Topic 2 Flashcards

Question

Optical Microscopes

Answer 1

- use light to form an image - cannot use to view organelles smaller than 0.2 micrometres, as this is their Max. resolution: ribosomes, ER, lysosomes - view nucleus and other larger organelles (may be able to see mitochondria, but not in great detail) - Max. useful magnification: X1500

Answer 2

- use electrons to from image: beam of electrons is condensed to form image by electromagnets. This greatly increases resolution, as a beam of electrons has a shorter wavelength than light microscopes, so a high resolving power - Max. resolution 0.2nm (1000x greater than light) - Max. useful mag x1,500,000 - used to observe smaller organelles: ribosomes, ER, lysosomes - TEM, SEM

Answer 3

- beam of electrons transmitted through specimen - denser parts absorb more electrons so appear darker on image ADVANTAGES: high resolution images, so internal structures within cells or even within organelles can be seen DISADVANTAGES: - only used on thin specimens - cannot view live specimens: vacuum inside TEM, so all water must be removed from specimen - lengthy treatment to prepare specimens means artefacts may be introduced - no colour images

Answer 4

- scan a beam of electrons across a specimen - beam bounces off surface of specimen and electrons detected, forming image: means SEMs produce 3D images ADVANTAGES: - used on thick/3D specimens - allow external 3D structure to be observed DISADVANTAGES: - lower resolution than TEMs - cannot be used to view live specimens - no colour images

Answer 5

cell fractionation: homogenisation, filtration, ultracentrifugation - carried out to obtain a pure sample of a specific organelle HOMOGENISATION: breaking up of cells - sample of tissue prepared in cold, isotonic, buffered solution: Ice cold (to reduce enzyme activity that could damage organelles), isotonic (same water potential as cells to prevent water entering organelles by osmosis, which would cause them to shrivel and burst), buffered (have a buffer solution added to prevent organelle proteins including enzymes from denaturing) - cells homogenised to break plasma membrane of cell and release organelles into solution (homogenate) FILTRATION: homogenate filtered through gauze to separate large cell debris, leaving filtrate ULTRACENTRIFUGATION: -filtrate placed in tube and tube placed in centrifuge to separate organelles - filtrate spun at low speed which causes densest organelles to form pellet at bottom of tube. Rest of organelles stay suspended in solution above pellet (supernatant) - supernatant spun again at higher speed and process repeated - process repeated at increasingly higher speeds removing supernatant and leaving pellet.

Answer 6

1st: - nuclei 2nd: - mitochondria, chloroplasts, lysosomes 3rd: - plasma membrane, ER, ribosomes

Answer 7

- chop up lettuce leaves - homogenise - solution must be cold to reduce enzyme activity - buffered solution to prevent pH affecting enzymes - isotonic to prevent osmosis and possible lysis or shrinkage of organelles - filter and centrifuge filtrate - centrifuge supernatant at higher speed - chloroplasts in second pellet.

Answer 8

- eukaryotic cell division - one round of cell division - genetically identical diploid cells made - used for growth and repair e.g. the clonal expansion of B cells in humoral immune response - used for asexual reproduction in single celled organisms

Answer 9

G1, S, G2, M G1- cell grows and new organelles and proteins are made S- DNA is synthesised. Cell replicates DNA ready to divide by mitosis G2- growth and prep for mitosis. Proteins made for cell division made. The replicated DNA is checked for mutations and cell destroyed if one is detected to prevent harm M- mitosis (cell division). Cycle starts and ends here.

Answer 10

- consists of G1, S and G2 - longest stage in cell cycle - Organelles double, the cell grows and DNA replicates. ATP content is increased to provide energy for cell division.

Answer 11

- either mitosis, which creates 2 identical diploid cells or meiosis, creating 4 genetically different haploid cells - Mitosis creates cells with identical DNA for growth and repair - meiosis creates gametes.

