Cell - the basic unit from which living organisms are made, consisting of an aqueous solution of organic molecules enclosed by a membrane. All cells arise from existing cells, usually by a process division

All cells have a cell membrane that separates the outside from the organised interior

contain DNA as genetic material (exceptions)

contain several varieties of RNA molecules and proteins -mostly

are composed of the same basic chemicals: carbohydrates, proteins, nucleic acids,

fats and vitamins.

Regulate the flow of nutrients and

that enters and leaves the cell.

Reproduce and are the result of reproduction

Require a supply of energy.

Dimensions of a cell:

Dimensions of a virus

Molecules move spontaneously by diffusion -

motion. Other forms of movement require energy via the

of ATP to cause:

Movement of molecules against conc gradient, movement of organelles, movement of cell membranes -

growth and migration of cells, cell division, muscle contraction via

Certain mutations lead to cancer such as: the switching on of 'divide' signals -

Switch off of don't divide signals -

Loss of correction mechanism of DNA

Loss of escape mechanism from

Loss of the limit on the number of times that a cell can

Loss of control-keeping mechanism

Ability to evade body defence mechanisms, ability to recruit blood vesicles into the growing tumour- tumour

Ability to migrate into the circulation-

Ability to establish tumours in wrong tissue

Viruses - Contain DNA or RNA as genetic material, show host specificity but infect all life forms. Example is human immunodeficiency virus (HIV). It uses the enzyme

to convert its own RNA genome into a DNA template which it integrates into the host

Bacteria- Contain a

of DNA but no defined nucleus. Nuclear area is where DNA is contained in nucleotides. Example is Shigella which is an invasive pathogen transmitted by the

route and has an infectious does of only 10-100 bacteria. It enters the cell via a

and replicates intracellularly. Using host

it spreads from cell to cell.

Fungi- Candida is a yeast infection that infects the genitals and the

Protozoa- Parasites that can infect the intestines, blood and other tissues. Complicated life cycle involving two hosts, infection is acquired through ingestion or through a vector

Helminth parasites- Examples include Ascaris and

A living system must be separated from the environment to maintain complex order. The cell is a bag contain substances relevant for its function. The bag is made up of the membrane. Forms the limit of the cell, it needs to be selectively permeable, impermeable to

but needs to be permeable to

and waste products. Phospholipids have a

head and a

tail, the most abundant phospholipid class is

There are are others such as phosphatidylserine, phosphatidylethanolamine etc

Fatty acid tails can be saturated or unsaturated, this decides how well packed they are, the more unsaturated the fatty acid, the

sparsely packed it is.

Phospholipids can

between layers of the membrane. They can diffuse between each other in the same layer leading to a dynamic membrane. Membranes are soluble to small, neutral molecules and fat-soluble molecules. They're impermeable to large, hydrophilic or charged molecules

Membrane proteins diffuse freely within small compartments and can hop between compartments. The proteins appear to be constrained by

and some appear to be fixed to the fences like

The fences are made up of membrane

The fences function by

-they physically prevent movement of molecules

Combination of concentration and

gradients generated by ions. Chemical gradient tends to move particles down the gradient and electrostatic tends to move particles according to their charge.

Equilibrium can be reached so that actual ratio of intra and extracellular concentration ultimately depends on existing

The dissipation of gradients is ultimately prevented by the action of

pumps. The high concentration of fixed ions inside the cell means that water is drawn in by

The pump maintains osmotic balance and stabilises cell volume by exporting

The gradient of this is exploited by certain cells in certain processes to drive transport of sugars and amino acids

The Na/K pump is found on the membrane of

cells and consists of 2 polypeptide chains, alpha and beta. The alpha chain spans the membrane

times forming a hydrophilic pore. It works by pumping out 3

and pumping in 2

It is mediated by successive conformational transitions of the pump molecule. Driven by phosphorylation of an aspartyl residue and is followed by hydrolysis of aspartylphosphate.

The membrane potential is due to a difference in electrical charge of the two sides of the membrane.. Potassium conc inside the cell is

to balance the fixed anions and is pumped into the cell. Sodium conc inside the cell is

More positive charges are pumped out than in so inside is more negative potential than outside causing membrane potential

Action potential occurs when the resting membrane potential is disturbed. They occur in elongated cells e.g nerves and muscles

This disturbance opens

channels which cause an influx to enter the cell and cause

from about -70mV to +50mV. During depolarisation, the

period occurs so channels are temporarily inactivated. The voltage gated potassium channels

to depolarise the cell. e.g The neuromuscular junction

Highly complex structure located between a motor neurone and a muscle. The neurotransmitter used in this is

This stimulation is what causes muscle contraction, depolarisation of the muscular postsynaptic membrane results in a propagated action potential. The wave of depolarisation extends into the

to transmit the activation signal into the core of each muscle cell.

It acts as a connective tissue, transports many substances to cells by connecting every part of the body, aids heat distribution, immunity, haemostats, support e.g

and maintains homeostasis. Blood gives to cells products of digestion, hormones, vitamins and

and takes from cells CO2, heat, H20 and

Major components of the blood are erythrocytes, leukocytes, platelets and

Erythrocytes main function is with respiratory transport. They're a biconcave disc shape which maximises

They're also flexible so can squeeze through small vessels. When arterial oxygen is low, a process is induced called

Low oxygen level is detected by the

which secretes a hormone called

This stimulates bone marrow stem cells to differentiate into erythrocytes

This increases oxygen carrying capability of the blood so blood oxygen levels of blood increase which is detected by kidney so levels of erythropoietin decrease.

Immature red blood cells contain ribosomes and are called

High circulating levels of these can be used for diagnosis of conditions like anaemia

Reticulocytes are removed through reticulo-endothelial system. Lifespan is about

Consists of 4 subunits, each a polypeptide with a haem group. Haem group contains ferrous iron (Fe2+) each of which binds a single

The oxidised form of haemoglobin contains

iron (Fe3+). This can't carry oxygen

There is a different form in the foetus with an oxygen affinity that is

Males have higher levels of haemoglobin than females - 15.8g/100ml in males vs

in females. It's broken down to form bilirubin as its major breakdown product.

Hb has a

affinity for oxygen due to the conformation of global molecules. When oxygen binds initially, it breaks the conformation and opens up the structure this means the second oxygen binds

Defined as low blood

concentration. There are 3 types of anaemia: Normocytic- characterised by a normal

Usually caused by acute blood loss

Microcytic anaemia - characterised by a small MCV - caused by a failure of

synthesis due to iron deficiency or menstruation

Macrocytic anaemia - characterised by a large MCV, this is caused by a failure of DNA synthesis and cell division leading to reduced division of

so there are fewer but larger erythrocytes. Folic acid deficiency- apparent in

Sickle cell anaemia is caused by a mutation in the gene that codes for haemoglobin leading to distorted erythrocytes. It is autosomal

Polycythaemia is a condition characterised by excess erythrocytes. This can be a physiological response to high altitudes