileum)
Describe structure of ileum
Folded Finger like projections- villi Microvilli Thin walls lined with epithelial cells Rich network of blood capillaries Situated at intersurface between lumen and blood and other tissues
How does the ileum and villi increase the efficiency of absorption
- Villi increase SA for diffusion
- Thin walled reducing diffusion pathway
- Contain muscle so can move, movement mixes contents of ileum so new material replaces material that’s been absorbed
- well supplied with blood vessels, Carry about absorbed molecules main diff grad
- microvilli increase SA
How are amino acids and monosaccharides absorbed
Diffusion and co transport
Absorption of triglycerides
- When micelles come into contact with epithelial cells on ileum they break down releasing monoglycerides and fatty acids
- non polar so diffuse across cell surface memabrne into epithelial
- transported to endoplasmic reticulum and recombined to triglycerides
- continue to Golgi, associated with cholesterol and lipoproteins forming chylomicrons, specialised for transport of lipids
- exocytosis out of epithelial cells enter lymphatic capillaries called lacteals, then pass into blood system
- triglycerides in chylomicrons hydrolysed by enzyme in endothelial cells and diffuse into cells
