AS Biology Revision Cards

Slide 1

Why animals need a large surface area to volume area:oxygen must be supplied for respirationheat generated by metabolism must be lostwaste i.e. CO2 and urea needs to be removedcells need to be supplied with nutrients i.e. Glucose, amino acids and mineral ionsFeatures of specialised exchange surfaces:large surface area to volume ratio speeds up the rate of exchangevery thin barrier allows materials to cross quickly reduce diffusion timePartially permeable to allow selected materials to crossMovement of the environmental medium e.g. Air to maintain a diffusion gradientmovement of the internal medium e.g. blood to maintain a diffusion gradient

Biology: mrs searles 1revision cardsTobi Ojo12.3Large organisms are multicellular: many cells so a greater surface areaLarge organisms develop specialised exchange surfacesThe bigger the ratio of surface area to volume the faster the rate of diffusionAmoeba: simple diffusion across outer surface since it has a large sa:vInsects: simple diffusion through spiracles in its exoskeleton. Sa:v gets smallHuman beings: sa:v is very small. The outer surface isn't big enough to allow enough gases to enter the body.Large organisms develop mass flow transport systems Respiration- when CO2, energy and H2O is made. If it's aerobic it takes place in mitochondria. Forms energy in the form of ATP.Glucose+oxygen>CO2+H2O+energy

Trachea- supported tube that connects the lungs to the outsideRib cage- protects the lungs in a bony boxIntercostal muscles- muscles that move the ribsAlveoli- air sacsBronchi- two smaller tubes that the trachea divides intoBronchioles- smaller tubes going to the alveoli Larger organisms need a larger area to exchange more substances. Often this is combined with a transport system to move substances around the body. Surface areas

are adapted to make it easier for molecules to cots from one side to another.

Examples of specialised exchange surfaces:walls of alveoli in the lungssmall intestines nutrients absorbedliver levels of sugar adjustedroot hairs of plants minerals absorbedhyphae of fungi

Inhalation (inspiration):Diaphragm contracts to become flatter and pushes digestive organs downExternal intercostal muscles contract to raise ribsVolume of chest cavity increasesPressure in cavity drops below atmospheric pressure then air moves into the lungs Exhalation (exportation):diaphragm relaxes and is pushed up by displaced organs underneathInternal intercostal muscles relax and ribs fallVolume of chest cavity decreasesPressure in cavity increases and raises above atmospheric pressure air moves out of lungsThorax- chest cavityThe lungs:The trachea, bronchi and bronchioles are airways that allow air in and out of the lungs. They must: Large enough to allow enough air slowDivide into smaller airways to reach the alveoliStrong enough so they don't collapse Flexible to allow movementAbel to recoil as pressure is changingTrachea and bronchi:Have similar structures. Both have thick walls bronchi is narrower. Walls mostly cartilageCartilage forms c-ring in trachea less I bronchiCartilage- glandular tissue, connective tissue, elastic fibres, smooth muscle, blood vesselsContains ciliates epithelium and goblet cells secrete mucusRoles of tissue:Cartilage- structural role supports the trachea and bronchi holding them open.Smooth muscle- can constrict thus controlling the flow of air in/out of the alveoli.

Smooth muscle- Useful if there are harmful substances in the air.Elastic fibres- as the smooth muscle relaxes the elastic fibres coils to their original size and shape. Dilates the airways.Goblet cells & glandular tissue- secretes and traps mucus.Ciliated epithelium- hair like structures called cilia which wafts mucus up the airway into the throat. Adaption of alveoli:large surface areaextremely thinlined with squamous epitheliumkept moist by fluid from epithelial cells- helps diffusion

Atrial systole- valves are fully open, atrium is contracting blood flows into left ventricle, semilunar valves still closed.

