cell growth and differation

Once the egg is fertilised by the sperm in sexual reproduction, they form a single diploid cell known as a

zygote

stem cells

Undifferentiated cells with the ability to become any cell type.

Differentiation:

The process in which a cell becomes "specialised" by turning some genes on and others off.

can a differentiated cell go back

no

potency

How many types of cells they can make.

Totipotent:

Can become any cell type.

Found in the zygote.

Pluripotent:

Become many cell types.

Found in the embryo.

embryonic stem cell types

totipotent

pluripotent

adult stem cell types

unipotent

multipotent

pluripotent

multipotent

Differentiate into a limited number of cells that belong to a specific tissue or organ

Found in bone marrow.

unipotent

A single cell type that can self renew.(E.g. Myoblasts can renew into skeletal muscle only).

regenerative medicine

Also known as 'stem cell therapy'.

There is current research into the potential use of stem cells to replace non-functional cells in degenerative disorders such as;

Parkinsons,

Alzheimer's

Multiple Sclerosis

Diabetes

Injuries to non-replicating cells such as the nerve cells in the spinal cord

challenges of stem cell therapy

Need to grow sufficient number of stem cells in the lab.

Harvest SC's from patient.

Need to store them in optimal conditions, (temperature, plentiful food) in the presence of specific signalling chemicals.

Need additional research to ensure cells differentiate into desired cell.

Need additional research to ensure self-renewal cell growth can be arrested/stopped

Induced Pluripotent Stem Cells

Induced pluripotent stem cells (iPSCs) are adult cells that have been genetically reprogrammed to an embryonic stem cell-like state by being forced to express genes and factors for maintaining the defining properties of embryonic stem cells

new stem cell technology advantages

(+) Avoid upsetting vocal minority groups

(+) Significantly less chance of rejection since they are self cells.

new stem cell technology negatives

(-) Potential instability, switching self renewal mechanisms on and off.

(-) Expensive/time consuming

what is cancer caused by

Caused by mutations to genes that normally regulate the cell cycle.

what is cancer

Cancer is a disease of the body's cells.

Errors in the cell cycle causing cells to replicate at an uncontrolled rate.

Uncontrolled growth of abnormal cells (dysplastic growth).

dysplasia

Dysplasia is characterised by cells and nuclei that are of abnormal shape and size

causes of cancer

genetics

environment (mutagens)

spontaneuos

how can environment cause cancer

Carcinogens - cancer causing chemicals

Radiation - breaks in DNA

Smoking

Illness

how can cancer be spontaneuos

over time the amount of mutations not caught by checkpoints adds up.

two groups of regulatory genes

Proto-oncogenes and Tumour suppressor genes

Proto-Oncogenes:

switch on replication.

oncogenes

when proto-oncogenes are mutated and cause continuous replication.

Tumour suppressor genes:

switch off replication.

where are tumour supressor genes

Checkpoint genes (G1, G2, Metaphases): proofread for typos

Cyclins: chromosome- spindle fibre attachment

Contact inhibition: aware of cells around them, so can control rate of growth

Cancer is generally caused by

a mutation in 5 different genes OR The mutation of 1 important gene

the 1 important gene

p53

p53 gene

Main control of cell cycle checkpoints, apoptosis, DNA repair.

apoptosis

"Programmed cell death" mediated by caspases

how many cells undergo apoptosis per minute

Approximately 300,000,000 cells undergo apoptosis a minute.

what does the process of apoptosis allow for

The process allows for cells that are damaged or that become obsolete (no longer needed) to be removed allowing for their replacement by new, healthy cells.

capasses

enzymes that cleave intracellular proteins

The two pathways of apoptosis

Intrinsic/Mitochondrial Pathway

Extrinsic/"Death receptor" Pathway

Intrinsic/Mitochondrial Pathway stages

1.Mitochondria detect intracellular damage and release Cytochrome C.

2.Cytochrome C activates caspases, resulting into the breakdown of organelles.

3.Cell begins to shrink as internal structures are broken down.

4. Membrane begins "blebbing" and the cell begins breaking down into apoptotic bodies.

5. After the breakdown of the cell following blebbing, apoptotic bodies are digested by phagocytes.

blebbing

the bulging of the plasma membrane

Apoptotic Bodies

small membrane-bound vesicles

Phagocytes

a type of cell that undergoes "cell-eating".

How does the immune system recognize damaged or diseased cells?

Via surface proteins on the damaged or diseased cells.

Which cells are mainly responsible for apoptosis in the extrinsic ("death receptor") pathway?

cytotoxic T-cells

What is the role of the immune system?

To protect the body from invading pathogens (disease-causing agents).

Extrinsic/"Death receptor" Pathway stages

1. Cytotoxic T-cells interact with a surface protein called MHC-1, which displays fragments of an invading pathogen.

2. Once a diseased cell is recognised, cytotoxic T-cells release signalling molecules that binds to receptor proteins on the surface of the damaged cell.

3. The binding of these molecules activates a series of intracellular events (including Cytochrome C release from the mitochondria) this process is known as signal transduction andultimately results in the activation of caspases.

What is the relationship between apoptosis and mitosis?

They work together to ensure the body has the correct number of cells.

What happens if apoptosis or mitosis occurs too fast or too slow?

The body may produce too many cells, which can potentially become cancerous.

How can some cells contribute to cancerous growth even if apoptosis is working normally?

Some cells do not respond to apoptosis signals and crowd healthy cells, leading to cancerous growth.

How do adult and embryonic stem cells differ in potency and use?

Embryonic stem cells: can become almost any cell type, used in regenerative medicine, ethical concerns.

Adult stem cells: limited cell types, used for tissue repair (e.g., bone marrow transplants), minimal ethical issues.

MHC 1 markers

proteins found on the surface of nearly all nucleated cells in the body (except mature red blood cells)

allow our immune system to recognise that a cell is a part of our body.

Describe how failure of apoptosis contributes to cancerous growth

If apoptosis fails, damaged cells don't die and continue to divide.

These cells can accumulate mutations, crowd healthy tissue, and form a tumor.

Combined with uncontrolled mitosis, this leads to cancerous growth.