Exchange and Transport Systems
- Created by: theawkwardgrape
- Created on: 02-01-17 15:36
Starch Digestion
Starch digestion
Mouth > duodenum > ileum.
Salivary amylase > pancreatic amylase > maltose.
1) Mouth - salivary amylase.
- Hydrolyses glycosidic bonds in starch, forms e.s.c., into maltose.
2) Duodenum - pancreatic amylase.
- Hydrolyses glycosidic bonds in starch to maltose.
3) Ileum - maltose.
- Hydrolyses glycosidic bonds in maltose into two alpha glucose molecules.
Digestion (ii)
3) Duodenum
- Recieves pancreatic juice and bile.
- Digestion of: starch, proteins and fats.
4) Ileum
- Contains membrane bound enzymes.
- Digestion of molecules hydrolysed to monomers - then absorbed into the bloodstream.
- The products of these enzyme reactions are close to the epithelial cell surface to allow transport by specific proteins.
Digestion (i)
1) Mouth
- Saliva - amylase for starch digestion.
- Chewing - increases SA of food for faster rate of enzyme action.
2) Stomach
- Mixes and churns food with gastric juice - protein digestion, HCl for optimum pH & kills bacteria.
Liver
- Produces bile which is stored in gall bladder.
- Bile - emulsifies fatsand neutralises food entering duodenum.
- Causes lipids to form small droplets, lipids broken by lipase, products stuck to salts to form micelles.
Pancreas
- Secretes pancreatic juice into the duodenum containing enzymes: amylase, lipade, exo- and endopeptidase and alkali.
Protein Digestion
Protein Digestion
Stomach > duodenum > ileum.
Endopeptidase > endo- and exopeptidase > dipeptidase.
1) Stomach - endopeptidase (pepsin) in gastric juice.
- Hydrolyses internal peptide bonds into smaller polypeptide chains.
2) Duodenum - endo- and exopeptidases in pancreatic juice.
- Hydrolyses internal and external peptide bonds into dipeptides and amino acids.
3) Ileum - dipeptidases.
- Hydrolyses peptide bonds in dipeptides into amino acids.
Lipid Digestion
Lipid digestion
Duodenum > ileum.
Lipase & bile salts > lipase.
1) Duodenum - lipase in pancreatic juice and bile salts.
- Bile released from gall bladder, which emulsifies fats.
- Lipase hydrolyses ester bonds into glycerol and x3 fatty acids.
- Bile salts, glycerol and fatty acids form micelles.
2) Ileum - lipase.
- Lipase hydrolyses lipids into glycerol and x3 fatty acids.
Glycerol and Fatty Acid Absorption
Glycerol and fatty acid absorption
- Simple diffusion.
- Glycerol and fatty acids are lipid soluble and move in between phospholipds into the cell from high to low conc.
- Fat formation.
- Smooth endoplasmic reticulum - glycerol and fatty acids are joined together by condensation.
- Lacteal.
- Simply diffucse into the lacteal (lymph vessel).
- Fluid in lacteal eventually drains into the bloodstream.
Amino Acid Absorption
Amino acid absorption
- Na+/K= pump (AT)
- Na ions actively transported out of cell into blood via pump.
- The conc of Na+ decreases in the cell.
- Na+/Amino acid co-transport protein (FD)
- Amino acid and Na+ in the lumen both bind to the protein.
- Move into the cell from high to low conc.
- Glucose transport protein (FD)
- Transported amino acid increases the conc inside the cell.
- Moves out of the cell and into blood via channel protein.
Glucose Absorption
Glucose Absorption
- Na+/K= pump (AT)
- Na ions actively transported out of cell into blood via pump.
- The conc of Na+ decreases in the cell.
- Na+/Glucose co-transport protein (FD)
- Glucose and Na+ in the lumen both bind to the protein.
- Move into the cel from high to low conc.
- Glucose transport protein (FD)
- Transported glucose increases the conc inside the cell.
- Moves out of the cell and into blood via channel protein.
