cells Flashcards
1
Q
cell surface membrane
A
- found in all cells
- phospholipid bilayer
- controls the entrance and exit of molecules
2
Q
nucleus
A
- double membrane (nuclear envelope)
- nuclear pores
- nucleoplasm
- chromosomes (protein-bound, linear DNA)
- nucleolus (site of rRNA production)
- site of DNA replication and transcription
- contains genetic code for each cell
3
Q
mitochondria
A
- double membrane
- inner membrane is called the crista
- mitochondrial matrix
- loop of mitochondrial DNA
- site of aerobic respiration and ATP production
4
Q
chloroplasts
A
- double membrane
- thylakoids that stack to make grana
- stroma containing photosynthetic enzymes
- found in plants
- site of photosynthesis
5
Q
golgi appartus and golgi vesicles
A
- folded membranes making cisternae
- secretary vesicles pinch off cisternae
- form glycoproteins
- form lysosomes
- transport, modify and transport lipids
6
Q
lysosomes
A
- bag of digestive enzymes
- hydrolyse phagocytic cells
- autolysis (break down dead cells)
- exocytosis (release enzymes outside cell to destroy)
- digest worn out organelles for reuse of materials
7
Q
ribosomes
A
- rRNA and protein
- 80s ribosomes in eukaryotes
- 70s ribosomes in prokaryotes, mitochondria and chloroplasts
- site of protein synthesis
8
Q
rough endoplasmic reticulum
A
- folded membranes called cisternae
- ribosomes on cisternae
- site of protein synthesis
9
Q
smooth endoplasmic reticulum
A
- folded membrane called cisternae
- synthesis and stores lipids and carbohydrates
10
Q
cell wall
A
- in plant and fungi
- in plants the wall is made of cellulose
- in fungi the wall is made of chitin
- provides structural strength to the cell to prevent bursting
11
Q
cell vacuole
A
- filled with cell sap
- single membrane called tonoplast
- makes cells turgid for support
- temporary store of sugars and amino acids
- pigments attract pollinators
12
Q
specialised cells
A
cells into tissues, tissues into organs and organs into systems
13
Q
structure of prokaryotic cells
A
- cell wall (murein)
- cell surface membrane
- cytoplasm
- capsule
- plasmids
- flagella
- ribosomes
14
Q
eukaryotic vs prokaryotic
A
- cytoplasm that lacks membrane-bound organelles
- smaller ribosomes (eukaryotes=80S and prokaryotes=70S)
- no nucleus; instead they have a single circular DNA molecule that is free in the cytoplasm and is not associated with proteins
- a cell wall that contains murein, a glycoprotein
- prokaryotes are much smaller
- may contain plasmids, a capsule and flagella
15
Q
structure of viruses
A
- genetic material (RNA)
- capsid (protein shell enclosing RNA)
- attachment proteins
- lipid envelope
16
Q
optical microscope
A
- a microscope that uses light to form an image
- poorer resolution due to light having longer wavelength of light
- lower magnification
- images are in colour
- can view living samples
- small organelles such endoplasmic reticulum, lysosomes and ribosomes are not visible
17
Q
transmission electron microscope
A
- TEMs use electromagnets (shorter wavelength) to focus a beam of electrons, which is then transmitted through the specimen.
- denser parts of the specimen absorb more electrons, which makes them look darker on the image you end up with.
- TEMs are good because they give high resolution images, so you see the internal structure of organelles like chloroplasts
- 2D image
- thin specimens
18
Q
scanning electron microscope
A
- SEMs scan a beam of electrons (shorter wavelength) across the specimen. this knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.
- sample must be in a vacuum
- must be stained
- the images you end up with show the surface of the specimen and they can be 3D
- SEMs are good because they can be used on thick specimens.
- they give lower resolution images than TEMs
19
Q
magnification
A
how many times larger the image is than the actual size of the object being viewed
20
Q
resolution
A
the minimum distance apart that two objects can be in order for them to appear as separate items.
the resolution in an optical microscope is determined by the wavelength of light, and the wavelength of the beam of electrons determine the resolution in an electron microscope.
