ORGANISMS AND ENVIRONMENT Flashcards
TOPIC 3
SURFACE AREA: VOLUME RATIO
surface area of an organism divided by its volume
larger organism, smaller ratio
FACTORS AFFECTING GAS EXCHANGE
surface area: volume ratio
diffusion pathway
concentration gradient
INSECTS USE TRACHEA TO EXCHANGE GASES
.Insects need to exchange gasses, but also need to need to limit water loss. These are opposing needs
.Branched, chitin-lined system of tracheae w/openings called spiracles
.Fast exchange of gasses as diffusion distance small at tracheoles
.No transport system as exchange is directly w/respiring tissues
.Body can be moved by muscles to move air so maintains concentration gradient for O2 and CO2
.Fluid in end of tracheoles that moves into tissues during exercise so faster diffusion through air to gas exchange surface-water potential lowered by osmosis
INSECTS REDUCE WATER LOSS
.have spiracles
.contain waterproof waxy cuticle + hairs around spiracles reduce evaporation
EXPLAIN MOVEMENT OF OXYGEN TO GAS EXCHANGE SYSTEM OF INSECT AT REST
oxygen used in respiration
oxygen gradient
oxygen diffuses in
HOW FISH PROVIDE LARGE SA:V RATIO
fish gills stacked gill filaments covered in many gill lamellae are positioned at right angles creates a large surface area for efficient diffusion
gills have lots of blood capillaries and are thin for a short diffusion path
COUNTERCURRENT SYSTEM
When water flows over gills in opposite direction to flow of blood in capillaries equilibrium not reached diffusion gradient maintained across entire length of gill lamellae-this maintains concentration gradient of oxygen
GAS EXCHANGE IN PLANTS
Palisade mesophyll is site of photosynthesis
oxygen produced and carbon dioxide used creates a concentration gradient
oxygen diffuses through air space in spongy mesophyll and diffuse out stomata
PLANT REDUCE WATER LOSS
.Stomata are usually open during day to allow gas exchange
.Water enters the guard cells and they become turgid, so open
.plant becomes dehydrated guard cells lose water and become flaccid
.Xerophytes are plants adapted for hot and dry conditions- lowers water potential as less water lost by osmosis as it traps moisture eg. Marram grass
.Rolled leaf shape as upper epidermis is facing inwards to trap humid air
.Reduced leaf surface area for transpiration
.Sunken stomata, humid air is trapped reducing water potential gradient between inside leaf and humid trapped air
.No stomata on exposed lower surface
.Hairs, trap moist air
.Thick cuticle, waxy covering reduced evaporation
ADAPTION OF ALVEOLI
.many alveoli= large surface area
.Alveolar epithelium and capillary endothelium are just one cell thick
.Short diffusion distance for O2 and CO2 between air and blood
.Many capillaries close to alveoli to maintain good blood supply and maintain steep concentration gradient
.Well ventilated to bring O2 to the surface and take CO2 away and maintain steep concentration gradient for O2 and CO2
STRUCTURE OF MAMMALIAN BREATHING SYSTEM PROVIDES EFFICIENT UPTAKE OF O2 TO BLOOD
- alveoli provide a large surface area
- walls of alveoli thin to provide a short diffusion pathway
- walls of capillary thin provides short diffusion pathway
- walls have flattened cells
- cell membrane permeable to gases
- many blood capillaries provide large surface area
- intercostal muscles maintain concentration gradient;
- wide trachea flow of air
- cartilage rings keep airways open
PASSAGE OF GAS EXCHANGE IN HUMANS
Mouth / nose -> trachea -> bronchi -> bronchioles -> alveoli -> alveolar epithelium -> capillary endothelium
INSPIRATION
External intercostal muscles contract and internal relax pushing ribs up and out diaphragm contracts and flattens
air pressure in lungs drops below atmospheric pressure as lung volume increases
air moves in down pressure gradient
EXPIRATION
External intercostal muscles relax and internal contract pulling ribs down and in diaphragm relaxes and domes air pressure in lungs increases above atmospheric pressure as lung volume decreases
