AQA BIOLOGY B2

Key Points - 

Cells may be specialised to carry out a particular function.

Examples of Specialised cells are FAT CELLS, CONE CELLS, ROOT HAIR CELLS, SPERM CELLS.

Looking closer-

FAT CELLS - little normal cytoplasm - plenty of room for large amounts of fat.

Very few mitochondria as they use little energy

Can expand up to 1000 times its original size. fatty fatty boom boom

CONE CELL (from human eye) - outer segment contains visual pigment.

Middle section packed with mitochondria (produce energy so v pigment can reform - this means eye can see continually in colour ) Smart ey ;) 

Final part is a specialised nerve ending, connects to optic nerve - carries impulses to your brain

ROOT HAIR CELLS - large permanent vacuole, affects movement of warer from the soil across the root hair cell

Positioned close to the xylem tissue

SPERM CELLS - Long tails with muscle-like proteins so they can swim towards egg 

Middle section full of mitochondria - provide energy for the tail to work 

Acrosome stores digestive enzymes for breaking down the outer layers of egg

Large nucleus which contains genetic information.

REMEMBER: CELLS -> TISSUES -> ORGANS-> ORGAN SYSTEMS-> WHOLE BODY

Diffusion is the net movement of particles from an area of HIGH CONCENTRATION to an area of LOWER CONCENTRATION.

It is a random movement. 

The rate is affected by; 

Temp 

The difference between two areas of concentration - called the CONCENTRATION GRADIENT. The bigger the difference, the steeper the gradient - the faster the rate will be. 

Examples of diffusion are; 

The diffusion of oxygen into cells of the body from the blood stream as the cells are respiring. 

Diffusion of CO2 into actively photosynthesising plant cells. 

Diffusion of simple sugars and amino acids from the gut through the cell membrans.