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CIE AS Level Biology > Topic 1 > Flashcards

Topic 1 Flashcards

1
Q

Define magnification.

A

It is the number of times an object is larger than its actual size.

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2
Q

What is the formula for magnification?

A
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3
Q

Define resolution.

A

Is the ability of a microscope to distinguish between two points/objects, where the higher the resolution of an image, the greater the details that can be seen.

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4
Q

How is resolution calculated?

A

Resolution is calculated as about 1/2 of shortest wavelength of the radiation used to view the specimen.

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5
Q

State some units of measurements and their conversions.

A
  1. 1 cm = 10⁴ μm = 10⁷ nm
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6
Q

What is the maximum magnification of a light microscope and what does it depend on?

A

x 1500, and it depends on the strength of the objective and eyepiece lenses.

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7
Q

Why can’t 2 points closer together than 200nm be distinguished as separate?

A
  1. As it uses visible light, organelles might be too small to interfere with light.
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8
Q

Why are most biological substances stained before being observed by a light microscope?

A

If an object is transparent, it will allow light waves to pass through it and therefore it won’t be visible. Staining allows them to become visible.

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9
Q

Describe some features of an electron microscope.

A
  1. Electron beam is used, as its wavelength is extremely short.
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10
Q

Why should an electron microscope be used rather than a light microscope?

A
  1. Electron beam is used.
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11
Q

Why should a light microscope be used rather than an electron microscope?

A
  1. Living specimens can be seen.
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12
Q

What is an eyepiece graticule?

A

Is a transparent scale of 100 divisions, placed in a microscope eyepiece.

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13
Q

What is a stage micrometer?

A

A microscope slide with a very accurate scale in micrometers engraved on it, allowing us to calibrate the eyepiece graticule.

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14
Q

Describe a prokaryotic cell.

A
  1. Diameter from 0.5-5.0 μm.
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15
Q

Describe a eukaryotic cell.

A
  1. Diameter up to 40 μm.
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16
Q

Describe the structure of a virus.

A
  1. Non-cellular, very small in size from 20 to 300nm.
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17
Q

Why are viruses called parasites?

A

They don’t show the typical features of living organisms (don’t feed, respire, excrete, move, grow or respond to the

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18
Q

What are membranous organelles?

A

These are organelles which are separated from cytoplasm by their membranes to have optimum pH and specific functions.

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19
Q

What do membranous organelles include?

A

Nucleus, mitochondria, chloroplast, large vacuoles, ER, Golgi apparatus, lysosomes, and secretory vesicles.

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20
Q

What do non-membranous organelles include?

A

Ribosomes, starch grains, glycogen granules, cilia, centrioles, and flagella.

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21
Q

Describe the endoplasmic reticulum.

A
  1. It’s a membrane bound organelle.
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22
Q

Describe the structure of the rough endoplasmic reticulum (RER).

A
  1. It is covered with many ribosomes (80S).
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23
Q

Describe the functions of the rough endoplasmic reticulum (RER).

A
  1. Protein/polypeptide synthesis by its ribosomes.
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24
Q

Define glycosylation.

A

Is the process by which a carbohydrate is covalently attached to a target macromolecule, typically proteins and lipids.

