Cell structure & levels of organisation

What is the level of organisation?

Organelles → cells → tissues → organs → organ systems

Organelles are…

Specialised sub-cellular structures found within living cells

Cells are…

The basic structural unit of a living organism

Tissues are…

A group of cells with similar structures that work together to perform the same function

Organs are…

A group of tissues that work together to perform specific functions

Organ systems are…

A group of organs with similar functions that work together to perform body functions

Label this diagram of a plant cell

Label this diagram of an animal cell

What organelles are found in both plant & animal cells?

Nucleus

Cytoplasm

Cell membrane

Mitochondria

Ribosomes

What organelles are found in just plant cells?

Cell wall

Vacuole

Chloroplasts

Nucleus

Contains genetic material

Like the ‘control center’ for the cell

Cytoplasm

Jelly like substance where organelles are found

Most chemical reactions occur here

Contains enzymes to catalyze these reactions

Cell membrane

Contains receptor molecules which identify & selectively control what enters & leaves the cell

Mitochondria

The site of aerobic respiration which provides energy for the cell

Ribosomes

The site of protein synthesis

Found on the rough endoplasmic reticulum

Chloroplasts

The site of photosynthesis which provides food for plants

Contains chlorophyll pigment which collects light needed for photosynthesis & also makes it green

Vacuole

A large sac filled with cell sap that pushes other organelles to the side of the cell to make the cell rigid

Plants have a large & permanent vacuole

Cell wall

A rigid outer-coating around the cell that provides strength & support

Made of cellulose in plants

What are specialised cells?

Cell that have developed specific characteristics in order to perform a particular function

(e.g. sperm cells, nerve cells, muscle cells, phloem cells, xylem cells, root hair cells)

What is cell differentiation?

The process in which cells become specialised by gaining new sub-cellular structures to be suited for its role

Cells can either differentiate once early on or throughout their whole lives

Stem cells are…

Undifferentiated cells which can undergo division to produce many similar cells

Some of these cells will differentiate to become specialised

Stem cells are important for…

Development, growth & repair

What are the 3 types of stem cell?

Embryonic stem cells

Adult stem cells

Meristems in plants

Embryonic stem cells

- Form when an egg & sperm fuse together & to produce a zygote

- Can differentiate into any type of cell in the body

- Scientists clone them & can direct what they differentiate into

- Can potentially be used to replace insulin-producing cells in those suffering from diabetes, new neural cells for diseases such as Alzheimer’s or nerve cells for those paralysed with spinal cord injuries

Adult stem cells

- Form in specific parts of the body including bone marrow, hair follicles, the brain, fat tissue, intestines, breasts & testes

- Can only differentiate into cells that grow in the region where they were formed (e.g. formed in bone marrow → blood cells)

Meristems in plants

- Found in the tips of roots & shoots

- Can differentiate into any type of plant cell throughout their life

- Can be used to make clones of the plant which is useful if the parent plant has desirable features, for scientific research or to save a rare plant from extinction

Advantages of stem cells in medicine

- Can be used to replace damaged cells

- Can grow organs for transplants

- Bone marrow transplants for adult stem cells can be used to treat blood cell cancers

- No rejection if it is made from the patients own cells

- Can be used to test drugs as an alternative to animal testing

Disadvantages of stem cells in medicine

- Destroys unused embryos which causes ethical issues

- No guarantee on the success rate or if there will be any long term effects

- Mutations could occur in cultured stem cells

- Difficult to find suitable stem cell donors