Chapter 3 - Transport and immunity Flashcards
What is the function of xylem and what does it transport (what direction)
- Xylem transports water and mineral salts from roots to plant stem
- It also helps support the plant
What is the function of phloem and what does it transport (what direction)
- Phloem transports substances that the plant has made e.g. glucose, from the leaves and storage organs to all other parts of the plant
Label this cross-section of a stem
Label this cross-section of a root
What is the path that water takes from the soil to the leaves
Water in soil –> Root hair cell –> Across root cortex cells –> into xylem vessels –> Up through xylem vessels in the stem –> Mesophyll cells in leaf
How does a root hair cell absorb water
By osmosis
How does a root hair cell abosrb mineral ions
By diffusion and active transport
What practical can be used to visibly see water uptake
- Stand a celary stalk in coloured water
- You will see the colour moving up, through the celary, through the stem and into the veins of the leaves
- If you cut the stem, you will see coloured dots which are xylem vessels through which coloured water is flowing upwards
What is the definition of transpiration
The loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata
How does transpiration occur in the leaf?
- Water moves out of the xylem vessels and into the palisade mesophyll and spongy mesophyll by osmosis
- Water seeps into the cell walls of the mesophyll cells
- Some of the water in these cell walls evaporate (from liquid water to water vapour)
- This produces a very high humidity in the air spaces in the leaf
- The water vapour diffuses out of the air spaces, through the stomata, into the air as water vapour
Why do mesophyll cells have a large surface area
- A lot of water can evaporate in a shorter period of time
- The interconnecting air spaces inside the leaf mean that the water vapour can easily diffuse through the leaf and out into the air through the stomata
Explain transpiration pull and cohesion
- Transpiration provides the pulling force that makes water flow up through xylem vessels
- When water vapour diffuses out through the stomata, it decreases the water potential inside the leaf.
- With less water in the leaf, the water pressure at the top is reduced, so that it is less pressure than at the bottom of the leaf.
- Water flows from the bottom of the xylem (high pressure) to the top of the xylem vessels (low pressure)
- THis force is called “Transpiration pull”
Why in transpiration does water flow up in an unbroken column
Because the water molecules are attracted to each other and held together by cohesion
How are leaves held out flat, to expose the maximum area to sunlight for photosynthesis
- (what features help them)
- Turgor pressure in mesophyll cells
- Xylem vessels in the veins of the leaf
How does wilting occur in a plant
- Wiltioccurs when transpiration is occuring faster than water being drawn up from the soil, the leaves dont have enough water and become floppy
How does wilting help a plant
- Helps a plant survive when it is short of water
- When the leaves collapse, a smaller surface area is exposed to the air, transpiration occurs slower, so the plant loses less water
What is the rate of transpiration affected by
- High tempurature speeds it up
- High humidity speeds it up
Why does high tempurature speeds up the rate of transpiration
- Water molecules have more kinetic energy at high tempuratures
- This speeds up the rate of evaporation on the surfaces of mesophyll cells, and speeds up the diffusion of water vapour through the leaf and out through the stomata
What is the definition of translocation
- The movement of sucrose and amino acids in phloem:
- From regions of production to regions of storage or where they are used in respiration and growth
What is a source and a sink
- A source is the part of the plant from which sucrose and amino acids are being transported to
- A sink is the part of the plant to which sucrose and amino acids are being transported to
What is special about the source and sink
They can be in different places at different times of year
In summer when sucrose is produced in leaves, where could the sucrose be transported to and for what reason
- The roots - changed into starch and is stored
- Flowers or fruits - changed into fructrose for nectar or to make the fruits sweet
- any part of the plant that requires energy - respiration
In winter when sucrose isn’t produced in leaves, where does energy come from
- The roots - where the starch is stored
- The starch is broken down to sucrose, is transported to leaves, converted to glucose, respiration occurs
In mammals what is the circulatory system made out of
- Blood vessels
- The heart
- Valves
What is the difference between double and single circulatory systems
- In single circulatory systems, blood passes through the heart once on a complete jounrey whereas it passes through the heart twice in double circulation systems
Why is double circulation better than single
- The blood goes back to the heart after being oxygenated
- More efficient at moving oxygen to the cells, because the oxygenated blood is given an extra “push” by the heart
