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AS Level AQA Biology: Unit 2 (Cells)

Big Dave Biology AS - Level Inglês 149 flashcards

AS Level AQA Biology: Unit 2 (Cells)

Flashcards do conjunto (149)

  1. 13.2: CellsN/A
  2. 23.2.1: Cell structureN/A
  3. 33.2.1.1: Structure of eukaryotic cellsN/A
  4. 4What are the main organelles of eukaryotic cells?- Cell-surface membrane
    - Nucleus
    - Mitochondria
    - Chloroplasts (plants only)
    - Golgi apparatus
    - Golgi vesicles
    - Lysosomes
    - Ribosomes
    - Rough endoplasmic reticulum
    - Smooth endoplasmic reticulum
    - Cell wall (plants only)
    - Vacuole (plants only)
  5. 5What is the function of the cell surface membrane?- Regulate entry and exit of molecules and ions
    - Maintain cell structure
    - Protect from outside hazards
  6. 6What is the structure of the cell-surface membrane?- Phosholipid bilayer
    - Intermittent transport proteins in bilayer
    - Cholesterol sometimes in bilayer
    - Proteins attached to the outside
  7. 7What does the structure of the cell surface membrane look like?What does the structure of the cell surface membrane look like?
  8. 8What is the function of the nucleus?- Contains hereditary DNA
    - Controls cell activity
    - Controls chemical reactions taking place
  9. 9What is the structure of the nucleus?- Surrounded by double membrane continuous with ER and studded with ribosomes
    - Nucleoplasm is granular, jelly-like material that makes up bulk of organelle
    - Nucleous are small spherical regions manufacturing ribosomal RNA and assembling ribosomes
    - Nuclear pores allow passage of large molecules e.g. mRNA - there are around 3000 pores, 40-100µm
  10. 10What does the structure of the nucleus look like?What does the structure of the nucleus look like?
  11. 11What is the function of mitochondria?Primary site for respiration in cells
    - Produces ATP
  12. 12What is the structure of the mitochondria?- Rod shaped, 1-10µm in length
    - Surrounded by double membrane controlling entry/exit of material, inner membrane folds to form extensions called cristae
    - Cristae form large surface area for the attachment of enzymes other proteins used in respiration
    - Matrix makes up rest of mitochondrion, containing protein, lipids, ribosomes and DNA that allows mitochondria to produce some proteins
  13. 13What does the structure of the mitochondria look like?What does the structure of the mitochondria look like?
  14. 14What is the function of chloroplasts?Primary site for photosynthesis in cells
  15. 15What is the structure of chloroplasts?- Disc shaped
    - Surrounded by double plasma membrane
    - Stroma is fluid-filled matrix in which second stage of photosynthesis takes place, contains starch grains
    - Grana are stacks of up to 100 disc-like structures called thylakoids
    - Thylakoids contain the pigment chlorophyll
  16. 16What does the structure of chloroplasts look like?What does the structure of chloroplasts look like?
  17. 17What is the function of the golgi apparatus?- Modifies proteins and lipids produced by ER and 'labels' them, allowing them to be sent to their correct destinations through golgi vesicle transport
    - Adds carbohydrates to proteins to form glycoproteins
    - Produces secretary enzymes
    - Secretes carbohydrates such as cellulose
    - Transports, modifies and stores lipids
    - Forms lysosomes
  18. 18What is the structure of the golgi apparatus?Stack of membranes making up flattened sacs called cisternae
  19. 19What does the structure of the golgi apparatus look like?What does the structure of the golgi apparatus look like?
  20. 20What is the function of golgi vesicles?Sacs used to transport molecules e.g. proteins and lipids in cells and around the body
    - Pick up molecules when absorbed by golgi apparatus and are secreted into the cytoplasm
  21. 21What is the structure of golgi vesicles?Lipid bilayer forming small sac
  22. 22What does the structure of golgi vesicles look like?What does the structure of golgi vesicles look like?
