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Biology OCR A A level > Cells > Flashcards

Cells Flashcards

(67 cards)

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1
Q

What are the three things that cell theory states?

A

Both plant and animal tissue is composed of cells
Cells are basic units of all cells
Cells only develop from existing cells

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2
Q

How does a compound light microscope work?

A

The objective lens is placed near the object and originally magnifies the image, the eyepiece lens then magnifies the image further

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3
Q

What are the pros of having an objective and eyepiece lens?

A

Allows for increased magnification

Reduced chromatic abberation

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4
Q

Describe the process of ‘sectioning’

A

Solid specimens are cut into very thin slices with a sharp blade

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5
Q

Describe preparation of a ‘dry mount’?

A

Solid samples cut into thin samples, specimen placed on centre of slide, cover slip placed over the top

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6
Q

Describe preparation of a ‘wet mount’

A

Sample placed in a suspension of liquid, coverslip placed on the slide at an angle

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7
Q

Describe preparation of ‘squash slide’

A

Wet mount prepared, lens tissue used to gently press down coverslip, done between two microscope slides to prevent cracking

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8
Q

Describe preparation of ‘smear slide’

A

Edge of slide used to smear sample to create one thin layer, microscope slide placed on the top

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9
Q

How does contrast in staining occur?

A

Different components take up different levels of stain so they appear different colours, making it more easily visible

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10
Q

Give 2 examples of positively charged dyes and explain how they work

A

Crystal violet and Methylene Blue

Attracted to negatively charged components which stains them

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11
Q

Give 2 examples of negatively charged dyes and explain how they work

A

Nigrosin or Congo Red
The dyes stay outside the cell so causes cell to be unstained which means it stands out against the background stained colour

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12
Q

Define magnification

A

How many times larger the image being viewed is than the actual image

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13
Q

Define resolution

A

The ability to see two objects as separate entities

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14
Q

How can resolution be increased?

A

By using a beam of electrons which has a wavelength thousands of times less than light

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15
Q

What is the equation for calculating magnification?

A

Size of Image/ Size of actual object

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16
Q

What is the limiting factor in light microscopy?

A

Resolution

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17
Q

What is an artefact?

A

A structure that is produced during the preparation of a slide

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18
Q

What is transmission electron microscopy?

A

A beam of electrons transmitted through a specimen and focused to produce an image

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19
Q

What is the resolution of a transmission electron microscope?

A

0.5nm

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20
Q

What is scanning electron microscopy?

A

A beam of electrons being sent across the surface of a specimen and reflected electrons are collected

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21
Q

What is the resolution of a scanning electron microscope?

A

3-10nm

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22
Q

What is fluorescence?

A

The absorption and reradiation of light

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23
Q

Explain how laser scanning confocal microscopy works

A

Single spot of focused light moved across the specimen
Fluorescence occurs from components with a dye
The emitted light is passed through a pinhole
Light in the plane of pinhole detected and creates an image

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24
Q

What is laser scanning confocal microscopy used in?

A

Diseases of the eye and aims to be used in endoscopic procedures

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25
What does the nucleus contain?
Genetic information in the form of DNA molecules
26
What is the and what is the role of the nuclear envelope?
Double membrane to protect DNA from damage in the cytoplasm
27
What is the role of nuclear pores?
Small holes in the cell membrane to allow molecules to leave
28
Describe the process of chromosomes forming
DNA associates itself with a protein called histone to form a complex called chromatin. Chromatin coils and condenses to form chromosomes.
29
What is the nucleolus responsible for?
Producing ribosomes
30
How does the nucleolus carry out its function?
Composed of RNA and proteins RNA is used to produce rRNA rRNA combined with proteins to form ribosomes
31
What is the role of the mitochondria?
Final site of cellular respiration, energy stored in the bonds becomes available in the form of ATP
32
Explain structure and function of the membranes within the mitochondria
2 membranes Folded to form cristae Membrane forming cristae contains enzymes used in aerobic respiration
33
What are vesicles and what are their roles?
Membranous sacs which have storage and transport roles
34
What are lysosomes and what are their roles?
Specialised vesicles which contain hydrolytic enzymes. Responsible for breaking down waste materials, phagocytosis and apoptosis.
35
What is the role of the cytoskeleton?
Network of fibres necessary for shape and stability of cell
36
What are microfilaments?
Contractile fibres formed of the protein actin
37
What are the roles of microfilaments?
Cell movement and cell contraction during cytokinesis
38
What are microtubules?
Globular tubulin proteins that polymerise to form tubes
39
What are the roles of microtubules?
Shape of cell, tracks for movement, physical segregation of chromosomes
40
What are the roles of intermediate fibres?
Mechanical strength and help maintain integrity
41
What is the centrosome and what is its role?
Two associated centrioles, involved in assembly and organisation of spindle fibres during cell division
42
What are the two roles of the flagella?
Motility and sensory organelle
43
What are the two types of cilia? Give an example of where each one is found
Stationary(nose) & Mobile(trachea)
44
What is the arrangement of microtubules in cillium?
9+2 (2 central, 9 around- wheel shaped)
45
What is the role of the smooth endoplasmic recticulum?
Lipid and carbohydrate synthesis and storage
46
What is the role of the rough endoplasmic recticulum?
Protein storage and synthesis
47
What is the role of the golgi apparatus?
Modifying proteins and packaging
48
Explain the process of protein production
Proteins synthesised on ribosomes on RER Passed into cisternae and placed into vesicles Vesicles moves proteins to golgi apparatus via cytoskeleton Vesicles enter via cis face, modified and leave via trans face Secretory vesicles move to cell membrane where leaves via exocytosis
49
What is a plant cell wall made of?
Cellulose
50
What are the roles of a plant cell wall?
Shape Rigidity Support Defence mechanisms
51
What is a vacuole?
Membrane lined sac in the cytoplasm containing cell sap
52
Why do plants have large vacuoles?
To maintain turgor by pushing contents of cell against cell wall
53
What is the tonoplast?
The membrane of a vacuole in a plant
54
What is the stroma?
The fluid enclosed in the chloroplasts
55
What are thylakoids?
Layers of internal membranes stacked on top of each other forming flattened sacs
56
What are the granum?
Several thylakoids stacked on top of each other
57
How are grana joined together?
By lamealle
58
What are chloroplasts?
Organelle responsible for photosynthesis
59
What is the role of grana?
Contain chlorophyll pigments where light dependent reactions occur during photosynthesis
60
How is DNA different in a prokaryote?
One molecule of DNA, a chromosome which is supercoiled to be more compact, with operons so certain genes are switched on and off at once
61
Where is DNA located in a prokaryote?
DNA free floating as plasmids in cytoplasm
62
What ribosomes are present in prokaryotic cells?
70S
63
What is a prokaryotic cell wall made from?
Peptidoglycan
64
What is the structure of a flagella in a prokaryotic cell?
Thinner, no 9+2 arrangement
65
How is energy supplied to flagella in prokaryotic cell?
Chemiosmosis not from ATP
66
What cell type is a prokaryotic cell?
Unicellular
67
What type of ribosomes are present in eukaryotic cells?
80S

Biology OCR A A level (17 decks)

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