air forced out down pressure gradient
VENTILATION RATE EQUATION
VR= TV x BR (breathing rate)
TIDAL VOLUME
volume of air in each breath
VENTILATION RATE
breaths per minute
FORCED EXPIRATORY VOLUME
maximum volume of air that can be breathed out in I second
FORCED VITAL CAPACITY
maximum volume of air breathed out forcefully after a deep breath
CARBOHYRATE DIGESTION
Starch is hydrolysed to maltose catalysed by amylase
Amylase is produced by salivary glands which release it into the mouth
Amylase is also produced by pancreas and released into small intestine
Membrane-bound disaccaridases are attached to membranes of epithelial cells in ileum
break down disaccharides eg. Maltose, into monosaccharides
using glycosidic bonds
LIPID DIGESTION
Lipids are hydrolysed to monoglycerides, and fatty acids catalysed by lipase
Lipase are made in pancreas and work in small intestine
Bile salts produced by liver emulsify large droplets of lipids into small droplets w/ larger surface area for lipase to work on monoglycerides and fatty acids form micelles w/bile salts using ester bonds
PROTEIN DIGESTION- HOW THE REACTION IS SPED UP
Endopeptidases hydrolyse bonds in protein + hydrolyse long polypeptides into shorter polypeptides- increases surface area for exopeptidase + speeds up full hydrolysis of proteins
Exopeptidase produced by pancreas and secreted into small intestine, hydrolyse bonds at end of proteins to remove single amino acids
Dipeptidases are located on cell surface membrane of epithelial cells in small intestine and separate dipeptides into two amino acids
PROTEIN DIGESTION-USING TRANSPORT METHODS
fallicitated diffusion of amino acid
co-tansport w/Na+ ion using carrier proteins
creates Na+ ion concentration gradient
Na+ is actively transported using ATP from cell to blood
fallicitated diffusion of amino acid out of blood
PRODUCTS OF DIGESTION ABSORBED ACROSS ILEUM EPITHELIUM CELL MEMBRANE
ileum is very long and is folded into structures called villi- increases surface area for absorption.
Each villus has a good capillary network, and a network of tubes called a lacteal which is part of lymph system-both rapidly remove absorbed molecules, maintain a steep concentration gradient
lining of ileum is made of one layer of epithelial cells and capillaries are one layer of endothelial cells – this ensures a short pathway for absorption
ADAPTION OF EPITHELIAL CELLS
cells have folds in the cell membrane called microvilli, further increasing surface area
membrane has more protein channels and carriers for more active transport, facilitated diffusion and co-transport
cell contains more mitochondria for more ATP production, allowing more active transport and co-transport
cell has more ribosomes, rough endoplasmic reticulum and Golgi body’s for protein synthesis and modification, to produce more membrane proteins
ABSORPTION OF MONOSACCHARIDE + AMINO ACIDS
Monosaccharides such as glucose and amino acids are taken up by co transport
1.Na+ is actively transported out of ileum cell into blood LOWERS concentration inside cell-produces concentration gradient
2.Na+ diffuses down gradient through protein and it brings glucose w/it by co-transport
3.Glucose moves out of cell by facilitated diffusion due to its concentration gradient- diffuses into capillary
ABSORPTION OF LIPIDS
micelles are made from bile salts + fatty acids + they make lipid soluble
fatty acids absorbed by diffusion
triglycerides reformed in SER
move to Golgi body produces chylomicrons (triglyceride + protein)
they package vesicles + they move + fuse w/cell membrane releasing chylomicrons
chylomicrons absorbed to laterals in villi
ROLE OF MICELLES
make lipid soluble as they are made from bile salts + fatty acids
transport lipids to epithelial cell
fatty acids absorbed by diffusion
Hb
.quaternary protein that carries oxygen around body
.Found in red blood cells
.Four chains has haem group (Fe) that can bind to an oxygen molecule making oxyhemoglobin
