Topic 2 Biology Flashcards
What is mitosis?
- When parent cells divide to produce 2 genetically identical daughter cells.
Why is mitosis essential?
- Growth and repair
What are the 4 stages of mitosis?
- Prophase, metaphase, anaphase, telophase
What happens during prophase?
- Chromosomes condense, getting shorter and fatter.
- Centrioles move to opposite poles.
- Nucleolus disappears.
- Nuclear envelope breaks down.
- Spindle fibres begin to form and attach to centromeres.
What happens during metaphase?
- Spindle fibres pull the chromosomes so they align at the centre/equator.
What happens during anaphase?
- Centromeres divide, separating each pair of sister chromatids.
- Spindle fibres shorten and pull chromatids to opposite poles of the cell.
- Chromosome reform.
What happens during telophase?
- Chromosomes uncoil.
- Spindle fibres disintegrate.
- Cytoplasm divides to form 2 separate cells (cytokinesis)
What happens during interphase?
- There is a period of cell growth and repair.
What happens during G1?
- Cell grows and increases in volume as new organelles and cytoplasm are made
What happens during S phase?
- Cell replicates its DNA.
What happens during G2 phase?
- Cell continues to grow and synthesise enzymes for mitosis.
What is the equation to measure the time it takes for each phase?
Cells in phase/total number of cells undergoing mitosis X total time of 1 cell cycle
What is the mitotic index? (and its equation)
- The proportion of cells undergoing mitosis in a tissue
- Number of cells undergoing mitosis/Total number of cells X 100
Why is the mitotic index essential?
Gives us an indication of whether cells are becoming cancerous.
What is cancer?
- Happens when genes that control cell division mutate, leading to uncontrolled cell division, leading to tumours forming.
What is a benign tumour?
- Tumours that do not spread to other parts of the body and are slow growing.
What is a malignant tumour?
- Tumours that invade neighbouring tissues and grow quickly.
How can treatments help cancer?
- Disrupt the cell cycle which stops the division of cells.
Why are treatments of cancer negative?
- Treatments do not distinguish between cancerous cells and normal body cells, so healthy cells get exposed.
What are 3 types of cancer treatments?
- Radiotherapy uses radiation to destroy cancer cells.
- Chemotherapy (drugs)
- Surgery (but this is hard)
What is binary fission
- The replication of DNA and plasmids.
- Circular DNA strands move to opposite poles.
- Cytoplasm divides and a new cell wall grows to divide the original cell into 2 identical daughter cells
- (results in a variable number of plasmids.
What are 3 features of the non-specific immune system?
- The response is immediate.
- The response is the same for all pathogens.
- The response involves physical barriers and phagocytosis.
What are 3 features of the specific immune system?
- The response is slower.
- The response is specific to each pathogen.
- The response involves lymphocytes.
What must lymphocytes be able to do?
- Distinguish between self and non-self material.
What are the proteins on the surface of cell membranes that are able to detect foreign material called?
- Antigens.
What is a phagocyte?
- A type of white blood cell which carries out phagocytosis.
What is phagocytosis?
- Mechanism by which cells engulf a pathogens to form a vesicle.
Outline phagocytosis in 6 steps…
1) Phagocyte is attracted to a foreign chemical left behind
2) Phagocyte attaches to chemicals on the surface pf the pathogen via receptors.
3) Cytoplasm of the phagocytes moves around the pathogen and engulfs it causing a phagosome to be produced.
4) A lysosome fuses with a phagosome, releasing lyzozymes enzymes into phagosomes.
5) Lyzozymes hydrolyse the pathogen.
6) Phagocyte presents pathogen’s antigens on its surface.
What are 3 features of T lymphocytes?
- Made in the bone marrow.
- Matured in the thymus gland.
- Involved in the cell mediated response.
What are 3 features of B lymphocytes?
- Made in the bone marrow.
- Matured in the bone marrow.
- Involved in the humoural response.
Outline the cell-mediated response in 4 steps…
1) Phagocytosis occurs
2) Phagocyte presents antigens on its surface.
3) T helper cells bind to the antigen via specific T-cell receptors.
4) The binding activates T helper cells to divide rapidly by mitosis.
What cells do T helper cells produce?
- Memory B cells
- Stimulate phagocytes to engulf pathogens by phagocytosis
- B cells
- Cytotoxic T cells.
What is the role of cytotoxic T cells?
- To kill abnormal cells and body cells infected by pathogens.
How do cytotoxic T cells kill abnormal cells?
- By producing perforin, a type of protein.
- Perforin makes holes in the membrane allowing full permeability causing cells to die.
What is an antibody?
- A protein produced by B lymphocytes in response to the presence of the antigen.
Outline the humoural response in 7 steps…
1) Surface antigens of an invading pathogen are taken in by endocytosis.