Answer 12

- the final stage - division of cytoplasm to create new cells

Answer 13

- chromosomes condense and become visible - centrioles separate and move to opposite poles of cell - nuclear envelope breaks down and chromosomes lie free in cytoplasm - nucleolus disappears

Answer 14

- chromosomes align along equator of cell - spindle fibres attach to centromere and chromatid

Answer 15

- chromosomes break at centrioles and sister chromatids move to opposite ends of cell. - sister chromatids now chromosomes - ATP required for energy, provided by respiration in mitochondria

Answer 16

- chromosomes arrive at opposite poles and begin to recondense - nuclear envelope begins to reform around each new set of chromosomes - spindle fibres break down.

Answer 17

- starts in anaphase and ends in telophase - cytoplasm divides forming 2 genetically identical diploid cells - occurs once a new nucleus has completely reformed at each pole of parent cell at end of telophase - In ANIMAL cells a cleavage furrow forms and separates the daughter cells - In PLANT cells, a cell plate forms at site of metaphase plate. This will reach the the cell walls of the parent cell and new cells produced, separating new daughter cells.

Answer 18

- calculated by counting how many cells are visible in the field of view (FOV) and the number of cells that are visible in a stage of mitosis Number of cells in mitosis/total number of cells X 100

Answer 19

- uncontrolled cell division (mitosis) - cancerous cells divide repeatedly and uncontrollably, forming a tumour - mutations occur in genes controlling cell division - mutations common, mostly do not cause cancer - most mutations result in early cell death or cell being destroyed by immune system - harmful mutation in original cell can be passed on to all cell descendants

Answer 20

- agents that may cause cancer - UV light, tar in tobacco smoke and X-Rays

Answer 21

do not spread from original site and do not cause cancer

Answer 22

- spread through body and invade and destroy other tissues, causing cancer - interfere with normal functioning of organ/tissue where theyre growing e.g. intestines, lungs or blood vessels.

Answer 23

- Malignant tumour cells can break off the tumours and travel through blood/lymphatic system to form secondary growths in other parts of the body - dangerous as can be difficult to detect, locate and remove secondary cancers.

Answer 24

- almost half of people with cancer possess mutated p53 gene, the gene that helps to control cell growth - BUT many other reasons why the control of cell division deteriorates, so no single cancer treatment - most treatments work by controlling rate of mitosis - Methotrexate: inhibits the synthesis of DNA nucleotides in cells - Vincristine + taxol: prevent the formation of the mitotic spindle.

Answer 25

- all contain lipids, proteins and carbohydrates (attached to proteins or lipids) - fluid mosaic model shows how phospholipids form a continuous bilayer, which is fluid as phospholipids constantly moving - proteins scattered through bilayer like mosaic tiles, which include channel proteins and carrier proteins, allowing large molecules and ions to pass through membrane - glycolipids and glycoproteins present - receptor proteins allow cell to detect chemicals released from other cells which signal to the cell to respond in some way e.g. insulin binds to receptor proteins on liver cells which tells the cell to absorb glucose

Answer 26

- controls what enters and leaves cell - partially permeable - ions may move across cell membrane via diffusion, osmosis or active transport - membranes around organelles divide cell into compartments, acting as a barrier between organelle and cytoplasm. e.g. substances needed for respiration (e.g. enzymes) kept together inside a mitochondrion by its membrane

Answer 27

- form bilayer - hydrophobic tails point in towards membrane interior, as membrane does not allow water soluble substances e.g. ions through it - hydrophilic heads point out towards membrane surface bilayer ensures water soluble molecules e.g. sugars, amino acids, proteins cannot leak out of cell and cannot get in. - can be chemically modified to act as signalling molecules. This can occur by moving within the bilayer to activate other molecules. This may also occur by being hydrolysed which releases smaller water soluble molecules that bind to specific receptors in cytoplasm.

