Biology - Transport System Edexcel IGCSE

All subtopics - Unicellular and Multicellular Organisms, Circulatory System, Role of the Xylem and Phloem, Root Hair Cells, Practical: Factors Affecting the ROT, Blood, Vaccinations, Platelets and Blood Clotting, Structure and Function of the Heart, Heart Rate and Exercise, Risk Factors for CHD, Blood Vessels

unicellular organisms

made of one cell, no need for transport systems because they can obtain the oxygen they need by diffusion through their cell membrane

properties of unicellular organisms

• large surface areas relative to their volume → short diffusion distance from the centre to the surface

• diffusion, osmosis, and active transport through cell membrane is sufficient for their needs

• no need for specialised exchange structures or transport systems

properties of multicellular organisms

• requires transport systems to supply all their cells with what they need fast enough

• consists of many cells arranged in multiple layers → increases distance between the external environment and internal cells

• requires specialised transport systems

circulatory system - animals

carries essential substances in the blood all around the body, such as:

• oxygen

• glucose

• carbon dioxide

• water

• waste

vascular system - plants

transports - through xylem and phloem:

• water

• nutrients

• sugars

• amino acids

xylem

• moves water and minerals from roots to shoots

• formed from a hollow tube of dead cells, reinforced by lignin → provides a route for the column of water to move through the plant by transpiration

phloem

• distributes sugars (sucrose) and amino acids from where they are produces / stored

• sucrose and amino acids are produced in the leaves while plants photosynthesise → transported to other parts of the plant

• formed from living cells forming a tube with holes through which substances can move

how is water important to plants?

• needed for photosynthesis

• maintain the turgor pressure in cells and keep their structure

transport of water into root hair cells - IMPORTANT

1. water is absorbed into the roots by osmosis (M1)

   → this is because there are high concentration of minerals in the root cells, therefore water is drawn into the cells from a high water potential in the soil to low water potential in the cells (M2)

2. The cells on the outer layer of the roots are specialised cells called root hair cells

root hair cell properties

• adapted for the efficient uptake of water (by osmosis) and mineral ions (by active transport)

• contains mitochondria which release energy for active transport

• increases the surface area of plant roots → increases the rate at which water and minerals can be taken up (transpiration)

transpiration stream - order

1. once inside the root cells (M1), water can pass into the xylem vessels to be taken up to the stem (M2) into the leaves

2. however, if the leave is photosynthesising, then water is lost through the stomata (M3)

transpiration - definition

the loss of water vapour from the parts of the plant that are above the ground (leaves, stem, flowers)

transpiration - function in plants

• transporting mineral ions

• providing water to keep cells turgid in order to support the structure of the plant

• providing water to leaf cells for photosynthesis

• keeping the leaves cool as heat energy is removed from the leaves when water evaporates

factors that affect transpiration

1. light intensity

2. temperature

3. wind speed

4. humidity

light intensity - effect on ROT

↑ light intensity = more stomata open = ↑ transpiration

• eventually, all the stomata will be open and any further increase in light intensity will not effect the ROT

temperature - effect on ROT

↑ temperature = more air particles move faster (↑ kinetic energy) = more water particles will evaporate = ↑ transpiration

wind speed - effect on ROT

↑ wind speed = moves away water surrounding the leaf = ↑ diffusion gradient = ↑ ROT

humidity - effect on ROT

↑ humidity in air = ↑ water in air = ↓ concentration gradient between inside and outside of leaf

• this overall decreases the transpiration gradient (slows down)

bubble potometer - what is it used for?

used to estimate the rate of transpiration

how to measure ROT? (factors that effect the ROT)

• light intensity = move the lamp closer / further away

• wind speed = using a fan

• temperature = changing the room temp.

• humidity = spraying different volumes of water in a bag and placing it over the shoot

process of using the bubble potometer

1. as transpiration occurs, the xylem sucks up more water

2. therefore, the bubble will move along the capillary tube → measure the distance the bubble moves

3. if you measure the distance and time, you can then calculate the ROT

method of setting up the bubble potometer

1. cut the shoot underwater at an angle to prevent air getting in the xylem

2. assemble underwater so no air can get in

3. check it is water and air tight

4. dry the leaves and leave time for them to acclimatise

5. remove from the beaker of water to introduce bubble and then place it back

calculate ROT using bubble potometer (formula)

ROT = distance moved by air bubble (m) / time (min)

corms evaluation - bubble potometer

change: change intensity of the light

organisms: the plant used in each repeat is the same species, size, age, number of leaves

repeat: repeat it several times to ensure the results are reliable

measurement 1: measure the distance travelled by the bubble

measurement 2: …in 30 mins (calculate the ROT)

same: control the temp., wind speed and humidity of the environment

components of blood

red blood cells, white blood cells, platelets and plasma

red blood cells (erythrocytes) - structure and their functions

• biconcave discs → gives them a large surface area to volume ratio to maximise diffusion of oxygen in and out

• no nucleus to maximise the available capacity to carry the protein haemoglobin

• produced in some bones, mainly ribs, vertebrae, and femur

• contain the red pigment haemoglobin which can reversibly bind with oxygen

what does oxygen and haemoglobin produce? (reaction)

oxygen + haemoglobin → (reversible reaction) oxyhemoglobin

white blood cells - structure an their functions

• larger than red blood cells and have a nucleus

  → different types have slightly different structures and functions

• when you are ill, white blood cells are produced to protect the body from infections and bacteria

• can repair tissue after an injury

types of white blood cells

• Phagocytes

• Lymphocytes

(both have different jobs

what is a phagocyte’s job and how do they carry it out?

job:

• carry out phagocytosis by ingesting pathogens

process: non-specific immune response

1. phagocytes 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

what is a lymphocyte’s job and how do they carry it out?

job:

• produces antibodies - antibody production

  → antibodies: proteins in a shape that is specific (complementary) to the antigens on the surface of the pathogen, they protect you when an unwanted substance enters your body

• they provide a specific immune response as the antibodies produced will only fit one type of antigen on a pathogen

process:

1. a pathogen enters the body. all pathogens and cells have chemicals called antigens on its surface

2. lymphocytes contain antibodies that fit the antigen; the lymphocytes are activated and multiply rapidly, producing more antibodies

3. the antibodies then bind to the pathogen, killing it

how do antibodies stop pathogens?

• causing bacteria to burst

• cause bacteria to stick together (clump up) → easier for phagocytes to ingest them

• neutralising toxins produced by the pathogens

plasma - structure and their functions

• straw-coloured liquid which the other components of the blood are suspended within

• very important for the transport of many substances including:

  • urea, hormones, carbon dioxide, digested food / mineral ions, cholesterol

• distributes heat energy (created in respiration) to cooler parts of the body / skin where heat can be lost