2) B cells process antigens and present them on cells.
3) T helper cells attach to receptors on the APC B cell to activate it.
4) B cells divides by mitosis (clonal selection) to produce plasma cells.
5) Plasma cells are produced which create antibodies specific to the antigen on the pathogen’s surface.
6) Antibody-antigen complex is formed causing agglutination, making it easier for phagocytes to engulf pathogens.
7) B cells form memory cells which can rapidly divide into plasma cells.
Why is the secondary response more efficient than the primary response?
- Secondary response allows antibodies to be produced at a faster rate.
- Memory B cells can divide rapidly into plasma cells that produce specific antibodies to the antigen.
What is a vaccine?
- The injection of an inactive pathogen which stimulates an immune response against a pathogen.
Why are vaccines important?
- Vaccines stimulate memory cell production against a disease for the future.
What is herd immunity?
- Herd immunity occurs when a large portion of a population becomes immune to a disease, either through vaccination or prior infection.
- thereby reducing its spread and protecting those who are not immune.
What is antigenic variability?
- Antigenic variability is the ability of pathogens to alter their surface proteins to evade detection by the host’s immune system.
What is active immunity?
- Active immunity is the protection against disease developed by an individual’s immune system after exposure to a pathogen or through vaccination.
What is passive immunity?
- Passive immunity is the temporary protection against disease gained by receiving antibodies from another source, such as maternal antibodies or antibody injections, without the immune system generating its own response.
What are membranes?
- Barriers between cells and its environment or between organelles and the cytoplasm.
What are 4 processes of movement between membranes?
- Diffusion, osmosis, active transport, co-transport.
What material are membranes made from?
- Lipids, proteins and carbohydrates.
Why are membranes given the fluid factor of the fluid-mosaic model?
- Because phospholipids are constantly moving.
Why are membranes given the mosaic model of the fluid-mosaic model?
- Packed with proteins.
What are intrinsic proteins?
- Proteins inside the membrane that span the two sides of the membrane.
What are the 2 types of intrinsic protein?
- Channel proteins that form water-filled tubes which allow water-soluble molecules to pass through.
- Carrier proteins which bind to molecules and change their shape, moving them across.
What are extrinsic proteins?
- Proteins that act as mechanical support for the membrane.
- They act as cell receptors for molecules such as hormones.
What are glycoproteins?
- Proteins with carbohydrates attached.
What are 2 uses of glycoproteins?
- Allows cells to attach to one another and form tissues.
- They also may act as receptors for hormones.
What are glycolipids?
- Proteins with lipids attached.
What are 2 uses of glycolipids?
- Cell recognition
- Cell adhesion
What is the role of cholesterol in membranes? (how does it carry out the function)
- Restricts the movement of other molecules in the membrane.
- Cholesterol fits between phospholipids and binds to the fatty acid tails to pack them more closely due to the hydrophobic nature of cholesterol.
What is diffusion?
- The net movement of molecules or ions from regions of high concentration to low concentrations.
What is the difference between simple and facilitated diffusion?
- Simple diffusion is the direct movement of molecules, but facilitated diffusion uses a channel/carrier protein such as glucose or amino acids.
What factors affect the rate of diffusion?
- The concentration gradient.
- The surface area
- The temperature
- The diffusion distance
- Size of particles
What is osmosis?
- The netmovement of water particles from a regions of high water potential to a region of low water potential across a partially permeable membrane.
What is water potential?
- The likelihood of water moving in/out of cells.
What is hypotonic?
- When water potential is lower outside the cell than inside leading to osmosis out of the cell.
What is hypertonic?
- When water potential is lower inside the cell than outside leading to water entering the cell by osmosis.
What does a steeper water potential gradient mean?
- A faster rate of osmosis.
What is active transport?
- Movement of molecules from a region where they’re low in concentration to one where their concentration is higher, against a concentration gradient.
What is the special feature of active transport?
- It requires the hydrolysis of ATP.
How does active transport work?
1) Molecule binds to a receptor on a carrier protein.
2) On the other side, ATP binds to the protein.
3) ATP is hydrolysed into ADP and Pi causing the protein to change shape and the opening of the other side.
4) The molecule is released onto the other side of the membrane.
5) The phosphate ion is released from the protein and retains its original shape.
6) Phosphate and inorganic ion recombine.
Why do humans need co-transport?
- Because the concentration of glucose is too low in the ileum.
How does co-transport take place?
1) Sodium ions are actively transported out of the epithelial cells into the blood in exchange for potassium ions.
2) Results in low concentration of sodium ions in epithelial cells, creating a gradient for facilitated diffusion of sodium ions from the lumen.
3) Sodium ions diffuse into the epithelial cells via a sodium-glucose co-transporter.
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