biology topic 2 Flashcards
1
Q
what is the structure of the cell surface membrane?
A
phospholipid bilayer embedded with proteins, selectively permeable
2
Q
what is the role of the cell surface membrane?
A
controls what enters and leaves the cell
3
Q
what is the structure of the nucleus?
A
nuclear pore, nuclear envelope, nucleolus, chromatin
4
Q
what is the role of the nucleus?
A
controls cells activity by transcription on mRNA, makes ribosomes
5
Q
what is the structure of the mitochondria?
A
double membrane- inner folded to form cristae, matrix
6
Q
what is the role of mitochondria?
A
site of aerobic respiration
7
Q
what is the structure of the Golgi apparatus?
A
fluid filled membrane bound sacs
8
Q
what is the role of the Golgi apparatus?
A
modifies and processes proteins, packages into vesicles, makes lysosomes
9
Q
what is the structure of lysosomes?
A
type of golgi vesicle containing lysozymes
10
Q
what is the function of lysosomes?
A
breaks down pathogens or dead parts of the cell
11
Q
what is the structure of ribosomes?
A
small subunit
12
Q
what is the function of a ribosome?
A
site of protein synthesis
13
Q
what is the structure of the rough endoplasmic reticulum?
A
ribosomes bound by membranes
14
Q
what is the function of the rough endoplasmic reticulum?
A
fold polypeptides and packages them into vesicles
15
Q
what is the structure of the smooth endoplasmic reticulum?
A
membranes without ribosomes
16
Q
what is the function of the smooth endoplasmic reticulum?
A
synthesises and processes lipids
17
Q
what is the structure of chloroplasts?
A
thylakoid membranes form grana, sit in stroma, surrounded by double membrane
18
Q
what is the function of chloroplasts?
A
contain chlorophyll which absorbs light for photosynthesis
19
Q
what is the structure of the cell wall?
A
made of cellulose in plants/algae and chitin in fungi, rigid
20
Q
what is the function of the cell wall?
A
prevents the cell from bursting and changing shape
21
Q
what is the structure of the cell vacuole?
A
contain cell sap, surrounded by tonoplast
22
Q
what is the function of the cell vacuole?
A
maintains pressure in the cell, stores unwanted chemicals
23
Q
what is a cell?
A
smallest unit making up a living thing
24
Q
what is a tissue?
A
group of specialised cells working together to form a function
25
what is an organ?
group of different tissues working together to perform a function
26
what is an organ system?
group of organised organs working together to form a function
27
what are the differences between prokaryotic and eukaryotic cells?
prokaryotic cells- no membrane bound organelles
prokaryotic cells- no nucleus instead have free floating DNA
prokaryotic DNA is not associated with proteins
prokaryotic cell is made of murein not cellulose
prokaryotic cells have smaller 70s ribosomes
28
what is the purpose of flagellum?
movement
29
what is the purpose of a capsule?
offers protection from the immune system
30
what is a plasmid?
loop of DNA
31
what is the structure of a virus?
acellular, non living, protein coat known as a capsid, attachment proteins to attach to the host cell, core of genetic material (DNA or RNA)
32
how do viruses replicate?
inject genetic information into host cells and use them to replicate
33
how does binary fission occur?
```
circular DNA and plasmids replicate
cell gets bigger
DNA loops move to opposite poles
cytoplasm begins to divide
forms 2 daughter cells- 1 copy of circular DNA but varying number of plasmids
```
34
how does an optical microscope work?
uses light to form a 2D image
35
what are the advantages of an optical microscope?
colour, can see living organisms
36
what are the disadvantages of an optical microscope?
2D, only used on thin specimens, low resolution, low magnification
37
how does a scanning electron microscope work?
uses electrons to form a beams of electrons scan the surface, knock of electrons which are gathered in a cathode ray tube to form an image
38
what are the advantages of a scanning electron microscope?
3D, high resolution, high magnification, can be used on thick specimens
39
what are the disadvantages of a scanning electron microscope?
can't see living organisms, lower resolution than TEM
40
how does a transmission electron microscope work?
electromagnets focus a beam of electrons onto a specimen, denser specimen-more absorbed-appears darker
41
what are the advantages of a transmission electron microscope?
high resolution, high magnification
42
what are the disadvantages of a transmission electron microscope?
can only be used on thin specimens
43
what is magnification?
how much bigger the image is compared to the real size
44
what is the equation for magnification?
image size/actual size
45
what is resolution?
the ability to distinguish between 2 objects
46
how to prepare a temporary mount?
put a drop of water onto a slide, use tweezers to place a thin specimen on top of this, add a drop of stain, add cover slip by carefully tilting and lowering it (try not to get any air bubbles)
47
how do you carry out cell fractionation?
homogenise the tissue using a blender to release organelles
place in a cold, isotonic buffered solution
filter the unwanted debris
centrifuge at a low speed
remove pellet of heaviest organelle and spin at a higher speed
48
why is the solution cold?
reduces enzyme activity so that organelles aren't broken down
49
what is the solution isotonic?
prevents osmosis happening
50
why is the solution buffered?
keeps pH constant so that enzymes don't denature
51
what is the order organelles are separated in?
