2.1.6 cell division, cell diversity and cellular organisation Flashcards
What are the three checkpoints in the cell cycle?
-G1 checkpoint
-G2 checkpoint
-Spindle fibre checkpoint
What is checked at the G1 checkpoint?
-cell size
-nutrients
-growth factors
-DNA damage
What is checked at the G2 checkpoint?
-cell size
-DNA replication
-DNA damage
What is checked at the Spindle fibre checkpoint?
-chromosome attachment to spindle
What happens at G0 in the cell cycle?
The cell leaves the cycle temporarily or permanently: for differentiation or DNA has become damaged and is not viable.
What happens at G1 in the cell cycle?
Cellular contents (apart from chromosomes) are duplicated, and protein synthesis and respiration occurs.
What happens at S stage in the cell cycle?
Each chromosome is duplicated.
What happens at G2 in the cell cycle?
Corrects any damage detected to the chromosomes, and cell increases in size.
The energy stores are also increased.
What happens in cytokinesis?
Cytoplasm is divided between the two daughter cells.
What happens in mitosis?
Nuclear division occurs-places one strand of each chromosome in each daughter nucleus.
Each nucleus is identical to parent nucleus.
What happens during Prophase in mitosis?
-Chromatin fibres condense to form chromosomes.
-Protein microtubules form spindle fibres linking to poles of the cell.
-Spindle fibres begin to move chromosomes to centre of the cell.
-Nuclear envelope disappears.
What happens during Metaphase in mitosis?
-Chromosomes are moved by the spindle fibres to form the metaphase plate.
What happens during Anaphase in mitosis?
-Centromeres divide: sister chromatids into daughter chromosomes.
-Cells elongate.
What happens during Telophase in mitosis?
-Nuclear envelope reforms.
-Chromosomes uncoil.
-Nucleolus reforms.
Why is mitosis important in life cycles?
-growth and tissue repair
-asexual reproduction
Why is meiosis important in life cycles?
-production of haploid cells
-genetic variation (by independent assortment)
What happens in Prophase 1 in meiosis 1?
-Chromosomes condense.
-Spindle formation begins.
-homologous chromosomes pair up-bivalents.
What happens in Metaphase 1 in meiosis 1?
-Bivalent pairs assemble along the metaphase plate.
-Independent assortment-paternal and maternal chromosomes can face either pole.
What happens in Anaphase 1 in meiosis 1?
-Homologous chromosomes pulled to opposite poles-chromatids stay joined.
-Sections of sister chromatids break off and re-join- exchange (genetic variation).
What happens in Telophase 1 in meiosis 1?
-Chromosomes assemble at poles.
-Nuclear membrane reforms.
-Chromosomes uncoil.
What happens in Prophase 2 in meiosis 2?
-Chromosomes condense.
-Nuclear envelope breaks down.
-Spindle formation begins.
What happens in Metaphase 2 in meiosis 2?
-Individual chromosomes assemble in the metaphase plate.
-Independent variation-more genetic variation.
What happens in Anaphase 2 in meiosis 2?
-Chromatids of individual chromosomes are pulled to opposite poles.
What happens in Telophase 2 in meiosis 2?
-Chromatids assemble at poles.
-Chromosomes uncoil.
-Nuclear envelope reforms.
How are Erythrocytes specialised for function?
-Flattened biconcave shape=>increased their surface area to volume ratio, essential for transporting oxygen around the body.
-No nuclei or many other organelles=>increases space available for haemoglobin.
-Flexible=>squeeze through narrow capillaries.
How are Neutrophils specialised for function?
-Multi-lobed nucleus=>makes it easier to squeeze through small gaps to get to site of infection.
-Granular cytoplasm contains many lysosomes=>contain enzymes used to attack pathogens.
How are Sperm cells specialised for function?
-Flagellum=>capable of movement
-Many mitochondria=>supply energy needed to swim.
-Acrosome on the head of the sperm contains digestive enzymes=>released to digest protective layers around the ovum and allow sperm to penetrate.
How are Palisade cells specialised for function?
-Chloroplasts=>absorb large amounts of light for photosynthesis.
-Rectangular box shape=>can be closely packed to form a continuous layer.
-Thin cell walls=>increasing the rate of diffusion of carbon dioxide.
-Large vacuole=>maintain turgor pressure.
-Chloroplasts can move in the cytoplasm=>absorb more light.
How are Root hair cells specialised for function?
-Root hairs(long extension)=>increase surface area of the cell, maximising the uptake of water and minerals in the soil.
How are Guard cells specialised for function?
-Pair of guard cells which form small openings called stomata=>necessary for carbon dioxide to enter plants for photosynthesis.
-Change shape=>loss of water causes them to close to stop any more water being lost.
-Cell wall of guard cell is thicker on one side=>the cell does not change shape symmetrically as its volume changes.
How is Squamous epithelium specialised for function?
-Made up of flat cells=>very thin
-Present when rapid diffusion across a surface is needed.
-Forms the lining of the lungs and allows rapid diffusion of oxygen into the blood.
How is Ciliated epithelium specialised for function?
-Made up of ciliated epithelial cells=>cilia that move in a rhythmic manner, sweeps mucus away.
-Goblet cells present=>releasing mucus to trap any unwanted particles present in the air, prevents particles from reaching the alveoli.
How is Cartilage specialised for function?
-Contains fibres of the proteins elastin and collagen.
-Firm connective tissue
-Prevents bones from rubbing together and causing damage.
How is Muscle specialised for function?
-Skeletal muscle fibres contain myofibrils containing contractile proteins=>allows muscle to contract.
What are the four main categories of tissues in animals?
-Nervous tissue.
-Epithelial tissue.
-Muscle tissue.
-Connective tissue.
How is Epidermis specialised for function?
-Waxy waterproof cuticle=>prevents water loss.
-Stomata=>allow carbon dioxide in, and water vapour and oxygen out.
How is Xylem tissue specialised for function?
-Elongated dead cells.
-Lignin coated walls=>strengthens walls which provides structural support for plants.
How is Phloem tissue specialised for function?
-Composed of sieve tube elements separated by sieve plates.
What are stem cells?
Stem cells are undifferentiated cells.
What is stem cell Potency?
Ability of a stem cell to differentiate into different cell types.
What is a Totipotent stem cell?
Stem cells can divide and differentiate into any type of cell.
What is a Pluripotent stem cell?
Stem cells that can self-renew and differentiate into any type of cell (except in the placenta).
What is a Multipotent stem cell?
Stem cells that can only differentiate and divide into a limited number of cell types.
Why do blood cells need to be produced from stem cells?
Erythrocytes only have a life span of 120 days and so need to be replaced constantly.
Where are blood stem cells found?
Blood stem cells are found in peripheral blood and bone marrow.
How long do neutrophils live?
Neutrophils live for about 6 hours (producing about 1.6 billion kg per hour).
Where are stem cells in plants found?
In meristem-Meristematic tissue is found wherever growth occurs in a plant.
What treatments can stem cells provide in medicine?
-Heart disease.
-Type 1 diabetes.
-Parkinson’s disease.
-Alzheimer’s disease.
-Macular degeneration.
-Birth defects.
-Spinal injuries.
-Burn treatments.
-Drug trials.
What are ethical reasons against stem cells?
-Using embryonic stem cells isn’t morally right, some believe life starts at conception.
