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Biology A-level > 2A Cell Structure and Division > Flashcards

2A Cell Structure and Division Flashcards

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1
Q

What is the formula for magnification?

A

Magnification = image size/actual size

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2
Q

Convert 4 mm to um

A

4000um

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3
Q

What is magnification?

What is it controlled by?

A
  • By how much an image is enlarged under a microscope

- The power of the lenses used

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4
Q

What is resolution?

What is it controlled by?

A
  • The minimum distance between two objects at which a microscope can distinguish them as separate entities
  • The wavelength of the illumination used
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5
Q

What are the 3 types of microscope?

A

Light microscope, TEM (Transmission Electron Microscope) and SEM (Scanning Electron Microscope)

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6
Q

Which type of microscope is the strongest?

A

TEM

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7
Q

Which type of microscope can you see colour?

A

Light microscope

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8
Q

Which type of microscope can you see 3D images with?

A

SEM

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9
Q

What can potentially be created with a TEM or SEM?

A

An artefact (a dust particle or air bubble)

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10
Q

What can we use to measure the size of an object?

A

An eyepiece graticule

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11
Q

What are the 3 stages of cell fractionation?

A
  • Keep cells in a cold, buffered isotonic solution
  • -> 1 Homogenisation
  • -> 2 Filtered
  • -> 3 Ultracentrifugation
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12
Q

What happens in homogenisation (Stage 1)?

A
  • Cells are broken up by a homogeniser (blender) to release the organelles by breaking up the plasma membrane
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13
Q

What happens in Filtration (Stage 2)?

A
  • The blended solution is filtered to remove any large tissue
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14
Q

What happens in Ultracentrifugation (Stage 3)?

A
  • filtrate placed in centrifuge + spun at a slow speed, heaviest organelles e.g. nuclei sink to the bottom and form a small pellet
  • Fluid at the top is removed (supernatant)
  • The supernatant is respun at a faster speed to gain the smaller organelles, this is repeated
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15
Q

Who discovered the first cells?

A

Robert Hooke in 1665

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16
Q

When were the first electron microscopes discovered?

A
  • Developed in the 1930s

- Allowed scientists to see their ‘ultrastructure

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17
Q

What are the components of the nucleus?

A
  • Nuclear envelope
  • Nuclear pores
  • Nucleoplasm
  • Chromosomes
  • Nucleolus
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18
Q

What is the function of the nuclear envelope?

A
  • It surrounds the nucleus and encases it

- Made from a 2 lipid bilayer

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19
Q

What is the function of the nuclear pores?

A
  • Transports molecules across the nuclear envelope

- i.e. RNA moving out, proteins moving in

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20
Q

What is the function of the nucleoplasm?

A
  • It is the substance in a cell’s nucleus

- Contains the chromosomes and nucleolus

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21
Q

What is the function of chromosomes?

A
  • They carry genetic info

- Made of DNA and proteins

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22
Q

What is the function of the nucleolus?

A
  • Makes ribosomes

- Largest structure in nucleus

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23
Q

What are the components in the mitochondria?

A
  • Double membrane
  • Cristae
  • Matrix
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24
Q

What is the double membrane (mitochondria)

A
  • Outer membrane covers like a skin
  • Inner membrane folded into layered structures
  • Inner membrane increases SA
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25
Q

What is the cristae (mitochondria)?

A
  • Folds made by inner membrane

- More space for chemical reactions to take place

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26
Q

What is the matrix (mitochondria)?

A
  • Fluid contained within the mitochondria
  • Own ribosomes and DNA floating in it
  • Contains granules which help with ion concentrations
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27
Q

What are the parts of a chloroplast?

A
  • Chloroplast envelope
  • Grana
  • Stroma
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28
Q

What is the Chloroplast envelope (membrane)?

A
  • Similar to structure of mitochondrial double membrane
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29
Q

What is the Grana?

A
  • Stack of disks known as thylakoids
  • Resembles a stack of coins
  • Site of light dependant reactions of photosynthesis
  • Connected by intergranal thylakoids
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30
Q

What is the Stroma

A
  • Colourless fluid surrounding grana
  • Contains enzymes required for photosynthesis
  • DNA and ribosomes also present
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31
Q

What are the two types of Endoplasmic reticulum?

