2 cells Flashcards
WAWAWA
explain the structures in a chloroplast?
. membrane
. DNA loop
. granum
. 70s ribosomes
. starch grain
. thylakoid
explain the structures in mitochondria?
. outer membrane
. circular DNA
. matrix
. intermembrane space
. inner membrane
. cristae
. 70s ribosomes
what si the cell surface membrane?
. controls exchange between cell and environment
. transport proteins embedded in membrane
. selectively permeable
. made of fluid phospholipid bilayer to allow exocytosis and endocytosis
. has receptors for cell recognition and attatchment
what is the nucleus?🆙
. contains dna/chromosomes/genetic info
. contains chromatin that condenses to form chromosomes of linear dna
. involved in protein synthesis - transcription of dna onoto rna copy
what is the nuclear envelope?
. has two membranes
. outer membrane is continuous with the endoplasmic reticulum
. separates DNA from the rest of the cell
. has nuclear pores to let rna leave and nucleotides enter
what is the nucleolus ?
. makes ribosomal DNA and ribosomes
. cells can have more than one nucleoli
what is the mitochondria?🆙
. site of aerobic respiration using atp
. contain circular DNA and 70s ribosomes for protein synthesis and self replication
. lots found in cells with high demand for atp energy e.g muscle cells, liver cells, secretary cells
what are the chloroplasts?🆙
. double outer membrane with stroma inside
. grana are several parallel stacked membrane thylakoids containing chlorophyll etc …
. often have starch grains
. contain 70s ribosomes
. have circular DNA that isn’t protein bound
. self replicating
what is the Golgi?
. stack of dynamic flattened cisternae formed from endoplasmic reticulum
. bud off to form vesicles
. packages and transports proteins from RER for transport and secretion out of the cell
. modifies proteins
. transports lipids
what are the lysosomes?
. type of golgi vesicle
. contains lysosomes (hydrolytic enzymes kept separately)
. breaks down unwanted organelles/structures/bacteria in phagocytosis
. lysosomes fuse with membrane of digestive vacuoles
what are the ribosomes?
. small
.synthesise protein from amino acids
. made of rna and protein
. 80s in eukaryotes
what is the endoplasmic reticulum?
. system of membranes through the cell
. continuous with nuclear membrane and golgi
. rough - has ribosomes, attaches to mrna in p synth, transport system
. smooth - no ribosomes, makes lipids and steroids
what is the cell wall?
. outside membrane
. prevents bursting
. permeable to solutes
. cellulose microfibril polysaccharide
what is different about cell walls in fungi?
. they’re made from chitin
what is the vacuole?
. small vesicles in animals and are large surrounded by tonoplast in plants
. functions as storage sites in plants but in animals may be formed in phagocytosis or act as contractile vacuoles
what structure do prokaryotes have?
ALL:
. cytoplasm lacking membrane bound organelles
. smaller ribosomes
. circular dna not associated with proteins
. murein containing cell wall
MANY:
. one or more plasmids
. capsule surrounding cell
. one or more flagella
describe viruses?
. are acellular, not living
. too small to see with light microscopes
. made up of core nucleic acid genetic material which is surrounded by a capsid protein coat and contains attachment protein
describe a HIV virus?
. has glycoprotein attachment protein
. capsid
. rna
. reverse transcriptase
. viral envelope
explain attachment proteins on viruses?
. bind to competitive receptors on surface of host cell
. inject genetic material into cell
. attachment proteins are specific to ne type of cell
what is a light microscope?
. uses lenses to focus beam of light through a specimen
. has a lower resolution
. can use a live specimen
. can show true colour
. there’s a simple slide and stain process
what is a transmission electron microscope?
. electromagnets used to focus beam of electrons through
. specimen must be in vacuum so dead
. thin specimen must be used
. complex staining
. black and white only
. highest resolution
what is a scanning electron microscope?
. electromagnets focuses beam of electrons onto specimen
.not as high resolution
. black and white but colour with computer can be added
. 3d images produced
how do you prepare a slide?
. add a drop of water so specimen sticks
. use a single layer of cells so light can pass through
. and a drop of stain to make cells/organelles visible
. cover slip and push gently to remove air bubbles
convert 1 mm into different units?
1mm = 1000um 10000000 nm 100000000000 pm
what is the equation for magnification?
m = i / a
what are the stages in cell fractionation?
. homogenisation - splitting cell open so organelles can leave
. cold - reduces enzyme activity
. isotonic - prevents organelles from shrinking/bursting
. buffer - maintains ph to prevent denaturing
. filtration - filters out large cell debris to prevent artefacts
. centrifugation - low speed nucleus out then inc speed to get pellets of chloroplasts, mitochondria, lysosomes, ribosomes (separates organelles depending on mass)
what does homologous chromosomes mean?
. pairs that are the same size with the same genes
what is mitosis?
. part of the cell cycle where eukaryotes divide producing two genetically identical daughter cells
what is the spindle fibre?
. globular protein
. attaches to chromosomes in cell division and separates them
describe the stages in the cell cycle?
