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A-Level OCR Biology > Chapter 2 - Basic components of living systems > Flashcards

Chapter 2 - Basic components of living systems Flashcards

(106 cards)

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1
Q

What are the two lenses of a compound light microscope?

A

The objective and eyepiece lens

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2
Q

Where is the objective lens positioned?

A

Near the specimen

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3
Q

Where is the eyepiece lens positioned?

A

Near your eye

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4
Q

How do the objective and eyepiece lens work together and what does this allow for?

A

The objective lens produces a magnified image, which is magnified again by the eyepiece lens. This allows for much higher magnification and reduced chromatic aberration

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5
Q

What are transmission electron microscopes (TEMs)?

A

Where a beam of electrons is transmitted through a specimen

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6
Q

What are scanning electron microscopes (SEMs)?

A

Where a beam of electrons Is sent across the surface of a specimen and the reflected electrons are collected to produce the image

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7
Q

What type of image will SEMs give?

A

3D

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8
Q

3 pros of light microscopes

A

Inexpensive
Small and portable
Simple sample preparation

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9
Q

In electron microscopes, what do the specimens have to be?

A

Dead

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10
Q

3 difference between light and electron microscopes

A

In electron a vacuum is required, black and white images are produced and specimens must be dead, whereas in light a vacuum is not required, the natural colour or staining of specimen is seen and specimens can be living or dead

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11
Q

What is an artefact?

A

A visible structure detail caused by the processing of the specimen, not a feature of a specimen

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12
Q

What often causes artefacts in light microscopes?

A

Bubbles trapped under the cover slip

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13
Q

What often causes artefacts in electron microscopes?

A

Changes in the structure of the cell are inevitable, due to the processing that samples must undergo

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14
Q

Which has the best resolution, SEMs or TEMs?

A

TEMs, with a resolving power of 0.5nm compared to 3-10nm

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15
Q

How do laser scanning confocal microscopes work?

A

It moves a single spot of focused light across a specimen (point illumination). This causes fluorescence, which is sent back up through a pinhole opening and detected by the detector

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16
Q

What is fluorescence?

A

The absorption and re-radiation of light

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17
Q

What happens to the out of focus light and what does this mean for the resolution in confocal microscopy?

A

The out of focus light is blocked and does not pass through the pinhole, and so is not detected. This light from other parts of the specimen would reduce resolution and cause blurring, however this is prevented

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18
Q

2 uses of confocal microscopes

A
  • Diagnosis of diseases of the eye

- Development of new drugs, as it can see the distribution of molecules

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19
Q

What does the use of a laser in confocal microscopes mean?

A

A higher light intensity, which improves illumination

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20
Q

What is the definition of resolution?

A

The shortest distance between two points that can be distinguished

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21
Q

Where is the nucleolus?

A

An area within the nucleus

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22
Q

What is the nucleolus composed of?

A

A higher density of proteins and RNA

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23
Q

What is the nucleolus responsible for?

A

Producing ribosomes

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24
Q

How are ribosomes formed?

