4ABCD

signals that act on the cell that secreted them

signalling molecules that act on cells that are close by

signalling molecules that act on cells that are far from the gland/organ

Peptides (proteins), Steroids (lipids)

Hormones, Neurotransmitters, Cytokines, Pheromones

•Involved in communication between immune cells

•Regulating inflammation

•Response to cell damage or pathogens (autocrine or paracrine)

•Fighting infection

Signalling that is excreted into the external environment

Influence behaviour or physiology of another organism (unconscious communications)

E.g. triggering aggressive behaviour, attracting a mate, food trails

Signalling molecule → reception → Transduction → Cellular response

Converting the signal in a form that can be relayed to its final destination (can be one step or many)

Hormones: Hormones are produced in endocrine glands and are secreted into the blood stream. Neurotransmitters: Neurotransmitters are released by presynaptic nerve terminal into the synapse.

Hormones: have stronger effects but are slower, Neurotransmitters: have weaker effects but are faster

Hormones: act on distant target cells (endocrine signalling)

Neurotransmitters: act on cells close by (paracrine signalling)

multicellular organisms, cell signaling allows for specialization of groups of cells.

By concentrating the necessary components inside a small region within the cell, cell compartmentalization improves the efficiency of several subcellular activities. Intracellular membrane systems create enclosed compartments separated from the cytoplasm of the cell.

after each round of replication the number of cells present doubles

Growth and Development

As we grow larger, our cells don’t actually become larger. Instead, we are simply made of more cells. Therefore, for a multicellular organism to grow and develop, it is important that cells replicate.

Maintenance and Repair

Cells are constantly dying as they age or become damaged. Cell replication allows these cells to be replaced

Reproduction

Prokaryotic and eukaryotic cells replicate to reproduce. When they replicate, they are enlarging their population.

A prokaryotic cell before binary fission

The circular chromosome is uncoiled and is replicated. Plasmids are replicated too

The cell elongates to prepare for cell division

Cell undergoes cytokinesis in which the cell pinches inwards creating a septum

A new cell wall and cell membrane is formed

Two genetically identical daughter cells are created

Gap 1 G1:

The new cell starts growing and replicating its organelles

Synthesis (S):

DNA replication occurs

Gap 2 (G2):

The cell continues to grow in preparation for division

Mitosis (M) and cytokinesis:

The single parent cell gives rise to two identical daughter cells.

Performing all cell function but not preparing for cell division

Mitosis is a type of cell division in which a whole cell divides

Cytokinesis is one of the steps of mitosis in which the cytoplasm of the cell divides.

•Occurs between divisions

•Longest part of cycle

•‘Normal life’ of cell

•DNA replication happens here

Chromosomes appear, nuclear membrane disappears and centrioles form as well as spindles made up from microtubules

Chromosomes line up across the center of the cell and attach to a spindle fiber

•Each pair of chromatids are separated at the centromere and moves to the opposite pole

•Nucleus membrane forms

•Cytoplasm divides into two

DNA needs to replicate before cell division in order for new body cells to maintain the same number of chromosomes as their parent cell.

End of G1,

grow or divide? Delay

•Checking DNA for any damage

•Got enough nutrients

•Cell size and growth is normal -> G0

End of G2,

• has an error occurred during DNA replication? If yes, then the cell must undergo apoptosis (programmed cell death).

• Check size is normal

During Mitosis (end of metaphase),

are the chromosomes aligned ok? Are the spindle fibres attached correctly? If not, apoptosis will occur.

uncontrolled and unmonitored cell division, this is commonly known as cancer.

the controlled death of cells in the body also called programmed cell death.

•Eg Tadpoles losing its tail and becomes a frog, or a human embryo losing the webbing between fingers and toes.

•Or when cells have reached the end of their life span, ware and tare or infection

•Controlling the number of cells in the body

•Damaged DNA

•Infection

•Caspase enzyme is responsible for apoptosis

•Signalling molecule produced

•Signal transduction occurs

•Stimulates enzymes

•It occurs in a number of steps

1.Mitochondrial Pathway (or intrinsic pathway)

2.Death Receptor Pathway (extrinsic pathway)

•Detect damage and release cytochrome c into the cytosol which activate caspase enzymes

•Immune cells release death signalling molecules that bind to the receptor proteins on the cell membrane, this initiates the caspase enzymes

1.Activation of caspase enzyme

2.Separation of adjacent cells

3.Collapse of the cells cytoskeleton

4.Cell shrinkage

5.Breakdown of organelles and nucleus

6.Blebbing of plasma membrane

7.Membrane breaks apart into vesical that secrete toxins

8.Phagocytosis of the apoptotic bodies by specialised cells (without spilling cells condense)

the process by which a cell uses its plasma membrane to engulf a large particle (form of endocytosis)

Vacuole v.s. Vesical

•Both are membrane bound organelles

•Vacuole is larger / Vesical is smaller

•Vacuole cannot fuse with the plasma membrane / vesical can

Stem cells are undifferentiated cells which can differentiate into specialised cells

development of a stem cell into a specialized cell with a particular function

cells which serve a unique particular function (and have a particular structure)

Self-renewal

Can replicate without disrupting their ability to differentiate (by producing both a differentiated cell and a new stem cell when they replicate)

Potency

Has the capacity to differentiate into different cell types (the higher the potency of a stem cell, the greater the number of cell types it can differentiate into)

1.Totipotent stem cells

1.Pluripotent stem cells

1.Multipotent stem cells

•Have the potential to become any cells/a complete new organism

•Occur in embryos (first month of development before the baby becomes a fetus)

•Then change into blastocyst which is a ball of cells with hollow outer layer (becomes placenta) with an inner mass (becomes fetus)

•Can give rise to all types of cells in a fetus (not placenta)

•These are the cells we are investigating for medical use

Give rise to cells that have a particular function \n (e.g. multipotent blood stem cells make white/ red blood cells and platelets)

blood cells, skin cells, muscle cells, nerves

are a type of pluripotent stem cell derived from adult somatic cells that have been genetically reprogrammed to an embryonic stem

(differentiation reversed)

•Beneficence

•Is there a benefit to this initiative?

•Non-maleficence

•Does it cause harm?

•Justice

•Is it fair to everyone? Does it benefit everyone equally?

•Respect

•Does it show respect/provide dignity to all affected?

•Integrity

•Is research doing what it's saying it is going to do?

1.Beneficence Is there a benefit to this initiative?

2.Non-maleficence Does it cause harm?

3.Justice Is it fair to everyone? Does it benefit everyone equally?

4.Respect Does it show respect/provide dignity to all affected?

5.Integrity Is research doing what it's saying it is going to do?