  23. 23What is the function of lysosomes?- Contain up to 50 enzymes e.g. lysozomes which hydrolyse cell walls of bacteria
    - Isolate enzymes from rest of cell before releasing them outside (exocytosis) to break down material or into a phagocytic vessel e.g. phagosome
    - Digest worn-out organelles so component chemicals can be reused
    - completely break down dead cells (autolysis)
  24. 24What is the structure of lysosomes?Formed when golgi vesicles contain enzymes such as proteases and lipases
    - up to 1µm in diameter
    - Lipid bilayer containing many enzymes
  25. 25What does the structure of lysosomes look like?What does the structure of lysosomes look like?
  26. 26What is the function of ribosomes?Site of protein synthesis in cells
    - 25% of all cell drymass
  27. 27What is the structure of ribosomes?80s ribosomes found in eukaryotic cells, around 25nm in diameter
    70s ribosomes found in prokaryotic cells, mitochondria and chloroplasts, slightly smaller
    - found in cytoplasm or studded into RER
    - made up of large and small subunit, contain ribosomal DNA and protein
  28. 28What does the structure of ribosomes look like?What does the structure of ribosomes look like?
  29. 29What is the function of the rough endoplasmic reticulum?Provides large surface area for protein synthesis and pathway for transport of materials
  30. 30What is the structure of the rough endoplasmic reticulum?Elaborate, 3D system of sheet-like membranes spread through cytoplasm
    - membranes enclose network of tubules and sacs called cisternae
  31. 31What does the structure of the rough endoplasmic reticulum look like?What does the structure of the rough endoplasmic reticulum look like?
  32. 32What is the function of the smooth endoplasmic reticulum?Synthesises, stores and transports lipids and carbohydrates
  33. 33What is the structure of the smooth endoplasmic reticulum?Elaborate, 3D system of sheet-like membranes spread through cytoplasm
    - membranes enclose network of tubules and sacs called cisternae
  34. 34What does the structure of the smooth endoplasmic reticulum look like?What does the structure of the smooth endoplasmic reticulum look like?
  35. 35What is the function of the cell wall?Provides mechanical strength
    - Holds cell in shape
    - Prevents bursting/shrivelling
  36. 36What is the structure of the cell wall?Microfibrils of cellulose embedded in a matrix
    - Layer called middle lamella holds adjacent cell walls together
    - In algae made of either cellulose or glycoproteins
    - In fungi are made up of chitin, glycan, glycoproteins
  37. 37What does the structure of the cell wall look like?What does the structure of the cell wall look like?
  38. 38What is the function of the cell vacuole?- Contains sugars and amino acids that can be used as a temporary food source
    - Contains pigments used to colour petals to attract pollinating insects
    - Support herbaceous plants by making cells turgid when filled with water
  39. 39What is the structure of the cell vacuole?Fluid-filled sac bounded by single membrane (tonoplast)
    - Usually one large one per plant cell
    - Contains solution of salts, sugars, amino acids, wastes and sometimes pigments e.g. anthocyanins
  40. 40What does the structure of the cell vacuole look like?What does the structure of the cell vacuole look like?
  41. 413.2.1.2 Structure of prokaryotic cells and of virusesN/A
  42. 42How do prokaryotic cells compare to eukaryotic cells?- Smaller
    - Simpler
  43. 43How does the structure of prokaryotic cells differ from eukaryotic cells?- No membrane-bound organelles in cytoplasm
    - Smaller ribosomes
    - No nucleus
    - Murein (glycoprotein) cell wall
  44. 44How is DNA found in prokaryotic cells?- Circular DNA not associated with proteins found in cytoplasm
    - Short circular plasmid
  45. 45What encases prokaryotic cells?Capsule
  46. 46How do prokaryotic cells move?One or more flagella attached to the outside that rotate
  47. 47What does the structure of prokaryotic cells look like?What does the structure of prokaryotic cells look like?
  48. 48What are viruses?Acellular, non living agents
  49. 49What is the structure of a virus?- Attachment proteins
    - Lipid envelope
    - Matrix
    - Capsid
    - Genetic material
    - Reverse transcriptase
  50. 50What does the structure of a virus look like?What does the structure of a virus look like?
