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Biology > Cell Structure > Flashcards

Cell Structure Flashcards

1
Q

When were cells first named?

A

In 1665 with the recent invention of the light microscope.

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2
Q

Give a brief summary of what cells contain.

A

Specialised organelles that perform specific roles.

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3
Q

What is magnification?

A

Magnification determines how large an object appears.

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4
Q

What is resolution?

A

Resolution determines how clear an image is.

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5
Q

Give 4 differences between eukaryotic and prokaryotic cells.

A
  1. E has nucleus, P does not.
  2. E has membrane-bound organelles, P does not.
  3. E has larger ribosomes.
  4. E has linear DNA, P has circular.
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6
Q

Which organelle is found in every cell?

A

Ribosome

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7
Q

How are the cell walls of plant cells and prokaryotic cells different?

A

Plant cell walls are made of cellulose whereas prokaryotic walls are made of murein.

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8
Q

Prokaryotes always have 5 structures. What are they?

A
  1. Cell wall
  2. Cell membrane
  3. Circular DNA
  4. Ribosomes
  5. Cytoplasm
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9
Q

Which 3 features of prokaryotes are only found in some species?

A
  1. Capsule
  2. Plasmid
  3. Flagellum
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10
Q

What is the difference between a capsule and a capsid?*

A

Capsids are found in viruses, whereas capsules are found in some prokaryotes.

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11
Q

Describe the cell surface membrane.

A
  • Phospholipid bilayer with membrane proteins.
  • Controls movement of substances into and out of the cell.
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12
Q

Describe the nucleus.

A
  • Surrounded by a nuclear membrane.
  • Contains DNA.
  • Contains nucleolus (where RNA and ribosomes are formed).
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13
Q

Describe the smooth endoplasmic reticulum.

A
  • Synthesises, stores, and transports lipids and carbohydrates/lipid synthesis.
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14
Q

Describe the rough endoplasmic reticulum.

A
  • Ribosomes embedded throughout.
  • Large surface area for protein synthesis.
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15
Q

Describe the cell wall of eukaryotes.

A
  • Rigid with cellulose or chitin.
  • Provides protection and support.
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16
Q

Describe chloroplasts.

A
  • In plant cells only.
  • Contains DNA and chlorophyll to carry out photosynthesis.
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17
Q

Describe mitochondria.

A
  • Has folded inner cristae and own DNA.
  • Respire to produce ATP/Site of aerobic respiration.
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18
Q

Describe ribosomes in eukaryotes.

A
  • 80s
  • Protein and RNA complexes for protein synthesis.
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19
Q

Describe lysosomes.

A
  • Contain hydrolytic enzymes which can hydrolyse anything, but the most common function is phagocytosis.
  • Secrete harmful substances out of cell.
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20
Q

Describe the Golgi apparatus.

A
  • Responsible for transport and modification of proteins.
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21
Q

Describe the permanent vacuole.

A
  • Only in plant cells.
  • When full of water, they make the cell rigid (which helps the plant to be rigid).
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22
Q

Describe flagella in cells.

A
  • Contain tails for locomotion.
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23
Q

Describe cilia in cells.

A
  • Membrane projections to increase surface area for absorption.
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24
Q

Describe centrioles in cells.

A

A pair of small cylindrical organelles outside of the nucleus.

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25
Q

What name is given to nuclear material where chromosomes are condensed and not visible?

A

Chromatin

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26
Q

How do prokaryotes divide? Why isn’t it called mitosis?

A
  • Binary fission
  • Because they have no chromosomes.
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27
Q

What formula is used to work out how many bacteria you end up with after some time?

A

Number to begin with x 2 to the number of generations.

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28
Q

What is a nucleolus or nucleoli (plural)?

A

A more densely staining region of the nucleus were the ribosomes are made.

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29
Q

What is a ribosome made out of?

A

Ribosomal RNA (rRNA and protein).

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30
Q

Give 3 features of plant cells that aren’t present in animals cells.

A
  • Chloroplasts
  • Vacuole
  • Cellulose cell wall
31
Q

What is a tonoplast?

A

Membrane of the permanent vacuole.

32
Q

Define a tissue.

A

Similar cells carrying out a similar function (i.e., they all come from the same type of stem cell.)

33
Q

Define an organ.

A
  • A structure with more than one tissue.
34
Q

What is point of homogenisation?

A

To burst open cells.

35
Q

What 3 precautions are necessary in homogenisation?

A
36
Q
A
  • It must be cold to slow down enzymes that would otherwise hydrolyse organelles.
  • Isotonic (same water potential) to prevent water movement into or out of organelles.
  • Buffered to prevent pH changes that may denature proteins.
37
Q

Explain how you use a centrifuge to get isolated mitochondria/chloroplasts/nuclei etc.?

A
  1. Centrifuge the homogenate at low speed. The first pellet will be the nuclei, as they are the most dense.
  2. If nuclei are not what you want, then pour the supernatant into a new test tube.
  3. Centrifuge this tube faster for longer.
  4. The pellet will be mitochondria or chloroplasts depending on the tissue (plant or animal) you started with.
38
Q

Why might you filter the homogenate between homogenisation and centrifugation?

A

To remove any whole cells (that didn’t break open) or debris.

39
Q

What are the four main types of microscopy?

A
  1. Optical microscopy
  2. Laser scanning confocal microscopy (LSCM)
  3. Transmission electron microscopes (TEM)
  4. Scanning electron microscopes (SEM)
40
Q

Describe an optical microscope.

A
  • Uses light to look at living samples.
  • At low resolution and magnification.
41
Q

Describe laser scanning confocal microscopes (LSCM).

