Cells & Microscopy

Properties of eukaryotic cells

• between 5 - 100 micrometres

• have mitochondria

• DNA in nucleus

• divides through process called mitosis

Nucleus

contains genetic material (DNA) and controls the cell's activities

Cytoplasm

jelly-like substance where most chemical processes happen

Cell membrane

controls movement in and out of the cell

Mitochondria

releases energy for the cell (through aerobic respiration)

Ribosomes

tiny structures where protein synthesis occurs

Cell wall

Strengthens the cell, in plants it is made of cellulose

Vacuole

Large sac in the cell that stores the cell’s sap and helps the cell to keep its shape

Chloroplasts

small green structures that absorb light energy for photosynthesis (which makes glucose)

Properties of prokaryotic cells

• do not have membrane bound nucleus

• between 0.2 - 2 micrometers

• always have a cell wall

• does not have nucleus (DNA is loose)

• has plasmids (additional rings of DNA)

• divides through binary fission

Plasmid

Small ring of DNA separate from chromosomal DNA and replicate independently

Cell differentiation

Process by which a cell changes to become specialised for its job

Most type of animal cells differentiate in

early stages of development

Most type of plant cells differentatiate

Throughout their life cycle

Red blood cells

• found in a blood animals

• function is to carry oxygen around the body to all the cells that need it

• has lots of a special chemical called haemoglobin that picks up oxygen

• has no nucleus to make room for more oxygen

• large surface area to pick up oxygen quickly

Sperm cells

• animal cell

• function is to fertilise an egg cell,

• has a tail for a swimming

• many mitochondria to supply energy

• head has digestive enzymes to penetrate

Nerve cell

• animal cell

• function is to carry electrical impulses around the body

• has a long and thin part called axon to travel around the body

• surrounded by a fatty sheath to insulate the nerve cells and increase speed of transit of nerve impulse

• has lots of branches to connect to other nerve cells

Root hair cell

• plant cell

• function is to absorb water and minerals from the soil

• has large surface area to provide space for absorbing water

• has large permanent vacuole to help store water and minerals

• has lots of mitochondria to provide them with energy to help absorb water

Xylem cell

• Plant cell

• function is to transport water and dissolved mineral ions upward from roots

• has long hollow tubes through which water and minerals can pass easily

• surrounded by rings of waterproof substance called lignin to withstand pressure from water (supports plant stem)

Phloem cell

• plant cell

• function is to transport food made by photosynthesis around plants

• has long tubes with sieve plates to lets substances flow

• has companion cells that have a lot of mitochondria for energy

• uses photosynthesis for food to transport

What is the equation for magnification?

magnification = image size/actual size

Chromosomes

long lengths of DNA and is coiled up to form the arms of the chromosomes

Genes

short sections of DNA that control characteristics

Mitosis

when a cell reproduces itself by splitting to form two identical offspring

Mitosis is used

to grow, develop or replace cells that have been damaged

How does mitosis work?

• after cell growth and DNA replication, the chromosomes line up at the centre of the cell and cell fibres pull them apart

• he two arms of each chromosome go to opposite sides of the cell

• membranes form around each of the sets of chromosomes to form nuclei, and lastly the cytoplasm and cell membrane divide

• two identical (clone) daughter cells have been produced.

Meiosis

a type of cell division where 4 gametes are produced and each have 23 (half) chromosomes

How does meiosis work?

• cell starts with 46 chromosomes

• chromosomes duplicate

• chromosomes then swap genes with each other

• cell divides producing 2 new cells

• divide for a second time producing 2 more cells (4 in total) with 23 chromosomes in each

• all new cells, called gametes, have a different set of genes

• takes place in ovaries and testes