```
nuclei
chloroplasts
mitochondria
lysosomes
endoplasmic reticulum
ribosomes
```
52
what are the stages in the cell cycle?
g1= cell grows, forms new organelles and proteins
s= interphase, DNA replicated forming sister chromatids
g2= cell grows, new proteins
mitosis
53
what happens in mitosis?
parent cell divides to form two genetically identical daughter cells
54
what happens in prophase?
chromosomes condense, nuclear envelope breaks down, centrioles move to opposite poles
55
what happens in metaphase?
chromosomes line up on the centre of the equator and spindle fibres attach to the centromere of a chromosome
56
what happens in anaphase?
spindle fibres contract which pulls chromatids to opposite poles of the cell so the centromere divides
57
what happens in telophase?
chromosomes uncoil, nuclear envelope reforms, spindle fibres break down
58
what happens in cytokinesis?
cytoplasm divides
59
why is mitosis important?
growth, repair, asexual reproduction
60
what is a malignant tumour?
cancerous tumour that can spread to affect other organisms
61
what is a benign tumour?
non cancerous tumour
62
how does chemotherapy work?
prevents DNA replication which prevents/slows mitosis
63
how does radiotherapy work?
damages DNA so the cell dies
64
why is the cell membrane described as having a fluid mosaic structure?
molecules within the membrane can move, proteins scattered throughout
65
what is a glycoprotein?
protein within a polysaccharide chain
66
what is a glycolipid?
lipid within a polysaccharide chain
67
what is the phospholipid bilayer?
phosphate heads= hydrophilic, attracted to water, fatty acid tails are hydrophobic so are repelled by water
68
what is the role of cholesterol?
regulates fluidity/increases stability by restricting the movement of molecules
69
what is diffusion?
passive movement of particles from an area of high concentration to an area of low concentration
70
what is the role of a carrier protein?
moves large molecules across a membrane, down a concentration gradient. the molecule attaches to the carrier protein, changes shape and is released on the other side of the membrane
71
what is the role of a channel protein?
forms pores in the membrane for charged particles to pass through
72
how can diffusion be maximised?
high concentration gradient, thin exchange surface, large surface area to volume ratio
73
what is Fick's Law?
the rate of diffusion is proportional to the (surface area x concentration difference)/ length of diffusion path
74
what is osmosis?
water moves from a solution of high to low water potential
75
what is water potential?
pressure exerted by moving water molecules, measured in kPa, pure water has 0kPa, potential falls with more solutes added- more concentrated=more negative water potential
76
what is hypotonic?
surrounding solution has a higher water potential, water moves in so cell could burst and becomes turgid
77
what is hypertonic?
surrounding solution has a lower water potential so water moves out, cell becomes flaccid
78
what is isotonic?
same water potential inside and outside of the cell, no net movement
79
what does the rate of osmosis depend on?
water potential gradient, thickness of the exchange surface, the surface area
80
how are carrier proteins involved in active transport?
molecule attaches to the carrier protein, protein changes shape, released on the other side
81
what provides the energy for active transport to go against a concentration gradient?
ATP hydrolysis reaction
82
how do co transporters allow active transport to occur?
bind 2 molecules at a time, concentration of one molecule moves the other against its own concentration gradient
83
what factors affect the rate of active transport?
speed of carrier proteins, number of carrier proteins available, rate of respiration
84
how does the sodium potassium pump work?
sodium ions actively transported out of epithelial cells by the sodium potassium pump so there is a higher concentration of sodium in the lumen
sodium ions and glucose move by facilitated diffusion into the epithelial cell from the lumen via a co transporter protein
this means there is a higher concentration of glucose in the epithelial cell than the blood
glucose moves out of the cell into the blood by facilitated diffusion
85
what is an antigen?
protein that generates an immune response
86
what are examples of non specific immunity?
skin, macrophages, tears
87
what are examples of specific immunity?