  51. 513.2.1.3 Methods of studying cellsN/A
  52. 52What is an optical microscope?Microscope using visible light shining through a sample to magnify the image
  53. 53What are some advantages of optical microscopes?- Sample can be living
    - Cheaper
    - Easy to use
  54. 54What are some limitations of optical microscopes?- Smallest resolution - 200nm
    - Smallest magnification
  55. 55What is a transmission electron microscope?A microscope that uses a beam of transmitted electrons that passes through a sample from beneath to reach a sensor on the other side
  56. 56What are some advantages of TEMs?- Highest resolution - 0.2nm
    - Highest magnification
  57. 57What are some limitations of TEMs?- Sample must be dead
    - Sample must be cut very thin
    - Produces flat photomicrograph
    - Sample must be small
    - Expensive
    - Requires special training
  58. 58What is a scanning electron microscope?A microscope that uses scattered beams of electrons from above to bounce off an object and give a 3D image
  59. 59What are some advantages of SEMs?- 3D image produced
    - Sample can be a surface
    - Large sample can be analysed at once
  60. 60What are some limitations of SEMs?- Expensive
    - Lower resolution than TEM - 10nm
    - Lower magnification than TEM
    - Requires special training
    - Specimen must be coated
  61. 61What is magnification?The number of times larger or smaller an image is than the real dimensions
  62. 62How is magnification calculated?Magnification = Image Size/Original Size
  63. 63What is resolution?The smallest distance apart two structures can be for them to visible as separate
  64. 64What is cell fractionation?The process of separating cell organelles by size whilst preserving their structure
  65. 65What is homogenisation?Breaking down the cell membranes of a sample by blending etc
  66. 66What conditions must the solution containing the homogenised sample be in?- Cold - to slow enzyme action
    - Isotonic - to prevent osmosis
    - Buffered - to maintain PH and prevent damage to organelles
  67. 67What is ultracentrifugation?The process of spinning a sample in a centrifuge to separate large organelles which sink (pellet) and smaller organelles which are suspended (supernatant), decanting the supernatant after each spin to separate organelles by size
  68. 68After how many spins are each organelle filtered out?- 1) Nuclei
    - 2) Mitochondria, chloroplasts, lysosomes
    - 3) Plasma membrane fragments, RER fragments
    - 4) Ribosomes
  69. 693.2.2 All cells arise from other cellsN/A
  70. 70What is not true of all cells in the body?All cells can divide (untrue)
  71. 71What is a chromatid?Each of the four parts of the chromosome in an x shape
  72. 72What is the centromere?The object holding the four chromatids together in the x shape
  73. 73What is the cell cycle?The cycle of replication of eukaryotic cells
  74. 74What are the stages of the cell cycle?- Interphase
    - Mitosis
    - Cytokinesis
  75. 75How long does the cell cycle take in humans?24 hours
  76. 76What is the percentage breakdown of time spent during each stage of the cell cycle?- Interphase - 90%
    - Mitosis - 7%
    - Cytokinesis - 3%
  77. 77What occurs during interphase?- Chromosomes replicate
  78. 78What happens during cytokinesis?The cell splits into two
  79. 79What are the stages of mitosis?- Prophase
    - Metaphase
    Anaphase
    - Telophase
  80. 80What happens during prophase?- Chromosomes come out of solution
    - Nuclear membrane breaks down
    - Spindle apparatus forms
    MASS OF CHROMOSOMES VISIBLE
  81. 81What happens during metaphase?- Spindle fibres pull chromosomes to line-up along equator of cell
    CHROMOSOMES VISIBLE IN LINE
  82. 82What happens during anaphase?- Spindle fibres pull chromatids apart by gripping centromere, pulling each half to opposite ends of the cell
    CHROMOSOMES AT OPPOSITE ENDS OF CELL VISIBLE
  83. 83What happens during telophase? (including cytokinesis)- Nuclei reform
    - Spindle apparatus breaks down
    - CELLS BEGINNING TO SPLIT VISIBLE
  84. 84What can be said of mitosis?It is a controlled process
  85. 85What factors control mitosis?- Environment
    - Growth factors - TGF
    - Weel & CDC2 genes
  86. 86What is binary fission?Splitting of prokaryotic cells into identical offspring
  87. 87What are the stages of binary fission?- Circular DNA and plasmid replicate
    - Cytoplasmic membrane elongates, separating copies of DNA molecules
    - Cell membrane invaginates
    - Cell wall forms completely
    - Cell split into two daughter cells
  88. 883.2.3 Transport across cell membranesN/A
  89. 89What can be said about the basic structure of all cell membranes?They are the same, from cell-surface membranes to membranes surrounding cell organelles
  90. 90What model describes the structure of cell membranes?Fluid-mosaic model
  91. 91What does the structure of the fluid mosaic model look like?What does the structure of the fluid mosaic model look like?