What do valves do
Prevent backflow of blood
What does the right atrium do
Recieves deoxygenated blood
What is the septum’s function
Separates oxygenated and deoxygenated blood
what is the right ventricles function
pumps deoxygenated blood to the lungs
What is the vena cavas function
Carries deoxygenated blood from the body
What is the aorta’s function
carries oxygenated blood to the body
What does the pulmonary artery do
carries deoxygenated blood to the lungs
What does the pulmonary vein do
carrries oxygenated blood from the lungs
what does the left atrium do
recieves oxygenated blood
What does the left ventricle do
pumps oxygenated blood to the body
What does the muscular wall of a heart do
Contracts to increase blood pressure
When the muscular walls of the heart contract what happens
- The walls of the heart squeeze the blood and push it out
- Blood moves out of the arteries, which carry blood away from the heart
- Blood flows back to the heart in the veins
How is the activity of the heart monitored
- recording electrical activity of the heart
- measuring the puse rate
- listening to the sounds of the valves closing
Why are the walls of the ventricles thicker than the walls of the atria
- Atria only have enough force to push blood into the ventricles
- Ventricles need enough force to push blood to the rest of the body
Why is the wall of the left ventricle thicker than the right ventricle
- The left ventricle has to produce enough force to give the blood sufficient force to pass through the whole body
- The right ventricle has to produce sufficient force to get to the lungs
What part of the heart does coronary heart disease affect, what does it do
- The coronary arteries - carry oxygenated blood to the heart muscle, allowing respiration to occur so muscle cells can contract
- The coronary arteries become blocked by blood clots or plaques (plaques contain cholestrol)
- If this occurs the heart cannot respire, hence cannot contract
What increases the risk of developing coronary heart disease
- Smoking
- Not enough excercise
- too much stress
- getting older
- being male
- lots of saturated fats in your diet
What reduces the chance of CHD
Regular excercise
How can coronary heart disease be treated
- Giving drugs, such as aspirin, reduces the likelihood of blood clots in the coronary artery
- Surgery to remove the blockage, this is called angioplasty
- Surgery to add an extra blood vessel that bypass the blockage
What occurs during one heart beat -
*
- Blood flows into the left atrium from the pulmonary vein and the right atrium from the vena cava
- The muslces in both atria contract forcing blood into the ventricles. The blood pressure forces atrioventricular valves open, allowing it to flow through
- The muslces in the walls of both ventricles contract, forcing blood into the aorta and pulmonary artery. The pressure of the blood forces semi lunar valves open, allowing it to flow through. The pressure of the blood also pushes up onto the atrioventricular valves, which snap shut, so the blood cannot go back up into the atria.
Compare the features of arteries, veins and capillaries
- Arteries - have thick muscular walls and relatively narrow lumen
- Veins - have much thinner walls, they also have valves
- Capillaries - smaller than arteries and veins, their walls are one cell thick
Arteries carry blood at high pressure that fluctuates, what adaptations does an artery need
- Thick, muscular walls to withstand high blood pressure
- Elastic tissue in their walls, which can expand and recoil as the blood pulses through
- a narrow lumen so that high-pressure blood speeds quickly to the body tissues or lungs
What do arteries divide into
- What do these furhter divide into
- What do these small features have as adaptations
- Ateries divide into arterioles
- Arterioles divide into capillaries
- Capilaries have walls one cell thick and have small gaps in them so soluble nutrients can easily move through them to or from body cells
- A narrow lumen so that vessels can penetrate deep into the tissues and get close to every cell; and also so that red blood cells inside the lumen are always close to the walls, so they can give up their oxygen quickly
- Capillaries join up to form venules
- Venules join up to form something
- what does something has as adaptations
- Venules join up to form veins
- Veins don’t have high blood pressure so they don’t have thick walls
- They have a wide lumen, to provide as little resistance as possible to the blood flowing through them
- Thery have valves to keep blood flowing in the right direction
Lymphatic system - how is body tissue formed
- Blood leaks out of capillaries
- this fills the space between the body cells
Lymphatic system - why is tissue fluid important
- Provides suitable environment for body cells and allowing substances to diffuse from blood to the cells, and from the cells to the blood
What are lymphatic vessels made up of
Tissue fluid collected into small, blind ending vessels
What is the function of lymphatic vessels
They carry tissue fluid back to the thorax, where it is emptied back into the blood system
What are lymph nodes
