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A Level Aqa Biology > Cells (3-3.8) Cell Structure > Flashcards

Cells (3-3.8) Cell Structure Flashcards

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1
Q

What are microscopes?

A

They are instruments that produce a magnified image of an object.

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2
Q

What is magnification?

A

How many times bigger the image is when compared to the object.

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3
Q

What is the magnification formula?

A

Magnification= size of image divided by size of real object

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4
Q

What is resolution?

A

The minimum distance apart that two objects can be in order to to them to appear as separate items

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5
Q

What is cell fractionation?

A

The process where cells are broken up and the different organelles they contain are separated out

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6
Q

What happens before cell fractionation?

A

The tissue is placed into a cold buffered solution of the same water potential as the tissue

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7
Q

What are the two stages of cell fractionation?

A

Homogenation and Ultracentrifugation

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8
Q

What is homogenation?

A

When cells are broken up by a homogeniser (blender) to release organelles from the cell. The homogenate is the filtered to remove debris and any complete cells

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9
Q

What is ultracentrifugation?

A

The process by which the fragments in the filtered homogenate are separate in a machine (centrifuge)

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10
Q

For animal cells, describe the ultracentrifugation in the steps

A

1) tube of filtrate is placed in the centrifuge, spun at low speed
2) heavy organelles (nuceli) forced to bottom of tube, where they form a thin sediment
3) fluid at top (supernatant) is removed, leaving just the sediment (nuclei)
4) supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before.
5) next heaviest (mitochondria) are forced to bottom of tube
6) at each increased speed, the next heaviest organelle is sediment Ed and separated out

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11
Q

Why do light microscopes have poor resolution?

A

They have a relatively long wavelength of light

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12
Q

What are the two main advantages of an electron microscope?

A

1) Electron beam has a very short wavelength - can resolve objects well (high resolving power)
2) electrons are negatively charged - the beam can be focused using electromagnets

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13
Q

What needs to be created in order for an electron microscope to work effectively?

A

A near-vaccum has to be created within the chamber of an electron microscope

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14
Q

What are the two types of microscopes?

A

1) Transmission Electron Microscope (TEM)
2) Scanning Electron Microscope (SEM)

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15
Q

What does a TEM consist of?

A

An electron gun that produces a beam of electrons that’s is focuses onto the specimen by a condenser electromagnet.

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16
Q

What is the resolving power of a TEM?

A

0.1 nm

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17
Q

What are the main limitations of a TEM?

A

1) Whole system must be in a vaccum, therefore living specimens cannot be observed.
2) a complex ‘staining’ process is required and even then the image is not in colour
3) specimen must be extremely thin
4) image may contain artefacts

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18
Q

How does the SEM work?

A

SEM directs a beam of electrons on to the surface of the specimen from above. Beams then passed back and forth across a portion of the specimen in a regular pattern. Electrons are scattered by the specimen and the pattern of this scattering depends if contours if the specimen surface.

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19
Q

Does the SEM have a lower resolving power than TEM?

A

Yes, around 20nm

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20
Q

What is an eyepiece graticule?

A

It is a glass disc that is placed in the eyepiece of a microscope

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21
Q

What is etched on the glass disc?

A

A scale

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22
Q

How long is the scale and in how many sub divisions?

A

10mm long and in 100-sub divisions

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23
Q

What must be done first with the graticule before being used?

A

It has to be calibrated for a particular objective lens

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24
Q

What microscope do you need to calibrate an eyepiece graticule?

