2a cell structure and division Flashcards
1
Q
what are the two types of cell
A
prokaryotic and eukaryotic
2
Q
what are prokaryotic organisms made from
A
prokaryotic cells
3
Q
what are eukaryotic organisms made from
A
eukaryotic cells
4
Q
what do both type of cells contain
A
organelles
5
Q
organelles
A
parts of cells each with a specific function
6
Q
organelles in an animal cell
A
- plasma membrane
- rough ER
- nucleolus
- nucleus
- smooth ER
- lysosome
- ribosome
- nuclear envelope
- golgi apparatus
- cytoplasm
- mitochondria
7
Q
organelles in a plant cell
A
same as animal cell and
- cellulose cell wall
- plasmodesmata
- vacuole
- chloroplasts
8
Q
algal cells
A
alot like plant cells, same organelles including cell wall and chloroplasts
9
Q
fungal cells
A
alot like plants cells but two key differences
10
Q
differences between fungal and plant cells
A
- cell walls made of chitin not cellulose
- dont have chloroplasts because they dont photosynthesise
11
Q
plasma membrane structure
A
the membrane found on the surface of animal cells and just inside the cell wall of other cells. made mainly of lipids and protein
12
Q
plasma membrane function
A
regulates the movement of sustances into and out of the cell. also has receptor molecules on it which allow it to respond to chemicals like hormones
13
Q
nucleus structure
A
a large organelle surrounded by a nuclear envelope (double membrane) which contains nuclear pores. the nucleus contains chromosomes and one or more structures called a nucleolus
14
Q
nucleus function
A
the nucleus controls the cells activities by controlling the transcription of DNA. DNA contains instructions to make proteins. the pores allows substances to move between the nucleus and the cytoplasm. the nucleolus makes ribosomes
15
Q
mitochondrion structure
A
they are usually oval shaped. they have a double membrane - the inner one is folded to form structures called cristae. inside is the matrix, which contains enzymes involved in respiration
16
Q
mitochondrion function
A
the site of aerobic respiration, where ATP is produced. they are found in large numbers in cells hat are very active and require a lot of energy.
17
Q
chloroplast structure
A
a small flattened structure found in plant and algal cells. it is surrounded by a double membrane and also has membrane inside called thylakoid membranes. these membranes are stacked up in some parts of the chloroplast to form grana. grana are linked together by lamellae - thin flat pieces of thylakoid membrane
18
Q
chloroplast function
A
the site where photosynthesis takes place. some parts of photosynthesis happen in the grana, and other parts happen in the stroma
19
Q
stroma
A
a think fluid found in chloroplasts
20
Q
golgi apparatus structure
A
a group of fluid-filled, membrane bound flattened sacs, vesicles are often seen at the edges of the sacs
21
Q
golgi apparatus function
A
it processes and packages new lipids and proteins. it also makes lysosomes
22
Q
golgi vesicle structure
A
a fluid filled sac in the cytoplasm surrounded by a membrane and produced by the golgi apparatus
23
Q
golgi vesicle function
A
stores lipids and proteins made by the golgi apparatus and transports them out of the cell
24
Q
lysosome structure
A
a round organelle surrounded by a membrane with no clear internal structure
25
lysosome function
contains hydrolytic enzymes. these are kept seperate from the cytoplasm by the surrounding membrane and can be used to digest invading cells or break down worn out components of the cell
26
ribosome structure
a very small organelle that either floats free in the cytoplasm or is attatched to the rough ER. its made up of proteins and RNA. it is not surrounded by a membrane
27
ribosome function
the site where proteins are made
28
rough ER structure
a system of membranes enclosing a fluid-filled space. the surface is covered with ribosomes
29
rough ER function
folds and processes proteins that have been made at the ribosomes
30
smooth ER structure
similar to rough ER but with no ribosomes
31
Smooth ER function
synthesises and processes lipids
32
cell wall structure
a rigid structure that surrounds cells in plants, algae and fungi. in plants and algae its made of cellulose. in fungi its made of chitin
33
cell wall function
supports cells and prevents them from changing shape
34
cell vacuole structure
a membrane-bound organelle found in the cytoplasm of plant cells. it contains cell sap- a weak solution of sugar and salts. the surrounding membrane is called the tonoplast
35
cell vacuole function
helps to maintain pressure inside the cell and keep the cell rigid this stops plants wilting. also involved in the isolation of unwanted chemicals inside the cell
36
what happens in multicellular eukaryotic organisms
cells become specialised to carry out specific functions
37
what does a cells structure help it to do
carry out its function. depending on what job it does a specialised cell can look very different to regular cells
38
how are epithelial cells in the small intestine specialised to absorb food efficiently
1. the walls of the small intestines have lot of villi to increase surface area for absorption
2. the epithelial cells on the surface of the villi have folds in their cell surface membranes called microvilli to increase the surface area even more
3. they also have lots of mitochondria to provide energy for the transport of digested food molecules into the cell
39
specialised cells group together to form
tissues
40
tissues
a group of cells working together to perform a particular function
41
tissues work together to form
organs
42
different organs make up an..