A
  • Rough endoplasmic reticulum

- Smooth endoplasmic reticulum

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32
Q

What is the rough endoplasmic reticulum?

A

Folds and processes proteins that have been made at the ribosomes

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33
Q

What is the smooth endoplasmic reticulum?

A

No ribosomes, lipid synthesis

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34
Q

What is the golgi apparatus?

A
  • Where things are packaged into vesicles and move out of the cell
  • For packaging and processes new lipids and proteins
  • Makes lysosomes
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35
Q

What are lysosomes?

A
  • Made in the golgi apparatus
  • Allow destruction of unneeded parts in the cell
  • Strong enzymes to help destruction
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36
Q

What 3 ways do cells differ?

A
  • Function
  • Shape
  • Number/type of organelles
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37
Q

What are the levels of organisation?

A
  • Specialised cell
  • Tissue
  • Organ
  • System
  • Organism
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38
Q

What are the features of a prokaryotic cell?

A
  • No nucleus –> DNA strands and plasmid rings
  • No membrane bound organelles
  • Ribosomes are smaller than ones in eukaryotes - 70s
  • 3 layer membrane; cell membrane, cell wall + capsule
  • Flagellum + pili attached
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39
Q

What does the capsule of a prokaryotic cell do?

A

It stops chemical attacks

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40
Q

What is a virus like?

A
  • Not a cell

- Non-living

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41
Q

What are the parts of a virus cell?

A
  • Nucleoproteins
  • Matrix
  • Capsid
  • Genetic material (DNA) (RNA)
  • Lipid envelope
  • Attachment proteins
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42
Q

What are attachment proteins?

A

Bind to receptor proteins on the host cell

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43
Q

What is the lipid envelopes role?

A

Derived to host cell membrane

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44
Q

What is DNA/RNA

A

Encodes virus proteins

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45
Q

What is a capsid?

A

Protein coat that encapsulates the DNA/RNA

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46
Q

What are nucleoproteins?

A

Accessory proteins the virus needs e.g. enzyme

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47
Q

What is the matrix (virus)?

A

Protein layer on the inside of the envelope

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48
Q

Your beautiful x

A

not

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49
Q

Do all cells have the ability to divide?

A

All do, some lose this ability

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50
Q

How many times do specialised cells go through the cell cycle?

A

Once

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51
Q

What sort of cells does mitosis produce?

A

Body cells

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52
Q

What sort of cell does meiosis produce?

A

Gametes

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53
Q

What is the purpose of mitosis?

A
  • Growth of tissues
  • Replacement of lost cells
  • Repair of damaged tissue
  • Asexual reproduction
  • Clones of T and B lymphocytes
  • Abnormally divide to form tumors
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54
Q

What are the parts of a homologous chromosome?

A
  • Chromatin –> two arms of an x shaped chromosome

- Centromere –> the middle

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55
Q

What is chromatin?

A

DNA when it is not wound up tightly as a chromosome

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56
Q

What is a chromosome?

A

Compacts X or Y shaped form of chromatin formed during cell division

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57
Q

What are chromatids?

A

Two identical arms of an X shaped chromosome

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58
Q

What is the centromere?

A

The point at which the chromatids join

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59
Q

What is a homologous chromosome?

A

Two chromosomes originating from one parent, containing the same genes, but different alleles

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60
Q

When does most of the cell cycle take place?

A

In the interphase

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61
Q

What are the 6 phases in the cell cycle?

A
  • Interphase
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
  • Cytokinesis
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62
Q

What happens in Interphase?

A
  • -> Cell grows + DNA replicates
  • -> Chromosomes not visible
  • -> Not strictly part of mitosis
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63
Q

What happens in Prophase?

A
  • -> Chromosomes condense + become visible
  • -> Centrioles move to opposite ends of the cell
  • -> Spindle apparatus forms from spindle fibres at the centrioles
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64
Q

What happens in the Metaphase?

A
  • -> Nuclear envelope breaks down

- -> Chromosomes align along the equator of the cell pulled by spindle apparatus

65
Q

What happens in the Anaphase?