A

A stage micrometer

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25
What is the scale on a stage micrometer?
2mm long and has 0.1nm (10micrometers)
26
How do you workout the graticule?
Mm divided by graticule x100
27
How do you calculate linear magnifications of drawings and photographs?
1) Measure length X-Y 2) convert measurement in drawing to microns (x1000) 3) new measurement divided by line representing in the cell = magnification
28
What is magnification formula?
Actual size divided by the size of the image
29
What is cell ultrastructure?
The internal structure of a cell that suits for it's own function
30
What are the main things in eukaryotic cells?
They have: A distinct nucleus Membrane bound organelles
31
What are the eukaryotic organisms?
They are: Animals Plants Algae Fungi
32
What is the nucleus function?
Control centre producing mRNA and tRNA which allows for protein synthesis inside the cell (assembles ribosomes)
33
What does the nucleus contain (5 structures)?
Nucleoplasm Chromatin Nuclear pores Nucleolus Nuclear envelope
34
What is the function of the nucleoplasm?
It's a jelly like substance making up the bulk of the nucleus
35
What is the function of Chromatin?
Protein bound linear piece of DNA
36
What is the function of the nuclear envelope?
It's controls the entry and exit of substances in and out the nucleus
37
What is the function of the nuclear pores?
Allows for the passage of large molecules out of the nucleus
38
What is the function of the Nucleolus?
It is a spherical region that synthesise rRNA and assembles ribosomes
39
What is the function of the mitochondria?
It is the site of aerobic respiration
40
What are the 4 structures found in a mitochondria?
Matrix (ribosomes and DNA) Cristae Outer membrane Inner membrane
41
What is the role of an outer membrane for a mitochondria?
It controls entry and exit of molecules
42
What is the role of the inner membrane for a mitochondria?
It contains Cristae (infolding of membrane) that have enzymes attached to carry out respiration.
43
What is the role of the matrix in a mitochondria?
It allows for the production of their own proteins and contains enzymes involved in respiration
44
What is the function of the endoplasmic reticulum?
It's a series of sheet like membranes that produces proteins to allow the rest of the cell to function
45
What are the two types of endoplasmic reticulum?
Rough and smooth
46
What does RER have on the outer surfaces of the membrane?
Ribosomes
47
What is the function of RER?
Large surface area for synthesis of proteins and gylcoproteins. Provides a pathway for the transport of substances like proteins through the cell
48
What is the function of SER?
Synthesise, store and transport both lipids and carbohydrates.
49
What is the function of the golgi apparatus?
modify, sort, and package macromolecules that are synthesized by the cell
50
What is the golgi apparatus made out of?
Cisternae and vesicles
51
What are cisternae?
Flattened sacs
52
What are vesicles?
Membrane sacs
53
What are the functions of the golgi apparatus?
Modification of proteins Add carbohydrates to some proteins Label proteins to be stored and sent to correct places Transported to vesicles to edge of the cell and then releasee Produce secretory ezymes Secretes carbohydrates Modify, transport and store lipids Form lysosomes
54
What is the function of lysosomes?
break down and recycle cellular waste and unwanted material.
55
What does lysosomes breakdown?
Ingested material
56
What do lysosomes hydrolyse?
Cell walls of bacteria (white blood cells)
57
What do lysosomes release to the outside of the cell and what is the process called and what does it do?
Enzymes, and the process is exocytosis and this means that it destroys material around the cell
58
What does autolysis mean?
Complete break down of cells after that have died
59
What is the function of ribosomes?
The site of protein synthesis
60
What are the two types of ribosomes?
80s and 70s
61
Where are 80s ribosomes found? And how big are they?
Found in eukaryotic cells, is around 25nm in diameter
62
Where are 70s ribosomes found? And what organelles are slightly smaller than 80s ribosomes?
Found in prokaryotic cells, mitochondria and chloroplasts, is slightly smaller
63
What whare the two sub units of ribosomes?
Small and large
64
What does each subunit contain in a ribosome?
rRNA and protein
65
What is the function of the cell wall?
Contribute to the overall strength of the cell wall and prevent the cell from bursting under the pressure created by osmotic entry of water. But also contributes to the movement of water through the plant.
66
What does the cell wall consist of?
Microfibrils of the polysaccharide cellulose, embedded in a matrix, a thin layer (middle lamella)
67
What are the cell walls of Algae made of?
Cellulose or gylcoproteins or a mixture of both
68
What are the cell walls of fungi not contain, but do contain instead?
Do not contain cellulose, but contains chitin (nitrogen containing polysaccharide), gylcan and glycoproteins.
69
What is the function of chloroplasts?
Carry out photosynthesis
70
What are the structures of chloroplasts?
Chloroplast envelope, the grana (stacks of thylakoid), chlorophyll, the stroma, grana membranes, DNA, ribosomes
71
What is the stroma?
A fluid filled matrix (synthesis of sugars) take place. Light in dependant reaction
72
What is within the stroma?
Starch grains
73
What does the grana membranes provide for the attachment of chlorophyll, electron carriers and ezymes that carry out the first stage of photosynthesis?
A large surface area
74
What does the fluid of the stroma possess needed to make sugars in the 2nd stage of photosynthesis?
ezymes
75
Why do chloroplasts contain DNA and Ribosomes?
So they can quickly and easily crate some of the proteins needed for photosynthesis
76
What is the function of a vacuole?
Supports herbaceous plants and parts of them by making the cells turgid, sugars and amino acids acts as temporary food store, pigments may colour pettles so they can also attract pollinating insects
77
What is a vacuole?