A
  • Use light in lasers to achieve a higher resolution than optical microscopes.
  • Cannot achieve the magnification of electron microscopes.
  • Allows for depth selection and can construct a 3d model using computers.
42
Q

Describe transmission electron microscopes (TEM).

A
  • Pass electrons through a sample.
  • Get high magnification and resolution of a cell’s organelles.
  • Can only provide a flat cross-sectional image.
43
Q

Describe scanning electron microscopes (SEM).

A
  • Bounces electrons off the surface for 3d surface view.
  • But has lower resolution.
44
Q

Why is greater magnification and detail possible with electron microscopes rather than light?

A

A beam of electrons has shorter wavelength which gives a much greater resolution.

45
Q

How do you know an image has come from SEM rather than TEM?

A
  • It will be 3d rather than 2d.
  • It will show the outsides of structures rather than internal structures.
46
Q

Give two advantages of light microscopy over electron.

A
  1. Easier and cheaper.
  2. Specimens can be living, so movement etc. can be observed.
47
Q

Give 4 ways in which a TEM is different to a SEM.

A
  1. TEM has higher resolution than SEM.
  2. TEM gives image of internal structures whereas SEM gives external.
  3. TEM gives 2d image whereas SEM gives 3d image.
  4. With TEM, sections much be thinner than SEM.
48
Q

How many micrometers in a millimetre?

A

1000

49
Q

How many nanometres in a millimetre?

A

1000000

50
Q

What is an artefact in microscopy?

A

Something in the image that was not naturally present but occurs as a result of the preparation of the slide.

51
Q

What is a cell?

A

Basic structural and functional unit of life.

52
Q

Define eukaryotic cell.

A

Cell with a nucleus and other membrane-bound organelles.

53
Q

Define ultrastructure.

A

The ultrastructure of a cell is those features which can be seen by using an electron microscope.

54
Q

What is the difference between the nucleus, nucleolus, and nuclear envelope?

A
  • Nucleus: Contains coded genetic information in the form of DNA. Directs protein synthesis and controls metabolic activities of the cell.
  • Nucleolus: Area within the nucleus responsible for producing ribosomes. Composed of proteins and RNA.
  • Nuclear envelope: Double membrane surrounding nucleus and protects it from damage. Has nuclear pores allowing molecules to move in and out of the nucleus.
55
Q

Describe the process of protein synthesis.

A
  1. RNA leaves nucleus through nuclear pores.
  2. Protein synthesised on ribosomes on RER.
  3. RER packages proteins and pinches them into vesicles for transport.
  4. Vesicles move to Golgi apparatus using cytoskeleton.
  5. In Golgi apparatus, vesicles fuse with cis face of Golgi.
  6. Proteins are structurally modified.
  7. They then leave in vesicles from trans face.
  8. Secretly vesicles carry proteins to cell membrane.
  9. Vesicles fuse with cell surface membrane releasing contents by exocytosis.
56
Q

What are the 3 components of the cytoskeleton .

A
  1. Microfilaments
  2. Microtubules
  3. Intermediate fibres
57
Q

Describe microfilaments.

A
  • Contractile fibres formed from protein actin.
  • Responsible for cell movement + contraction during cytokinesis.
58
Q

Describe microtubules.

A
  • Globular tubular proteins polymerise to form rubes that form scaffold-like structure.
  • Determines shape of cell + are tracks for organelle movement e.g., vesicles.
  • Spindle fibres are microtubules.
59
Q

What component of the cytoskeleton are spindle fibres?

A

Microtubules

60
Q

Describe intermediate fibres.

A
  • Mechanical strength + help maintain integrity.
61
Q

Describe the 3 functions of the cytoskeleton in a cell.

A
  1. Strength
  2. Shape
  3. Movement
62
Q

Describe the importance of the cytoskeleton in the shape and behaviour of neutrophils.

A
  • Neutrophils have multi-lobed nucleus and are very flexible to squeeze through small gaps so they can get to the site of infection.
63
Q

Describe the importance of the cytoskeleton in the movement of cilia.

A
  • Cilia/flagella - 9+2 arrangement.
  • 2 central microtubules + 9 pairs.
  • Pairs of parallel microtubules slide over one another - beating motion.
64
Q

Define prokaryotic cell.

A

Cells with no membrane-bound nucleus or organelles.

65
Q

What are examples of eukaryotic cells?

A

Plant, animal, fungi

66
Q

What are examples of prokaryotic cells?

A

Bacteria

67
Q

Describe prokaryotic cell wall.

A
  • Murein or peptidoglycan.
  • Maintains structure.
68
Q

Describe prokaryotic ribosomes.

A
  • Smaller: 70s
  • Responsible for protein synthesis.
69
Q

Describe bacterial flagellum.

A
  • Thinner
  • No 9+2
  • Rotates with whip-like movement to propel cell along.
70
Q

Describe plasmid (P)

A

Rings of DNA in cytoplasm

71
Q

Describe bacterial chromosome (P)

A
  • Supercoiled to make compact.
  • Genes are grouped into operons so turned on/off together.
72
Q

Describe pili (P)

A
  • Organelles of adhesion allowing bacteria to colonise environmental surfaces or cells, and resist flushing.
73
Q

Describe slime capsule (P)

A
  • Mucus layer
  • Defence, moisture
74
Q

Describe endosymbiotic theory.

A
  • Evidence that mitochondria and chloroplasts were one primitive bacterial cells.
  • Symbiosis occurs when two different species benefit from living and working together.
  • Endosymbiosis is when one organism lives inside the other.
  • This theory describes how a large host cell and indigested bacteria could easily become dependant on each other for survival, resulting in a permanent relationship.
  • Over millions of years of evolution, mitochondria and chloroplasts have becomes more specialised and today, they cannot live outside the cell.

Biology (25 decks)

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