cell biology and the principles of organisation - by evana o

an organelle

a tiny, specialised structure that performs a specific function inside a cell

also known as a ‘subcellular structure’

a cell

the ‘basic building blocks’ that make up all living organisms

each cell has a specific function

a tissue

a group of specialised cells with a similar structure and function

an organ

a group of different tissues working together to perform a specific function

an organ system

a group of organs working together to perform a specific function, organised in a system

an organism

a group of organ systems working together to form a living being

examples of organelles

mitochondria, a nucleus, etc.

an example of a cell

heart cell

an example of a tissue

heart muscle tissue

an example of an organ

heart

an example of an organ system

circulatory system

an example of an organism

a human

the correct order of the levels of organisation (from smallest to largest)

organelle → cell → tissue → organ → organ system → organism

a specialised cell

a cell with unique structures that make it better adapted to its specific, unique function

differentiation

the process that cells undergo in order to become specialised to their specific functions

differentiation often involves cells gaining new organelles, in order to be better suited to their role

specialised animal cells

sperm cells are specialised, as they:

• have streamlined heads and long tails for easier/faster swimming to the ovum (egg cell)

• have lots of mitochondria to release more energy from respiration, so that the cell can move

muscle cells are specialised, as they:

• have lots of mitochondria to release more energy from respiration for contraction (contraction of muscles causes movement)

• have special protein fibres that can change length and slide over each other, causing muscles to move

specialised plant cells

root hair cells are specialised, as they:

• have a large surface area (due to their long shape and long root hairs) which allows for more space for absorbing water and ions from the soil into the plant

• have a large permanent vacuole which helps to speed up the movement of water from the soil to the cell