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Section 2- Cell structure Flashcards

1
Q

What is resolution?

A

The minimum distance apart 2 objects can be in order for the to appear as separate items.

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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

How do you convert from millimetres to micrometres?

A

Multiply by 1000

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4
Q

What of these organelles does a virus have?

  • Cell-surface membrane
  • Nucleus
  • Cytoplasm
  • Capsid
A

Only capsid

no cell-surface membrane, nucleus, cytoplasm

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5
Q

Why can mitochondria look different to one another?

A

Very in shape

Cut in different planes

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6
Q

What are 3 reasons why mitosis is important to organisms?

A

Asexual reproduction
Growth in organisms
Repair in organisms

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7
Q

What are 3 ways DNA in chloroplast is different to DNA in nucleus?

A

Fewer genes

Shorter in length

No introns

Circular not linear

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8
Q

Why are organelle structures not visible in optical microscopes?

A

Resolution is not high enough

Light microscope have longer wavelength

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9
Q

What organelle is found in both chloroplast and prokaryotic cell?

A

Ribosomes

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10
Q

What type of cell wall is found in plants, algae, fungi and prokaryotes?
(cellulose, murein, chitin)

A

Plants: cellulose

Algae: cellulose

Fungi: chitin

Prokaryotes: murein

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11
Q

What is the structure of a prokaryote?

A

Cell wall

Capsule: protects bacteria form other cells

Cell-surface membrane

Circular DNA

Plasmid: has genes that may aid survival of bacteria

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12
Q

What is the difference between prokaryotic and eukaryotic cells?

A 
Eukaryotic cells:
Distinct nucleus with envelope
DNA associated with proteins
No plasmids, DNA is linear
Membrane bound organelles
Ribosomes are larger

Prokaryotic:
No nucleus
Some DNA in plasmids
No membrane-bound organelles
Ribosomes are smaller
Cell wall made of murein
Have capsule
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13
Q

What 2 types of molecules are ribosomes made from?

A

Ribosomal RNA

Protein

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14
Q

What is the molecule found in the cell walls of bacterial cells?

A

Murein

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15
Q

Why can light microscopes only distinguish between 2 objects if they are 0.2um apart?

A

Due to the relatively long wavelength of light.

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16
Q

What are the evaluative points for a light microscope?

A

Low resolution

  • Due to long wavelength of light
  • Limits magnification

Able to view living specimen

Able to see colour (with stain)

Simple preparation

Artefacts are rare

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17
Q

What are the evaluative points of an electron microscope?

A

Uses beam of electrons to produce an image

High resolution
-Short wavelength of electrons

Sample must be dead
-Chamber is a vacuum

Image produced is black and white

Preparation is complicated

Artefacts are common

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18
Q

What are the 2 types of electron microscope?

A

Transmission electron microscope

Scanning electron microscope

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19
Q

What is a transmission electron microscope?

A

Passes beam of electrons through a very thin specimen

Parts of the specimen allow electrons to pass through and so appear bright

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20
Q

What are the limitations of a transmission electron microscope?

A

Difficult preparation limits resolution

System is a vacuum = dead specimen

Image is 2D and black and white

May contain artefacts

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21
Q

What is a scanning electron microscope?

A

Produced a 3D image of the surface of the object

Resolution isn’t as high

3D image can be built by computer analysis of the pattern and secondary electrons

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22
Q

What are the 2 processes of cell fractionation?

A

Homogenisation

Ultracentrifugation

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23
Q

What 3 kind of solutions does a tissue need to be placed in before cell fractionation?

A

Cold
Isotonic
Buffer

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24
Q

What does a tissue need to be placed in a cold solution before cell fractionation?

