Transport Systems Flashcards
Unicellular Organisms & Diffusion.
This exchange of substances occurs across the cell membrane
There are three transport processes that living organisms use for exchange: diffusion, osmosis and active transport
Unicellular (single-celled) organisms like amoeba have very large surface areas (SA) in comparison to their volumes
This means that the distance between the surface of the organism to its centre is very small
As a result, unicellular organisms do not need to have specialist exchange surfaces or transport systems; as diffusion, osmosis and active transport through the cell membrane occur at a sufficient rate to meet the organisms needs.
What is the need for a transport system in multicellular organisms?
Multicellular organisms, like humans, have bodies made up of more than one cell
The bodies of these organisms contain many layers of cells, meaning that the distance between the surface of the organism to its centre is relatively long and the diffusion distance is too great to rely on diffusion alone
Diffusion to all of the cells would take far too long
Diffusion cannot occur at a sufficient rate to meet the needs of the organism, so larger organisms usually have transport systems
The transport system in animals is the circulatory system which carries the necessary substances around the body in the blood
The transport system in plants is the vascular system:
The xylem moves water and mineral ions from roots to shoots
The phloem moves sugars and amino acids to where they are needed in the plant.
What is the structure and function of the phloem?
Phloem vessels transport food materials (mainly sucrose and amino acids) made by the plant from photosynthesising leaves to non-photosynthesising regions in the roots and stem (pronounced: flow-em)
This means that movement can be in any direction around the plant
The phloem has structural features different to the xylem
The cells are living cells and are not hollow
Substances move from cell to cell through pores in the end walls of each cell.
What is the structure and function of the xylem?
Xylem vessels transport water and minerals (pronounced: zi-lem) from the roots to the stem and leaves
The xylem has some key structural features
It is composed of dead cells which form hollow tubes
Xylem cells are strengthened by lignin and so are adapted for the transport of water in the transpiration stream.
What are the components of blood?
Blood consists of red blood cells, white blood cells, platelets and plasma
Over half of the volume of the blood is made up of plasma
The majority of the other half is made up of red blood cells
The remaining fraction consists of white blood cells and platelets.
Which substances is plasma important for the transport of?
Carbon dioxide - the waste product of respiration, dissolved in the plasma as hydrogen carbonate ions and transported from respiring cells to the lungs
Digested food and mineral ions - dissolved particles absorbed from the small intestine and delivered to requiring cells around the body
Urea - the waste substance produced in the breakdown of proteins by the liver. Urea is dissolved in the plasma and transported to the kidneys
Hormones - chemical messengers released into the blood from the endocrine organs (glands) and delivered to target tissues/organs of the body
Heat energy - created in respiration (an exothermic reaction), heat energy is transferred to cooler parts of the body or to the skin where heat can be lost.
What are the adaptions of red blood cells?
Red blood cells are specialised cells which carry oxygen to respiring cells
They are adapted for this function in 3 key ways
They are full of haemoglobin, a protein that binds to oxygen to form oxyhaemoglobin
They have no nucleus which allows more space for haemoglobin to be packed in
The shape of a red blood cell is described as being a ‘biconcave disc’ this shape gives them a large surface area to volume ratio to maximise diffusion of oxygen in and out.
What is the role of white blood cells in the immune system?
These specialised cells defend against pathogenic microorganisms
There are two main types of white blood cell:
Phagocytes
Lymphocytes.
What is the role of the phagocytes in the immune response to disease?
Phagocytes carry out phagocytosis by engulfing and digesting pathogens
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
This is a non-specific immune response
Phagocytes can be easily recognised under the microscope by their multi-lobed nucleus and their granular cytoplasm.
What is the role of the lymphocytes in the immune response to disease?
Lymphocytes can easily be recognised under the microscope by their large round nucleus which takes up nearly the whole cell and their clear, non-granular cytoplasm
Lymphocytes produce antibodies
Antibodies are Y-shaped proteins with a shape that is specific (complementary) to the antigens on the surface of the pathogen
This is a specific type of immune response as the antibodies produced will only fit one type of antigen on a pathogen. Antibodies attach to the antigens and cause agglutination (clumping together).
This means the pathogenic cells cannot move very easily
At the same time, chemicals are released that signal to phagocytes that there are cells present that need to be destroyed.
What is immunity?
The body’s immune system is highly complex, with white blood cells being the main component
Once a pathogen has entered the body the role of the immune system is to prevent the infectious organism from reproducing and to destroy it
An organism has immunity when they have sufficient levels of antibodies to protect it from a particular disease
As a result, they do not suffer from the disease or its symptoms.
What is the response to infection?
The pathogen enters the blood stream and multiplies
A release of toxins (in the case of bacteria) and infection of body cells causes symptoms in the patient
Phagocytes that encounter the pathogen recognise that it is an invading pathogen and engulf and digest (non-specific response)
Eventually, the pathogen encounters a lymphocyte which recognises its antigens
The lymphocyte starts to produce specific antibodies to combat that particular pathogen
The lymphocyte also clones itself to produce lots of lymphocytes (all producing the specific antibody required)
Antibodies cause agglutination of pathogens
Phagocytes engulf and digest the agglutinated pathogens
After the patient has recovered, they retain antibodies specific to the disease as well as memory cells (lymphocytes that recognise the pathogen)
If the patient encounters the same pathogen again, it will trigger a secondary immune response
Memory cells can produce much larger quantities of the required antibody in a much shorter time to fight off the pathogen before the patient suffers any symptoms.
What are the causes of coronary heart disease?
In coronary heart disease (CHD), layers of fatty material (plaque) build up inside the coronary arteries
These fatty deposits are mainly formed from cholesterol
There are two sources of cholesterol in the body:
Dietary cholesterol (from animal products eaten)
Cholesterol synthesised by the liver.
What are the risk factors which will increase the chances of coronary heart disease?
Obesity
Carrying extra weight puts a strain on the heart.
Increased weight can lead to Type 2 diabetes which further damages your blood vessels.
High blood pressure
This increases the force of the blood against the artery walls and consequently leads to damage of the vessels.
High cholesterol
Speeds up the build up of fatty plaques in the arteries leading to blockages.
Smoking
Chemicals in smoke cause an increase in plaque build up and an increase in blood pressure
Carbon monoxide also reduces the oxygen carrying capacity of the red blood cells.
Key features of arteries?
Carry blood at high pressure away from the heart
Carry oxygenated blood (except the pulmonary artery)
Have thick muscular walls containing elastic fibres
Have a narrow lumen
Blood flows through at a fast speed
The structure of an artery is adapted to its function in the following ways
Thick muscular walls containing elastic fibres withstand the high pressure of blood and maintain the blood pressure as it recoils after the blood has passed through
A narrow lumen also helps to maintain high pressure.