21
Q
formula for magnification
A
magnification = size of image/size of real object
22
Q
cell fractination
A
- used to isolate organelles so they can be studied
- homegenisation used to break cells apart using a blender or vibration
- placed in cold, isotonic buffer solution
23
Q
order of cell fractination
A
nuclei, chloroplasts, mitochondria, lysosomes, ER, ribosomes
24
Q
cell ultracentrifugation
A
- centrifuge spins at high speeds and the centrifugal forces causes pellets of the densest organelle to form at the bottom
- supernatant is removed and spun at increasingly faster speeds
25
phases of mitosis
(interphase) prophase, metaphase, anaphase and telophase (cytokinesis)
26
interphase
G1 (gap phase 1) - cell grows and new organelles and proteins are made
S (synthesis) - cell replicates its DNA ready to divide
G2 (gap phase 2) - cell keeps growing & proteins needed for cell division are made
27
prophase
- DNA supercoils
- nuclear envelope disintergrates
- centrioles divide and move to poles
- spindle fibres form
28
anaphase
- centromeres spilt
- chromatids move to separate poles
29
metaphase
- centromere attaches to spindle fibres
- chromosomes line up at equator
30
telophase
- chromosomes lengthen
- spindle fibres disintergrate
- nucleus starts to reform
31
cytokinesis
causes cell to split into two disntinct daughter cells with idenitcal nuclei
32
binary fission
- replication of circular DNA and plasmids
- division of cytoplasm
-produces 2 daughter cells
33
virus replication
- virus attaches to host cell receptor proteins
- genetic material is released into host cell
- genetic material and proteins are replicated by host cell 'machinery'
- viral components assemble
- replicated viruses released from host cell
34
phospholipid bilayer properties
allows movement of non-polar, lipid soluble and small molecules to pass through the membrane
35
fluid mosaic model
fluid
- membrane can change shape as molecules can move
mosaic
- phospholipids, proteins, glycoproteins, glycolipids, cholesterol
36
simple diffusion
- net movement of particles
- passive process (no ATP)
- high concentration to low concentration
37
facilitated diffusion
- net movement of particles
- passive process (no ATP)
- high concentration to low concentration
- through use of intrinsic proteins
38
osmosis
- movement of water
- area of high water potential to an area of low water potential
- across partially permeable membrane
39
active transport
- active process (ATP)
- low concentration to high concentration
- uses carrier proteins
- ATP binds to carrier protein and is hydrolysed, changes shape
40
co-transport
- coupled movement of molecules through carrier (cotransporter) protein
- combination of AT and FD
41
co-transport of glucose and sodium ions
- sodium ions actively transported out of the epithelial cell into blood
-reduces sodium ion concentration in epithelial
- sodium ions can the diffuse from lumen down their concentration gradient into epithelial cell
- does this through a co-transporter protein
- glucose or amino acids are actively transported
- glucose moves by facilitated diffusion from the epithelial cell to the blood
42
identified by the immune system
- pathogens
- cells from other organisms of the same species
- abnormal body cells
- toxins
43
antigen
foreign protein that stimulates an immune response
44
antigen variablility
pathogenic DNA can frequently mutate so previous immunity is no longer effective as memory cells have memory of old antigen shape
45
phagocytosis
- phagocytes detect antigen and bind
- phagocyte changes shape and engulfs pathogen
- pathogen is contained in phagosome vesicle
- lysosome fuses with phagosome
- lysozyme released into phagosome which hydrolyses pathogen
46
controls cell-mediated response
t-lymphocytes
47
controls humoral response
b-lymphocytes
48
cell-mediated response
- once pathogen has been destroyed, the antigens are positioned on the cell surface (antigen-presenting cell)
- helper T cells have receptors which bind to antigens on APC
- this activates helper T cell to divide by mitosis to make clones that diffrentiate into different cells
- remain as helper T cells
- cytotoxic (killer) T cells
- memory T cellls
- stimulate macrophages
49
helper T cells
stimulate B cells to divide and secrete antibodies
50
killer T cells
destroy abnormal cells by releasing perforin protein which makes a pore in membrane so substances can't leave or enter cell
51
memory T cell
remain in the blood to provide long term protection
52
humoral response
- antigens in blood collide with complementary antibody on B cell
- B cell takes in antigen by endocytosis and presents it on its cell surface membrane
- B cell collides with helper T cell
- B cell divides by mitosis and diffrentiates
- makes memory B cells or plasma cells
53
plasma cells
secrete antibodies
54
memory B cells