Answer 28

-present in some cell membranes - regulates fluidity of membrane - hydrophobic tails and hydrophillic heads - fit between phospholipid molecules with head out and tail in - bind to hydrophic tails, causing phospholipids to pack more closely together, which restricts movement of phospholipids, making membranes less fluid and more rigid. This stabalises membrane when temps are too high - prevent phospholipid molecules packing too closely together when temps are too low, preventing membrane from freezing and fracturing - helps maintain shape of animal cells, which don't have cell walls. Particularly important for cells not supported by other cells such as red blood cells which float free in blood. - contributes to impermeability of membrane to ions - increases mechanical strength and stability of membranes

Answer 29

- both contain carbohydrate chains extrinsically so they can act as receptor molecules. This allows them to bind with certain substances at cell surface - 3 main receptor types: signalling for hormones and neurotransmitters, receptors involved in endocytosis, receptors involved in cell adhesion and substitution - some act as markers or antigens for cell to cell recognition

Answer 30

- lipid with carbohydrate attached - carbohydrate chain projects out into fluid surrounding cell

Answer 31

- proteins with carbohydrate chains attached - chains project out into fluid surrounding cell

Answer 32

- Transport proteins create hydrophilic channels to allow ions and polar molecules to travel through membrane - each transport protein is specific to a particular ion/molecule - allow cell to control which substances enter/leave.

Answer 33

less fluid when there is: increased proportion of fatty acid chains as the chains pack together tightly and high number of intermolecular forces between chains - more fluid when there is: increased proportion of unsaturated fatty acid chains as chains are bent so are less tightly packed together and less intermolecular forces. At higher temps, molecules move more freely as have more energy, increasing membrane fluidity.

Answer 34

the net movement of particles from an area of higher concentration to an area of lower concentration, down a concentration gradient. - Simple diffusion: molecules diffuse directly through cell membrane - random movement of molecules/ions caused by natural kinetic energy of molecules/ions - continues until equilibrium is reached (molecules/ions evenly spread in given volume/space)

Answer 35

oxygen and carbon dioxide diffuse directly through cellmembranes because they are small, so can pass through spaces between phospholipids. They are also non polar and so souble in lipids, so can dissolve in hydrophobic bilayer.

Answer 36

No This means only lipid soluble non polar molecules can diffuse through membrane

Answer 37

- steepness of concentration gradient (steeper, faster rate) (diffusion slows over time as concentration gradient decreases) - temp (higher rate, due to more kinetic energy making molecules/ions move faster) - thickness of exchange surface (thinner, shorter diffusion pathway, faster rate) - surface area (largere.g. SA of cell membrane, faster rate)

Answer 38

Fick's Law rate of diffusion (proportional to) SA X concentration difference/ thickness of membrane

Answer 39

The movement of particles from an area of high concentration to an area of lower concentration with the help of a protein channel/carrier, down concentration gradient - Large molecules and charged molecules (polar molecules/ions) cannot diffuse through phospholipid bilayer - use channel proetins/carrier proteins to diffuse through membrane

Answer 40

- water filled pores that allow charged substances to diffuse through membrane - diffusion of charged substances does not occur freely as most channel proteins are gated, so they close and open to control the exchange of ions

Answer 41

- move large molecules across the membrane - switch between 2 shapes, unlike carrier proteins that have a fixed shape - Large molecule attaches to binding site of protein and the protein changes shape and molecule is released on opposite side of membrane - binding site open to one side of membrane first, then the other when protein changed shape

Answer 42

- concentration gradient (higher, faster rate up to a point, until equilibrium is reached) - number of channel and carrier proteins (once all proteins in a membrane are in use, facilitated diffusion cannot get faster, even if concentration gradient increases)

Answer 43

- the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane - down concentration gradient - pure water has a water potential of zero and adding solutes to it lowers the water potentail. Water potential is always negative, the more negative, there is a higher concentration of solutes in solution.

