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.