Surface Area : Volume
Surface area to volume ratio
- Affects how quickly substances are exchanges
- SMALL SA : V = BIGGER ANIMALS
- BIG SA : V = SMALLER ANIMALS
Cubes
SA: SA of one face x 6
V: height x width x length
Cell
SA: 4πr2
V: πr2 x height
Digestion - Basics
Digestion basics
Digestion is the process of the hydrolysis of large insoluble molecules into smaller soluble ones.
1) Mouth > oesphagus > 2) stomach > 3) duodenum > 4) ileum (blood) > 5) large intestine.
1) Salivary amylase pH 7-8
2) Gastric juice
- HCL and Pepsin - endopeptidase
3) Bile 3) Pancreatic juice
- Amylase, lipase, endo- and exopeptidase.
4) Dipeptidases
- Lipase, maltase, sucrase, lactase, dipeptidases.
Lung Disease (i)
1) Tuberculosis
- Infected - immune system cells build a wall around bacteria which forms small, hard lumps.
- Infected tissue cells die, decreases tidal volume - less air inhaled, less O2 for cells, less respiration so patients breathe faster.
- Symptoms: persistent cough, chest pains, shortness of breath, fatigue.
2) Fibrosis
- Formation of scar tissue as a result of infection.
- Scar tissue is thicker, less elastic so can't hold as much air - decreases tidal volume, decreases rate of diffusion and distance of diffusion increases.
- Ventilation rate increases.
- Symptoms: shortness of breath, dry cough, chest pain, fatigue weakness.
Gas Exchange in Humans
Gas exchange in humans
Structure
- Trachea > Bronchus > Bronchioles > Alveoli
- Internal and external intercostal muscles. (IEM and EIM)
Ventilation
Consists of inspiration and exhilation.
- Inspiration
- Diaphragm flattens and contracts > external EIM contract > ribs up and out > increase volume in thorax and decrease in pressure > alveoli expand.
- Expiration
- Diaphragm relaxes and curves upwards > EIM relax > ribs fall > decrease in volume in thorax and decrease in pressure > alveoli shrink.
Single-celled Organisms
Single-celled organisms
- Substances can diffcuse directly in/out across cell surface membrane.
- Meets gas exchange requirements - allows removal of heat produced during metaboilc reactions.
- Small distance - faster diffusion rate.
- Large SA:V - so no specialised gas exchange system needed.
Gas Exchange in Insects
Gas exchange in insects
- Spiracle > trachea > air sac > tracheole > muscle cell.
- O2 diffuses directly into respiring cells.
Rate of diffusion of O2 increases during flight...
- Increased respiration > releases substances which decreases water potential > draws water into cells > increases SA of water diffusion can take place.
Adaptations.
- Large SA - many branching tracheoles next to muscle cells.
- Short diffusion distance - muscle cells close to spiracles on body surface.
- Maintains O2 diffusion gradient - respiring muscles use O2 and release CO2 so O2 is always lower and CO2 higher in cells than air outside.
Lung Disease (ii)
3) Asthma
During an attack, airways become inflamed.
- Smooth muscle lining bronchiones contracts, increeases mucus.
- Constriction makes it difficult to breathe.
- Air flowing in and out of lungs, decreases severely - max vol of air breathed out in one second decreases.
4) Emphysema
Foreign particles become trapped in alveoli.
- Loss of elastin = alveoli don't recoil to expel air leading to destruction of alveoli walls - decreases surface area therefrore rate of gaseous exchange.
- Causes: smoking, long-term effect of air pollution.
- Inflammation caused > attraction of phagocyte > phagocyte produces enzyme breaking down protein.
- Symptoms: shortness of breath, wheezing, increased ventilation rate.
Gas Exchange in Plants (ii)
Diffusion gradient for CO2 maintained...
- During daylight, photosynthesis uses CO2 so the conc of CO2 in mesophll cells is lower than the air outside the leaf.
Respiration and gas exchange
- No photosynthesis at night > stomata close > no uptake of CO2.
- Respiration only requires O2 + releases CO2.
Control of water loss
- Thick waterproof cuticle - so evaportation decreases.
- Sunken stomate - less area where water can evaporate.
- Small leaves - SA decreases for evaportation.
- Hairy leaves - traps water vapour which decreases water potential gradient.