  92. 92What structures make up the fluid-mosaic model?- Phospholipid bilayer
    - Proteins
    - Glycoproteins
    - Glycolipids
    - Cholesterol may also be present within bilayer
  93. 93How much of the cell membrane is protein?Less than 50%
  94. 94What types of protein are found in the cell membrane?- Channel proteins (running through, used in facilitated diffusion)
    - Extrinsic protein (outside, attach and remove themselves)
    - Carrier proteins (used in active transport)
    - Lipid-bond proteins (inside membrane, very rare)
    - Glycoproteins (protein with sugar tail, used in signalling)
  95. 95What effect does cholesterol have on the cell membrane?- Adds strength to membrane
    - Hydrophobic so prevents loss of water and ions
    - Pulls together fatty acid tails of phospholipids, limiting movement
  96. 96In what ways can substances pass through the cell membrane?- Diffusion
    - Osmosis
    - Facilitated diffusion
    - Active transport
    - Co-transport
  97. 97How may cells be adapted for better transport?- Increased surface area
    - Increase in number of channel & carrier proteins
  98. 98What is diffusion across the cell membrane?- Uncontrolled movement of small molecules through lipid bilayer along concentration gradient
  99. 99What factors limit diffusion across the cell membrane?- Size of particles - only smaller particles can diffuse
    - Lipid solubility - only lipid soluble molecules can diffuse
    - Charge - only uncharged molecules can diffuse
    - Water solubility - molecules dissolved in water cannot diffuse as they are repelled by the hydrophobic tails
  100. 100What is facilitated diffusion across the cell membrane?Diffusion of larger, water soluble molecules through transport proteins along concentration gradient
  101. 101What is the role of channel proteins in facilitated diffusion?Larger molecules including water diffuse through specific channel proteins, as they would be too large to diffuse conventionally or would be repelled, that act as tubes through the lipid bilayer
  102. 102What is the role of carrier proteins in facilitated diffusion?Polar/charged molecules pass through specific carrier proteins, as they would be repelled by the lipid bilayer, with an ATP molecule binding to the carrier protein to recognise if the molecule is travelling along the concentration gradient and energy is only needed if it is not
  103. 103What is osmosis across the cell membrane?Net movement of water from an area of high water potential (closest to 0Ψ) to one of low water potential (furthest from 0Ψ)
  104. 104How does water potential affect osmosis across the cell membrane?- Concentration of ions (solute) in or out of a cell can affect the water potential - large ion concentration lowers water potential
    - Water enters or exits cells based on where the water potential is highest
  105. 105What can occur if the water potential gradient is too large in animal cells?- Too low water potential inside cells leads to excessive water entering and bursting the cell
    - Too high water potential inside cells leads to excessive water leaving and shrivelling the cell
  106. 106Why are plant cells resistant to extreme water potential gradients?- Permanent vacuole full of salty cell sap reduces the water potential of the cell
    - Cellulose cell wall provides mechanical strength that prevents bursting and shrivelling, leading to the cell becoming turgid when it fills with water as the vacuole fills and presses outwards
  107. 107What is active transport across the cell membrane?Movement of molecules against the concentration gradient through specific carrier proteins, requiring the use of ATP
  108. 108How is ATP used during active transport across the cell membrane?The phosphate bonds of ATP are hydrolysed, producing phosphate groups and releasing the energy needed to power the carrier proteins to move molecules against the concentration gradient
  109. 109What is co-transport across the cell membrane?Simultaneous movement of ions across a membrane through transport proteins
  110. 110What are the steps involved in the absorption of sodium ions and glucose into the ileum?- Sodium ions in cells transported into blood and potassium is transported from the blood into cells via active transport through the antiport (sodium-potassium pump)(requiring ATP), lowering the concentration gradient of sodium inside
    - Glucose and sodium in the lumen enter cells through co-transport through the symport (requiring ATP), sodium moves along concentration gradient, glucose against it
    - Glucose enters the blood through facilitated diffusion through carrier proteins along the concentration gradient
  111. 111In what ways is the ileum adapted for rapid absorbtion?- Villi
    - Microvilli
    - Thin walls
    - Capillary network
  112. 112What is cholera?Disease caused by vibrio cholerae bacteria which sits in the ileum
    - carried in contaminated water
    - causes rapid loss of water through vomiting and diarrhoea
    - treated by oral rehydration therapy - patient given salt and sugar in water that nourishes patient so they survive whilst their immune system fights the disease (sugar and salt increase concentration rate to aid absorption, water replaces that lost)
  113. 1133.2.4: Cell recognition and the immune systemN/A
  114. 114What are antigens?Small chemical markers on the surface of cells that allow them to be recognised as foreign and an immune response triggered. Some cells may present more than one type of anigen.
