Levels of Organisation & Cell Structure

Organelles

A component within a cell that carries out a specific task

Cells

Basic functional and structural units in a living organism

Tissues

A group of cells of similar structure working together to perform a particular function

Organs

Made from a group of different tissues working together to perform a particular function

Organ systems

Made from a group of organs with related functions, working together to perform body functions within the organism

Nucleus

• contains genetic material in chromosomes which control how cells grow and work

• Controls cell division

Cytoplasm

• supports cell structures

• Site of many chemical reactions

• Contains water and many solutes

Cell Membrane

• holds the cell together

• Controls substances entering and leaving the cell

Cell wall

Gives the cell extra support and defines its shape

Chloroplasts

• site of photosynthesis, providing food for plants

• The chlorophyll pigments absorb light energy needed for the reaction to occur

Vacuole

• contains cell sap

• Used for storage of certain material

• Also helps support the shape of the cell

Mitochondria

• site of aerobic respiration, providing energy for the cell

• Cells with high rates of metabolism will have significantly higher numbers of mitochondria than cells with lower numbers of reactions taking place in them

Ribosomes

Site of protein production in protein synthesis

Vesicles

Used to safely transport substances from one part of the cell to another

Cell differentiation

The process by which a cell becomes specialised

Specialised cell

Those that have developed certain characteristics that allow them to perform particular functions. These differences are controlled by the genes in the nucleus.

Why do animal cells loose the ability to differentiate early in life?

Most cells differentiate at an early stage of development

How are red blood cells adapted to transport oxygen?

• no nucleus

• More space for haemoglobin

• Large surface area

How are root hair cells adapted for absorbing water & mineral ions into the plant?

• long, hair-like structures

• large surface area

How are sperm cells adapted for fertilisation?

• large nucleus

• King tai

• Many mitochondria

How are muscle cells adapted for contraction?

• elongated

• Contain many mitochondria

• Can contract

Ethical disadvantages of stem cells in medicine

• messing with ‘nature’

• Involves the destruction of human embryos which is potential human life

Medical disadvantages of stem cells in medicine

• No gaurentee of success

• Difficulty in finding suitable stem cell donors

• Have to store the patients cells

• Mutations, some behave like cancer cells

• Can be contaminated with viruses

• Have to be collected before birth

Advantages of stem cells in medicine

• no rejection

• No need to find a donor

• No need for tissue typing