Answer 44

No The 2 solutions have the same water potential (isotonic) cells in an isotonic solution will not gain/lose water as there is no difference in water potential between cell and solution Osmosis does not occur

Answer 45

Yes Cell is placed in a solution with a higher water potential (hypotonic), so will swell, as water moves into it by osmosis

Answer 46

Yes cell is placed in a solution with a lower water potential (hypertonic), so may shrink as water moves into it by osmosis

Answer 47

plant water placed in pure water/dilute solution, water moves into plant by osmosis due to being placed in hypotonic solution -

Answer 48

- water potential gradient (higher, faster rate. Only up to certain point, as over time difference in water potential on either side decreases) - thickness of exchange surface (thinner, faster rate) - SA of exchange surface (larger SA, faster rate)

Answer 49

The movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration - requires carrier proteins (specific to a particular molecule/ion) - molecule attaches to protein, protein changes shape and this moves molecule across membrane - energy required to make carrier proteins change shape.

Answer 50

Passive - energy required to make carrier proteins change shape so it can transfer the molecules/ions across cell membrane - energy required provided by ATP produced in respiration. ATP is hydrolysed into ADP+ Pi to release energy

Answer 51

- active transport usually moves solutes against the conc. gradient, but facilitated diffusion does this down the conc. gradient. - active transport requires energy, facilitated diffusion does not

Answer 52

- reabsorption of useful molecules and ions into the blood after filtration into the kidney tubules - absorption of some products of digestion from the digestive tract - loading sugar from the photosynthesising cells of leaves into the phloem tissue for transport around the plant - loading inorganic ions from the soil into root hairs

Answer 53

the coupled movement of substances across a cell membrane via a carrier protein - 2 types of molecules are moved across membrane at same time- the movement of one is dependent on the other - involves combination of facilitated diffusion and active transport - uses co transporters (type of carrier protein) - concentration gradient of one molecule is used to move the other molecule against its own conc. gradient

Answer 54

- sodium ions actively transported out of epithelial cells in ileum, into the blood. Creates a concentration gradient (higher concentration of sodium ions in lumen of ileum than inside cell) - this causes sodium ions to move into the epithelial cell from the ileum by facilitated diffusion, carrying glucose molecules via sodium-glucose co transporter proteins. Co transporter carries glucose into cell with sodium, so concentration of glucose inside cell increases - glucose diffuses out of cell into blood, down its concentration gradient through a protein channel by facilitated diffusion.

Answer 55

- speed of individual carrier proteins (faster, faster rate) - number of carrier proteins present (more, faster rate) - rate of respiration in cell and availability of ATP (if respiration is inhibited, active transport cannot take place)

Answer 56

root hair cells: adapted for the absorption of water and mineral ions from the soil - shape increases SA of cell, so rate of water reuptake by osmosis higher - thin walls, decreasing diffusion distance - permanent vacuole with cell sap, which is more concentrated than soil water. Ensures a high water potential gradient is maintained for osmosis. Epithelial cells of small intestine: - microvilli, increases SA so rate of diffusion of products of digestion faster - each villus of small intestine has a constant blood supply which continuously transports products of digestion away from epithelial cells. This maintains a high concentration gradient across the epithelial cell exchange surface.

Answer 57

Neurones and muscle cells: involved in transmission of electrical impulses around body - have cell membranes with channel proteins for sodium, potassium and calcium ions - opening and closing of these channel proteins - opening and closing of channel proteins and number of them helps to speed up electrical transmission along neurone membrane (during nerve impulses) and in muscle cells (muscle contraction)

Answer 58

- molecules that generate an immune response by lymphocyte cells when detected by body - usually proteins located on the surface of cells - specialised glycoproteins/glycolipids

Answer 59

- antigens are present on the surface of molecules and identify the molecule. - they help the immune system identify: pathogens cells from other organisms of same species (this is harmful to those with organ transplants) abnormal body cells (e.g. cancer cells) Toxins (released by some pathogens)

Answer 60

- The DNA of a pathogen can mutate frequently, so if mutation occurs in gene that codes for the antigen, the antigen will change shape - any previous immunity to this pathogen (naturally/vaccination) is no longer effective as all memory cells in blood will have a memory of old antigen - influenza virus matches and changes antigens fast, so new vaccine has to be created each year

