Cell Biology

Plant cells 

Plant cells usually have all the bits that animal cells have, plus a few extra things that animal cells don't have: 

1.) Rigid cell wall - made of cellulose. It supports the cell and strengthens it. 

2.) Permanent vacuole - contains cell sap, a weak solution of sugar and salts. 

3.) Chloroplasts - these are where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll, which absorbs the light needed for photosynthesis. 

This is a plant cell with all key elements highlighted and labelled. 

Animal Cells 

The different parts of a cell are called subcellular structures. Most animal cells have the following subcellular structures - make sure you know them all: 

1.) Nucleus - contains genetic material that controls the activities of the cell. 

2.) Cytoplasm - gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemcial reactions. 

3.) Cell membrane - holds the cell together and controls what goes in and out. 

4.) Mitochondria - these are where most of the reactions for aerobic respiration take place. Respiration transfers energy that the cell needs to work. 

5.) Ribosomes - these are where proteins are made in the cell. 

This is an animal cell with all key points highlighted and labelled. 

Large Multicellular Organisms

Cells are the basic building blocks of all living organisms. Specialised cells carry out a particular function. The process by which cells become specialised for a partiular job is called diffferentiation. Differentiation occurs during the development of a multicellular organism. These specialised cells form tissues, which form organs, which form organ systems. Large multicellular organims (eg. squirrels)have different systems inside them for exchanging and transporting materials. 

Similar Cells are organised into tissues 

Atissue is a group of similar cells that work together to carry out a particular function. It can include more then one type of cell. 

In mammals (like humans), examples of tissues include: 

1.)  Muscular tissue, which contracts (shortens) to move whatever it's attached to. 

2.) Glandular tissue, which makes and secretes chemicals like enzymes and hormones. 

3.) Epithelial tissue, which covers some parts of the body, eg. the inside of the gut. 

Tissues are organised into organs 

An organ is a group of different tissues that work together to perform a certain function. 

For example, the stomach is an organ made of these tissues: 

1.) Muscular tissue, which moves the stomach wall to churn up the food. 

2.) Glandular tissue, which makes digestive juices to digest food. 

3.) Epithelial tissue, which covers the outside and inside of the stomach. 

Organs are Organised into Organ Systems

An organ system is a group of organs working together to perform a particular function. 

For example, the digestive system (found in humans and other mammals) breaks down and absorbs food. It's made up of these organs: 

1.) Glands (eg. the pancreas and salivary glands), which produce digestive juices. 

2.) The stomach and small intestine, which digest food. 

3.) The liver, which produces bile. 

4.) The small intestine, which absorbs soluble food molecules. 

5.) The large intestine, which absorbs water from undigested food, leaving faeces. 

Organ Systems work together to make entire oganisms. 

Osmosis 

Is the movement of water molecules between a semi-permiable membrane 

Diffusion 

Is the movement of molecules from a high concentration to a low concentration 

Active transport

Is the movement of molecules from a low concentration to a high concentration 

Osmosis 

Is the movement of water molecules between a semi-permiable membrane 

Diffusion 

Is the movement of molecules from a high concentration to a low concentration 

Active transport

Is the movement of molecules from a low concentration to a high concentration 

Osmosis

This is a digram of how osmosis is perceived with every labelled and key points highlighted.

Diffusion 

This is a diagram of the movement of molecules from a high concentration to a low concentration in a gradient (diffussion)

Active transport 

This is a diagram showing the movement of cells from a low concentration to a high concentration.