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Biology A-level > Cell Structure > Flashcards

Cell Structure Flashcards

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1
Q

What is a light microscope used for?

A

Observing living and dead specimen

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2
Q

What are the pros and cons of a light microscope?

A

Pros: Cheap, portable, easy to use, can study living specimens
Cons: Limited magnification, poor resolution

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3
Q

What is magnification?

A

A measure of how much larger the image of a specimen looks under the microscope

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4
Q

What is resolution?

A

The ability to distinguish two adjacent individual points as separate

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5
Q

By what process are large quantities of cell organelles collected?

A

Cell fractionation

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6
Q

What is cell fractionation?

A

The process of breaking up cells to separate out the organelles

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7
Q

The tissues to be fractionated are stored in a cold, osmotically balanced buffer, why?

A

Cold- reduces enzyme activity breaking down organelles.
Isotonic- Prevents bursting or shrinking due to osmosis
Buffered- Prevents pH fluctuations altering organelle and enzyme activity

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8
Q

What are the two stages of cell fractionation?

A

Homogenisation and ultracentrifugation

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9
Q

What is homogenisation?

A

Breaking up cells in a blender, releasing organelles into the homogenate

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10
Q

What is homogenate?

A

Fluid containing cell organelles, prior to ultracentrifugation

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11
Q

Why is the homogenate filtered?

A

To remove whole cells and large debris

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12
Q

How is ultracentrifugation carried out?

A

The homogenate filtrate is loaded into a centrifuge which spins until the heaviest is collected at the bottom. The remaining fluid is collected and spun at higher speeds.

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13
Q

What is the fluid collected from the centrifuge called?

A

Supernatent

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14
Q

What is the solid left in the centrifuge after the supernatent is collected called?

A

Sediment

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15
Q

What is a TEM used for?

A

Observing the internal ultrastructure of cells under high magnification and resolution

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16
Q

What is a SEM used for?

A

Viewing the surface of objects under high magnification and resolution

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17
Q

What are the limitations of a TEM?

A
  • Thin specimen
    preparation may create artefacts
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18
Q

What are TEM artefacts?

A

Created during sample preparation. May be mistaken for cellular components

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19
Q

What is the difference between a TEM and SEM?

A

TEM sends a beam of electrons through the specimen whilst SEM bounces electrons off the surface

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20
Q

What is the difference in images between the TEM and SEM?

A

TEM- 2D
SEM- 3D

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21
Q

What is an eye-piece graticule?

A

Small ruler on a light microscopes eye piece. Used to measure specimens

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22
Q

What is a stage micrometer?

A

A mm long ruler etched onto a slide. It has 100 divisions. Used to calibrate the eye piece graticule

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23
Q

What is the structure of the nucleus?

A

Nucleoplasm, double membrane (nuclear envelope), chromosomes, nucleolus

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24
Q

What is the function of the nucleus?

A

Stores the human genome controls the cell by providing instructions for protein synthesis