remain in blood and divide by mitosis to make plasma cells
55
antibody
protein specific to an antigen which is secreted by plasma cells
56
antibody structure
- immunoglobins
- quaternary structure with two heavy polypeptide chains and two light polypeptide chains
- bonded by disulphide bonds
- contstant and variable region
- variable region has antigen-binding site
57
antigen-antibody complexes
antibody attaches to antigen at variable region
58
agglutination
antibodies are flexible and can clump multiple antigens together, making it easier for phagocytes to locate them
59
vaccines
small amounts of dead or weakened pathogens introduced to the body to stimulate the humoral response
60
herd immunity
arises when a sufficiently large proportion of the population has been vaccinated which reduces the risk of a pathogen spreading
61
active immunity
involves the production of antibodies and the development of memory cells, antibodies appear 1-2 weeks after exposure
62
natural active immunity
producing antibodies in reponse to pathogenic infections
63
artifical active immunity
producing antibodies in reponse to exposure of attenuated pathogen (e.g. vaccine)
64
passive immunity
acquisition of antibodies from another source so memory cells are not created, response is immediate
65
natural passive immunity
receiving antibodies from another organism (e.g. antibodies from breast feeding)
66
artifical passive immunity
receiving manufactured antibodies via external delivery (e.g. blood transfusion of monoclonal antibodies)
67
structure of HIV
core- 2 RNA strands and reverse transcriptase enzyme
capside- outer protein coat
lipid envelope- extra outerlayer taken from host cell's membrane
attachment proteins- help attach HIV to host cell
68
retrovirus
makes DNA from RNA using reverse transcriptase
69
replication of HIV
- attachment proteins attach to receptors on helper T cell
- RNA enters the cell
- reverse transcriptase converts RNA to DNA
- viral DNA is incorported into helper T cell nucleus
- DNA transcribed into viral mRNA
- translated into HIV proteins
70
AIDS
- HIV causes helper T cells to die
- B cells no longer activated and decreased phagocytosis
- no antibodies produced
- body cannot fight off infections
71
monoclonal antibody
antibodies artificially derived from a single B cell clone
72
monoclonal antibodies for targeting medication to specific cell types by attaching a therapeutic drug to an antibody
- monoclonal antibodies with antibody complementary to antigens on outside of cancer
- antibodies with drugs on attach to cancer cells
- drugs delivered directly to cancer and kill them
73
monoclonal antibodies for medical diagnosis
pregnancy test, influenza, hepatitis, chlamydia
74
ELISA test (HIV)
- HIV antigens bound to bottom of reaction vessel
- blood sample added
- HIV-specific antibodies bind to antigens (primary antibodies)
- unbound antibodies are washed out
- secondary antibody with enzyme attached binds to primary antibodies
- reaction vessel washed out again
- coloured substrate added which binds to secondary antibody
- reaction vessel changes colour if individual hs HIV
75
ethical issues of vaccines
- animal testing
- human testing
- side effects
- epidemics (difficult to decide who gets vaccine first)
76
ethical issues of monoclonal antibodies
- animal testing
- side effects
77
why is the soultion cold?
to reduce enzyme activity
78
why is the solution isotonic?
prevents osmosis which could cause organelles to shrivel or burst
79
why is the solution buffered?
prevent damage from pH change (dentauration)
80
mitotic index
number of cells undergoing mitosis/total number of cells
81
purpose of mitosis
one round of division
- creates 2 genetically identical daughter cells
- creates diploid cells
- asexual reproduction
- growth and repair
82
how can cancer treatments control the rate of cell division?
- prevent DNA replication
- disrupt spindle fibre formation
83
conversion of centimetres to millimetres to micrometres to nanometres
x10, x1000, x1000
84
why are viruses non-living?
they are acellular, have no metabolism and cannot self replicate
85
role of cholesterol
steroid molecule that binds to fatty acid tails to restict movement and reduce fluidity
86
role of glycoproteins/lipids
cell signalling and cell recognition
87
why does the membrane form a phospholipid bilayer?
hydrophillic phosphate (-ve) heads attract water and hydrophobic fatty acid (no charge) tails repel water
88
factors that affect membrane permeability
temperature, pH and use of a solvent
89
carrier protein
binding site of carrier protein changes shape to allow large molecules to diffuse down
90
channel protein
water filled gated pore that allow charged substances to diffuse down
91
factors that affect transport
concentration/water potential gradient
diffusion distance
surface area
amount of intrinsic proteins
temperature