T lymphocytes, B lymphocytes
88
what is innate immunity?
immediate response, limited response, not specific, no memory
89
what is adaptive immunity?
response takes time, specific response, memory
90
what are phagocytes?
specialised white blood cells that engulf and destroy pathogens
91
what is phagocytosis?
when pathogens are engulfed by phagocytes
92
what happens in phagocytosis?
phagocyte recognises the foreign antigen
phagocyte engulfs pathogen
pathogen contained in a phagocytic vacuole
lysosome fuses with the phagocytic vacuole
phagocyte acts as an antigen presenting cell or digests the pathogen
93
what are examples of antigen presenting cells?
macrophages and dendritic cells
94
what role do T cells play in adaptive immunity?
form the cell mediated response
95
where do T cells originate?
thymus
96
how are T cells activated?
encounter complementary antigen presented by antigen presenting cells, activated in the lymph, migrate to infection site
97
what is the role of helper T cells?
release chemical signals, activate/stimulate phagocytes and cytotoxic T cells, activate the maturation of B cells
98
what are cytotoxic T cells?
cells that release cytotoxins which trigger cell death (apoptosis)
99
what is the role of B cells in adaptive immunity?
humoral response
100
how are B cells activated?
antibody on B cell meets complementary antigen- clonal selection
101
what is clonal expansion?
when the B cell proliferates (divides)
102
what does an activated B cell divide into?
plasma cells that secrete a specific antibody, memory B cells that prepare for a second infection
103
what do antibodies and antigens bind to form?
an antigen antibody complex
104
what is the structure of an antibody?
```
2 binding sites to join 2 pathogens at the same time= agglutination
disulphide bridge=stabilises the tertiary structure
hinge region= allows the molecule to be flexible
variable region= provides the specificity
constant region= shows what class of antibody
```
105
what is the primary immune response?
the first time the pathogen infects, slower as the immune response needs to adjust
106
what is the secondary immune response?
reinfection with the same pathogen, quicker and stronger response as the memory B cells are activated to form plasma cells, and memory T cells are activated
107
what is antigenic variation/
when pathogens alter their surface antigens, so they are not recognised by the immune response
108
what is passive immunity?
immunity you get from being given antibodies made by a different organism, doesn't require exposure, immediate protection, no memory cells produced
109
what is active immunity?
immunity you get when your immune system makes its own antibodies, requires exposure to antigen, immunity takes time to develop, long term protection as memory cells are produced
110
why are vaccines helpful?
contain antigens from a pathogen, induce active immunity without all symptoms, can lead to herd immunity
111
what is herd immunity?
when it is hard for the pathogen to spread as the majority of a population are immune
112
what are the limitations of vaccines?
may develop the disease before immunity levels are high enough, antigens may mutate, some pathogens hide from the body's immune system, ethical/religious/medical objections
113
what are monoclonal antibodies?
antibodies produced from genetically identical B cells, identical in structure
114
why are monoclonal antibodies useful in medicine?
specific- can be used as a targeted therapy or medical diagnosis
115
how do pregnancy tests work?
placenta produces a hormone called hCG which is found in a mother's urine, the test contains antibodies specific for hCG bound to a coloured bead, the urine sample and antibody moves up the test strip, test region has immobilised antibodies for hCG
116
what is direct monoclonal antibody therapy?
specific antibody binds to the antigen on the cancer cells, blocks chemical signals leading to uncontrolled growth which reduces tumour development
117
what is indirect monoclonal antibody therapy?
drug attached to monoclonal antibody, antibody binds to the antigen on cancer cells, brings the drug to the site of the tumour which leaves to cancer cell death
118
what does ELISA stand for?
enzyme linked immunosorbent assay
119
what is the purpose of an ELISA test?
can see if a patient has antibodies for specific antigens, can be used for medical diagnosis
120
how does an ELISA test work?
antigens from a patient's sample are bound to inside a well plate
detection antibody (enzyme attached) is complementary to the antigen of interest
if the antigen of interest is present the detection antibody binds
the well is rinsed and the substrate solution is added- if the antigen is present the enzyme will react and a colour change will occur
121
what is HIV?
human immunodeficiency virus- leads to AIDS
122
what is the latency period?
after HIV has initially rapidly replicated and the person has experienced symptoms, HIV replication drops to a low level and the person will not experience symptoms
123
what is the structure of HIV?
core contains RNA and reverse transcriptase
capsid contains RNA
lipid envelope containing attachment proteins
124
how does HIV replicate?
attachment protein attaches to receptor molecule on T helper cell
capsid released into the T helper cell, release RNA into helper T cell cytoplasm
reverse transcriptase used to make a complementary strand of DNA from the viral RNA template
double stranded DNA made and inserted into human DNA
helper T cell enzymes make viral proteins from viral DNA
viral proteins assemble into a new virus which buds from cell to cell to infect other cells
125
how can HIV be controlled?
drugs target HIV only enzymes, no current cure/vaccine, best to prevent
