Biology- cells

Light microscopes

• cheap to make

• allow you to see outline of cells

Electron microscopes

• Allow you to see finer details like organelles (sub-cellular structures)

• Have a greater resolving power

• Higher resolution

Equation for magnification

Magnification= image size / object (cell) size

How long are cells

A few micrometers long

How to convert micro meters to mm

Divide by 1000

Organelles

Sub-cellular structures

Eukaryotic

Complex cells which include all animal or plant cells

Prokaryotic

Smaller and similar (bacteria)

What do animal cells contain

• Nucleus

• Cytoplasm

• Cell membrane

• Mitchondria

• Ribosomes

What do plant cells contain

Everything the animal cell contains plus:

• Cell wall

• Permanent vacuole

• Chloroplasts

What does a bacteria cell have?

• cell membrane

• Cell wall

• Cytoplasm

• May contains small rings of dna called plasmids

Nucleus

Contains genetic material that controls the activity of the cell

Cytoplasm

Gel like substance where most of the chemical reaction takes place. It contains enzymes

Cell membrane

Holds the cell together and controls what goes in and out

Mitochondria

Where most of the reactions for aerobic respiration take place. Respiration transfers energy that the cell needs to work

Ribosomes

Where proteins are made in the cell

Cell wall

• made of cellulose

• Supports the cell and strengthens it

Permanent vacuole

• contains cell sap

• a weak solution of sugar and salts

Chloroplasts

• where photosynthesis occurs which makes food for the plant

• Contain a green substance called chlorophyll

Chlorophyll

Absorbs light needed for photosynthesis

Plasmids

Small rings of dna in prokaryotic cells

Binary fission

How bacteria reproduce, they divide every 20min

How many chromosomes in human cells

• 23 pairs (46)

• diploid cells

How many cells is Gametes (egg/sperm)

• 23

• Haploid cells

How are new (diploid) cells made

By mitosis

Stem cells

• specialise to perform specific functions

• Found in animal EMBRYOS and plant MERISTEMS

Where are some stem cells made

• Made in your bone marrow

• But these can only specialise into BLOOD CELLS

Embryo clones use

• Used to treat conditions without them being rejected by the patients body

• Can also be used to preserve species or produce crops with desired traits

Diffusion

The movement of particles from an area of HIGH CONCENTRATION to that of a LOW CONCENTRATION (“down the concentration GRADIENT”). This is passive as it requires no energy.

Osmosis

• the diffusion of water across a SEMI-PERMEABLE MEMBRANE to balance the concentrations of solution inside and outside a cell.

• Water must move as larger molecules cannot fit through the holes

• Water move IN if the concentration is higher OUTSIDE

Active transport

• The movement of particles through a membrane via CARRIER PROTEINS.

• This requires energy, and so can move them AGAINST concentration gradient