.cooperative nature of oxygen binding: First molecule of oxygen to bind causes change in shape of Hb, uncovers other binding sites making binding of further oxygens easier
OXYHAEMOGLOBIN
oxygen has bound to haemoglobin
ASSOCIATE
oxygen binds to haemoglobin-loading
DISSOCIATE
oxygen leaves oxyhaemoglobin-unloading
PARTIAL PRESSURE
pressure created by a gas in a specific space
AFFINITY
readily oxygen associates to haemoglobin
BOHR EFFECT
effect of carbon dioxide on affinity of Hb-more carbon dioxide lower affinity of Hb for oxygen
Hb CURVE IN LOADING + UNLOADING OF O2
Hb has a high affinity for O2 in alveoli-more O2 is loaded at high pp of O2 transporting more O2 as its more readily available + binding of O2 is easier
Hb has low affinity in respiring tissue-more O2 is unloaded at low pp of O2 transporting less O2 as its less readily available + binding of O2 is harder
EFFECT OF CO2 ON OXYHEMOGLOBIN CURVE
carbon dioxide dissolves in liquid, carbonic acid forms decreases pH causing Hb to change shape-shifting to right
affinity decreases at respiring tissues
more oxygen is unloaded
LARGE ORGANISM USE MASS FLOW
Surface area:volume ratio too small
Distance for diffusion too long
Mass flow takes gases and nutrients close to all cells
ARTERIES
folded endothelium
narrow lumen-maintains pressure
no valves
high pressure but pressure drops when ventricles relax, but stays quite high due to elastic recoil of walls
Pressure decreases with distance from heart as there is resistance to blood flow due to friction with larger surface area of walls and dissipation of energy in elastic recoil
Thick wall to resist pressure-Thick layer of elastic tissue stretches with high pressure pulse then recoils maintaining pressure pushing blood further-Smooths out flow- Thick muscle prevents rupture
VEINS
non-folded endothelium
wide lumen-fit large amount of blood + lower resistance
valves-no back flow
low pressure-large volume means low flow rate
Thin walls as pressure is low- Walls are squeezed by skeletal muscle and breathing movements to push blood
CAPPILLARIES
Small diameter but many: No cell is far from capillary so short diffusion distance for respiratory gasses-Takes blood as close as possible to cells for rapid transfer of oxygen, carbon dioxide and glucose between blood and respiring cells
Friction of blood w/ walls and large total cross sectional area lowers pressure and slows blood flow which enhances exchange
Thin wall one cell thick endothelium layer: Short diffusion distance and slow flow for maximum transport-Smooth lining for smooth flow
Narrow lumen: Blood cells just fit in the capillaries so reduces diffusion distance to haemoglobin in red blood cells
Capillary pores: allow some substances eg. Water, white blood cells to leak out through wall-This reduces pressure
TISSUE FLUID FORMED+ REABSORBED
1.hydrostatic pressure of blood high at arterial end due to contraction of left ventricle
2.water and small soluble molecules forced out of capillary e.g amino acids, salt ions and glucose
3.reduces volume and therefore pressure in capillary
4.plasma proteins and large molecules e.g. blood cells remain
5.lowers water potential of blood
6.water moves back into venous end of capillary osmosis
7.lymph system collects any excess tissue fluid which returns to blood
WHY THE LEFT SIDE IS THICKER THAN RIGHT SIDE
blood is to be pumped to all body systems so higher pressure is needed- right side of heart pumps blood to lungs only, so less resistance
Additionally higher pressure to lungs would force more fluid out at capillaries which would impair gas exchange
AORTA
Carries oxygenated blood from L ventricle to general body
VENA CAVA
Carries deoxygenated blood back to R atrium from body
PULMONARY ARTERY
Carries deoxygenated blood from R ventricle to lungs
PULMONARY VEIN
Carries oxygenated blood back to L atrium from lungs
CONORARY ARTERIES
Supply the heart muscle tissue with oxygenated blood
BICUPSID VALVE
Prevents backflow of blood from L ventricle to L atrium
TRICUPSID VALVE
Prevents backflow of blood from R ventricle to R atrium
