2) Structure and functions in living organisms - transport Flashcards
Why unicellular organisms can rely on diffusion for movement of substances in and out of the cell
-have very large surface area: volume
-do not need to have specialist exchange surfaces or transport systems
-diffusion is fast due to short distances required for substances to travel
Need for transport system in multicellular organisms
-small SA:vol
-distance between the surface of the organism to its centre is relatively long
-diffusion, osmosis and active transport cannot occur at a sufficient rate
Phloem function
-transport food materials (mainly sucrose and amino acids) made by the plant from photosynthesising leaves to non-photosynthesising regions in the roots and stem
-movement can be in any direction around the plant
Phloem structural features
-cells are living cells, not hollow
-substances move from cell to cell through pores in the end walls of each cell
Xylem function
-transport water and minerals from the roots to the stem and leaves
Xylem structures
-composed of dead cells which form hollow tubes
- strengthened by lignin
Root hair cells
Adapted for the efficient up take of water by osmosis, and mineral ions by active transport
-single-celled extensions of epidermis cells in the root
-increase SA:vol
Uptake of water by the root
High proportion of dissolved minerals and sugars in the cytoplasm give it a low water potential - water moves into the root hair cells by osmosis
root hair cell –> root cortex cells –> xylem –> leaf mesophyll cells
Transpiration
Loss of water vapour from the parts of the plant that are above ground
1. evaporation of water at surfaces of spongy mesophyll cells - has air spaces which creates a large surface area
2. diffusion of water vapour through the stomata as there is a concentration gradient
Process/ effect of transpiration
- Evaporation creates a slight shortage of water in the leaf so more water is drawn from xylem to replace it
- this draws more water from roots, and there is a constant transpiration of water through the plant
-water molecules pull each other up the xylem as they are cohesive
Need for transpiration
-transporting mineral ions
-providing water to keep cells turgid - support strucutre
-provide water to leaf cells for photosynthesis
-keep leaves cool - use of heat energy to convert water into water vapour as it leaves the plant helps to cool the plant down
Factors affecting rate of transpiration
-wind speed
-humidity
-light intensity
-temperature
Factors affecting rate of transpiration - wind speed
If higher, transpiration higher
-airflow removes water vapour from the air surrounding the leaf
-increases concentration gradient between the leaf and the air
-increases water loss
Factors affecting rate of transpiration - humidity
If higher, more transpiration
-concentration gradient is weaker
-less water lost
Factors affecting rate of transpiration - light intensity
If higher, more transpiration
-guard cells become turgid, stomata open
-allow water to be lost
Factors affecting rate of transpiration - temperature
If higher, more transpiration
-particles have more kinetic energy
-water molecules evaporate from the mesophyll
-diffuse away faster than at low temperatures
Practical: Factors Affecting Transpiration - mass potometer
- Set up a potometer.
- Set up the necessary environmental factors
- Temp: use a temperature-controlled room or water bath
- Humidity: Wrap the shoot in a plastic bag with varying degrees of vapour.
- Wind speed: fan
- Light intensity: lamp - Allow time for the apparatus to equilibrate.
- Record the starting position of the air bubble in the capillary tube.
- Leave for 1 hour.
- Record the final position of the air bubble
- calculate distance moved, and volume of water absorbed by the plant
- Repeat steps 1-7, changing the factor at fixed intervals
Composition of blood
-consists of red blood cells, white blood cells, platelets, plasma
-55% - plasma
-1% - white blood cells and platelets
-45% - red blood cells
Role of plasma
-mostly water
-other substances dissolved:
-nutrients - glucose, waste products, urea, CO2
-transport heat energy from respiring tissues
-protein molecules (plasma proteins) that remain in the blood all the time
-hormones
Red blood cells (erythorcyte)
Specialised cells which carry oxygen to respiring cells
Adaptations of red blood cells
-full of haemoglobin - protein that binds to oxygen to form oxyhaemoglobin
-no nucleus - allows more space for haemoglobin to be packed in
-bioconcave disc shape - gives large SA:vol to maximise diffusion of oxygen in and out
White blood cells
-part of the body’s immune system
-specialised cells defend against pathogenic microorganisms
-two types:
-phagocytes
-lymphocytes
Phagocytes
- have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells
- Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it - phagocytosis
-non-specific immune response
Lymphocytes
- produce complementary antibodies (soluble proteins that pass into the plasma) Pathogens have chemical markers (antigens) on their surfaces, which antibodies recognize.