organ system
43
what are prokaryotic cells compared to eukaryotic cells
smaller and simpler
44
example of prokaryotic cells
bacteria
45
cytoplasm of prokaryotic cell
no membrane bound organelles. it has ribosomes but they are smaller than those in a eukaryotic cell
46
plasma membrane in prokaryotic cells
mainly made of lipids and proteins. controls the movement of substances into and out of the cell
47
flagellum prokaryotic cell
long hair like structure that rotates to make the prokaryotic cell move. not all prokaryotes have a flagellum. some have more than one
48
DNA prokaryotic cell
doesn't have a nucleus. instead DNA floats free in the cytoplasm. its circular DNA, present as one long coiled-up strand. its not attached to any histone proteins
49
plasmids prokaryotic cells
small loops of DNA that arent part of the main circular DNA molecule. plasmids contain genes for things like antibiotic resistance and can be passed between prokaryotes. plasmids are not always present in prokaryotic cells. some prokaryotic cells have several
50
cell wall prokaryotic cells
supports the cell and prevents it from changing shape. its made of a polymer called murein. murein is a glycoprotein
51
what do some prokaryotes also have
a capsule made up of secreted slime. it helps protect bacteria from attack by the cells of the immune system
52
viruses
nucleic acids surrounded by a protein - not alive
53
viruses vs bacteria
smaller.
- no plasma membrane
- no cytoplasm
- no ribosomes
54
what do viruses do
invade and reproduce inside the cells of organisms. - these cells are known as host cells
55
Genetic material in viruses
contain a core of genetic material either DNA or RNA
56
what is the protein coat around the core of a virus called
the capsid
57
attatchment proteins viruses
sick out from the edge of the capsid. these let the virus cling on to a suitable host cell
58
what is binary fission
cell replicates its genetic material before physically splitting into two daughter cells
59
what kind of cells replicate by binary fission
prokaryotic cells
60
process of binary fission
1. the circular DNA and plasmids replicate. the main DNA loop is only replicated once, the plasmids can be replicated loads of times.