  115. 115What kind of cells can be recognised in this way?- Bacteria
    - Fungi
    - Foreign cells
    - Foreign cells of the same species
    - Abnormal body cells e.g. cancer cells
  116. 116What are the types of leucocytes (white blood cells)?- Phagocytes - non-specific
    - Lymphocytes - specific
  117. 117What is a phagocyte?A leucocyte (white blood cell) capable of engulfing, absorbing and breaking down small cells and particles e.g. bacteria
  118. 118What is phagocytosis?The destruction of cells presenting foreign antigens by leucocytes (white blood cells) called phagocytes.
  119. 119What are the stages of phagocytosis?- Phagocyte chemically attracted to products of foreign cell
    - Phagocyte engulfs foreign cell
    - Foreign cell encased in vacuole called phagosome
    - Lysosomes release enzymes called lyzozymes which enter phagosome and break it down
    - Foreign antigens presented on phagocyte's cell-surface membrane
  120. 120What does the process of phagocytosis look like?What does the process of phagocytosis look like?
  121. 121What is cell-mediated immunity?Immune response that does not involve antibodies
  122. 122What is a T cell?- involved in cell-mediated immunity
    - mature in thymus gland
  123. 123What are the stages of cell-mediated immunity?- Phagocytosis of a cell presenting a foreign pathogen
    - Phagocyte presents foreign antigen on its cell surface membrane
    - T-helper cells in body come into contact with phagocyte and bind to foreign antigen
    - Th cells stimulated to undergo reproduction and differentiation of offspring cells, producing further Th cells and Tc cells creating a large-scale response
    - Tc cells are stimulated to produce perforin, which creates holes in the surface membrane of cells presenting the foreign antigen
    - Some Th cells survive as memory cells, which can live in the body for decades, ready to create a new immune response by reproducing and differentiating should the foreign pathogen be presented again
  124. 124What does the process of cell-mediated immunity look like?What does the process of cell-mediated immunity look like?
  125. 125What is hummoral immunity?Immune response involving antibodies
  126. 126What is a B cell?- involved in hummoral (fluid) immunity
    - Mature in bone marrow
  127. 127What are the stages of hummoral immunity?- Phagocytosis of a cell presenting a foreign pathogen
    - Phagocyte presents foreign antigen on its cell surface membrane
    - B cells in fluid come into contact with phagocyte and bind to foreign antigen
    - Th cells in the body bind to and stimulate B cells to undergo reproduction and differentiation of offspring cells, producing further B cells and plasma cells
    - Plasma cells secrete antibodies, which bind to the surface of infected cells, marking them for destruction
    - Some B cells survive as memory cells, which can live in the body for decades, ready to create a new immune response by reproducing and differentiating should the foreign pathogen be presented again
  128. 128What does the process of hummoral immunity look like?What does the process of hummoral immunity look like?
  129. 129What are antibodies?Y-shaped proteins which aid destruction of foreign antigens and pathogens, with each being specific to an antigen
  130. 130What is the structure of an antibody?- Y-shaped protein
    - Made up of 4 polypeptide chains
    - Binding site made up of chain of amino acids
    - Made up of 2 heavy chains and 2 light chains
    - Binding site specific to an antigen
  131. 131What does the structure of an antibody look like?What does the structure of an antibody look like?