A
  • -> Centromeres split, allowing chromatids to separate

- -> Chromatids move towards poles, pulled by the spindle fibers

66
Q

What happens in the Telophase?

A
  • -> Spindle fibres disperse
  • -> Nuclear envelope reforms
  • -> Chromosomes decondense
67
Q

What happens in Cytokinesis?

A
  • -> A ring of protein filaments form around the equator of the cell
  • -> It tightens and the cell splits into 2 cells
68
Q

How are each of the checkpoints in the cell regulated?

A

With control genes

69
Q

How are tumors created?

A

Mutated control genes cause cells to divide uncontrollably

70
Q

What are the risk factors for tumors?

A
  • Smoking
  • Diet
  • Obesity
  • Physical activity
  • Sunlight
71
Q

What are the two types of tumor?

A

Benign and Malignant

72
Q

What is a Benign tumor like?

A

Non-cancerous and doesn’t spread

73
Q

What are Malignant tumors like?

A

Fast growing, often spread and are classed as cancer

74
Q

What are the treatments for cancer?

A
  • Surgery
  • Radiotherapy
  • Chemotherapy
75
Q

What does surgery (tumors) do?

A

Removes the tumor (usually benign)

76
Q

What does radiotherapy do?

A

The radiation damages the DNA in cells (usually malignant)

77
Q

What does chemotherapy do?

A
  • Blocks enzymes in DNA synthesis
  • Prevents DNA unwinding
  • Inhibits synthesis of new nucleotides
  • Prevents development of the spindle
78
Q

How do you focus a SEM (microscope)?

A

Using a condenser electromagnet

79
Q

What does the specimen for a SEM (microscope) need to be like?

A
  • Doesn’t have to be thin
  • Cannot be living
  • Must be in a vacuum
80
Q

What may be created when using a SEM or TEM (microscope)?

A

An artefact (a dust particle or bubble)

81
Q

What sort of image is produced using a SEM (microscope) ?

A
  • No colour (can add false colour)

- 3D image using computer analysis

82
Q

What is a negative about SEM (microscope)?

A
  • Can produce an artefact

- Has a complicated prep

83
Q

What does transmission mean (TEM)?

A

electrons go through specimen

84
Q

What does scanning mean (SEM)?

A

scans surface

85
Q

What sort of image is produced using a TEM (microscope)?

A
  • 2D image

- no colour (can add false colour)

86
Q

How does a TEM (microscope) focus?

A

a condenser magnet

87
Q

What are the limitations of a TEM (microscope)?

A
  • cannot look at living things
  • has to be in a vacuum
  • must be a thin specimen
  • complicated prep
  • may produce an artefact
  • no colour image
88
Q

How do viruses replicate?

A

Via taking over a host cell

89
Q

What are the 5 stages of virus replication?

A
  1. Viral contents release
  2. Virus enters cell
  3. Viral RNA enters nucleus
  4. Viral mRNA makes viral proteins
  5. New viral particles are released
90
Q

What are spindle fibres?

A

Pull apart chromosomes during cell replication

91
Q

What are the parts of a eukaryotic cell?

A
  • Plasma membrane
  • RER
  • Nucleolus
  • Nucleus
  • SER
  • Lysosome
  • Ribosome
  • Nuclear envelope
  • Golgi apparatus
  • Cytoplasm
  • Mitochondrion
92
Q

What are the parts of a plant cell?

A
  • Plasma membrane
  • Chloroplast
  • RER
  • Cell wall (plasmodesma)
  • Mitochondria
  • Golgi apparatus
  • Vacuole
  • SER
  • Cytoplasm
  • Nucleolus
  • Nucleus
  • Ribosome
  • Cell wall
93
Q

What are algal cells?

A

They’re a lot like plant cells - they have all the same organelles, including a cell wall and chloroplasts

94
Q

What are fungal cells like?

A

A lot like plant cells but with 2 key differences:

  • Their cell walls are made of chitin, not cellulose
  • They don’t have chloroplasts (bc they don’t photosynthesis)
95
Q

What is the cell surface membrane?

A

It’s made of mainly lipids and proteins

96
Q

What is the nucleus like?

