Unit 2 Flashcards
Cells
magnification =
image/real
define resolution
minimum distance in which two points can be distinguished
what is a limitation of a light microscope
low resolution
what is the difference between transmission and scanning electron microscope images (TEM) (SEM)
Scanning has a 3D image
what are limitations of TEM and SEM
- 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
name the first step of cell fractionalisation
homogenise the sample
what conditions must the homogenate be in
- cold to prevent enzyme action
- buffered to not denature any enzymes
- isotonic to mot effect water potential
name the second step of cell fractionalisation
filter the larger debris
describe centrifugation
spin at a low speed, remove pellet of largest organelle (nuclei) then spin at a slightly higher speed ect.
whats the supernant
the rest of the sample after the pellet has been removed
describe the structure of the nucleus
double membrane containing nuclear pores, inside is chromatin and the nucleolus
function of the nucleus
controls cell and holds genetic information
function of the cell-surface membrane
let things in and out, and cell recognition
describe the function of the rough endoplasmic reticulum
the many ribosomes fold and synthesise proteins
describe the function of the smooth endoplasmic reticulum
produces and processes lipids
describe the function of the golgi apparatus
processes and packages proteins and lipids, and produces proteins
describe the structure of mitocondria
double membrane, inner membrane has cistrae and theres a liquid matrix
function of mitocondria
respiration - synthesis of ATP
function of centrioles
produced spindle fibers for cell division
describe the structure of ribosomes
a large and small sunbit
describe the function of ribosomes
protein synthesis
describe the function of lysosomes
vesicles containing digestive enzymes, break down pathogens and stuff
what do prokaryotic cell have that eukaryotic cells don’t
cell wall, capsule, mesosomes (version of mitocondria), plasmid, pili, flagellum
what do eukaryotic cell have that prokaryotic cells don’t
mitocondria, nucleus, r/s endoplasmic reticulum, golgi apparatus
differences between prokaryotic and eukaryotic
prokaryotic are unicellular, they have no nucleus, smaller
what protein are bacterial cell walls made out of
murein
what are the stages of mitosis
prophase, metaphase, anaphase and telophase, and cytokinesis
describe prophase
chromosomes coil and condense, spindle fibres form
describe metaphase
chromosomes line up and the spindle fibres attack to the centromeres
describe anaphase
centromeres divide and the two sister chromatids move to opposite poles of the cell
describe telophase
nuclear membrane reforms, spindle fibres breakdown
describe cytokinesis
cytoplasm divides and two daughter cells are produced
why is mitosis important
growth, repair and reproduction
describe the three stages of interphase
G1 - growth and production of organelle. S - DNA replicates. G2 - growth and organisation
describe binary fission
circular DNA replicates, cell grows and cytoplasm divides
what is the fluid mosaic model
the membrane has both structure and fluidity
what function intrinsic proteins do have in the phospholipid bilayer
carrier proteins allow water soluble molecules in and out
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
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
what function do cholesterol have in the phospholipid bilayer
helps the cell surface membrane remain fluid
define diffusion
passive movement of small non-polar lipid soluble molecules from a high to low concentration, ex; oxygen, carbon dioxide
define facilitated diffusion
polar molecules moving passively through a channel protein from a high to low concentration
define osmosis
diffusion of water molecules from a high to low water potential through a partially permeable membrane
define active transport
transport of all molecules through carrier proteins from a high to low concentration
define exocytosis/endocytosis
transport of particles in vesicles that fuse with the cell surface membrane
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
name four factors of diffusion
surface area, diffusion pathway, temperature and diffusion gradient
Fick’s law - rate of diffusion=…
…surface area⨉concentration difference/diffusion distance
name differences between bacteria and viruses
viruses are smaller, rely on a host and have no cell wall, cell surface membrane, cytoplasm, ribosomes
name two physical barriers for pathogens
skin (tough keratin barrier) and stomach acid (denatures proteins of cell surface)
non-specific response - describe inflammation
histamine is released by damaged tissue causing vasodilatation which increases blood flow to the infected area
non-specific response - describe lysozyme action
digestive enzymes in tears denature proteins of cell surface
non-specific response - describe interferon
prevent viruses from spreading to other cells by stopping protein synthesis
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)
define antigen
proteins present on the surface of cells which can trigger an immune response
define antibody
proteins produced by immune response, specific to antigen
define agglutination
where antibodies attach to make phagocytosis more efficient
how are the antibodies complementary to the antigens
different variable sites (in contrast to the constant region)
describe the constant region of the antibody
2 light chains and 2 heavy chains connected by disulfide bonds
purpose of B plasma cells
produces antibodies
purpose of t helper
stimulates immune response
purpose of t killer
kill infected cells and foreign cells
define antigenic shift
mutation leasing to a different antigen
why are people give two injections of a vaccine
memory cells are produced, meaning longer lasting immunity
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)
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)
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
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
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)
