2) Structure and functions in living organisms - transport

Question 1

Why unicellular organisms can rely on diffusion for movement of substances in and out of the cell

Answer 1

-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

Question 2

Need for transport system in multicellular organisms

Answer 2

-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

Question 3

Phloem function

Answer 3

-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

Question 4

Phloem structural features

Answer 4

-cells are living cells, not hollow
-substances move from cell to cell through pores in the end walls of each cell

Question 5

Xylem function

Answer 5

-transport water and minerals from the roots to the stem and leaves

Question 6

Xylem structures

Answer 6

-composed of dead cells which form hollow tubes
- strengthened by lignin

Question 7

Root hair cells

Answer 7

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

Question 8

Uptake of water by the root

Answer 8

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

Question 9

Transpiration

Answer 9

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

Question 10

Process/ effect of transpiration

Answer 10

1. Evaporation creates a slight shortage of water in the leaf so more water is drawn from xylem to replace it
2. 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

Question 11

Need for transpiration

Answer 11

-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

Question 12

Factors affecting rate of transpiration

Answer 12

-wind speed
-humidity
-light intensity
-temperature

Question 13

Factors affecting rate of transpiration - wind speed

Answer 13

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

Question 14

Factors affecting rate of transpiration - humidity

Answer 14

If higher, more transpiration
-concentration gradient is weaker
-less water lost

Question 15

Factors affecting rate of transpiration - light intensity

Answer 15

If higher, more transpiration
-guard cells become turgid, stomata open
-allow water to be lost

Question 16

Factors affecting rate of transpiration - temperature

Answer 16

If higher, more transpiration
-particles have more kinetic energy
-water molecules evaporate from the mesophyll
-diffuse away faster than at low temperatures

Question 17

Practical: Factors Affecting Transpiration - mass potometer

Answer 17

1. Set up a potometer.
2. 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
3. Allow time for the apparatus to equilibrate.
4. Record the starting position of the air bubble in the capillary tube.
5. Leave for 1 hour.
6. Record the final position of the air bubble
7. calculate distance moved, and volume of water absorbed by the plant
8. Repeat steps 1-7, changing the factor at fixed intervals

Question 18

Composition of blood

Answer 18

-consists of red blood cells, white blood cells, platelets, plasma
-55% - plasma
-1% - white blood cells and platelets
-45% - red blood cells

Question 19

Role of plasma

Answer 19

-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

Question 20

Red blood cells (erythorcyte)

Answer 20

Specialised cells which carry oxygen to respiring cells

Question 21

Adaptations of red blood cells

Answer 21

-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

Question 22

White blood cells

Answer 22

-part of the body’s immune system
-specialised cells defend against pathogenic microorganisms
-two types:
-phagocytes
-lymphocytes

Question 23

Phagocytes

Answer 23

1. have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells
2. Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it - phagocytosis
   -non-specific immune response

Question 24

Lymphocytes

Answer 24

1. produce complementary antibodies (soluble proteins that pass into the plasma) Pathogens have chemical markers (antigens) on their surfaces, which antibodies recognize.
2. Antibodies attach to the antigens and clump them together
3. Act as a label on the pathogen, so that it is more easily recognized by a phagocyte
4. produce antitoxins to neutralize toxins released by pathogens
   -production of antibodies after the first exposure - primary immune response

Question 25

Immune system - response to infection

Answer 25

1. Pathogen enters the blood stream, multiplies, releases toxins
2. Phagocytes encounter the pathogen, recognise it is a pathogen and engulf and digest it
3. The pathogen encounters a lymphocyte which recognises its antigens
4. The lymphocytes starts to produce specific antibodies to combat that particular pathogen
5. Lymphocyte clones itself to produce lots of lymphocytes - producing the specific antibody required
6. Antibodies cause agglutination (clumping) of pathogens
7. Phagocytes engulf and digest the agglutinated pathogens
8. After patient has recovered, they retain antibodies specific to the disease and memory cells
9. If patient encounters the same pathogen again, it will trigger a secondary immune response
10. 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

Question 26

How vaccines work

Answer 26

1. In the bloodstream, antigens in the vaccine can trigger an immune response
2. Lymphocytes recognise the antigens in the bloodstream
3. Activated lymphocytes produce antibodies specific to the antigen encountered
4. Memory cells and antibodies remain circulating in the blood stream
5. Future infection by the same pathogen will trigger a response faster and larger than initial response
6. Pathogen is unable to cause disease, individual is immune

Question 27

Platelets

Answer 27

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

Question 28

Heart - oxygenated and deoxygenated blood

Answer 28

-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

Question 29

Veins

Answer 29

Carries blood from the body towards the heart
-vena cava, pulmonary vein

Question 30

Arteries

Answer 30

Carry blood away from the heart to the body
-aorta, pulmonary artery

Question 31

Capillaries

Answer 31

Link arteries and veins

Question 32

How blood is moved through the heart

Answer 32

1. Blood enters the atria
   -won’t pass into ventricles as bi and tricuspid valves are closed
2. Walls of the atria contract
   -increased pressure of blood in an atria
   -force open valves
   -blood goes to ventricles
3. When ventricles are full, it contracts
   -increased pressure of blood in the ventricles
   -close bi and tricuspid valves
   -blood cannot return to atria
4. Ventricles contract, pressure increases
   -forces open semilunar valves
   -blood ejected into aorta/ pulmonary artery
5. Ventricles empty, high pressure in aorta/ pulmonary artery close valves
6. Cycle begins again

Question 33

Adaptation of the heart

Answer 33

-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

Question 34

Adaptation of the heart - walls of the heart are made of cardiac muscles

Answer 34

-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

Question 35

Structure of the heart

Answer 35

Draw it

Question 36

Coronary heart disease

Answer 36

-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

Question 37

Factors affecting coronary heart disease

Answer 37

-hereditary
-high blood pressure
-diet
-smoking
-stress
-no exercise
-high cholesterol

Question 38

Artery structure

Answer 38

-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

Question 39

Veins structure

Answer 39

-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

Question 40

Capillaries structure

Answer 40

-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

Question 41

Circulatory system

Answer 41

-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

Question 42

Adrenaline

Answer 42

-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