Answer 61

- phagocytes are white blood cells produced in bone marrow and stored there until distributed around body in blood. Two types: neutrophils, macrophages - phagocytes engulf and digest pathogens using digestive enzymes via endocytosis - They fuse with pathogen and enclose them in phagocytic vacuole (phagosome) with a lysosome (phagolysosome). After pathogen is engulfed and destroyed by lysozymes, antigens presented on surface of phagocyte (phagocyte becomes antigen-presenting cell)

Answer 62

- neutrophils: move towards pathogen and cell surface receptors attach to pathogen antigens. Phagosome formed by engulfing and trapping pathogens (endocytosis). Lysosome fuses with phagosome (forms phagolysosome) and releases lysozymes that hydrolyse pathogen which produces a bacterium that is absorbed by phagocyte. - neutrophils die after -puss is sign of dead neutrophils Macrophages: do not destroy pathogen completely. They cut pathogens up so they can display antigens on surface (becomes antigen presenting cell and can be recognised by lymphocytes). - long lived cells, do not die after

Answer 63

antigen specific and produces responses specific to one type of pathogen only. It relies on lymphocytes produced in the bone marrow: B cells and T cells

Answer 64

Cell mediated

Answer 65

- Macrophages engulf and digest pathogens by phagocytosis. They become antigen-presenting cells. - Immature T cells leave bone marrow to mature in Thymus. Mature T cells have T cell receptors specific to one antigen - Specific T helper cells with receptor that fits the antigens on the macrophage will bind. The T cell is activated and it then produces interleukins which stimulate more T cells to be produced. - clones T cells may become more T helper cells to produces more interleukins, killer T cells or memory T cells to destroy infected pathogens

Answer 66

- B cells have complementary antibodies on surface and will bind to complememntary antigens on pathogens mambrane - B cell engulfs and presents pathogen on surface - T helper cells bind to antigens on presenting B cell (clonal selection) - Interkeukins produced by T cells activate other B cells - B cells divide by mitosis to produce many different B cells (Plasma and Memory cells) (clonal expansion) - clones plasma cells produces specific complementary antibodies to bind to pathogens antigen, disabling them or causes agglutination/neutralisation

Answer 67

a protein produced by immune system that are complementary to a specific antigen

Answer 68

- Y shaped - antigen binding site that is specific to particular antigen - variable region that varies in different antibodies due to variable amino acid sequence (primary structure) - hinge region allows spatial flexibility to branches of variable region, so can bind to more than one antigen - constant region is related to class of antibody which enables antibody to bind to receptors and attach to cells e.g. phagocytes - heavy and light polypeptide chain

Answer 69

- plasma cells produced by activated B cells are identical to B cells and secrete lots of antibodies specific to one antigen - monoclonal antibodies bind to antigen on surface of pathogen to form many antigen-antibody complexes - antibody has 2 binding sites so can bind to 2 pathogens simultaneously- causes pathogens to clump together (agglutination)- either neutralises pathogen or acts as a marker to attract phagocytes to phagocytose many pathogens at same time and destroy the pathogen - neutralisation- antibodies act as antitoxins, binding with toxins produced by pathogens, which makes them harmless.

Answer 70

- 4 polypepride chains forming Y shape - complememtary to single antigen - form antigen-antibody complexes which serve as markers for phagocytes to destroy attached cells. - 2 binding sites means they can clump cells together making them easier for phagocytes to find (agglutination)

Answer 71

- results from the introduction of antibodies from another person/animal - natural passive immunity is the result of crossing of mother's antibodies through the placenta and presence in breast milk - passive artificial immunity is where antibodies are injected into the body

Answer 72

- results from the production of antibodies by the immune system in response to the presence of an antigen - natural active immunity arises from being exposed to antigen/ getting the disease - active artificial immunity is acquired through vaccinations which stimulate the immune system and lead to antibody production.'

Topic 2 Flashcards

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