biology transport in humans part 1

Why don’t very large cells exist?

In a larger cell, surface area to volume ratio is less

1. more nutrients is required while it is harder for nutrients to reach the centre

2. More waste products would be produced and removed slower. Hence, accumulation of waste products and lack of nutrients would kill a cell that is too large

3. Smaller SA:V ratio decrease rate of exchange of heat, gases, nutrients and waste.

Why is a transport system not needed for a simple organism

A simple organism is smaller in size, shorter distance between cells and external environment, exchange of materials occur quicker by diffusion + larger SA:V ratio increases rate of diffusion

Why is a transport system needed for a complex multicellular organism

A complex multicellular organism is larger and more complex so metabolic requirements increases, amount of materials moving in and out of the body yet diffusion rate decreases due to smaller SA:V ratio and most cells are not in contact with external environment so direct exchange not possible as distance materials must travel increases. Hence, diffusion alone is too slow and inefficient for nutrients to reach all parts of the body to sustain life so a transport system is needed

What is blood and its components(%)

1. Blood is a specialised connective tissue

2. It is made up of 45% red blood cells, <1% white blood cells and platelets that is suspended in plasma(plasma makes up 55% of blood)

Describe and state the method to separate the substances in blood.

Centrifugation of blood is a technique of separating substances using centrifugal force, based on differences in relative densities of blood components.

Characteristics of plasma(Appearance, components and function of components, function of plasma)

1. Plasma is a clear yellowish liquid part of blood after the removal of cellular components

2. Plasma contains natural antibodies which recognise and bind to specific antigens on the red blood cells (erythrocytes)

3. 90% of plasma is the following substances dissolved in water: 1. Proteins: antibodies, fibrinogen and prothrombin for blood clot and mostly albumin to regulate water potential of blood 2. Dissolved food substances like glucose, amino acids, fats and vitamins 3. Excretory products like urea via deamimation of amino acids, Carbon dioxide and creatinine 4. hormones like insulin 5. Ions to maintain osmotic balance and pH of blood at 7.4 and regulates membrane permeability (Na,K,Mg,Ca,Cl,HCO3)

4. Function: plasma carries soluble materials to be transported around the body and distributes heat around the body to maintain a uniform temperature

Characteristics of erythrocytes (percentage of blood,where it’s produced and destroyed, lifespan, function and others)

1. Erythrocytes are red blood cells which constitute 99% of cells in the blood

2. It is produced in the bone marrow and destroyed in the liver and spleen

3. It has a limited life span of 120 days

4. It transports oxygen from lungs to all parts of the body

5. Red blood cells have proteins called antigens on their surface

How is the erythrocyte adapted to its function? (4)

1. The erythrocyte’s cytoplasm contains haemoglobin to facilitate transport of oxygen, with each haemoglobin consisting of 4 globular protein submits, each associated with a heme group that has a Fe2+ ion at the centre. The blood is purple-blue when oxygen unloaded to form a deoxyhaemoglobin in tissues, which binds reversibility to oxygen and carbon dioxide(to a lesser extent), allowing one haemoglobin protein to bind to 4 oxygen molecules to form a red oxyhaemoglobim in the lungs.

2. The red blood cell lacks a nucleus and most other organelles so more haemoglobin can be packed into the cell, enabling it to carry more oxygen(99% of oxygen is bound to haemoglobin for transport of blood)

3. It has a bioconcave shape(thinner central portion) to increase SA:V ratio for faster diffusion of oxygen into and out of the cell and optimise blood flow in blood vessels

4. It has a flexible and deformable membrane to squeeze through narrow capillaries to become bell shaped.

How is carbon dioxide transported in the blood and % of each

1. Dissolved in solution in plasma-5% as carbon dioxide is 20 times more soluble in water than oxygen

2. Carbon dioxide is bound to haemoglobin to form carbaminohaemoglobin -5%

3. As bicarbonate ions-90%

Characteristics of leukocytes (appearance and quantity (compared to erythrocytes), produced where, life span, function, movement)

1. Leukocytes are white blood cells which are larger but fewer in number than erythrocytes

2. Colourless as they do not contain haemoglobin

3. Irregular shape

4. Mostly Produced in bone marrow like erythrocytes

5. Limited lifespan of a few days

6. Has a nucleus

7. Cells of the immune system to help defend against infectious diseases and foreign particles

8. Mobile-able to move, change shape and squeeze through walls of thinnest blood capillaries

Characteristics and function of phagocytes

1. Lobes nucleus

2. Granular cytoplasm

3. Engulfs and ingests foreign particles, bacteria, dead cells, cell debris by PHAGOCYTOSIS

4. Pus produced at a wound is accumulation of dead tissue, bacteria and white blood cells

3 main types of phagocytes and function

1. Neutrophils→most abundant(60%), first to respond to bacterial infections, phagocytose bacteria and signal other cells in the immune system to respond

2. Monocytes→ largest white blood cell that differentiate into macrophages or dendritic cells(messengers to lymphocytes)

3. Macrophages→ specialised monocytes that migrated from the bloodstream into any tissue in the body where they detect and phagocytosis bacteria and dead cells

Characteristics of lymphocytes

Lymphocytes is a type of white blood cell with a

1. Large rounded nucleus

2. Small amount of non-granular cytoplasm

3. Second most abundant white blood cell (25-35%)

4. 2 main types: T cells and B cells

Function of T cells and B cells

T cells: directly destroys infected or cancerous cells, gives off signals to activate B cells to produce antibodies to neutralise toxins produced by bacteria

B cells: produce antibodies that bind to antigens on the surface of bacteria and virus, causing them to clump together to make it easier for phagocytes to engulf and destroy them.

Define antigen

An antigen is a substance than induces the formation of antibodies because it is recognised by the immune system as foreign to the body. A different antigen is recognised by a different antibody.

What’s tissue rejection and how to prevent

Tissue rejection is when antigens present on transplanted tissues/organs are recognised as foreign by the recipients’s immune system, which destroys the foreign tissue. This can prevented by ensuring that donor is of close relation(tissue match, similar antigens expressed on cell surfaces), take immunosuppressant drugs, and a bone marrow transplant

what are platelets? Function?

Platelets are not true cells, they are fragments of bone marrow cells that are pinched off. Platelets are tiny fragments of cytoplasm enclosed by a membrane that clots blood.

Describe the process of blood clottting

Clotting occurs when

endothelium(innermost layer in direct contact with blood) of a blood vessel is damaged→platelets trigger biochemical pathway that catalyses conversion of soluble plasma fibrinogen into insoluble fibrin threads that form a network that entangles blood cells to form a clot that prevents excessive loss of blood & entry of foreign pathogens.

What happens when a different blood groups are mixed?

Wrong antibody binds to antigen on red blood cells, causing agglutination/clumping of red blood cells as the blood types are incompatible, blocking blood vessels in vital organs, leading to death

What are the antigens and antibodies present in blood group A, what blood group can blood group A donate to and receive from?

Contains antigen A and antibody B.

Can donate to blood group A and AB

Can receive from A and O

What are the antigens and antibodies present in blood group B, what blood group can blood group B donate to and receive from?

Blood group B contains B antigen and A antibody, can donate to B and AB, can receive from B and O

What are the antigens and antibodies present in blood group AB, what blood group can blood group AB donate to and receive from?

Contains antigen A and antigen B, contains no antibody, can only donate to blood group AB, can receive from A,B,AB and O(universal acceptor)

What are the antigens and antibodies present in blood group O, what blood group can blood group O donate to and receive from?

Contains no antigens, contains a and B antibody, can donate to A,B,AB and O(universal donor), can receive only from O