SEMILUNAR VALVE
Prevents backflow of blood from arteries to ventricles
CORDS
Prevent valves from inverting
ATRIUM
Contracts to force blood into the ventricle
VENTRICLE
Contracts to force blood into aorta / p artery
SUGGEST WAYS STUDENTS COULD IMPROVE QUALITY OF SCIENTIFIC DRAWING IN THIS DISSECTION
do not use sketching
ensure lines are continuous
Add labels
Add magnification
Draw all parts to same size
Do not use shading
DESCRIBE PRECAUTIONS STUDENTS SHOULD TAKE WHEN CLEARING AWAY AFTER DISSECTION
Carry + wash sharp instruments by holding handle
Disinfect instruments + surfaces
Disinfect hands
Put organ/paper towels in a bag
GIVE SAFETY PRECAUTIONS THAT SHOULD BE FOLLOWED WHEN DISSECTING HEART
Use a sharp scalpel
Wash hands
Disinfect bench + equipment
Cover any cuts
Cut away from self/others/on a hard surface
Safe disposal
VENTICULAR DIASTOLE
Heart relaxes-both atria + ventricles
Pressure drops
Blood fills atria from veins
this is often referred to as passive filling
ATRIAL SYSTOLE
Cardiac muscle in atria contract
Pressure in atria increases
higher pressure in atria than ventricles opening the atrio-ventricular valve
Blood forced into ventricles
Valves in veins stop blood going back into veins
VENTRICULAR SYSTOLE
Ventricles contract from base upwards, causes increase in blood pressure
Ventricular pressure higher than atrial pressure shutting AV valve, preventing back flow into atria
Ventricular pressure higher than aortic pressure, opening semi-lunar valve
Blood forced through semilunar valves into arteries
AFTER VENTRICULAR SYSTOLE
heart fully relaxes again there is lower pressure in ventricles than in arteries semi-lunar valves close, preventing back flow of blood into ventricles- elastic recoil of arteries means arteries initially expand to accommodate high volume of blood forced out of ventricles but then recoils, decreasing diameter of vessel again, maintaining high blood pressure and ensuring continual forward flow of blood, away from heart
ATHEROMA
- damage to endothelial cells
macrophage + lipid from blood clump together from fatty streaks - white blood cells, lipids + connective tissues build up + harden-may develop atheroma
- blood flow restricted-increasing blood pressure + cause aneurysm or blood clots
ANEURYMS
swelling of arteries-Blockage of artery increases blood pressure, when high pressure blood travels through weakened and damaged blood vessel it starts to push inner layers of blood vessel through elastic layer-forms a balloon-like swelling if aneurysm bursts this results in a haemorrhage
THROMBOISIS
blood clot-Damage to artery wall causes a rough surface- causes blood platelets and fibrin to build up at site of damage forming a blood clot- could cause a complete blockage of an artery or could break away and block a blood vessel elsewhere
HOW ATHEROMA REDUCES BLOOD FLOW RESULTING IN HEART ATTACK
Heart muscle is no longer supplied with sufficient blood
muscle requires oxygen and glucose from the blood for respiration and ATP production
Prevention of respiration causes heart muscle to become damaged and possibly to die
CARDIAC OUTPUT EQUATION
CO=HR x SV
CARDIAC OUTPUT
total volume of blood pumped out by heart in 1 minute
HEART RATE
number of full cardiac cycles in a minute
STROKE VOLUME
total volume of blood pumped out of heart in 1 full cardiac cycle
SETTING UP POTOMETER
Set up equipment under water and cut shoot under water so that air bubbles do not enter xylem and break continuous water column
Seal joins with Vaseline – prevents leaks air being drawn in
Dry off leaves after removing from water, this would decrease water potential gradient and effect rate of transpiration
Use large number of leaves for measurable rate
Draw an air bubble in
Leave to equilibrate then measure distance air bubble moves in a given time
Move bubble back t start using reservoir of water and repeat to increase reliability or set up new condition
POTOMETER BEING USED TO MEASURE RATE OF WATER UPTAKE
- Record distance moved by bubble in set time