Ventricle systole- av valves are closed, semilunar valves are open, ventricles are contacting

Valves prevent back flowCardiac muscle:Contracts without fatigue Appears a striped under microscopeContains actin & myosin proteinsLots of mitochondria Cavity of alveolus:Low co2 concentration, high O2 concentrationEndothelial cell of capillary:High co2 concentration, low O2 concentration inside red blood cells

Spirometers:wear a nose clip- so they don't breathe through nose and make results invalidair right seal around mouth piecedisinfect mount piecefresh air in chamberVolume in spirometer drops in first minute because oxygen I'd being used by respiration and co2 being breathed out is absorbed by the sodalime. So overall volume goes down.Inspiration reserve volume- Is how much air can be breathed in I've and above normal tidal wave volume when you take in a big breathInspiratory reserve volume- is how much more air can be breathed out over and above the amount that is breathed in a tidal volume breath.A person breathes onto the mouthpiece and the volume of air in the air chamber changes. The movement caused by this change is recorded by the recording pen. Tidal volume- is the volume of air when a person is breathing quietly.Vital capacity- is the maximum volume of air exchanged from full expiration to full inspiration.Residual volume- is the volume of air that always remains in the lungs even after the biggest possible exhalationDead Slavs if the air in the bronchioles, bronchi and trachea.

Histamine:A drug for allergy. Stops the symptoms of an allergic reaction. Histamine is released by cells as part of an allergic reaction. Histamine binds to the receptors on the membrane of target cell as it has a complimentary shape. This triggers a response inside of the cell it also increases permeability of capillary. Histamine suppresses body's natural responses. Single circulatory systems:1 path to the heart, 1 circuit, closed system (blood travels in blood vessels) Blood pressure reduced Does not flow quicklyLimits rate at which oxygen and nutrients deliveredDouble circulatory systems: 2 paths to the heart, 2 circuits, lungs, closed system, blood flows through the heat twice in a single cycle. Humans have a higher demand for oxygen.Heart can increase blood pressureOpen circulatory system- blood not always in vesselsClosed circulatory system- blood always remains in vessels

Factors that affect the need for transport system:Size, sa:v ratio, how active organism is Structure of heart:covered by tough membrane- pericardiumencloses the pericardial fluidneeded to lubricate the movement of heart in pericardiumleft- oxygenated blood, right- deoxygenated bloodStructure of cardiac muscle;epicardium is outer layer of the heart wallendocardium is inner layermade if epithelial cells and connective tissuemyocardium is middle layer

Atrium is thin walled and elastic pumps blood a short distance to the ventricle, small amount of muscleVentricle is thicker muscular walls pumps blood further to lungs or bodyDiastole- the ventricle are relaxed, the av valves aren't fully open, semilunar valves are closed

Heart is myogenic- initiate its own contractionAtria and ventricles have own natural frequency of contractionAtrial muscles contract at higher frequency than ventricles. Inefficient pumping Red blood cells- transports oxygen around the bodyCapillaries- acts as a passage where oxygen and nutrient in blood are delivered to tissue.Sino atrial node(SAN) generates electrical activity. Wave of excitation spreads through walls of both atria causes muscles to contract. - atrial systole

Atrioventricular node (AVN) wave of excitation goes down purkyne tissue. At base of septum(apex) excitation spreads out across ventricles causing contraction.ECG- electrocardiogramUsed to measure electrical activity in heart. Electrical activity in the heart spread through other surrounding tissues and can be picked up using sensors on the skin.

(fibrillation) could be caused if all 4 chambers are not synchronised.The SA node is a patch of tissue located in the heart which generates electrical activity. The wave of excitation causes the atria to contract. The excitation in the av node is delayed so the atria can fully contract. Afterwards the wave of excitation passes down the septum/apex and spreads up the walls of the ventricle resulting in the ventricles contracting.