A

A large organelle surrounded by a nuclear envelope which contains many pores

The nucleus contains chromosomes and a nucleoluse

97
Q

What’s a mitochondria like?

A

Usually oval shaped

They have a double membrane - inner one is folded to form structures called cristae

Inside the matrix are enzymes involved in respiration

98
Q

What is structure of the chloroplast?

A

Small flattened structure found in plant & algal cells

99
Q

What sort of membrane do chloroplasts have?

A

Surrounded by a double membrane & also has membranes inside called thylakoid membranes

100
Q

What happens when thylakoid membranes are stacked in chloroplasts?

A

These membranes are stacked up in some parts of the chloroplast to form grana

101
Q

How are grana linked?

A

Grana are linked by together by lamellae

102
Q

What are the lamellae in grana like?

A

Thin, flat pieces of thylakoid membrane

103
Q

What is the golgi apparatus like?

A

A group of fluid-filled membrane-bound flattened sacs

Vesicale are often seen at the edge of the sacs

104
Q

What is the golgi vesicle like?

A

A small fluid-filled sac in the cytoplasm

Surrounded by a membrane & produced by the golgi apparatus

105
Q

What is the function of the golgi vesicle?

A

Stores lipids & proteins made by the Golgi apparatus and transports them out of the cell

106
Q

What is a lysosome like?

A

A round organelle surrounded by a membrane - with no clear internal structure

It’s a type of golgi vesicle

107
Q

What are the enzymes in lysosomes called?

A

lysozymes

108
Q

What are the 2 main parts of a ribosome?

A

Small subunit

Large subunit

109
Q

Where is a ribosome found in the cell?

A

Either floats free in the cytoplasm or is attached in the RER

110
Q

What are ribosomes made up of?

A

Proteins and RNA - it’s not surrounded by a membrane

111
Q

What is the RER?

A

A system of membranes enclosing s fluid-filled space

Surface is covered with ribosomes

112
Q

What is the cell wall made from in plants & algae?

A

Made mainly of the carbohydrate cellulose

113
Q

What is the cell wall in fungi made of?

A

Chitin

114
Q

What is cell sap made up of?

A

A weak solution of sugar and salts

115
Q

What is the surrounding membrane of a vacuole called?

A

Tonoplast

116
Q

What is the the role of the vacuole?

A

Helps to maintain pressure inside the cell & keep the cell rigid - this stops plants wilting

Also involved in the isolation of unwanted chemicals inside the cell

117
Q

You’re doing so well keep going haha

A

Don’t stop you will fail otherwise

Hope ur having fun :))))))))

“Don’t know the solution until there’s a problem” - Daniel Digges (29/09/20)

118
Q

What is the magnification equation?

A

Magnification=size of image/size of real object

119
Q

What is magnification definition?

A

How much bigger the image is than the specimen.

120
Q

What is resolutions definition?

A

Resolution is how detailed the image is.More specifically, it’s how well a microscope distinguishes between two points that are close together.

121
Q

What are the two types of microscope?

A

Optical (light) and electron

122
Q

What are features of an optical microscope?

A
  • They use light to form an image
  • They have a maximum resolution of about 0.2 micrometres.This means you can’t see organelles smaller than 0.2 micrometres like ribosomes and lysosome.You can see the nucleus though.
  • The maximum useful magnification of an optical microscope is about x1500
123
Q

What are features of an electron microscope?

A
  • They use electrons to form an image
  • They have a higher resolution than optical microscopes so give a more detailed image
  • They have a maximum resolution of around 0.0002 micrometres.
  • The maximum useful magnification of an electron microscope is about x1 500 000
124
Q

What are the two types of electron microscopes?

A

Scanning or transmission

125
Q

What is a limitation of transmission electron microscopes?

A

They can only be used on thick specimens

126
Q

Why do some parts of the specimen look darker in transmission electron microscopes?

A

Because denser parts of the specimen absorb more electrons which makes them look darker on the image you end up with.

127
Q

What do TEM’s use to focus the beam of electrons?

A

Electromagnets which transmit beam of electrons through the specimen

128
Q

Do TEM’s have high or low resolution?

A

High resolution which helps them see the internal structure of organelles like chloroplasts.