A

RNA is used to produce ribosomal RNA, which is then combined with proteins

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25
What are mitochondria the site of?
The final stages of cellular respiration
26
Where is ATP stored?
Mitochondria
27
What are vesicles?
A single membrane with fluid inside
28
What are the roles of vesicles?
Storage and to transport materials around the cell
29
What are lysosomes?
Specialised forms of vesicles that contain hydrolytic enzymes, which can be used to break down cells
30
What are the roles of lysosomes?
Breakdown of waste material in cells: - Programmed cell death - Breakdown of pathogens ingested by phagocytes
31
What is apoptosis?
Programmed cell death
32
What are the 3 components of the cytoskeleton?
Microfilaments Microtubules Intermediate fibres
33
What are microfilaments?
Contractile fibres formed from the protein actin
34
What are microfilaments responsible for?
Cell movement | Cell contraction during cytokinesis
35
What are microtubules formed from?
Globular tubulin
36
What are microtubules responsible for?
Determine the shape of the cell | Act as tracks for the movement of organelles around the cell
37
What do intermediate fibres do?
Give mechanical strength to cells | Help maintain cell integrity
38
What are centrioles composed of?
Microtubules
39
What are centrioles responsible for?
They form centrosome, which is responsible for the assembly and organisation of the spindle fibres during cell division
40
What is the smooth endoplasmic reticulum responsible for?
Lipid and carbohydrate synthesis | Storage
41
What is the rough endoplasmic reticulum responsible for?
The synthesis and transport of proteins
42
What is Golgi apparatus formed from?
Cisternae
43
What cell type is procaryotic?
Unicellular
44
What cell type is eukaryotic?
Unicellular but mostly multicellular
45
How do prokaryotic cells reproduce?
Binary fission
46
How do eukaryotic cells reproduce?
Asexual or sexual
47
What is the difference between binary fission and mitosis?
Mitosis is nuclear fission therefore only in eukaryotic cells. Binary fission is very similar to mitosis, however binary fission is for prokaryotic cells
48
What surrounds the nucleus?
The nuclear envelope
49
What is the cell wall primarily made out of in plants?
Cellulose
50
What is the cell wall made out of in fungi?
Chitin
51
What is the cell wall primarily made out of in animal cells?
There is no cell wall in animals
52
What is the general structure of a plant cell?
- A large vacuole in the centre of the cell - Cytoplasm surrounding the vacuole contains chloroplasts and a nucleus - Cell surface membrane and cell wall
53
What are vacuoles?
Membrane lined sacs in the cytoplasm containing cell sap
54
What do plant vacuoles contain?
Cell sap
55
What is the membrane of a vacuole in a plant cell called?
The tonoplast
56
What is the permeability of plant cell membranes?
It is selectively permeable, which means that some molecules can pass through but others cannot
57
What is found on rough endoplasmic reticulum?
Ribosomes
58
What do secretory vesicles do?
Carry proteins that are to be released from the cell
59
What happens on the ribosomes of endoplasmic reticulum?
Proteins are synthesised
60
What happens during protein production after the protein is synthesised?
They pass into the cisternae of the rough endoplasmic reticulum and are packed into transport vesicles
61
What happens during protein production after the newly synthesised proteins are packed into transport vesicles?
The vesicles move towards the Golgi apparatus via the transport function of the cytoskeleton
62
What happens during protein production as the proteins reaches the Golgi apparatus?
The proteins fuse with the cis-face of the Golgi apparatus before leaving the trans face in secretory vesicles
63
During protein production, what do the secretory vesicles do?
They carry proteins that are to be released from the cell. They fuse with the cell-surface membrane and release their contents by exocytosis
64
What two locations do you find ribosomes?
On rough endoplasmic reticulum and floating in the cytoplasm
65
What are ribosomes the site of?
Protein synthesis
66
Are ribosomes surrounded by a membrane and if so what are its properties?
No it is not
67
What is secretion?
Transport of out the cell
68
What are flagella and cilia?
Extensions that protrude from some cell types
69
What do flagella look like?
One long whip-like tail
70
What do cilia look like?
Many short hair-like extensions
71
What two forms can cilia be?
Stationary and mobile
72
What are the main roles of stationary cilia?
On the surface of many cells and have important functions in sensory organs (e.g. nose)
73
What are the main roles of mobile cilia?
Beat in a rhythmic manner, creating a current which causes fluids or objects to move
74
What is the permeability of plant cell walls?
Freely permeable
75
What is the 2 key purposes of plant cell walls?
- Give structure and shape to the cell | - Defence mechanism, protecting the contents of the cell from pathogens
76
What two structures are unique to plant cells?
- Vacuoles (if they appear in animal cells they are small and transient) - Chloroplasts
77
Where are chloroplasts found?
In the green parts of the cell (e.g. leaves and stem, but not in roots)
78
What membrane structure do chloroplasts have?
Double membrane
79
What membrane structure do mitochondria have?
Double membrane
80
What is the structure of the inner membrane of mitochondria and what does this form?
It is highly folded to form structures called cristae
81
What is the fluid interior of mitochondria called?
The matrix
82
What does mitochondria contain that is special, and what does this allow them to produce?
They contain a small amount of DNA, which allow them to produce their own enzymes and reproduce themselves
83
What is the stroma?
The fluid enclosed in the chloroplast
84
What are thylakoids?
Flattened sacs, which are formed by the internal network of membranes in chloroplasts
85
What do several thylakoids stacked together form?
Grana (singular Granum)
86
What are lamellae?
The membranes that grana are joined by
87
What do grana contain?
Chlorophyll pigments
88
What do chloroplasts contain that allow them to make their own proteins?
DNA and ribosomes
89
What is the purpose of the internal membranes?
To provide a large surface area that is required in photosynthesis
90
What is stroma similar to?
Cytoplasm in non-plant cells
91
Where are starch grains located in chloroplasts?
In the stroma
92
What is the singular of flagella?
Flagellum
93
What are extremophiles?
Organisms that were able to live in early Earth, which was very hostile
94
How is DNA in prokaryotes packaged?
- Only one molecule of DNA (a chromosome) | - This chromosome is supercoiled to make it more compact
95
What are the genes on the chromosome in prokaryotes grouped into, and what does this mean?
The genes are grouped into operons, which mean some genes are turned on and some off at times
96
What size are eukaryotic and prokaryotic ribosomes comparatively?
Eukaryotic ribosomes are larger than prokaryotic ribosomes
97
Which ribosomes are bigger, in eu or pro?
In eu the ribosomes are bigger
98
What is murein?
Another name for peptidoglycan, which is what pro cell walls are made from
99
How is eu cells DNA packaged?
- Multiple chromosomes that are supercoiled - Each wraps around a number of proteins called histones - This forms a complex for efficient packaging
100
What are histones?
What chromosomes in eu wrap around
101
What is chromatin?
The complex in which DNA forms in eu cells
102
Are eu organelles membrane bound?
Some are, some aren't
103
Are pro organelles membrane bound?
No
104
Why are cells stained?
To increase contrast | Cell components can more easily be distinguished
105
2 other roles of mitosis outside of the growth and repair of tissues
- Asexual reproduction | - Production of new stem cells
106
What is empty magnification?
Where increasing the magnification past a certain point results in no higher increase in resolution. So although the image will be more magnified, the resolution will remain low

A-Level OCR Biology (21 decks)

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