unit 2 Flashcards
(113 cards)
1
Q
what is the cell membrane structure
A
phospholipid bilayer with embedded intrinsic and extrinsic proteins
2
Q
what is the cell membrane function
A
selectively permeable barrier, controls passage of substances in and out of the cell, barrier between internal and external cell environments
3
Q
nucleus structure
A
nuclear pores, nucleolus, DNA, nuclear envelope
4
Q
nucleus function
A
site of transcription & pre-mRNA splicing- mRNA production, site of DNA replication, nucleolus makes ribosomes, nuclear pore allows movement of substances to/from cytoplasm
5
Q
mitochondria structure
A
double membrane with inner membrane folded into cristae, 70s ribosomes in matrix, small and circular DNA, enzymes in matrix
6
Q
mitochondria function
A
site of aerobic respiration, produces ATP
7
Q
chloroplast structure
A
thylakoid membranes stacked into grana which are linked by lamellae, stroma contains enzymes, contains starch granules, 70s ribosomes, small circular DNA
8
Q
chloroplast function
A
chlorophyll absorbs light for photosynthesis to produce organic molecules (glucose)
9
Q
which organisms contain chloroplasts
A
plants, algae
10
Q
golgi apparatus structure
A
fluid-filled & membrane-bound sacs, vesicles at edge
11
Q
golgi apparatus function
A
modifies proteins received from RER, packages them into vesicles to transport to cell membrane for exocytosis, makes lysosomes
12
Q
lysosome structure
A
type of golgi vesicle containing digestive enzymes
13
Q
lysosome function
A
contains digestive enzymes, e.g. lysozymes to hydrolyse pathogens/cell waste products
14
Q
RER function
A
site of protein synthesis, folds polypeptides to secondary and tertiary structures, packaging into vesicles to transport to golgi
15
Q
SER function
A
synthesises and processes lipids
16
Q
cell wall function
A
provides structural strength & rigidity & support to cell, helps resist osmotic pressures
17
Q
ribosome structure
A
small and large subunit, made of protein and rRNA, free floating in cytoplasm & bound to RER, 70s in prokaryotes, mitochondria and chloroplasts, 80s in eukaryotes
18
Q
ribosome function
A
site of translation in protein synthesis
19
Q
RER structure
A
system of membranes with bound ribosomes, continuous with nucleus
20
Q
SER structure
A
system of membranes with no bound ribosomes
21
Q
cell wall structure
A
plants- made of microfibrils of cellulose, fungi- made of chitin, bacteria- made of murein
22
Q
cell vacuole structure
A
fluid-filled, surrounded by a single membrane called a tonoplast
23
Q
contrast prokaryotic & eukaryotic cells
A
prokaryotic cells are smaller, prokaryotes have no membrane bound organelles and eukaryotes have membrane bound organelles, prokaryotes have smaller 70s ribosomes and eukaryotes have larger 80s ribosomes, prokaryotes have no nucleus- free floating DNA and eukaryotes have a nucleus, DNA not associated with histones in prokaryotes and DNA associated with histones in eukaryotes, prokaryotic cell wall made of murein and eukaryotic cell wall made of cellulose/chitin
24
Q
occasional features of prokaryotes
A
plasmids- loops of DNA, capsule surrounding cell wall- helps agglutination & adds protection, flagella for movement
25
cell vacuole function
makes cells turgid- structural support, temporary store of sugars & amino acids, coloured pigments attract pollinators
26
How do protein carriers work
bind with a molecule e.g. glucose which causes a change in the shape of the protein, this change in shape enables the molecule to be released to the other side of the membrane
27
How do protein channels work
tubes filled with water enabling water-soluble ions to pass through the membrane, selective, channel proteins only open in the presence of certain ions when they bind to the protein
28
features of viruses
non-living and acellular, contain genetic material & capsid & attachment proteins, some (HIV) contain a lipid envelope + enzymes (reverse transcriptase)
29
what is magnification
how many times larger the image is compared to the object
30