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25
Describe the structure of the smooth endoplasmic reticulum (SER).
1. It is not covered with ribosomes.
26
Describe the function of the smooth endoplasmic reticulum (SER).
Synthesis of lipids and steroids such as cholesterol and the reproductive hormones oestrogen and testosterone.
27
Describe the structure of ribosomes.
1. They are small, non-membranous organelles.
28
What are the two types of ribosomes?
1. 70S which are small (18 nm) and found in prokaryotes, mitochondria and chloroplast.
29
Describe the function of ribosomes.
1. Site of translation and protein synthesis.
30
Describe the structure of the Golgi apparatus.
1. Appears as a stack of flattened membrane bound sacs called cisternae, with no connections between membranes.
31
How is the stack in Golgi vesicles formed?
The stack is being constantly formed at one end from fusion of vesicles which bud off from the ER and are broken down again at the other end to form Golgi vesicles that can move to the cell membrane to empty its content to the exterior of cell by exocytosis.
32
Describe the functions of the Golgi apparatus.
1. Golgi apparatus collect, process and allow chemical modification of proteins and lipids.
33
Describe how proteins made by the ribosomes reach the reach the cell surface membrane.
1. Proteins synthesized in the ribosomes are attached on the RER.
34
Describe the structure of lysosomes.
1. Exist in nearly all animal cells.
35
Explain why lysosomes contain hydrolytic enzymes.
To carry out the digestion of:
36
Where are the enzymes present in lysosomes synthesized?
1. Synthesized on RER and transported to Golgi body.
37
Describe the functions of lysosomes.
1. Releases enzymes outside the cell by exocytosis.
38
Define phagocytosis.
Substances (such as bacteria) are engulfed into phagocytes by endocytosis, to be digested by digestive enzymes.
39
Describe the structure and adaptations of mitochondrion.
1. About 1 μm in diameter.
40
What does porin (protein) do?
Forms wide, aqueous channels allowing the access of small, water-soluble molecules from the surrounding cytoplasm into the inter membrane space, and the exit of the synthesized ATP molecules to cell.
41
What is the function of cristae?
To increase surface available to carry more ATP synthase for
42
Define matrix.
Interior solution containing loops of DNA and 70S ribosomes to allow mitochondria to synthesize their own proteins and to replicate independently.
43
What is intermembrane space?
Is a fluid space between 2 membranes.
44
What are the functions of mitochondrion?
1. Site of aerobic respiration (in matrix solution and in the
45
Describe the role of ATP.
1. Once ATP is made, it leaves the mitochondria.
46
What is the endosymbiont theory?
Mitochondria and chloroplast were thought to originally be a prokaryotic cell that were engulfed by eukaryotic cells, as they have 70S ribosomes and circular DNA molecules.
47
Why do liver cells contain a lot of mitochondria?
Liver cells contain about 2000 mitochondria for more aerobic respiration and ATP production, which is used in:
48
Describe the structure of centrioles.
1. Non-membranous organelles.
49
Describe the functions of centrioles.
1. During nuclear division, they replicate at interphase, then move to poles and act as MTOCs to assemble spindle fibers.
50
Describe the structure of microtubules.
1. Long, rigid hollow tubes found in cytoplasm.
51
What do microtubules form?
Form part of the spindle fibers, which are attached to centromeres so sister chromatids can move to opposite poles during anaphase.
52
What are cilia and flagella?
1. They are whip like beating extensions of many eukaryotic cells.
53
What is the difference between cilia and flagella?
Cilia are short and numerous whereas flagella are long and are found one or two per cell.
54
Describe the structure of cilia.
1. Surrounded by an extension of cell surface membrane.
55
What are A and B microtubules?
1. A microtubule is a complete ring of 13 protofilaments.
56
Why is the structure of cilia referred to as "9 + 2" structure?
1. 2 as it has two central microtubules.
57
How does the beating mechanism of cilia and flagella occur?
1. The beating motion of cilia and flagellum is caused by the dynein (protein) arms which allows contact with the neighboring microtubules (MTDs).
58
What are the functions of cilia and flagella?
1. Single celled organisms use the beating action of cilia and flagella for locomotion.
59
What are microvilli?
1. Finger-like extensions of the cell surface membrane.
60
How are centrioles seen through different microscopes?
With an electron microscope we can see the 2 centrioles just outside the nucleus, while with a light microscope we see them as one only.
61
Where are centrioles located?
Centrioles found at the bases of cilia and flagella, where they are known as basal bodies, acting as MTOCs.
62
Describe the structure and adaptations of the nucleus?
1. Contains chromatin that is seen all the time except during cell division.
63
What are chromatin?
Loosely coiled state of chromosomes made of DNA coiled around histone proteins.
64
What is the nucleolus made up of?
It is a dense, spherical structure made from DNA, RNA and proteins.
65
What are the functions of the nucleus?
1. Controls all cell activities as it contains chromatin which carries genes responsible for controlling cell division, activities and inheritance.
66
What are the structures and adaptations of chloroplasts?
1. It is about 4-10 μm in diameter, so it can be seen and measured by a light microscope.
67
What does the internal membranous system in chloroplasts consist of?
1. Thylakoid: disc shaped cavities, their membrane carrying chlorophyll and enzymes.
68
What are the overall functions of the chloroplasts?
Site of photosynthesis.
69
What is the thylakoid a site of?
1. Light dependent reactions occur, where light energy is absorbed by chlorophyll.
70
What is the stroma a site of?
1. Light dependent reactions occur, involving carbon fixation by converting carbon dioxide into sugars in Calvin's cycle.
71
Describe the large and permanent vacuole in plant cells.
It is a sap-filled sac surrounded by a single membrane called tonoplast which controls exchange between cytoplasm and
72
What are the functions of the permanent vacuole in plant cells?
1. Gives turgidity to plant cells by building up turgor pressure on cell wall.
73
Describe the structure of the cell wall and plasmodesmata.
1. It is about 5 μm thick.
74
Describe the functions of the cell wall and plasmodesmata.
1. Gives the plant cell a definite shape.
75
What are the similarities between chloroplasts and mitochondria?
Both share 70S ribosomes, circular DNA, and double membrane bound organelles.
76
What are the differences between bacteria and mitochondria?
1. Mitochondria has no cell wall.
77
List the organelles according to their size starting from the largest.
Mitochondria > Nucleoli > Lysosomes > Centrioles > Ribosomes.
78
What organelles can be seen by a light microscope?
Nucleus, Cell wall, Cell membrane, Vacuole, Chloroplast, Mitochondria (with no details), and Nucleoli.
79
What organelles can only be seen with an electron microscope?
Lysosomes, Centrioles, Ribosomes, Endoplasmic reticulum, Golgi body, Chloroplast grana, and all organelles seen by a light microscope.
80
Describe the structure of cellulose.
1. Lie parallel to each other, joined by intermolecular hydrogen bonds.
81
Where are microfibrils embedded?
Microfibrils are embedded in matrix, which has pectin that acts as a glue-like material holding microfibrils and preventing them from sliding against each other.
82
Describe the secondary cell wall.
1. More rigid and thicker, providing higher tensile strength and support.
83
When does the secondary cell wall form?
Once the primary cell wall stops growing, the secondary thickening takes place by lignin deposition.
84
What are the functions of plant cell walls?
1. Mechanical strength and support for individual cells and the plant as a whole.
85
Describe some means of supports for plants.
1. Lignification.
86
What are the functions of vacuoles?
1. Provide support.
87
How do vacuoles provide support?
1. The solution in the vacuole is relatively concentrated.
88
How do vacuoles in plant cells increase growth size?
Osmotic uptake of water into the vacuole is responsible for most of the increase in volume of plant cells during growth.
89
Define tissue.
A group of the same type of cells that perform one or more particular function.
90
Define organ.
Group of tissues that form a part of the body with a specific

CIE AS Level Biology (1 decks)

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