- Antibodies attach to the antigens and clump them together
- Act as a label on the pathogen, so that it is more easily recognized by a phagocyte
- produce antitoxins to neutralize toxins released by pathogens
-production of antibodies after the first exposure - primary immune response
Immune system - response to infection
- Pathogen enters the blood stream, multiplies, releases toxins
- Phagocytes encounter the pathogen, recognise it is a pathogen and engulf and digest it
- The pathogen encounters a lymphocyte which recognises its antigens
- The lymphocytes starts to produce specific antibodies to combat that particular pathogen
- Lymphocyte clones itself to produce lots of lymphocytes - producing the specific antibody required
- Antibodies cause agglutination (clumping) of pathogens
- Phagocytes engulf and digest the agglutinated pathogens
- After patient has recovered, they retain antibodies specific to the disease and memory cells
- If patient encounters the same pathogen again, it will trigger a secondary immune response
- Memory cells produce much large quantities of the required antibodies in a much shorter time to fight off the pathogen before the patient suffers any symptoms
How vaccines work
- In the bloodstream, antigens in the vaccine can trigger an immune response
- Lymphocytes recognise the antigens in the bloodstream
- Activated lymphocytes produce antibodies specific to the antigen encountered
- Memory cells and antibodies remain circulating in the blood stream
- Future infection by the same pathogen will trigger a response faster and larger than initial response
- Pathogen is unable to cause disease, individual is immune
Platelets
Fragments of cells that are involved in blood clotting
1. When skin is broken, platelets arrive to stop the bleeding
2. release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin
3. Form insoluble mesh across the wound, trap red blood cells, form a clot
4. Clot dries, develops into a scab to protect the wound from bacteria entering
Heart - oxygenated and deoxygenated blood
-oxygenated blood from the lungs enters the left side of the heart, pumped to body
–left side has a thicker wall - high pressure blood
-deoxygenated blood from the body enters the right side of the heart and pumped to the lungs
–right ventricle is pumping blood at lower pressure to the lungs
Veins
Carries blood from the body towards the heart
-vena cava, pulmonary vein
Arteries
Carry blood away from the heart to the body
-aorta, pulmonary artery
Capillaries
Link arteries and veins
How blood is moved through the heart
- Blood enters the atria
-won’t pass into ventricles as bi and tricuspid valves are closed - Walls of the atria contract
-increased pressure of blood in an atria
-force open valves
-blood goes to ventricles - When ventricles are full, it contracts
-increased pressure of blood in the ventricles
-close bi and tricuspid valves
-blood cannot return to atria - Ventricles contract, pressure increases
-forces open semilunar valves
-blood ejected into aorta/ pulmonary artery - Ventricles empty, high pressure in aorta/ pulmonary artery close valves
- Cycle begins again
Adaptation of the heart
-divided into right and left by septum - wall of the left ventricle is much thicker as it pumps blood to the rest of the body - higher pressure
- valves - blood can only flow in one direction
-walls of the heart are made of cardiac muscles
Adaptation of the heart - walls of the heart are made of cardiac muscles
-therefore can contract + relax without becoming fatigued
-coronary arteries carry blood to capillaries to supply heart muscle with oxygen and nutrients
-coronary veins return blood to right atrium
Structure of the heart
Draw it
Coronary heart disease
-coronary arteries are narrow
-easily blocked by cholesterol - a build up of fatty substances
-cut off supply to area of cardiac muscle
-muscle cannot receive oxygen and glucose - cannot respire and release energy
-cannot contract
-heart attack
Factors affecting coronary heart disease
-hereditary
-high blood pressure
-diet
-smoking
-stress
-no exercise
-high cholesterol
Artery structure
-carry blood at high pressure away from the heart
-carry oxygenated blood -except pulmonary artery
-have thick muscular walls containing elastic fibres
–can withstand the high pressure of blood and maintain blood pressure
-have a narrow lumen
Veins structure
-Carry blood at low pressure towards the heart
-Carry deoxygenated blood (other than the pulmonary vein)
-Have thin walls
-Have a large lumen - reduces resistance to blood flow under low pressure
-Contain valves -prevent backflow of blood
Capillaries structure
-Carry both ox + dox blood at low pressure within tissues
-Have walls that are one cell thick -substances can easily diffuse in and out of them
-Have ‘leaky’ walls - allow blood plasma to leak out and form tissue fluid surrounding cells
Circulatory system
-draw it
-vena cava, pulmonary vein – towards heart
-aorta, pulmonary artery – away from heart
-pulmonary artery – towards lungs
-pulmonary vein – away from lungs
-renal artery – towards kidney
-renal vein – away from kidney
-hepatic portal vein – towards liver
-hepatic artery – towards liver
-hepatic vein – away from liver
Adrenaline
-secretion from adrenal glands
-increases heart rate as part of a ‘fight or flight’ response
-muscles release more energy
-increased supply of oxygen for aerobic respiration
-deliver more oxygen, heart rate, stroke volume increases