Biology Revision notes

Página 1

Key concepts in biology

Cells

Organisms can be Eukaryotic or Prokaryotic

All living things are made up of cells. Cells can either be eukaryotic or prokaryotic. Eukaryotic cells are complex and include all animal and plant cells. Prokaryotic cells are smaller and simpler, e.g. bacteria. Eukaryotes are organisms that are made up of eukaryotic cells. A prokaryote is a prokaryotic cells, it's a single celled organism.

Plant and animal cells have similarities and differences

The different parts of a cell are called subcellular structures. Most animal cells have the following subcellular structures:

Nucleus – contains genetic material that controls the activities of the cell

Cytoplasm – gel-like substance where most of the chemical reactions happen

Cell membrane – holds the cell together and controls what goes in and out

Mitochondria – these are where most of the chemical reactions for respiration take place. Respiration transfers energy that the cell needs to work

Ribosomes – these are involved in translation of genetic material in the synthesis of proteins

Plant cells usually have the same subcellular structures, plus a few extras:

Rigid cell wall – made of cellulose. It supports the cell and strengthens it.

Large vacuole – contains cell sap, a weak solution of sugar and salts. It maintains the internal pressure to support the cell.

Chloroplasts – these are where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll.

Bacteria cells have no nucleus

Bacteria cells are a lot smaller than plant or animal cells and have the following subcellular structures:

Chromosomal DNA – controls the cell's activities and replication. It floats free in the cytoplasm

Ribosomes

Cell membrane

Plasmid DNA – small loops of extra DNA that aren't part of the chromosome. Plasmids contain genes for things like drug resistance, and can be passed between bacteria.

Flagellum – a long, hair like structure that rotates to make bacterium move. It can move the bacteria away from harmful toxins and towards beneficial things like nutrients or oxygen.

Key concepts in biology

Cells

Organisms can be Eukaryotic or Prokaryotic

All living things are made up of cells. Cells can either be eukaryotic or prokaryotic. Eukaryotic cells are complex and include all animal and plant cells. Prokaryotic cells are smaller and simpler, e.g. bacteria. Eukaryotes are organisms that are made up of eukaryotic cells. A prokaryote is a prokaryotic cells, it's a single celled organism.

Plant and animal cells have similarities and differences

The different parts of a cell are called subcellular structures. Most animal cells have the following subcellular structures:

Nucleus – contains genetic material that controls the activities of the cell

Cytoplasm – gel-like substance where most of the chemical reactions happen

Cell membrane – holds the cell together and controls what goes in and out

Mitochondria – these are where most of the chemical reactions for respiration take place. Respiration transfers energy that the cell needs to work

Ribosomes – these are involved in translation of genetic material in the synthesis of proteins

Plant cells usually have the same subcellular structures, plus a few extras:

Rigid cell wall – made of cellulose. It supports the cell and strengthens it.

Large vacuole – contains cell sap, a weak solution of sugar and salts. It maintains the internal pressure to support the cell.

Chloroplasts – these are where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll.

Bacteria cells have no nucleus

Bacteria cells are a lot smaller than plant or animal cells and have the following subcellular structures:

Chromosomal DNA – controls the cell's activities and replication. It floats free in the cytoplasm

Ribosomes

Cell membrane

Plasmid DNA – small loops of extra DNA that aren't part of the chromosome. Plasmids contain genes for things like drug resistance, and can be passed between bacteria.

Flagellum – a long, hair like structure that rotates to make bacterium move. It can move the bacteria away from harmful toxins and towards beneficial things like nutrients or oxygen.

Página 2

Specialised Cells