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The regular sequence of growth and division that cells undergo
Specialised cells
Interphase: cell growth and DNA replication Composed of G1, S-phase and G2 Mitotic phase: mitosis and cytokinesis
The cell cycle is controlled by regulatory proteins both inside and outside the cell, also known as 'checkpoints'. The checkpoints are G1, G2, and M.
G1 phase- cell growth- cells increase in size and synthesises new proteins and organelles S phase- DNA replication G2- continuation of growth - more proteins and organelles are made ready for mitosis.
cell size, nutrients, growth factors, DNA damage
Cell size, DNA replication, DNA damage
prophase, metaphase, anaphase, telophase
Mitosis is important for cell growth, repair and replacement of cells, and asexual reproduction.
In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA, in the form of two sister chromatids joined by a centromere, tightly coiled many times around proteins called histones that support its structure.
- chromosomes condense, becoming short and fat - tiny bundles of protein called centrioles move to the poles of the cell - the nuclear envelope begins to breakdown
-Chromosomes line upon along the equator of the cell - Spindle fibres attach to the centromere of each chromosome - Metaphase checkpoint checks all chromosomes have been attached to the spindle correctly
- centromeres divide separating each chromosome into sister chromatids - the spindle fibres contract and pull the chromatids to opposite ends of the cell.
-Chromatids uncoil and become long and thin, now called chromosomes. - The nuclear envelope begins to reform around each pole. - the cytoplasm begins to split
The cytoplasm fully divides. There are now two genetically identical daughter cells.
Growth, tissue repair, asexual reproduction in plants, animals and fungi.
Production of haploid cells and genetic variation by independent assortment and crossing over
Contains half the necessary chromosomes, ie gametes such as sperm and egg cells.
A cell which contains the full number of chromosomes in homologous pairs.
N
2n
Two chromosomes with the same set of genes, in the same sequence, sometimes with different alleles
Meiosis is a type of cell division that produces gametes with half the normal amount of chromosomes
Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II
- chromosomes condense and become short and fat - homologous chromosomes pair up - crossing over occurs - centrioles move to opposite poles - nuclear envelope begins to breakdown
- Spindle fibres form and attach to centromeres on the homologous pairs. - Homologous chromosomes line up along the equator
- Spindle fibres contract and homologous pairs are pulled apart to opposite poles - this is independent assortment
- Nuclear envelope reforms around each group of chromosomes - cytokinesis occurs and two haploid daughter cells are formed.
the same steps in meiosis 1 but with half the number of chromosomes.
crossing over and independent assortment
a single cell that can replicate itself or differentiate into many cell types - effectively an 'undifferentiated' cell.
the process by which unspecialised cells develop into their mature forms and functions, called specialised cells.
- biconcave shape: large SA for gas exchange - no nucleus: more room for haemoglobin
- multi-lobed nucleus for flexibility - flexible cell surface membrane for phagocytosis - many lysosomes for hydrolysis of pathogens
By undifferentiated stem cells in bone marrow
Very thin to allow rapid gas exchange
Have small hairs (cilia) which waft substances in a certain direction in a beating motion.
- long flagellum for propulsion - many mitochondria for ATP production for swimming - Acrosome containing digestive enzymes for fertilisation
- many chloroplasts for photosynthesis - thin walls for CO2 diffusion - long and upright for correct orientation for photosynthesis
- large surface area for adsorption - thin, permeable cell wall - extra mitochondria for ATP for active transport
Cell wall is thicker on one side so the cell doesn't change shape symmetrically in response to light.
Totipotent cells are cells that can differentiate into any type of body cell and extra embryonic tissue
Cells that are capable of developing into many tissues and organs, but not extra embryonic tissues.
a cell that can differentiate into a few closely-related cell types
Present in adult mammals , only differentiate into one type of cell eg skin cells
A tissue is a group of similar cells that work together to carry out a particular function
Squamous epithelium tissue Ciliated epithelium tissue Muscle tissue Cartilage
Xylem and phloemW
Meristems in roots and stems
Cambium meristem
A group of different tissues that work together to perform a certain function.
The lungs Leaf
An organ system is a group of organs working together to carry out a particular function
respiratory system and circulatory system
a group of organ systems working together to perform the same function
- replacing heart cells to treat heart disease - replacing brain cells to treat Alzheimer's - replace dopamine-producing cells to treat Parkinson's - replace beta cells to treat diabetes type I - to research how organisms grow and develop, which helps to understand developmental diseases like cancer.