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A-Level Biology > Unit 2 > Flashcards

Unit 2 Flashcards

Cells

1
Q

magnification =

A

image/real

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2
Q

define resolution

A

minimum distance in which two points can be distinguished

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3
Q

what is a limitation of a light microscope

A

low resolution

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4
Q

what is the difference between transmission and scanning electron microscope images (TEM) (SEM)

A

Scanning has a 3D image

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5
Q

what are limitations of TEM and SEM

A
  • vacuum so specimens cannot be living
  • specimen must be very thin (particularly with TEM) so electrons can move through so artefacts are more likely
  • SEM has a lower resolution than TEM
  • expensive
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6
Q

name the first step of cell fractionalisation

A

homogenise the sample

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7
Q

what conditions must the homogenate be in

A
  • cold to prevent enzyme action
  • buffered to not denature any enzymes
  • isotonic to mot effect water potential
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8
Q

name the second step of cell fractionalisation

A

filter the larger debris

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9
Q

describe centrifugation

A

spin at a low speed, remove pellet of largest organelle (nuclei) then spin at a slightly higher speed ect.

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10
Q

whats the supernant

A

the rest of the sample after the pellet has been removed

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11
Q

describe the structure of the nucleus

A

double membrane containing nuclear pores, inside is chromatin and the nucleolus

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12
Q

function of the nucleus

A

controls cell and holds genetic information

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13
Q

function of the cell-surface membrane

A

let things in and out, and cell recognition

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14
Q

describe the function of the rough endoplasmic reticulum

A

the many ribosomes fold and synthesise proteins

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15
Q

describe the function of the smooth endoplasmic reticulum

A

produces and processes lipids

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16
Q

describe the function of the golgi apparatus

A

processes and packages proteins and lipids, and produces proteins

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17
Q

describe the structure of mitocondria

A

double membrane, inner membrane has cistrae and theres a liquid matrix

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18
Q

function of mitocondria

A

respiration - synthesis of ATP

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19
Q

function of centrioles

A

produced spindle fibers for cell division

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20
Q

describe the structure of ribosomes

A

a large and small sunbit

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21
Q

describe the function of ribosomes

A

protein synthesis

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22
Q

describe the function of lysosomes

A

vesicles containing digestive enzymes, break down pathogens and stuff

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23
Q

what do prokaryotic cell have that eukaryotic cells don’t

A

cell wall, capsule, mesosomes (version of mitocondria), plasmid, pili, flagellum

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24
Q

what do eukaryotic cell have that prokaryotic cells don’t

A

mitocondria, nucleus, r/s endoplasmic reticulum, golgi apparatus

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25
differences between prokaryotic and eukaryotic
prokaryotic are unicellular, they have no nucleus, smaller
26
what protein are bacterial cell walls made out of
murein
27
what are the stages of mitosis
prophase, metaphase, anaphase and telophase, and cytokinesis
28
describe prophase
chromosomes coil and condense, spindle fibres form
29
describe metaphase
chromosomes line up and the spindle fibres attack to the centromeres
30
describe anaphase
centromeres divide and the two sister chromatids move to opposite poles of the cell
31
describe telophase
nuclear membrane reforms, spindle fibres breakdown
32
describe cytokinesis
cytoplasm divides and two daughter cells are produced
33
why is mitosis important
growth, repair and reproduction
34
describe the three stages of interphase
G1 - growth and production of organelle. S - DNA replicates. G2 - growth and organisation
35
describe binary fission
circular DNA replicates, cell grows and cytoplasm divides
36
what is the fluid mosaic model
the membrane has both structure and fluidity
37
what function intrinsic proteins do have in the phospholipid bilayer
carrier proteins allow water soluble molecules in and out
38
what function do glycoproteins have in the phospholipid bilayer
carbohydrate bound to extrinsic proteins that act as receptors and attach to other cells to form tissues
39
what function do glycolipids have in the phospholipid bilayer
carbohydrate bound to a lipid that acts as receptors and attach to other cells to form tissues
40
what function do cholesterol have in the phospholipid bilayer
helps the cell surface membrane remain fluid
41
define diffusion
passive movement of small non-polar lipid soluble molecules from a high to low concentration, ex; oxygen, carbon dioxide
42
define facilitated diffusion
polar molecules moving passively through a channel protein from a high to low concentration
43
define osmosis
diffusion of water molecules from a high to low water potential through a partially permeable membrane
44
define active transport
transport of all molecules through carrier proteins from a high to low concentration
45
define exocytosis/endocytosis
transport of particles in vesicles that fuse with the cell surface membrane
46
describe the co-transport of glucose in the ileum
3Na out and 2K in the epithelial cell by active transport, creating a low concentration. Na+ ions moves in through facilitated diffusion taking glucose (and amino acids) with the ions
47
name four factors of diffusion
surface area, diffusion pathway, temperature and diffusion gradient
48
Fick's law - rate of diffusion=...
...surface area⨉concentration difference/diffusion distance
49
name differences between bacteria and viruses
viruses are smaller, rely on a host and have no cell wall, cell surface membrane, cytoplasm, ribosomes
50
name two physical barriers for pathogens
skin (tough keratin barrier) and stomach acid (denatures proteins of cell surface)
51
non-specific response - describe inflammation
histamine is released by damaged tissue causing vasodilatation which increases blood flow to the infected area
52
non-specific response - describe lysozyme action
digestive enzymes in tears denature proteins of cell surface
53
non-specific response - describe interferon
prevent viruses from spreading to other cells by stopping protein synthesis
54
non-specific response - describe phagocytosis
- chemotaxis - chemicals released by pathogen attract phagocyte - phagocyte attaches to pathogen in oppsinsation - phagocyte engulfs pathogen in membrane - lysosomes attach, releasing lysozomes to hydrolysis - useful products absorbed (antigens for antigen-presenting cells)
55
define antigen

proteins present on the surface of cells which can trigger an immune response
56
define antibody
proteins produced by immune response, specific to antigen
57
define agglutination

where antibodies attach to make phagocytosis more efficient
58
how are the antibodies complementary to the antigens

different variable sites (in contrast to the constant region)
59
describe the constant region of the antibody
2 light chains and 2 heavy chains connected by disulfide bonds
60
purpose of B plasma cells

produces antibodies
61
purpose of t helper

stimulates immune response
62
purpose of t killer

kill infected cells and foreign cells
63
define antigenic shift
mutation leasing to a different antigen
64
why are people give two injections of a vaccine

memory cells are produced, meaning longer lasting immunity
65
describe the cell mediated response
- phagocytosis - antigen-presenting cell finds antibody - clonal selection (t cell with antibody binds to antigen presenting cell which divides by mitosis to produce antibodies and memory cells)
66
describe the structure of HIV
- outer lipid envelope, then matrix, then capsid, with attachment proteins - inside the capsid is RNA and reverse transcriptase (enzyme that form DNA from RNA)
67
describe how HIV replicates
- attachment proteins bind to t helper cells and capsid fused with the cell surface membrane
 - RNA and reverse transcriptase enter the cell - reverse transcriptase converts HIV RNA to DNA which moves into nuclear pore - transcribed to mRNA, then diffusing out - translocated to ribosomes for protein synthesis - exocytosis - proteins break off
68
describe the ELISA test
- antibody is bound to the well, sample possibly containing antigen is added - wash. add enzyme - wash. add substrate which will change the colour if binds to enzyme - measure colour change
69
what things are taken into account when deciding to give vaccines

- cost - severity of side effects - number of people who need it (herd immunity) - ease of transport and administration (does it need to be refrigerated)

A-Level Biology (9 decks)

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