Arehythmias:A change in the rhythm of your heartbeat. When the beady beats too fast, it's called tachycardia. When it beats too slow, it's called bradycardia. Beats can be irregular.Atrial fibrillation:This causes the ventricles to contract faster than normal. When this happens the ventricles don't have enough time to fill completely with blood to pump to the lungs and body.Artery and related function:thick walk- stops bursting/withstands pressurenarrow lumen- to maintain pressureelastic tissue- allows stretchingelastic recoil- it can maintain its shape under high pressurecollagen- structure and supportsmooth muscle- maintain pressuresmooth endothelium- reduce friction, allows blood to flow easilyArtery, aorta, arteries, arterioles, capillariesVein:Similar to arteries but transport blood at a lower pressure so they aren't as strong.They have three layers, each layer is thinner.Capillaries:Smallest blood vessels they distribute oxygenated blood from the arteries out to tissue of your body then move deoxygenated blood from tissues back to veins.Tissue fluid:Colourless fluid (no red blood cells) that is formed from blood plasma by pressure filtration through capillary walls (forcing the liquid out needs to get buried a to cell)Only small molecules get filteredSurround all the cells of the body and all exchanges between blood and cells occur through it.Blood cells: red blood cells (erythrocytes), white blood cells (leucocytes), platelets (cell fragments) help blood clot.Plasma- fluid that carries around all the water, glucose, amino acids, urea and some of the co2Blood - carries materials around the body: plasma 55%, blood cells 45%Phagocytes/ neutrophil-Engulf bacteria by phagocytosis.Lymphocyte- the release of antibodies.Human Lymphatic system:System of thin tubes that run throughout body called lymph vessels. Lymphatic systems jobs: drains fluid into bloodstream from tissue, filters lymph, filters blood, fights infections

Lymph flows through lymphatic vessels passes through lymph nodes where it gains white blood cells and antibodies. Excess fluid returns to blood ensures that tissue do not fill with too much. Tissue fluid build up is a result of a blockage. This occurs when the fluid can't get to the lymph and be drained.Partial pressure of oxygen- the concentration of oxygen available.Percentage saturation- represents the amount of oxygen being carried by oxyhemoglobin i.e. Low saturation haemoglobin has been used in other cells.Picks up ions. Shape changes after 1st molecule because picking up oxygen making it easier to pick up more. Oxygen uptake: Oxygen diffuses into blood plasma in the lungs. It enters the red blood cells. Then it is taken up by haemoglobin which takes it out of solution thereby maintains concentration gradient allowing further oxygen to enter the cell. 1. At low pO2 it is hard for oxygen molecules to attach2. As pO2 rises and some oxygen molecules attach to haemoglobin it becomes easier to attach. Explains shape of curve.3. As it becomes saturated it becomes more difficult for oxygen to attach to haemoglobin.Foetal haemoglobin has more Myoglobin found in muscles. The speciation curve well to left of haemoglobin. It is an oxygen store which enables the muscle to continue contracting. It only releases oxygen at a vet low partial pressure of oxygen.Bohr shift:This is whenCO2 level increases (pCOs) the haemoglobin dissociation curve shifts to the right.Haemoglobin is more efficient at releasing oxygen since tissue becomes more active and the rate of respiration increase. Tissue receives more oxygen . When CO2 decreases oxygen is picked up by haemoglobin more efficiently. CO2 transport:blood carries CO2 partly in plasmacombined with haemoglobin in rbcs forming carbaminohaemoglobinpartly as hydgencarbonate HCO3 ions

oxygen than normal haemoglobin (have high affinity for oxygen) in order to survive and receive oxygen from the placenta. After baby is born haemoglobin goes to normal. If women and baby both have foetal haemoglobin the baby wouldn't get enough oxygen. Dissociation curve is to the left if maternal.