They are located in lymphatic vessels and contain high concentrations of white-blood cells
What does blood contain
- Plasma, a pale yellow fluid in which blood cells float
- Red blood cells
- White blood cells
- Platelets
What features do red blood cells have
- They don’t have a nucleus
- They contain a red pigment called haemoglobin which combines with oxygen in the lungs and releases it in body tissues
- The lack of nucleus makes space for more haemoglobin
- shaped like a biconcave disc for larger surface area and speeds up diffusion of oxygen in and out of the red-blood cell
What do white-blood cells do
They protect the body against disease by:
- Engulfing and digesting pathogens; this is called phagocytosis
- Producing antibodies, which attach to pathogens and help destory them
What features od white-blood cells have
- They are larger than red-blood cells
- They always have a nucleus
What are the two types of white-blood cell
- Phagocytes - often have lobed nucleus. Their role is to destroy pathogens by phagocytosis
- Lymphocytes - have a large. round nucleus that almost fills the cell. These secrete antibodies
What is a platelet
Tiny cells fragments that help the blood to clot
How do blood clots occur
- A soluble protein in the plasma called fibrinogen is converted to fibrin
- This forms a mesh of fibres across the wound
- Red blood cells and platelets get trapped in the mesh, forming a clot
What is plasma
- Blood plasma is mostly water
- Contains dissolved substances that are being transported from one part of the body to another
- e.g. mineral ions, soluble nutrients, hormones, carbon dioxide
What is a pathogen
A disease-causing organism
What is a transmissable diesease
A disease in which the pathogen can be passed from one host to another
How can a pathogen be transmitted
- Direct contact - blood of two blood coming into contact
- Indirect contact - e.g. contaminated surfaces, by breathing in air containing droplets of liquid sneezed out by someone with a respiratory disease
What defences does the body have in place to stop pathogens entering the body
- Mechanical barriers - the skin is a tough, impermeable barrier that most pathogens cannot get through
- Chemical barriers - hydrochloric acid in the stomach kills many of the bacteria present in the food we eat and water we drink
- White blood cells - use phagocytosis and antibodies to destroy pathogens once they are inside the body
What does vaccination do
- Helps protect people against transmissable disease
- Giving a dose of weakened pathogen so that white blood cells learn how to destroy that pathogen
- This reduces the number of people in whom a pathogen can breed, hence reducing spread of disease
Give three examples where food hygiene can reduce the chance of pathogens entering the body
- Keeps hands, tools and work surfaces clean, so they cannot transfer pathogens to the food
- Do not allow food to remain in a warm environment for long periods of time. Keep it in cold conditions (growth of bacteria is slowed) or in very hot conditions (bacteria is killed)
- Keep cooked meat away from raw meat so that bacteria cannot be transferred from the raw meat
Give an example of where personal hygiene can reduce the transmission of pathogens
- Wash hands frequently, dont put hands near your mouth
- Do not cough or sneeze into the air or over another person
How can waste disposal be made to sure to not spread pathogens
- Cover bins containing food waste, so prevent access by rats and flies
- Ensure all waste is properly disposed of in land-fill sites
What are antibodies
Proteins produced by lymphocytes
When only do lymphocytes produce antibodies
When they come into contact with its specific antigen
What is an antigen and where are they produced/found
- A molecule foreign to the body
- It may be found on the surface of a pathogen or produced by a pathogen and is circulating around the blood
How are antibodies specific to an antigen
They are shaped in a certain way so that it is complementary to fit the binding site
What happens when an antibody binds to its antigen
It can -
- Directly destroy the antigen, or the pathogen to which the antigen belongs
- Mark the antigen, so that phagocytes will come and destroy it by phagocytosis
How does active immunity occur
- When a lymphocyte first encounters its specific antigen, it divides over and over to produce clone cells of itself
- These clone cells secrete large quantities of the specific antibodies that to the antigen
- If enough of these antibodies are made the pathogen is destroyed
After the antibodies are secreted from the clone cells what happens
- (think memory)
- Some of the lymphocytes become memory cells which remain in the body for many years
- If the same pathogen enters the body again, these memory cells can produce the antibody neccessary to destroy it
- Then you are immune to that pathogen
What is the definiton of active immunity
Defence against a pathogen by antibody production in the body
Definition of passive immunity
- Short-term defence against a pathogen by antibodies acquired from another individual, for example mother to infant
- Lymphocytes do not take any part