- Leaves rolled inwards - water molecules collected in curled space to decrease water potential gradient and stomata protected from wind as it increases rate of diffucision and evaporation.
Gas Exchange in Plants (i)
Gas exchange in plants
Guard cells > stoma(ta) > spongy mesophyll layer> air spaces > mesophyll tissue.
Mesophyll tissue
- Columnar tissue - more packed in a single layer.
- Chloroplast - circulate to get maximum light.
- Cell wall - thin pathway for O2,
- Big vacuole - pushes chloroplasts closer to cell surface for more light absorption.
Adaptations of leaves
- Thin - short diffusion distance.
- Stoma - CO2 can enter lead, number of stomata per unit area relates to O2 uptake.
- Mesophyll cells - have air spaces to CO2 can diffuse faster
- Large total SA of mesophyll cells - increase rate of gas exchange.
Gas Exchange in Fish
Gas exchange in fish
- Occurs over gills > lower conc of O2 in water than air.
- Structure: gill arch > gill filaments > lamellae.
- Short diffusion distance - epitheliun of lamellae and endothelium of blood capillaries.
- Diffusion gradient maintained - lamellae have a supply of blood capillaries and continual flow of water.
- Countercurrent system - blood and water flow in opposite directions, higher conc of O2 in water always meeting lower conc of O2 in blood.
Structural Adaptations of the Ileum
Structural adaptations of the ileum
- Villi and microvilli - increases the SA, higher number of transport proteins to increase rate of absorption.
- Single later of epithelial cells - shorter diffusion patheay which increases the rate of diffusion/absorption.
- Large network of branched capillaries - increases SA for faster absorption, continual blood flow which maintains a high gradient.
- Many mitochondria - supplies plenty of ATP for active transport.
Haemoglobin
Haemoglobin
An oxygen carrying protein - known as oxyhaemoglobin when bound to O2.
Structure
- 4 polypeptide chains linked together - quaternary.
- Each chain is linked to a haem group - Fe2+
- Each Fe2+ binds to one oxygen molecule therefore one haemoglobin molecule binds to a maximum of four oxygen molecules.
Affinity of Hb for O2
Attraction - the tendency it has to bind with O2.
- PO2 is the measure of O2 concentration.
- As PO2 increases, affinity for O2 increases.
- O2 loads/associates in high PO2 conditions.
- O2 unloads/dissociates in low PO2 conditions.
Haemoglobin - The Bhor Effect
The Bhor effect
Effect of an increased concentration of CO2 in blood results in a reduction of haemoglobin's affinity for O2.
- Due to the decrease in pH as carbonic acid is formed which increases H+.
- Increase in PCO2 shifts the graph to the RIGHT - Hb releases more O2 to respiring tissues.
- The higher the volume of CO2 produced, the lower the affinity of Hb for O2 and the higher the amount of O2 which dissociates.
The Heart - Overview
Lungs
Pulmonary vein
Left atrium
Left ventricle
Aorta
Body
Vena Cava
Right atrium
Right ventricle
Pulmonary artery
The Heart - Adaptations
Adaptations of the heart
- Left ventricle is thicker and has more muscular walls - allows more powerful contractions to pump blood at a further distance.
- Ventricles have thicker walls than atria - ventricles push blood out of the heart, atria have a shorter distance.
- Atrioventricular valves link atria to ventricles - stops backflow of blood.
- Cords/tendons attach valves - stops atrioventricular valves being forced up into the atria when ventricles contract.
Heart valves
- Higher pressure behind valve = opened.
- Higher pressure infront of valve - closed.
- Flow of blood is only in one direction.
The Heart - The Cardiac Cycle
The cardiac cycle
The sequence of contraction and relaxation of the heart chambers and the opening and closing of valves during one heart beat.
1) Atrial Systole
- Atria fill with blood from vena cava/pulmonary vein.
- Atria contracts - increases pressure so AV valves open and decrease the volume.
- Ventricles fill with blood.
2) Ventricular Systole
- Ventricle contracts - increase pressure and decrease volume.
- Pressure in ventricle is higher than atria - AV valve shuts.