129
Q

What is a limitation of scanning electron microscopes?

A

They have lower resolution images than TEM’s

130
Q

Can SEM’s be used on thick specimens?

A

yes unlike TEM’s

131
Q

What do the images you end up with from SEM’s show?

A

They show the surface of the specimen.They can also show the 3-D shape.

132
Q

How does a scanning electron microscope work?

A

SEM’s scan a beam of electrons across the specimen.This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.

133
Q

How do you prepare a temporary mount of a specimen on a slide?

A

1-Start by pipetting a small drop of water onto the slide.Then use tweezers to place thin section of specimen on water drop.
2-Add a drop of a stain.Stains used to highlight objects in a cell
3-Finally,add the cover slip.To do this stand the slip upright on the slide then carefully tilt it to cover specimen.Try not to get any air bubbles under there

134
Q

What does cell fractionation do?

A

Separate organelles

135
Q

What are the three steps to cell fractionation?

A
  • Homogenisation-breaking up the cells
  • Filtration-Getting rid of big bits
  • Ultracentrifugation-Separating the organelles
136
Q

What is homogenisation?

A

-It is done by grinding the cells up or vibrating them.This breaks up the plasma membrane and release the organelles into the solution.The solution ice-cold to reduce enzyme activity.Solution should also be isotonic.A buffer solution should be added to maintain Ph.

137
Q

What is filtration?

A

Homogenised solution is filtered through a gauze to separate any large cell debris or tissue debris.The organelles are much smaller than the tissue so they filter through

138
Q

How many steps of ultracentrifugation are there?

A

2

139
Q

Step 1 of ultracentrifugation?

A

Cell fragments poured into a tube

The tube is put into centrifuge & spun at a low speed

Heaviest organelles, like nuclei, get flung to the bottom of the tube by the centrifuge.

Form a pellet at the bottom

Rest of the organelles are suspended in fluid above sediment called the supernatant.

140
Q

Step 2 of ultracentrifugation?

A

Supernatant is drained off, poured into another tube & spun in centrifuge at higher speed

This is repeated over and over again with the pellet at the bottom getting lighter and lighter.

141
Q

Give an example of a prokaryotic cell?

A

Bacteria cell

142
Q

What is the cytoplasm in a prokaryotic cell like?

A
  • No membrane-bound organelles

- Has ribosomes (small)

143
Q

What is the structure of the flagellum like?

A

Long, hair-like structure

144
Q

What does the flagellum do?

A

Rotates to make cell move

145
Q

What is the DNA like in a prokaryotic cell?

A
  • No nucleus, so floats free in cytoplasm
  • Circular DNA (one long coiled up strand)
  • Not attached to histones
146
Q

What is the structure of plasmids?

A

Small loops of DNA

147
Q

What do plasmids do?

A

Contain genes for antibiotic resistance

148
Q

What does the capsule in the eukaryotic cell do?

A

Protect bacteria from being attacked by cells of the immune system

149
Q

What is the capsule made of?

A

Slime

150
Q

What does the plasma membrane do?

A

Controls movement of substances into and out of the cell

151
Q

What polymer is the cell wall made of?

A

Murein

152
Q

What does the cell wall do?

A

Supports cells and prevents from changing shape

153
Q

Name the parts of a prokaryotic cell?

A
  • cytoplasm
  • flagellum
  • plasmids
  • cell wall
  • capsule
  • plasma membrane
  • circular DNA
154
Q

Are viruses smaller than bacteria?

A

yes

155
Q

What do bacteria have that viruses don’t?

A
  • cytoplasm
  • plasma membrane
  • ribosomes
156
Q

What is found on the surface of a to a virus?

A

Attachment protein

157
Q

What is the protein coat around the core called in a virus?

A

Capsid

158
Q

How do prokaryotic cell reproduce?

A

binary fission

159
Q

What are the 4 stages of binary fission?

A

1 - circular DNA (once) and plasmids (multiple times) replicate
2 - cells grow and DNA loops move to opposite ends of the pole
3 - cytoplasm begins to divide (new cell walls form)
4 - cytoplasm divides and 2 daughter cells are produced, each having one copy of DNA and variable plasmids

Biology A-level (20 decks)

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