- Use πr 2h to calculate volume
3.Convert all measurements to same units - Divide volume by time taken
5.Would need to move air bubble back onto scale
TRANSPIRATION OF XYLEM
- water is lost by transpiration
- diffusion of water vapour through stomata-lowers water potential of leaf cells + water moves from higher water potential in xylem to leaf cells by osmosis
- water draws up xylem + creates tension
- water molecules cohere together by hydrogen bonds + forms continuous column of water
- water molecules stick to xylem cell walls by adhesion
- water enters roots from soil by osmosis-travels across root cortes to xylem
XYLEM STRUCTURE
.Consists of dead cells
.Cells walls contain lignin which water can adhere to and which provide strength to xylem to prevent inward collapse
.No cytoplasm or organelles for no impeded flow
.No end walls that form a continuous system of tubes for water transport
.allows water to move as a continuous column with no impeded flow
.Pits
.Allow horizontal movement of water
SIEVE TUBE ELEMENTS
living cells with no nucleus and just a few organelles so less resistance to flow
end cell walls have perforations in them called sieve plates
COMPANION CELLS
Very active cells next to the sieve tubes’ Connected to sieve tubes by plasmodesmata
Lots of mitochondria– provide ATP to sieve tubes for active movement of sucrose
TRANSLOCATION OF PHOLEM
1.Source produces glucose which is then converted to sucrose
2.Sucrose solution is actively loaded into phloem from companion cells
3.Water potential in phloem decreases Water moves in from xylem by osmosis
4.Hydrostatic pressure builds up, forcing sucrose solution along phloem by mass flow to sink
5.At sink sucrose moves from phloem into sink cell- lowers sinks water potential so water moves down gradient into sink
6.Water re-enters xylem by osmosis
Sucrose is used in respiration or stored
EVALUATING MASS FLOW HYPOTHESIS- TO BE 100% THEY NEED
- Downward unidirectional flow
- Higher to lower pressure
- Sucrose moves from source to sink
- Process is active
RINGING EXPERIMENTS
Bark containing the phloem can be removed from stems to prevent movement of organic substances
bulge forms above ring- fluid above ring has a higher concentration of sugars than below indicating a gradient
Explanation
Swelling is caused by build up of sugar solution- cannot flow any further because sugar solution is transported in phloem, which has been removed
Bulge is above the ring due to downward flow of the sugar solution
Link to Mass Flow
As the bulging of bark only occurs on one side of ring and not both, it suggests that flow of solutes is predominantly happening in one direction
APHIDS
Aphids pierce phloem at top and bottom of stems- remove the aphid just leaving mouthpart
Sap flows out and flows out quicker at top indicating a pressure gradient
Explanation: There is a pressure in phloem causing the sap to ooze out- no hydrostatic pressure in transport in xylem
Link to Mass Flow
Shows that there is a high hydrostatic pressure in phloem which is needed for mass flow- hydrostatic pressure is greatest at leaf which supports the mass flow hypothesis
AUTORDIOGRAPHY
radioactive tracer can be used to track organic substances
Use 14CO2 which is converted into sugars.
Detect using photographic film
Explanation: radioactive carbon in carbon dioxide is incorporated into sucrose-occurs at leaf -sucrose is transported towards roots, which is sink
Link to Mass Flow
Proves movement from source to sink
EVIDENCE CONTRADICTING MASS FLOW HYPOTHESIS
Different organic substances travel at different rates in the phloem
If it was just mass flow all molecules would be forced to flow at same rate fluid is pushed from a higher to lower pressure
Different substances move in opposite directions in same sieve tube – showing bidirectional flow, something not possible with just mass flow
Sieve plates would create a barrier to mass flow-lot of pressure would be needed for solutes to get through at a reasonable rate.