A fluid filled sac bounded by a single membrane.
78
What is the single membrane around the vacuole?
Tanoplast
79
What is cell specialisation?
When a cell becomes specialised to perform a specific function.
80
In an embryo, what is common with all the cells
They are all identical
81
What are all cells in a human created by?
Mitotic divisions from the fertilised egg
82
How then does the cell become specialised?
Some genes are switched on (expressed) and some switched off in any one cell, at any one time.
83
The shape of the cells vary but what else?
The number of each organelle
84
What are tissues?
Collection of cells that work together to perform a specific function
85
Where are epithelial tissues found?
Animals and consist of sheets of cells
86
Where is the xylem found?
Plants and is made of number of similar cell types
87
What is an organ?
Collection of tissues that work together to perform a specific function
88
Why are capillaries not organs, big veins and arteries are?
Capillaries have just one tissue
89
What is an organ system?
Collection of organs that work together to perform a specific function
90
What doe the digestive system do?
Digests and processes food
91
What does the respiratory system do?
Used for breathing and gas exchange
92
What does the circulatory system do?
Pumps and circulates blood
93
What are the common structures of a prokaryotic cell?
Cell surface membrane, ribosomes, food stored as gylcogen granules and lipid droplets, DNA is circular and is not associated with proteins, cytoplasm, Cell wall
94
What are the three structures that are not all found in prokaryotic cells?
Plasmid, capsule and flagellum
95
What is a plasmid?
Small circular piece of DNA
96
What is a capsule?
Mucilaginous layer of slime
97
What is a flagellum?
Its a similar like tail used for locomotion
98
In bacteria, what is the cell wall made up of?
Murein (peptidoglycan) - polymer of polysaccharide and peptide
99
What is the role of the cell surface membrane?
Acts as a differentially permeable layer, controlling the entry and exit of chemicals
100
What is the role of the capsule?
Protects bacterium from other cells and helps groups of bacteria to stick together for further protection
101
Viruses are acellular, what does this mean?
Viruses are not cells
102
Are viruses living or non living? And why?
Non living because they do not reproduce by themselves (with a host only) and cannot process metabolic reactions to allow reproduction.
103
What does viruses contain that can reproduce only in a host?
Nucleic acids
104
What is a capsid?
A nucleic acid which is enclosed within a protein coat
105
Mitosis produces two ________ ____ that have the same number of _______________ as the parent cell and each other.
daughter cells, chromosomes
106
Meiosis produces _ daughter cells, each with ____ the number of chromosomes of the parent cell
4, half
107
What is mitosis?
a division of a cell that results in each of the daughter cells having an exact copy of the DNA as the parent cell.
108
Mitosis is always preceded by a period during which the cell is not dividing, what is this process called?
Interphase
109
What is interphase?
A period of considerable cellular activity that includes a very important event, the replication of DNA.
110
Two copies of DNA after DNA replication remain where in a cell?
the centromere
111
What happens in prophase?
1) Chromosomes become visible 2) Chromosomes shorten and thicken 3) Centrioles move to opposite poles of the cell 4) Spindle fibres form from the centrioles 5) nuclear envelope breaks down 6) nucleolus disappears
112
What happens in Metaphase?
1) Chromosomes come across to be made up of 2 chromatids 2) chromatids are joined by the centromere 3) spindle fibres attach to the chromosomes attach to the centromere 4) the chromosomes are pulled to the equator by the spindle fibres to which they are attached to
113
What happens in Anaphase?
1) centromere divides into 2 2) spindle fibres pull the individual chromatids of each chromosome towards opposite poles 3) now can be referred as chromosomes
114
What happens in telophase ?
1) chromosomes reach their respective poles and become longer and thinner, finally disappearing all together. 2) left widely spread chromatin 3) spindle fibres disintegrate and the nuclear envelope and nucleolus re-forms.
115
what happens in cytokinesis?
the cytoplasm divides into 2, a separation in 2 daughter cells.
116
Cell division in prokaryotic cells takes place by a process called?
Binary Fission
117
What happens in binary fission? (4 simple steps)
1) Circular DNA molecule replicate and both copies attach to the cell membrane 2) plasmids replicate 3) cell membrane grows between 2 DNA molecules, pinching inwards, dividing of cytoplasm into 2 4) cell wall forms between 2 DNA molecules, original cell into 2 daughter cells , each with copy of circular DNA and variable number of plasmids.
118
How do viruses replicate?
1) attaching to the host cell with attachment proteins on their cell surface membrane 2) injects its nucleic acid into cytoplasm of host cell 3) produces viral components inside cell 4) assembles new viruses
119
What are the 3 importance for mitosis?
Growth, repair and reproduction.
120
In the Cell Cycle there are 3 stages what are they in order?
1) interphase 2) nuclear division (mitosis or meiosis) 3) cytokinesis)
121
What is the length of a complete cell cycle in a mammalian cell? What % is interphase?
24 hours, 90% interphase
122
The rate of mitosis can be affected by what?
1) the environment of the cell and by growth factors 2) two types of gene - mutations
123
in the treatment of cancer, how can we block a part of the cell cycle to kill dividing abnormal cells?
1) preventing DNA from replicating 2) inhibiting he metaphase stage of mitosis by interfering with spindle formation
124
Use of drugs can disrupt the cell cycle of healthy cells, why is this bad?
Hair producing cells divide rapidly and are vulnerable to damage
125
Drugs are useful for killing abnormal cells. True or False
True
126

A Level Aqa Biology (10 decks)

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