- Pressure in atria is higher than blood vessels - semi-lunar valve opens.
3) Diastole
- Ventricles and atria relax.
- Blood returns and fills atria - high pressure in vena cava/pulmonary vein.
Circulatory and Cardiovascular System
Circulatory and cardiovascular system
Consists of heart and blood vessels.
- Mammals have a double circulatory system - blood is pumped to the heart and to the rest of the body.
- Ensures that blood is pumped at a high pressure to the body after the pressure has been reduced after pressing through the lungs.
Bood Vessels
Aorta > arteries > arterioles > capillaries > venules > veins > vena cava
The Heart - Blood Vessels (i)
Blood Vessels
1) Aorta
- High pressure - LV contracts powerfully.
- Stretches to stop bursting and recoils to maintain pressure.
2) Capillaries
- Drop in pressure.
- Pores in capillaries so molecules leak out to give to cells.
3) Veins
- Lower pressure as pressure is lost at capillaries.
- Leg movement - skeletal muscles - contract and squeeze on veins to open SLV which increases pressure.
- No leg movement = blood flows down and SLV shuts to prevent backflow.
The Heart - Blood Vessels (ii)
Arteries
- Carry the blood from the heart to the body at high pressures.
- Thicker wall - to withstand pressure.
- Smaller lumen.
- Contain more elastic fibres and smooth muscle tissue.
- Transport blood at higher pressure - elastic tissue stretches and recoils for smooth pressure surges, endothelium allows arterty to stretch.
Aorta
- When LV contracts, aorta enlargens due to elasticity - retains blood.
- When LV relaxes, artery wall recoils and forces blood to body tissues.
- Provides a smooth flow of blood and maintain relatively high pressures.
The Heart - Blood Vessels (iii)
Arterioles
Network of small arteries directing blood to different areas in the body.
- High proportion of smooth muscle than elastic fibres.
- Contract/relax smooth muscle - regulares blood flow to different tissues and organs.
- Contracting causes vasoconstriction - reduces blood flow to capillaries.
- Relaxation causes vasodilation - increases blood flow to capillaries.
Veins
Carry blood back to the heart under low pressure.
- Wider lumen
- SLV valve
- Thinner layer of muscle and elastic tissue.
Capillaries
Give substances to cells.
- One endothelial cell thick - short diffusion distance.
- Narrow lumen - slow blood flow for more time for diffusion.
- Large number - large total SA for exchange which reduces blood flow.
Total Cross Sectional Area and Velocity of Flow
- As total CSA increases, velocity of flow decreases.
- Each capillary has a tiny CSA but there are many of them so overall it is large.
- Walls of arteries, arterioles and veins...
- Fibrous outer coat - for protection.
- Middle layer of smooth muscle cells and elastic tissue.
- Inner layer of endothelial cells.
Mass Transport in Plants - Xylem
Xylem
Tissue that transports water and mineral ions in solution - moves up from roots to leaves.
Strucutre and function
- Long tube like structure.
- Made up of dead tissue.
- No organelles - no obstruction to flow.
- Hollow - minimal resistance to flow of water and ions.
- Cell wall strengthened by lignin - so it doesn't collapse, support/rigidity and impermeable.
- No end walls - no interruption to flow of water and ions.
- Bordered pits (holes) - allows water and ions to move laterally (sideways) to adjacent vessels.
Mass Transport in Plants - Cohesion-Tension Theory
Cohesion-tension theory
1) Water evaporates from leaves at the 'top' of the xylem.
2) Lowers water potential in cells - water moves out of xylem into cells.
3) Creates 'tension' - vessel diameter decreases while transpiration happens.
4) Water molecules cohesive due to hydrogen bonds - forms continuous column maintained by bonds and adhesion (attracted to xylem wall).
5) Water molecules move up the xylem.
6) Causes water to move/drawn into the roots.
Greater rate of transpiration, faster speed of water in xylem, greater amount of water absorbed by roots.
Mass Transport in Plants - Transpiration
Transpiration
Evaporation of water from a pants surface (leaves).
- Water evaporates from the moist cell walls and accumulates in the spaces > the stomata open > water moves out the leaf > decreases the water potential gradient (low outside).