Haemoglobin: globular protein. Contains 4 polypeptide chains. Contains 4 harm groups for binging O2. Hydrostatic pressure is generated in the heart by the ventricle muscles contracting. Hydrostatic pressure drops as blood moves away from the heart because the surface area of the capillaries are much larger than the arteries since there are more and smaller vessels. This means the pressure is spread and less.Training at Altitude:Long-distance races are dominated by African athletes who spend most of their lives at altitude and whose bodies get used to making the most of the oxygen. When the body has to make a limited supply of oxygen it produces more rbcs. Oxygen is delivered to muscles.Haemoglobin consists 4 subunits (haem group- Fe2+ & polytides) The haem group can hold oxygen it attracts it. If theres a low partial pressure/oxygen tension (pO2) it hard to associate with O2 (1st molecule) but after the molecule it causes a slight change in the shape of haemoglobin which makes it easier to attract 2 more O2. when it comes to the 4th subunit its hard to reach 100%How is CO2 transported?CO2 diffuses into the red blood cells and combines with water with the help of carbonic anhydrase (enzyme). The product of this reaction is carbonic acid which dissociates releasing hydrocarbonate ions out of the blood cell. And CL enter the cell (maintains charge/CL shift) Haemoglobonic acid is formed. Additionally oxyhaemoglobin enters cell and dissociates releasing o2 to blood plasma.Carbon monoxide:Carbon monoxide can combine with haemoglobin meaning O2 will no longer be able to this is cause carbon monoxide has a higher affinity. This can cause problems with the transport of oxygen.The air pressure is lower at high altitudes than at sea level. This causes shortness of breath. To compensate more rbcs are made from 45% to 70%. This acclimatisation takes about a week. People living permanently at altitudes have adaptations: broader chests, larger lung capacity, larger heart, more haemoglobin.Functions in plants:Leaves: trapping sunlight and converting it into energy. Key role in photosynthesis . Controls the entry of gaseous exchange.Stems: transport system move things around. Support/structure. Xylem and phloem.Roots: absorb water/ dissolved minerals. Roots anchor plant. Transport in multicellular plants:Theres two distinct parts: leaves site to photosynthesis, roots absorb water. They need to be connected this is done by the vascular bundle which goes through the roots up the stem into the leaves. Strength/ support.Vascular tissue in stem: Vascular bundles found at edge of stem. Xylem are found towards the inside. Phloem towards the outside. Cambium between it.Parenchyma- living tissue made of thin walled prenchyma cells, the most abundant type of cell in plant body. Function is to heal and regenerate new cells also for photosynthesis storage.Collenchyma- tissue for strengthening plants.Solmenchyma- tissue for strengthening, often described as fibres and can be long and tapered. Structure: Xylem tissueTubes- water dissolved minerals carrying tissue in the vascular bundle these are vessel elements (verticle chain of dead cells) / tracheids.Fibres- to help support plantLiving parenchyma cells.Has perforation plates.Cell walls impregnated with lignin.Pits/ no content.

Structure: PhloemHas sieve tube elements, elongated structures, cells are living contain small amount of cytoplasm within membrane, cells have some mitochondria, no nucleus, golgi, ribosomes. Each have perforated end walls sieve plates.Companion cells carry out functions which sieve tubes cant cause of lack of organelles.Materials pass through plasmodesmata, link two cells.Xylem functions:Narrow lumen increase height, water rises (capillary action)Long cells arranged continuos columnCell walls thickened(lignin) dont collapseDead cells no cytoplasm/nucleusAnnular, spiral thickening allows elongation/ bending.

saturation but it eventually does. When oxygen attached its called oxyheamoglobin. Cells need oxygen for respiration so when its need o2 is released from oxyhaemoglobin this is dissociation. Also to maintain a steep diffusion gradient haemoglobin takes up o2 so more oxygen can diffuse into the blood. Fetal haemoglobin needs to be higher so it can pick o2 from envirome

Vascular tissue in root: vas tissue distributed throughout plant. Xylem are phloem found together in vascular bundles. `vas bundle in the centre, structure gives strength.Vascular tissue in leaf: form midrib and veins in leaves. Two major groups: dicotyledons, monocotyledons. Xylem on top of the phloem.