equation for magnification
magnification=image size/actual size
31
what is resolution and how is it determined
the minimum distance between two objects in which they can still be viewed as separate, determined by wavelength of light (for optical microscope) or electrons (for electron microscopes)
32
optical microscopes
beam of light used to create image, glass lens used for focusing, 2D coloured image produced
33
evaluate optical microscopes
poorer resolution due to long wavelength of light so small organelles are not visible, lower magnification, can view living samples, simple staining method, vacuum not required
34
transmission electron microscopes
beam of electrons passes through the sample used to create image, focused using electromagnets, 2D black&white image produced, can see internal structure of cell, structures absorb electrons and appear dark
35
evaluate TEMs
high resolving power, high magnification, extremely thin specimens required, complex staining method, specimen must be dead, vacuum required
36
scanning electron microscopes
beam of electrons pass across sample used to create image, focused using electromagnets, 3D black&white image produced, electrons scattered across specimen producing image
37
evaluate SEMs
high resolving power, high magnification, can use thick specimens, complex staining method, specimen must be dead, vacuum required
38
why calibrate eyepiece graticule
calibration of the eyepiece is required each time the objective lens is changed, calibrate to work out the distance between each division at that magnification
39
purpose of cell fractionation
break open cells & remove cell debris, so organelles can be studied
40
what is homogenisation
process by which cells are broken open so organelles are free to be separated, done using homogeniser (blender)
41
homogenisation conditions
cold- reduces enzyme activity preventing organelle digestion (from lysosomes), isotonic- prevents movement of water by osmosis so that no bursting/shrivelling of organelles, buffer- resists pH changes preventing organelle/enzyme damage
42
ultra-centrifugation
homogenate filtered solution to remove cell debris, solution placed in a centrifuge which spins at a low speed initially, then increasingly faster speeds to separate organelles based on their density, supernatant first out (most dense) is nucleus then chloroplasts then mitochondria then lysosomes then SER/RER then ribosomes (least dense)
43
binary fission
involves circular DNA & plasmids replicating, cytokinesis creates two daughter nuclei, each daughter cell has one copy of circular DNA and a variable number of plasmids
44
45
What are the main stages of the cell cycle?
1) Interphase (G1, S, G2)
2) Nuclear division - mitosis or meiosis
3) Cytokinesis
46
What occurs during Interphase?
It is the longest stage in the cell cycle where DNA replicates (S-phase) and organelles duplicate while the cell grows (G1 & G2-phase).
47
What happens to DNA during Interphase?
DNA replicates and appears as two sister chromatids held by a centromere.
48
What is Mitosis?
One round of cell division resulting in two diploid, genetically identical daughter cells.
49
What are the purposes of Mitosis?
Growth and repair (e.g. clonal expansion).
50
What are the phases of Mitosis?
Mitosis is comprised of prophase, metaphase, anaphase, and telophase.
51
What occurs during Prophase?
Chromosomes condense and become visible, the nuclear envelope disintegrates, and in animals, centrioles separate and spindle fibre structure forms.
52
What happens during Metaphase?
Chromosomes align along the equator of the cell, and spindle fibres released from poles attach to the centromere and chromatid.
53
54
What happens to spindle fibres during anaphase?
Spindle fibre contracts (using ATP) to pull chromatids, centromere first, towards opposite poles of the cell.
55
What occurs to the centromere during anaphase?
The centromere divides in two.
56
What are sister chromatids?
Sister chromatids are the two identical halves of a duplicated chromosome.