. interphase - longest phase, chromosomes double up to exist as identical chromatids, cell metabolically active and increases in size
. protein synchesis is happening
. replication of DNA and centrioles
MITOSIS:
.prophase - chromatids condense and thicken from chromatin, get visible as 2 chromatids joined at centromere, nuclear envelope and nucleoli disappear
. metaphase - chromosomes line up at the equator of miotic spindle, attached by centromere
. anaphase - chromosomes split as centromere divides as spindle contracts, sisters chromatids separated, pulled to opposite poles by centromere
. telophase - chromosomes elongates and uncoil, nuclear envelope reforms and nucleus reappear as 2 new nuclei formed
. cytokinesis - cytoplasm divides by membrane cleavage, very quick
what is cancer?
. rapid or uncontrollable cell division that can lead to a tumour
what is the calculation for mitotic index?
. mitotic index = cells with visible chromosomes / total visible cells
explain some cancer treatments?
. drugs and radiotherapy both affect the cell cycle but can lead to cell death
. affects cancerous cells the most though as they divide quickest
. some drugs prevent synthesis of enzymes forcing cell to kill itself (G1)
. radiation and drugs damage dna, in cell cycle cells checked for damage so could stop them replicating for another reason so more likely to kill themselves
. other drugs stop dna making nucleotides or inhibit formations of miotic spindle
explain binary fission?
. replication process in prokaryotes
1. circular dna and plasmids undergo replication
2. dna loop only replicated once and plasmids can be any amount
3. cell divides into 2 cells containing roughly half the cytoplasm, one copy of the circular dna and any number of plasmids
explain how viruses reproduce?
. aren’t living so cant reproduce in typical way
. inject nucleic acid into a host cell
. can use either prokaryotes and eukaryotes to reproduce
,once nucleic acid is inside a host, host dna replicates and protein synthesis system makes more virus components that are then assembled into viral particles
Why is it called the fluid mosaic model?
. Fluid components can move in lipid bilateral
. Mosaic has many proteins of different shapes and size embedded in it
What does the cell membrane do?
. Selectively permeable
. Allows small lipid soluble molecules through
. Maintains water potential
What is the cell surface membrane made up of?
. Phospholipid bilayer - allows passage of non polar substances gives membrane fluidity
. Extrinsic proteins - on surface
. Intrinsic proteins - act as carriers
. Protein channels - allow facilitated diffusion, hydrophilic linings
. Glycoprotein and lipid - bind with water to stabilise
. Cholesterol - maintains fluidity and stability
What can and can’t pass through the bilayer?
. Can - small no polar, lipid soluble substances only
. Can’t - water soluble, larger molecules
What are the roles of protein in the cell membrane?
. Enzymes - digest disaccharide membranes of epithelial cells
. Channels - allow specific ions through
. Carriers - transport substances in and out
. Receptors - for hormones
What are the roles of carbohydrates in the cell membrane?
. Attach to lipid/proteins outside membrane, form glycoproteins/ glycolipids
. allow cells to recognise each other
What is simple diffusion?
. Movement of molecules from an area of higher to lower concentration, passive and doesn’t us energy from atp
. Affected by conc gradient, distance of travel, temp, size of molecule, membrane sa, lipid solubility
What is facilitated diffusion?
. Molecules diffusing across cell membranes from an area of higher to lower concentration using protein carriers or channels, passive
Describe a channel protein?
. Hydrophilic, specific to one type of molecule, open and close, no. Can affect rate
What is active transport?
. Movement of molecules against a concentration gradient, requires energy from atp
. Respiratory inhubitors can affect rate
What is co transport?
. Simultaneous transport of one substance across a membrane coupled with the simultaneous transport of another substance across the same membrane in the same direction, active
What is osmosis?
. Movement of water from a solution of higher water potential to solution of low what potential there a partially permeable membrane, passive
What is water potential?
. Tendency of water to leave or enter a system or cell kpa
What is isotonic?
. solution of the same water potential
What is hypertonic?
. concentrated solution with lower water potential
What is hypotonic?
. Dilute solution with very high water potential
Describe what happens to plants and animal cells in hyper/hypotonic solutions?
. Hypertonic - P: Loses volume, inner cell crenates, plasmolysis A: Loses volume crenates
. Hypotonic - P: Vacuole and cytoplasm increase in volume, turgid A: gains volume, lysis
What is an antigen?
. Foreign body that causes an immune response – found on the surface of pathogens
What does the immune system response to?
. Toxins, abnormal cells I.E.cancer, other peoples cells, antigen presenting cells
What is antigenic variability?
. Some pathogens change surface antigens as DNA mutate which changes the tertiary structure of the surface protein
Explain phagocytosis?
. Phagocyte - originate and mature in bone marrow
. Phagocyte recognises foreign antigens and engulfs pathogen into Phagosome
. Lysosome fuses with the Phagosome releases lysozymes into it
. Lysozymes hydrolyse pathogen and absorb products
. Antigens are displayed on phagocyte cell membrane
. Non specific response
Name examples of antigen presenting cells?