In the arteries the blood plasma moves out of the blood and forms tissue fluid. The hydrostatic pressure is greater than water potential. This is why the relative pressure is higher at the arteries than the veins.Mass flow:Movement of water into phloem. Pressure forces phloem sap to move toward the sink.Mass flow carries substances along the phloem it can occur in either direction but goes down hydrostatic pressure gradient.Source- builds pressureSink reduces pressureTranslocation:Phloem transport more sugars and other chemicals made by plant (assimilates). Transported in live cells ex. Sieve & companion cells. Source: sugar production site photosynthesis, starch breakdown in storage area where sucrose is released.Sink: sugars uptake site, growing areas, storage areas, fruits+seeds where sucrose is removed and sent to xylem.Phloem structure: nucleus & many organelles in Ccells allows spaceCellulose walls- strength/ burstingElements elongated and arranged continuous columnPeforated walls allows water flowCompanion cells many mitochondria ATP for translocation.Can flow either wayWater uptake: Epidermis has root hairs, minerals absorbed by active transport using ATP. Minerals reduce WP of cytoplasm. WP in cell was lower than soil. Water is taken up across membrane by osmosis. 3 pathways for water in cells: apoplast, symplast and vacuolar. Before water gets into the xylem it travels through the cortex and central structure.Endodermis has a waterproof strip called casparian strip. This blocks apoplast pathway forcing water to go through symplast pathway. Endodermis moves minerals into xylem by active transport. WP in xylem decreases and water moves in (osmosis). Casparian strip controls substance by forcing water into cytoplasm, creates water potential in xylem, stops back flow (via apoplast pathway)Apoplast: water between cellulose in cell walls. Water moves through spaces. Water doesnt pass through plasma membrane. Dissolved mineral ions & salt can be carried.Symplast: water enters cytoplasm through plasma membrane. Passes between cells through plasmodesmata. Water can flow through linked cells. 3 explanations to move water up the stem: root pressureBecause the xylem has a lower water potential water is pushed up by metres. However its not enough if push water to the top of a large plant.Capillary action: forces also attract the water molecules to the side of the xylem adhesion. The narrowness of xylem means that this can pull water up the xylem.Transpiration pull: water molecules are attracted to each other by forces of cohesion. Molecules leave the leaf by evaporation and the molecules are held together is pulled up like a chain causing tension. Water evaporates from guard cells so water moves in from neighbouring cells.Transpiration: the loss of water by evaporation from the upper parts of the plant. Stomata occurs mainly in leaves & accounts for 90% water lost.Cuticle waxy external layer limits water loss account 10%Lenticils loosely packed cells on surface through water is lost.Factors affecting transpiration rate:Number of leavesNumber, size, position of stomataPresence of cuticleLightTemperature: rate of evaporation, diffusionRelative humidityAir movement + water availabilityPlants living in dry, arid places have adaptations to reduce water loss. These are called xerophytes.Adaptations: hairs limit air movementLeaf rolled reduction in surface area.Thick waxy cuticle reduces water loss through cuticles.Stomata in pits moist air trapped close to the area of water loss reducing rate of water loss. Stamatas' closed during light.Reduced no. stomata reduces no. of pores through which water loss occurs.Deep root roots tap into lower water.Phloem loading at source: ATP is used by companion cells to actively transport H+ ions out of cytoplasm into tissue. This sets up a diffusion gradient and the H+ ions diffuse back in. Proteins enable H+ ions to bring sucrose molecules into companion cells (co transporter proteins). As the sucrose builds it diffuses into sieve elements through plasmodesmata.Leaf structure: Phototropism is a growth response which allows shoots to grow towards light. Large leaf surface area is held perpendicular to the light source.Leaves are thin so there's few cell layers to absorb light.Leaf mosaic is arrangement of leaves in a pattern which minimises overlapping.Shoot system holds leaves in optimum positionEtiolation causes rapid elongation of internodes.