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25
What is the structure and function of the nucleolus?
Spherical region of the nucleus, produces ribosomes.
26
What is the structure and function of the nuclear envelope?
Double membrane embeded with channel proteins, forming pores. Separates the nucleus with the rest of the cell. Pores allow ribosomes and mRNA to leave the nucleus
27
What is the structure of the RER?
Continues with nuclear envelope. Large SA formed by folding Covered with ribosomes
28
What is the function of the RER?
Synthesis of proteins and glycoproteins. Provides a pathway to transport materials
29
What is the structure and function of the SER?
A system of fluid filled membranes and no ribosomes. Synthesises, stores and transports lipids and carbohydrates
30
What is the structure and function of the golgi apparatus?
Sack of flattened membrane bound sacs called cisternae. Vesicles from ER bring products to be modified. Adding sugar= glycoproteins. Adding lipids= glycolipids
31
What is the structure and function of ribosomes?
Made of rRNA. 2 subunits, large and small. Protein synthesis
32
What is the structure and function of the mitochondria?
Site of aerobic respiration, producing ATP Inner membrane folded into cristae with fluid filled matrix
33
What is the structure and function of lysosomes?
Membrane bound sacs containing hydrolytic enzymes. Break down cells after death and destroy foreign matter.
34
What is the structure and function of the chloroplast?
Granum stacked into thylakoids surrounded by a fluid matrix called the stroma. Site of photosynthesis
35
What is the structure and function of cell wall?
Made of polysaccharides, bundles of cellulose fibres in plants, chitin in fungi. Allows solutions through
36
What is the structure and function of the vacuole?
Has membrane called the tonoplast, fluid filled membrane. Contains salts, sugars, amino acids, waste and sometimes pigments. Provides structure by making cells turgid. temporary food store and provides colours to plants attracting insects
37
What is the structure and function of the plasma membrane?
Phospholipid bi layer, cholesterol, proteins, glycolipids, glycoproteins. Separates cell contents from external environment. controls what enters and exists the cell.
38
Why do multicellular organisms have specialised cells?
Specific functions can be performed
39
What is the hierarchy of organisation in terms of cells in an organism?
Cells, tissues, organs, organ system, organism
40
How do cells become specialised?
Certain genes are expressed and certain genes are not
41
What is a tissue?
A group of similar cells working together to perform a specific function
42
Describe epithelial tissue
Sheet of cells that typically line organs. Protective or secretory.
43
What is an organ?
A collection of tissues, coordinated to preform specific functions
44
What is an organ system?
A group of organs working together as a single unit
45
What is the difference between prokaryotic and eukaryotic cells?
Eukaryotic- Larger and have a membrane bound nucleus Prokaryotic- Smaller and have no nucleus or nuclear envelope
46
What is the main structures of bacterial cells?
Cell wall, capsule, cell surface membrane, circular DNA, plasmids
47
What is the role of the cell wall in bacteria?
Physical barrier, protects against damage and osmotic lysis
48
What is the role of the capsule in the bacteria?
Protects against other cells, allows bacteria to stick together for protection
49
What is the role of the cell surface membrane?
Differentially permeable, controls entry and exit of chemicals
50
What is the role of circular DNA in bacteria?
Contains genetic information for replication
51
What is the role of plasmids in bacteria?
Possess genes that may aid survival
52
How is the organisation of DNA different from pro to euk?
Pro DNA is not associated with proteins, euk DNA are wrapped around histones
53
How are plasmids different from pro to euk?
Prokaryotes have rings of DNA called plasmids
54
How are organelles different from pro to euk?
Pro has no membrane bound organelles
55
How do ribosomes differ from pro to euk?
Pro- 70s euk- 80s
56
How do cell walls differ from pro to euk?
Pro- Made of meurin Euk- Cellulose in plants, chitin in fungi
57
What is the basic structure of the virus?
Extra lipid coat, capsid
58
Where do viruses reproduce?
Host cells
59
What do attachment proteins allow the virus to do?
Identify itself and attach to a host cell
60
What are the two methods of cell division?
Mitosis and meiosis
61
What is the stage of the cell cycle in which the cell is not dividing?
Interphase
62
What are the main stages of mitosis?
Prophase, metaphase, anaphase, telophase and cytokinesis
63
Describe prophase?
- Nuclear envelope breaks down - Chromosomes condense - Nucleolus disappears - Spindle fibres start to form spindle apparatus
64
How is prophase different between animals and plants?
2 centrioles move the poles of the cell, plants do not have centrioles
65
Describe metaphase
Chromosomes are made of two chromatids that line up along the equator. Microtubles attach to centromeres pulling the chromosomes along the spindle apparatus
66
Describe anaphase
Sister chromatids pulled to opposite poles by spindle fibres. The chromatids are now chromosome
67
. What can stop anaphase?
Chemicals that destroy spindle fibres
68
Where does energy for anaphase come from?
Mitochondria which surround spindle fibres
69
Describe telophase
Nuclear envelope reforms around each set of chromosomes. - Chromosomes disappear leaving chromatin - Nucleolus reappears
70
What happens during cytokinesis?
Cell separates. Membrane pinches in to fuse causing the cytoplasm to divide
71
What is the name of the cell division in prokaryotes?
Binary fission
72
What happens in binary fission?
1. Circular DNA replicates and attaches to the cell membrane 2. Plasmids replicate 3. Cell membrane pinches in between the DNA to divide the cytoplasm 4. New cell wall forms in the middle of the cell dividing it into two identical daughter cells.
73
How do viruses replicate?
Attach to CD4 on T helper cell using attachment proteins. Fuses with membrane to inject reverse transcriptase and RNA into host cell which replicates the virus
74
What is happening during interphase?
DNA and organelles replicated
75
How are tumours linked to cell division?
Caused by uncontrolled cell division
76
What are the types of tumours?
Benign or malignant (cancerous)
77
Why do cells replicate by mitosis?
Growth and repair (replace damaged cells)
78
What affects the rate of cell division?
Environment, growth factors and 2 genes
79
What happens if the genes controlling cell division are damaged
Uncontrolled mitosis
80
If uncontrolled mitosis due to mutation occurs, how does this affect cells being created?
Typically they die or are destroyed as they are structurally and functionally different
81
If damaged cells created the genetic mutation survive, what could happen?
Clone themselves and form tumours

Biology A-level (22 decks)

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