A

Reduces activity of enzymes which may break down organelles

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25
Why does a tissue need to be placed in a isotonic solution before cell fractionation?
Prevent shrining and bursting due to osmosis
26
What does a tissue need to be placed in a buffer solution before cell fractionation?
To maintain a constant pH, avoiding damage to organelles
27
Why is a tissue firstly placed in a homogeniser and filtered before going in a centrifuge?
Releases organelles from the cells | Filtered to remove any whole cells and large debris (cell wall)
28
What is the process of cell fractionation?
1. Tissue placed in cold, isotonic, buffer solution. 2. Homogenisation 3. Filter homogenate 4. Centrifuge homogenate and collect sediment 5. Spin at faster speeds and collect sediment
29
What is the order of organelles in the sediment of an animal cell when centrifuged?
Nuclei Mitochondria Lysosomes
30
What is the structure and function of the mitochondria?
Double membrane: controls entry and exit of material Cristae (extensions of inner membrane): provide large surface area for enzyme attachment Matrix: contains proteins, lipids, ribosomes, DNA that allow mitochondria to control production of proteins
31
What is the structure and function of the chloroplast?
Chloroplast envelope: controls entry and exit of substances Grana: stacks of thylakoids which contain the chlorophyll Granal membranes provide large surface area Stroma: contain starch grains Grana & stroma: both for photosynthesis
32
What is the structure and function of the chloroplast?
Chloroplast envelope: controls entry and exit of substances Grana: stacks of thylakoids which contain the chlorophyll Stroma: contain starch grains Grana & stroma: both for photosynthesis
33
What is the structure and function of the smooth endoplasmic reticulum?
Synthesises and processes lipids Secretes steroids System of hollow tubes: allows transport of substances within cells Site of carbohydrate and lipid metabolism
34
What is the structure and function of the rough endoplasmic reticulum?
Covered in ribosomes: synthesise proteins which are transported through cell cavities Hollow tubes: allow transport of substances within the cell Folds and processes proteins that have been made at the ribosomes. Provides large surface area for synthesis of proteins and glycoproteins
35
What is the structure and function of the golgi apparatus?
Processes and packages new lipids and proteins Makes lysosomes Flattened membrane cavities: allows internal transport Vesicles: contain material to be secreted and protect molecules Connected to RER: proteins are modified before secretion
36
What is the structure and function of the lysosomes?
Vesicles which contain hydrolytic enzyme (lysozyme): break down old organelles Used to digest invading cells or break down worn out component of the cell
37
What is the structure and function of the ribosome?
80s- eukaryotic cells 70s- prokaryotic cells, mitochondria, chloroplast 2 subunits both made of protein and rRNA Provide binding site for mRNA which allow translocation of DNA code
38
What is the structure and function of the ribosome?
80s- eukaryotic cells 70s- prokaryotic cells, mitochondria, chloroplast 2 subunits both made of protein and rRNA Provide binding site for mRNA which allow translocation of DNA code
39
What is the structure and function of the cell wall?
Consists of microfibrils of cellulose embedded in a matrix Provide strength and rigidity
40
What is the structure and function of the vaculole?
Single membrane = tonoplast Fluid filled sac of cell-sap (sugar & salts) Helps to maintain pressure inside - stop plant wilting
41
Why is the electron microscope able to resolve objects better than the light microscope?
The electron microscope uses a beam of electrons that has a much smaller wavelength than light
42
Why do specimens have to be kept in a near-vacuum in order to be viewed effectively using an electron microscope?
Electrons are absorbed by molecules in the air which would prevent the electrons reaching the specimen
43
Why can the theoretical resolving power of an electron microscope not always be achieved?
Preparation of specimens may not be good enough Higher energy electron beam is required and this may destroy the specimen
44
Why can the theoretical resolving power of an electron microscope not always be achieved?
Preparation of specimens may not be good enough Higher energy electron beam is required and this may destroy the specimen
45
What is cell differentiation?
When a cell develops specific structures and becomes specialised to carry out a particular function
46
What are some common cell adaptations?
Folded membrane / microvilli = increase surface area Increases mitochondria = large amounts of ATP for active transport Walls one cell thick to reduce diffusion distance