. Infected body cells present viral antigens on the surface
. A phagocyte which has engulfed and destroyed a pathogen will present antigens on the surface
. Cells of transplanted organs have different shapes antigens
. Cancer cells of abnormally shaped Antigens
What cells are involved in the specific immune response?
. Lymphocytes are involved in specific T cells mediated response B cells part of humoral response
Explain the cell mediated response?
. Pathogen invades body
. Phagocyte presents antigen
. activates specific T helper cells
. Cytotoxic t cells kill pathogens helper T cells find the antigen on pathogen surface and stimulate specific B cells
. memory T cells remain in lymph nodes and activate B cells if secondry contact made
What is an antibody?
. Made by B cells, find the antigens to clumps in togethers (agglutination) to aid phagocytosis, are proteins found in plasma, tissue fluid and milk
What are the constant variable regions on an antibody?
. Constant region-the same sequence of amino acids
. Variable region- specific tertiary to one antigen
Explain the humoural response?
. Pathogen invades body
. Antibody on B-cell binds and forms antigen antibody complex
. this and t helper cell chemicals activate the cell which divides by mitosis into plasma cells
. Plasma cells are clones that secrete specific monoclonal antibody which is transported by blood
. Antibodies bind with antigens, form complex and stimulates phagocytosis
. Memory B cells continue to secrete antibodies for many years and can produce rapidly if second contact with the same pathogen
How does antigenic variability allow a pathogen to evade recognition?
. Some pathogens change the surface antigens as virus mutates which stops the body from recognising it which results in a primary response each time has no memory cells for the new anti-gen is no longer complimentary, this allows pathogen to evade
Explain the primary response?
. First contact with antigen, slower not as many body cells to produce specific antibodies, patient will develop symptoms as pathogen increases and damages cells, B and T cells produce memory cells that stay for time
Explain the secondary response?
. Second contact with antigen, clonal selection much faster, more antibodies produced in short space of time, rapid response that prevents full infections a person is immune
What is a vaccine?
. Contains the antigen in a dead/weakened form which stimulates the production of antigen presenting cells, antibodies, plasma cells, and memory cells
How do vaccines work?
. Specific T-helper cells detect antigens and stimulate specific B cells
. B cells divide by mitosis to give plasma cells that produce antibodies and memory cells
. Second dose we produce antibodies in a secondary immune response so fast and larger production of antibodies
What is an attenuated strain?
. Less virulent or mutated form that doesn’t cause disease
How do vaccines control disease?
. Provides artificial active immunity with memory cells
.  most people vaccinated when young
. Herd immunity interrupts transmission through crowd
. Ring vaccination vaccinate all around victims prevent spread
What’s the difference between active and passive immunity?
. Active immunity – requires exposure to antigen, takes time for protection to develop, long-term, memory cells, immune system makes on antibodies
. Passive immunity-doesn’t require exposure to antigen, immediate reception, short-term, no memory cells, given antibodies from elsewhere
What are the ethical issues with vaccination?
. Test on animals and development and production
. Risks people in medical trials
. Expensive so takes money from other treatments
. Priorities, who gets it first in an epidemic
Describe the structure of HIV virus?
. Has lipid envelope, reverse transcriptase/enzymes, RNA/genetic material, glycoprotein, attachment protein, capsid,
Explain HIV replication?
. Attachment proteins attach to receptor molecules On host helper cell
. Captain released into cell, uncoats and releases RNA into cytoplasm
.  reverse transcriptase makes complimentary DNA strand for viral RNA
. Makes double-stranded DNA, is inserted into Host cell DNA
. Host cell enzymes used to make viral protein and RNA which are embedded in new viruses
. New virus buds off and infect other cells
What are the aids symptoms?
. Helper T cell count drops
. Immune system deteriorates until it fails
. Person no more vulnerable to other infections
. Antibiotics don’t work against it
What is a monoclonal antibody and what are they used for?
. The single type of antibody with the same shape artificially produce from a single clone of plasma cells, used in medical treatments and diagnosis
. Uses in cancer: cancer cells of antigen is called tumour markers, specific monoclonal antibody combines a tumour markers, anti-cancer drugs can be attached to the specific antibodies, drugs accumulate where there’s cancer reducing side-effects
. Uses in tests: antigen binds to complimentary specific antibodies in result window, mobile antibodies also bind to antigen, buildup of mobile antibodies builds up dye create invisible line, create antibody antigen antibody complexes
What are the ethical issues with monoclonal antibodies?
. Deliberately induces cancer in mice
How does the ELISA test get carried out?
. Antigen attached to the test well
. Blood sample added, complimentary antibodies bind to antigen, well is washed
. Second antibodies are attached added, binds to 1st antibodies if present and attach to antigen, well washed
. Yellow substrate added, if enzyme-linked antibody present will turn blue
. Control will also be used to show that only the enzyme is causing change of colour and that washing of unbound antibody is affective
