- Diffusion is the net movement of particles from high to low concentration.
- Factors affecting rate of diffusion: temperature, concentration gradient, surface area of the membrane.
- Osmosis is the net movement of water from a highly to a less concentrated solution (low water potential) through a partially permeable membrane.
- Active transport is the movement of particles from an area of lower to higher concentration.
- Active transport happens in root hair cells to take up mineral ions from soil.
- Diffusion and osmosis require no energy. Active transport requires energy from respiration as it works against the concentration gradient.
- Stages of the cell cycle: cell growth, DNA replication, movement of chromosomes, cytokenesis, more cell growth.
- Mitosis is a type of cell division where one cell divides to form two identical daughter cells.
- the cell grows, ribosome and mitochondria grow and increase in number, protein synthesis occurs, all 23 pairs of chromosomes in the cell are replicated.
- Mitosis: The chromosomes line up at the equator (diameter) of the cell and fibres pull each chromosome of the ‘X’ to the left/ right of the cell.
- Cytokinesis: A nucleus forms around each of the sides with chromosomes and two identical daughter cells form. Each contains the same 46 chromosomes as the original cell.
- Mitosis is important in growth and development, and when replacing damaged cells, and in asexual reproduction.
- Cell differentiation: when cells grow and specialise with specific structures.
- Sperm, nerve, muscle, root hair cells have a lot of mitochondria to provide energy from respiration. Sperm cells are streamlined for swimming. Nerve cells have a long axon to move long distances. Root hair cells have a high S.A so more water can move in.
- Stem cells are present in embyronic and adult animal cells and meristems in plants. They can divide to produce different cell types for development, growth and repair.
- Embryonic stem cells: form when egg and sperm cell fuse to form a zygote. They can form any type of cells and could be cloned.
- Adult stem cells may be found in bone marrow and can form many types of cells.