47
What is the role of plasmids in prokaryotes?
Small ring of DNA that carries non-essential genes
48
What is the role of the flagella in prokaryotes?
Rotating tail propels organism
49
What is the role of the capsule in prokaryotes?
Protects bacterium from other cells and help groups of bacteria to stick together for further protection
50
What is the role of the circular DNA in prokaryotes?
Contains genetic material
51
What is the basic structure of a virus?
Capsid: protects genetic information Envelope Attachment proteins Genetic information
52
What are the 5 stages of a viruses life cycle?
``` Attachment Entry Replication Assembly Release ```
53
What are the 3 phases of the cell cyle?
Interphase: cell growth and DNA replication G1= cell growth S phase= DNA synthesises G2= proteins synthesised Nuclear division: mitosis/ meiosis Cytokinesis: division of cytoplasm
54
What is mitosis for?
Growth Repair Replacement Asexual reproduction
55
What is an advantage and disadvantage of mitosis?
Genetic make-up of parent has enabled survival and reproduction Genetic variation is limited
56
What are the 4 phases of mitosis?
Prophase Metaphase Anaphase Telophase
57
What happens during prophase of mitosis?
Chromosomes condense getting shorter and fatter Nuclear envelope breaks down, chromosomes lie free Centrioles start moving opposite ends, forming spindle
58
What happens during metaphase of mitosis?
Chromosomes line up along equator Chromosomes become attached to spindle by centromere
59
What happens during anaphase of mitosis?
Centromere divides, separating into chromatids Spindles contract, pulling chromatids to each pole
60
What happens during telophase of mitosis?
Chromatids reach opposite poles on the spindle Chromatids uncoil, becoming long & thin Nuclear envelope forms
61
How does cell division in prokaryotes occur?
Binary fission 1. Circular DNA molecule replicated, both copies attach to cell membrane 2. Cell membrane begins to grow between 2 DNA molecules, begins to pinch inwards 3. New cell wall forms between 2 molecules of DNA, divides original cell into 2 identical daughter cells
62
What are malignant tumours?
Grow rapidly Less compact Invade surrounding tissues More likely to be life-threatening
63
What is cancer caused by?
Mutation in gene causes uncontrolled mitosis Mutations can form clones of themselves, forming tumours
64
How do drugs normally treat cancer?
Prevent DNA replicating Inhibit metaphase by interfering with spindle formation
65
Why do ciliated cells contain relatively large numbers of mitochondria?
ATP produced is needed for the movement/ wafting of cilia.
66
Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells.
Nucleotide structure is identical Nucleotides joined by phosphodiester bond Eukaryotic DNA is longer, contains introns Eukaryotic DNA is linear, prokaryotic is circular Eukaryotic DNA is associated with histones, prokaryotic is not.
67
What would be a method of testing for starch?
Thin slice sample Stain with iodine
68
Why would a student use a homogeniser?
To break open cells
69
Why would a solution be buffered?
No change in pH To prevent denaturation of proteins
70
Why would students use a stain that turns DNA blue when observing mitosis?
Make chromosome visible Chromosome contains DNA
71
What would be a method of displaying results in a pie chart?
Draw circle (Number of section/ Total number) X 360 Use protractor
72
What is the stage of the cell cycle during which chromosomes replicate?
S phase in Interphase
73
What is a process that occurs during G1 and G2 of the cell cycle?
Growth of cell
74
How common is a flagellum in eukaryotic and prokaryotic cells?
Sometimes present in both
75
How could you improve a biological drawing?
``` No shading No overlapping lines Scale Title Labels of key features ```
76
When a fish is removed from water, their lamellae stick together. How can this be damaging to fish?
Lamellae stick together, surface area is reduced so not enough oxygen is absorbed
77
A different set of results were obtained when count was repeated in mitotic index with a different garlic root tip. Give two reasons for the difference in results.
Genetic difference, time, chance, age of root tip
78
What are 2 reasons why it is important to the count number of organelles in several parts of a tissue?
To obtain a reliable mean Distribution may not be uniform
79
What happens within a vacuole after it fuses with the lysosome?
Enzymes used in hydrolysis Digestion of bond
80
Why would an image of low magnification be of little use when studying cells?
Low resolution as wavelength of light is too long
81
Why do ciliated cells contain large numbers of mitochondria?
ATP is needed for movement of cilia

Biology (25 decks)

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