  132. 132How do antibodies aid the destruction of pathogens?Agglutination - antibodies stick together surrounding antigen, making it easier for phagocyte to find and destroy them
    - Attach to infected cells, marking them for phagocytosis
  133. 133What is the difference between passive and active immunity?Active immunity - body actively produces antibodies/antitoxins to fight an infection
    Passive immunity - antibodies/antitoxins administered by injection or other means, temporary immunity, antibodies not replaced
  134. 134What is the purpose of vaccines?Provide individuals with artificial passive immunity (exposing them to weakened/small sample of disease to stimulate immunity)
    - prevent spread of disease by reducing number of people who can be infected
  135. 135What is herd immunity?Concept that immunising a large proportion of a population further reduces spread by reducing the chance that unvaccinated individuals will come into contact with the diease
  136. 136What is Human Immunodeficiency Virus (HIV)?- 34 million cases 2010
    - 1 million in US, 20% unaware
    - 1985 - new law regarding screening of blood donors - homosexual men banned from donating
    - leads to AIDS, slows immune system
    - transmitted through sexual contact, open wounds, shared needles
    - not transmitted through saliva, sweat, tears, insects
  137. 137What is the structure of HIV?What is the structure of HIV?
  138. 138How does HIV attack the immune system?- Enters bloodstream and circulates
    - Binds to CD4 on surface of T helper cells and enters
    - Converts RNA to virus genetic material
    - Enters nucleus and reprogrammes cell
    - RNA travels to ribosome and begins protein synthesis
    - Makes viruses
  139. 139How does HIV lead to Acute Immune Deficiency Syndrome?- Reduces number of T helper cells
    - Attacks and destroys memory cells
    - In healthy person - 800-1200 Th cells in 1mm^3 of blood, in AIDS sufferer only 200 Th cells
    - Body can't produce adequate immune response
    - Death occurs from secondary infections
  140. 140Why are antibiotics ineffective against viruses?Antibiotics break down cell membranes, which viruses do not have
  141. 141How can AIDS be treated?- Drugs to reduce levels of HIV
    - Drugs to support weakened immune system
  142. 142What are monoclonal antibodies?Antibodies produced by a single line of cells
  143. 143How can monoclonal antibodies be used in cancer treatment?- Cancer treatment - specific antibody with chemotherapy drug attached to constant region injected into patient which attaches to cancerous cell receptor and delivers drug directly
  144. 144How can monoclonal antibodies be used in prostate cancer diagnosis?- Prostate cancer diagnosis - PSA protein produced and given to patient, urine/blood sample taken, if sample contains lots of activated antibodies the patient has cancer
  145. 145How can monoclonal antibodies be used in pregnancy tests?HCG is an antigen presented by the placenta
    - antibody that binds to HCG has marker attached to constant region
    - when urine comes into contact with test
    - antibody is activated if HCG is present and marker colour is shown creating the second line on the test
  146. 146What are some ethical concerns regarding the use of vaccines & monoclonal antibodies?- Monoclonal antibodies are created by infecting mice with disease
    - Issues with vaccine testing/should they be compulsory?
    - Multiple sclerosis patients' immune systems triggered by MA causing mass release of lymphocytes that attacked cells
    - TG1u12 chemical was drug tested on healthy patients, causing organ failure within minutes
  147. 147What is the Enzyme-linked Immunosorbant Assay and what is it used for?Biological test for antigens or infections within a sample, used to test for:
    - AIDS
    - Pregnancy
    - TB
    - Hepitits
  148. 148What are the stages of the ELISA test- Sample washed to remove excess antigens
    - Antibody specific to disease antigen being tested for applied to sample, bonding to the disease antigen if it is present
    - Second antibody specific to the first antibody with attached enzyme applied to same, bonding to the first antigen
    - Substrate added to sample, bonds to second antigen, producing
  149. 149What are the steps involved in the indirect ELISA?- Sample washed to remove excess antigens
    - 1st antibody added to sample and binds to antigen if present
    - 2nd antibody with attached enzyme binds to 1st antibody
    - Substrate added to sample and binds to enzyme causing colour change
    - Intensity of colour change indicates quantity of antigen
    - If antigen is not present, the two antibodies will not bind and there will be no colour change

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AS - Level Biology (Unit 2) FlashCards sobre AS Level AQA Biology: Unit 2 (Cells), criado por Big Dave em 19-01-2016.
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