Factors affecting transpiration
- Light Intensity.
- Lighter = increase in ROT > stomata open to allow sunlight/CO2 enter, water moves out.
- Temperature.
- Higher = molecules have kinetic energy, increase in water potential inside & outside, water moves out.
- Humidity.
- Lower humidity = air around is dry so maintains water potential gradient. Water potential gradietn increases between leaf and air.
- Air movement.
- Windy = removes water from leaves as water potential increases.
Mass Transport in Plants - Transpiration and Affec
How transpiration affects...
1) Rate at which water moves up the xylem.
2) Absorption in roots.
As transpiration increases:
- Transpiration stream - water moving up the xylem will increase.
- Absorption in the roots will increase - due to cohesion-tension.
Mass Transport in Plants - Potometer
Potometer
Measures the rate of water uptake of the leafy shoot.
- Assumes: rate of water uptake = rate of transpiration.
- Not all water taken in is lost via transpiration.
- Some water used for photosynthesis.
- Some water used to maintain turgidity.
Rate of transpiration = distance bubble travels
time taken
- Changing environmental factors
- Add vaseline to lead > waxy cuticle.
- Fan to create air current > steep water potential.
- Tie a transparent bag around the leaf > creates humidity.
- Use a lamp > light intensity.
Mass Transport in Plants - Phloem
Phloem
Tissue that transports organic substances (e.g. sugar) both up and down the plant.
Respiring cells, growing area, storage areas.
Structure and function
- Made up of many sieve tubes.
- Made up of living cells - sieve elements.
- Doesn't have nucleus and few/no organelles - assosiacted with a companion cell which does have organelles.
- Sieve plate between each sieve tube.
- Companion cells carry out living functions for the sieve element cells.
Mass Transport in Plants - The Mass Flow Hypothesi
Translocation is the movement of solutes from sources to sinks.
Enzymes maintain concentration gradient from the source to the sink.
1) Source - where sugars are made in mesophyll cells in leaves.
- Glucose converted to sucrose > actively transported by companion cells into sieve tube cells (decreases W.P.G).
- Water enters by osmoses from xylem and companion cells > creates high pressure inside sieve tubes.
2) Sink - where sugars are used.
- Solutes removes from phloem used up in respiration or stored as starch > increases WP in sieve tubes > water moves out sieve tube into sink > decreases pressure in sieve tubes.
3) Flow
Pressure gradient formed from source to sink end > gradient pushes along sieve tube towards sink = mass flow.
Mass Transport in Plants - Transport of Sucrose in
Transport of sucrose in phloem
1) Leaf carries out photosynthesis, produces glucose which is converted into sucrose.
2) Companion cells actively transport sucrose into the phloem.
3) Sucrose in phloem decreases WP so water moves from xylem to phloem via osmosis.
4) Causes hydrostatic pressure gradient - sucrose moves down phloem (translocation).
5) Root (sink) removes sucrose from phloem via active transport.
6) Increases WP in phloem, so water from phloem moves back into xylem.
Mass Transport in Plants - Supporting Evidence for
Supporting evidence for mass flow
- Ringing experiments
- Remove ring of phloem so transport is prevented.
- Bulge forms, the fluid has a higher conc of sugars than below - sugars can't move past.
- Downwards movement.
- Radioactive tracers
- 14C used to track movement of organic substances - autoradiography.
- Demonstrates translocation of subsrances from source to sink overtime.
- Aphid mouthpoarts
- Aphids pierce the phloem and bodies are removed, leaving mouthparts behind - allows sap to flow out.
- Sap flows out quicker nearer to the leaves than further down the stem.
- Pressure gradient.
- Respiratory inhibitors
- Stops respiration therefore stops ATP production.
- Mass flow stops.
- Mass flow requires ATP for active transport.
Mass Transport in Plants - Refuting Evidence for M
Refuting evidence for mass flow
- Sugar travels to many different sinks, not just the one with the lowest water potential.
- Sieve plates would create a barrier to mass flow.
- A lot of pressure would be needed for the solutes to get through at a reasonable rate.
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