Cell Biology Mind Map (GCSE)

Animal and plant cells. Their genetic material is enclosed in a nucleus.

Bacterial cells. Much smaller than eukaryotic cells, with no nucleus. Their genetic material is a single loop of DNA, and they may also have small rings of DNA called plasmids. They have a cell wall, cell membrane and cytoplasm.

• Nucleus: contains genetic material and controls the cell's activities
• Cytoplasm: where most chemical reactions happen, controlled by enzymes
• Cell membrane: controls what enters and leaves the cell
• Mitochondria: where aerobic respiration happens
• Ribosomes: where proteins are made

Plant cells have everything an animal cell has, plus:

• Chloroplasts: absorb light for photosynthesis
• Permanent vacuole: filled with cell sap
• Cell wall: made of cellulose, strengthens the cell

As an organism develops, cells become specialised for a particular job. Most animal cells differentiate early in life, while many plant cells can differentiate throughout life.

A tail to swim, many mitochondria to release energy, and enzymes in the head to get into the egg.

Long, with branched connections, to carry electrical impulses around the body.

Can contract, and contain many mitochondria to release the energy needed.

A large surface area to absorb water and mineral ions from the soil.

Xylem cells form hollow tubes, strengthened with lignin, that carry water and mineral ions. Phloem cells carry dissolved sugars, and have end walls called sieve plates.

Uses light, is cheap, and can be used to view living cells, but has limited magnification and resolution.

Much higher magnification and resolution, so it shows sub-cellular structures such as ribosomes and the inside of mitochondria. It helped scientists understand cells in far more detail.

magnification = size of image / size of real object

Rearrange it to find the real size: real size = image size / magnification. For example, an image 10 mm wide at x100 magnification shows an object 0.1 mm (100 µm) wide.

• 1 millimetre (mm) = 1000 micrometres (µm)
• 1 micrometre (µm) = 1000 nanometres (nm)

Cells are usually measured in micrometres. Convert both sizes to the same unit before using the equation.

Found in the nucleus, made of DNA, and each carries many genes. Body cells have chromosomes in pairs: human body cells have 23 pairs.

The cell grows, the number of sub-cellular structures such as ribosomes and mitochondria increases, and the DNA replicates so there are two copies of each chromosome.

One set of chromosomes is pulled to each end of the cell, and the nucleus divides.

The cytoplasm and cell membrane divide, forming two genetically identical cells.

Mitosis is used for growth, for repair, and for asexual reproduction.

Can differentiate into almost any type of cell.

Found in places such as bone marrow. They can form many types of cell, including blood cells, but not as many as embryonic stem cells.

Tissue at the tips of roots and shoots that can differentiate into any type of plant cell throughout the plant's life. Used to clone rare plants, and crops with useful features such as disease resistance.

An embryo is made with the same genes as the patient, so stem cells from it would not be rejected by the patient's body.

Stem cells may treat conditions such as diabetes and paralysis. Against that, there are ethical and religious objections to using embryos, and a risk of transferring viral infections.

The net movement of particles from an area of higher concentration to an area of lower concentration. Examples: oxygen and carbon dioxide in gas exchange, and urea moving from cells into the blood. It is faster with a steeper concentration gradient, a higher temperature and a larger membrane surface area.

The diffusion of water from a dilute solution to a more concentrated solution through a partially permeable membrane.

Required practical: measure the change in mass of plant tissue, such as potato, in different concentrations of salt or sugar solution.

The movement of substances from a more dilute solution to a more concentrated solution, against the concentration gradient. It needs energy from respiration. Examples: root hair cells absorbing mineral ions from the soil, and sugar being absorbed from the gut into the blood.

Single-celled organisms have a large surface area to volume ratio, so diffusion is enough. Larger organisms need exchange surfaces adapted with a large surface area, a thin membrane, a good blood supply and, in animals, ventilation.