57
telophase
chromosomes at each pole become longer and thinner again, spindle fibres disintegrate + nucleus reforms
58
mitotic index
used to determine proportion of cells undergoing mitosis
59
equation for mitotic index
mitotic index=number of cells in mitosis/total number of cells (x100 for percentage but can also be in decimal)
60
fluid mosaic model
describes the lateral movement of membranes, with scattered embedded intrinsic and extrinsic proteins, membrane contains glycoproteins & glycolipids & phospholipids and cholesterol
61
phospholipids in membranes
they align as a bilayer, hydrophilic heads are attracted to water, hydrophobic tails repelled by water
62
cholesterol
present in eukaryotic organisms to restrict lateral movement of the membranes, adds rigidity to membrane- resistant to high temperatures & prevents water + dissolved ions from leaking out
63
selectively permeable membrane
lipid soluble (hormones e.g. oestrogen), small molecules, non polar molecules (e.g. oxygen)
64
simple diffusion
net movement of molecules from an area of high concentration to an area of lower concentration, down a concentration gradient, until equilibrium is reached, passive, does not require ATP
65
facilitated diffusion
passive process using protein channels/carriers, down a concentration gradient, used for ions and polar molecules (e.g. sodium ions), used for large molecules (e.g. gluscose), no ATP required
66
osmosis
net movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane, passive, no ATP required
67
water potential
pressure created by water molecules, measured in kPa, pure water has water potential of 0kPa, the more negative/lower the water potential means the more solute must be dissolved (more concentrated)
68
hypertonic solution
when the water potential of a solution is more negative/lower than the cell, water moves out of the cell by osmosis, both animal and plant cells will shrink and shrivel
69
hypotonic solution
when the water potential of a solution is more positive/higher than the cell( more dilute), water moves into the cell by osmosis, animal cells will lyse/burst, plant cells will become turgid
70
isotonic
when the water potential of the surrounding solution is the same as the water potential inside the cell, no net movement in water, cells would remain the same mass
71
active transport
the movement of ions and molecules from an area of lower concentration to an area of higher concentration, against a concentration gradient, uses ATP, uses carrier proteins, carrier proteins act as selective pumps to move substances
72
role of carrier protein in active transport
when molecules bind to the receptor- ATP will bind to protein on inside of membrane and is hydrolysed to ATP/Pi, protein changes shape and opens inside membrane
73
co-transport
the coupled movement of two substances across a membrane when one is unable to cross the membrane itself, involves a co-transport protein, involves active transport, e.g. absorption of glucose/amino acids from lumen of intestines
74
which molecules do lymphocytes identify
pathogens (bacteria, fungi, viruses), cells from organisms of other species (transplants), abnormal body cells (tumour cells), toxins (released from bacteria)
75
what are antigens and what do they do
proteins on the cell-surface membrane, they trigger an immune response when detected by lymphocytes
76
antigenic variability
when pathogenic DNA mutates causing a change in shape of antigen, previous immunity is no longer effective as memory cells dont recognise new shape of antigen, specific antibody no longer binds to new antigen
77
physical barriers to pathogens
skin, stomach acid, lysozymes in tears
78
phagocytes
non-specific immune response, phagocytes become antigen-presenting cells after destroying pathogen
79
T-lymphocytes
made in bone marrow and mature in thymus gland, involved in cell mediated immune response, respond to antigen-presenting cells (APCs)
80
antigen-presenting cells
any cell that presents a non-self antigen on their surface: infected body cells, macrophage after phagocytosis, cells of transplanted organ, cancer cells
81
role of T helper cells
have receptors on their surface that attach to antigens on APCs, become activated-clonal selection
82
role of cloned T helper cells
some remain as T helper cells and activate B lymphocytes, stimulate macrophages for phagocytosis, become memory cells for that shaped antigen, become cytotoxic killer T cells
83
cytotoxic T cells
destroy abnormal/infected cells by releasing perforin so that any substances can enter or leave the cell and this causes cell death
84
B lymphocytes
made in bone marrow and mature in bone marrow, involved in humoral immune response, involves antibodies
85
humoral response