2. the cell gets bigger and the DNA loops move to opposite poles of the cell
3. the cytoplasm begins to divide and new cell walls begin to form
4. the cytoplasm divides and two daughter cells are produced. each daughter cell has one copy of the circular DNA but can have a variable number of copies of the plasmids
61
what do viruses use host cells to do
replicate thempselves
62
what do viruses use their attachment proteins to do
bind to complementary receptor proteins on the surface of host cells
63
why can some viruses only infect one type of cell
have differennt attachment proteins and therefore require different receptor proteins on host cells
64
why dont viruses undergo cell division
because they are not alive
65
how do viruses divide
they inject their DNA or RNA into the host cell, this hijacked cell then uses its own machinery to do the virus's dirty work and replicate the viral particles
66
what do microscopes produce
a magnified image of a sample
67
magnification
how much bigger the image in than the specimen
68
magnification formula
magnification = size of image/size of real object
69
resolution
how detailed the image is
- how well a microscope distinguishes between two points that are close togher
70
two main types of microscope
optical (light) and electron
71
how do light microscopes work
use light to form an image
72
resolution light micorscopes
maximum resolution of about 0.2 micrometers. this means you cant use a light microscope to view organelles smaller than 0.2 micrometers including ribosomes, ER and lysosomes. you may be abke to make out mitochondria but not in perfect detail. you can also see the nucleus
73
magnification light microscope
maximum useful magnification is about x1500
74
how do electron microscopes work
use electrons to form and image
75
resolution electron microscope
higher resolution then light microscopes so give a more detailed image
have a maximum resolution of about 0.0002 micrometers
76
magnification electron microscopes
maximum magnification is about x1 500 000
77
transmission electron microscopes
- use electromagnets 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.
- good because they give high resolution images, so you see the internal structure of organelles,
- can only be used on thin specimens
78
scanning electron microscopes
- scan a beam of electrons across the specimen. this knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image
- the images you end up with show the surface of the specimen and they can be 3D.
- good because they be used on thick specimens
- give lower resolution images
79
how do you prepare a temporary mount of a specimen on a slide
- pipette a small drop of water onto the slide
- use tweezers to place a thin section of your specimen on top of the water drop
- add a drop of stain
- add a cover slip, stand the slip upright next to the water droplet then carefully tilt and lower it so it covers the specimen to avoid air bubbles (you can also use the tip of a needle)
80
cell fractionation
seperating organelles from the rest of the cell
81
steps of cell fractionation
homogenisation
filtration
ultracentrifugation
82
homogenisation
breaking up the cells
- cells are grinded up in a homogeniser. this breaks up the plasma membrane and releases the organelles into solution. the solution must be kept ice cold to reduce the activity of enzymes that break down organelles. the solution should also be isotonic, meaning it should have the same concentration of chemicals as the cells being broken down to prevent damage through osmosis. a buffered solution should be added to maintain pH
83
filtration
getting rid of the big bits
- the homogenised solution is filtered through gauze to seperate any large cell debris or tissue debris, like connective tissue, from the organelles. the organelles are much smaller than the debris, so they pass through the gauze.
84
ultracentrifugation
seperating the organelles
- your left with a solution containing a mixture of organelles. to seperate a particular organelle from the other you use ultracentrifugation
85
process if ultracentrifugation step 1
1. cell fragments are poured into a tube. the tube is the put into a centrifuge and is spun at a low speed. the heavest organelles get flung to the botto of the tube by the centrifuge. they form a thick sediment at the bottom - the pellet. the rest of the organelles stay suspended in the fluid - the supernatant
86
centrifuge
a machine that separates material by spinning
87
the pellet
thick sediment at the bottom of a centrifuge
88
the supernatant
the fluid above the sediment
89
process of ultracentrifugation step 2
the supernatant is drained off, poured into another tube and spun in the centrifuge at a higher speed. again the heaviest organelles form a pellet at the bottom of the tube. the supernatant containing the rest of the organelles is drained off and spun in the centrifuge at an even higher speed
90
process of ultracentrifugation step 3
this process is repeated at higher and higher speeds until all the organelles are seperated out. each time the pellet at the bottom of the tube is made up of lighter ad lighter organelles
91
mitosis
cell division that produces genetically identical cells
92
two types of cell division in eukaryotes
mitosis and meiosisw
93
what happens during mitosis
a parent cell dived to produce two genetically identical daughter cells containing an exact copy of the DNA of the parent cell.