APC activates B cell, B cell undergoes clonal selection and expansion-rapid division by mitosis, differentiate into plasma cells/memory B cells, plasma cells produce antibodies
86
B memory cells
derived from B lymphocytes, remember specific antibody for particular antigen, will rapidly divide by mitosis and differentiate in plasma cells upon secondary encounter, resulting in large numbers of antibodies rapidly
87
antibodies
quaternary structure proteins made of 4 polypeptide chains, different shaped binding sites=variable region, complementary to a specific antigen
88
agglutination
antibodies have two binding sites and are flexible-clumps pathogens together, makes it easier for phagocytes to locate and destroy pathogen
89
passive immunity
antibodies introduced into body, plasma cells and memory cells not produced as no interactions with antigen, short-term immunity, fast acting
90
active immunity
immunity created by own immune system-antibodies produced, exposure to antigen, plasma cells and memory cells produced, long-term immunity, slower acting
91
natural active immunity
after direct contact with pathogen through infection, body creates antibodies and memory cells
92
artificial active immunity
creation of antibodies and memory cells following introduction of an attenuated pathogen or antigens, vaccination
93
vaccinations
small amount of dead or attenuated pathogens injected/ingested, humoral response activated, memory cells are able to divide rapidly into plasma cells when re-infected
94
primary vs secondary response
primary=first exposure to pathogen, longer time for plasma cell secretion & memory cell production, for the secondary response memory cells divide rapidly into plasma cells so a large number of antibodies produced upon re-infection
95
herd immunity
when enough of the population is vaccinated so pathogen is not transmitted and spread easily, provides protection for those without vaccine
96
monoclonal antibodies
a single type of antibody that can be isolated and cloned, antibodies that are identical-from one type of B lymphocyte, complementary to only one antigen
97
uses on monoclonal antibodies
medical treatment-targeting drugs by attaching antibody complementary to tumour cell antigen, medical diagnosis-pregnancy tests
98
pregnancy test
ELISA test which uses 3 monoclonal antibodies and enzymes to test for HCG
99
purpose of ELISA test
detect the presence and quantity of an antigen, used for medical diagnosis e.g. HIV
100
ethical issues with monoclonal antibodies
requires mice to produce antibodies and tumour cells, requires a full cost-benefit analysis
101
HIV structure
core=RNA and reverse transcriptase, capsid=protein coat, lipid envelope is taken from host cells membrane, attachment proteins so it can attach to helper T cells
102
HIV replication
attaches to CD4 receptor on helper T cells, protein fuses with membrane allowing RNA and enzymes to enter, reverse transcriptase makes DNA copy and this is inserted into nucleus, nucleus synthesises viral proteins
103
Auto Immunodeficiency Syndrome (AIDS)
when HIV has destroyed too many helper T cells the host is unable to produce adequate immune response to other pathogens, host susceptible to opportunistic infections
104
role of antibodies in ELISA
first antibody added is complementary to antigen in well and attaches, second antibody with enzyme added which attaches to first antibody as complementary, when substrate solution added then enzyme can produce colour change
105
why vaccines may be unsafe
inactive virus may become active-viral transformation, non-pathogenic virus can mutate and harm cells, side effects of immune response, people may test positive for disease
106
why are antibiotics ineffective against viruses
viruses are inside host cells where antibiotics cannot reach, antibiotics affect parts of bacteria that viruses do not have (e.g. cell wall)
107
why do you wash well in ELISA
To remove unbound 2nd antibodies, otherwise: enzyme may be present which leads to a colour change which leads to a false positive
108
pathogens
microorganisms that cause a disease by releasing toxins or killing cells/tissues
109
cytokinesis
final stage in the cell cycle where the cytoplasm splits into 2 and creates 2 new cells
110
uncontrolled mitosis
uncontrolled cell division can lead to the formation of tumours and of cancers, many cancer treatments are directed at controlling the rate of cell division
111
viral replication
following injection of their nucleic acid into host cell, the infected host cell replicates the virus particles
112
cell adaptations for rapid transport across membranes
increase in surface area or membrane, increase in the number of protein channels/carriers in the membranes
113
antigen-antibody complex
when a complementary antibody binds to an antigen, this clumps pathogens together (agglutination)