94
why is mitosis needed
for the growth of multicellular organisms and repairing damaged tissues
95
the cell cycle
consists of a period of cell growth and DNA replication. mitosis happens after that. interphase is subdivided into three seperate growth stages called G1, S, and G2
96
where does the cell cycle start and end
with mitosis
97
gap phase one
cell grows and new organelles and proteins are made
98
synthesis
cell replicates its DNA, ready to divide by mitosis
99
gap phase two
cell keep growing and proteins needed for cell division are made
100
what do not all multicellular have the ability to do
divide
101
what are the four division stages of mitosis
- prophase, metaphase, anaphase, and telophase
102
interphase
comes before mitosis in the cell cycle
103
prophase
the chromosomes condense, getting shorter and fatter. tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle. the nuclear envolope breaks down and chromosomes lie free in the cytoplasm.
104
metaphase
the chromosomes line up along the middle of the cell and become attached to the spindle by their centromere
105
anaphase
the centromeres divide, seperating each pair of sister chromatids. the spindles contract, pulling chromatids to opposite poles of the spindle, centromere first. this makes the chromatids appear v- shaped
106
telophase
the chromosomes reach the opposite poles on the spindle. they uncoil and become long and thin again. they are now called chromosomes again. a nuclear envolope forms around each group of chromosomes, so there is now two nuclei. division of the cytoplasm finishes in telophase ( starts in anaphase ) there are now two daughter cells that are genetically identical
107
what is cancer the result of
uncontrolled cell division
108
what are mitosis and the cell cycle controlled by
genes
109
what can a mutation in a gene cause
uncontrolled cell division
110
tumour
formed when cells keep on dividing to make more and more cells
111
what is cancer
a tumour that invades the surrounding tissue
112
what do some cancer treatments target
the cell cycle
113
what are some cancer treatments designed to do
control the rate of cell division in tumour cells by disrupting the cell cycle, killing the tumour cells
114
what is the flaw with killing the tumour cells
they dont distinguish tumour cells from normal cells, meaning they also kill normal body cells that are dividing
115
why is this form of treatment still used
tumour cells divide more frequently then normal cells so the treatments are more likely to kill tumour cells.
116
what are the two phases cancer treatments target
G1 and S
117
how do cancer treatments affect G1
some chemical drugs prevent the synthesis of enzymes needed for DNA, if these arent produced the cell is unable to enter the synthesis phase, distrupting the cell cycle and causing the cell to kill itself
118
how do cancer treatments affect s phase
radiation and some drugs damage DNA. at several points in the cell cycle the DNA in the cell is checked for damage. if severe damage is detected the cell will kill itself - preventing further tumour growth.
119
How can we observe mitosis
stain root tips and squah them
120
how to prepare and stain a root tip to observe mitosis
1. cut 1cm from the tip from a growing root
2. prepare a boiling tube containing 1m hydrochloric acid and put in a water bath at 60 degrees celcius
3. transfer the root tip into the boiling tube and incubate for 5 minutes
4. use a pipette to rinse the root tip well with cold water. leave the tip to dry on a paper towel
5. place the root tip on the microscope slide and cut 2mm from the very tip, dispose of the rest
6. use a mounted needle to break the tip open and spread the cells out thinly
7. add a few drops of stain and leave for a few minutes
8. place a cover slip over the cells and push down firmly to squash the tissue
9. place under microscope and observe mitosis
121
why does it need to be the tip
because thats where growth occurs
122
why do we use stain
to make the chromosomes easier to see under a microscope
123
why do we squash the root with a cover slip
to make the tissue thiner and allows light to pass through it
124
how can you use a microscope to observe the prepared slide
1. start by clipping the slide youve prepared onto the stage
2. select lowest powered objective lens
3. use the coarse adjustment knob to bring the stage up to just below the objective lens
4. look down the eyepiece, use the coarse adjustment knob the move the stage downwards away from the objective lens until the image is rougly in focus
5. adjust the focus with the fine adjustment knob until you get a clear image
6 swap to a higher powered objective lens if needed.
125
what is mitotic index
the proportion of cells undergoing mitosis
126
mitotic index formula
mitotic index = number of cells with visible chromosomes/ total number of cells observed
127
artefacts
things you can see that arent part of the cell or specimen
e.g. dust, air bubbles, fingerprints
- usually made during the preperation of slides.
