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A LEVEL - Biology (P2) > 2A - Cell Structure And Division > Flashcards

2A - Cell Structure And Division Flashcards

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1
Q

What are the two types of cell?

A
  • Prokaryotic

* Eukaryotic

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2
Q

What are prokaryotic organisms made of?

A

Prokaryotic cells - if they are single-celled, they may BE prokaryotic cells.

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3
Q

What are eukaryotic organisms made of?

A

Eukaryotic cells

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4
Q

What are eukaryotic cells?

A

Larger, complex cells -> Found in advanced organisms such as animals

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5
Q

What are prokaryotic cells?

A

Smaller, simpler cells -> Found in basic organisms, such as bacteria

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6
Q

Which cell type is more basic?

A

Prokaryotic cells

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7
Q

Give some examples of eukaryotic organisms.

A
  • Animals
  • Plants
  • Algae
  • Fungi
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8
Q

Give some examples of prokaryotic cells.

A

• Bacteria

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9
Q

What are organelles?

A

Parts of cells with specific functions.

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10
Q

What are the organelles of an animal cell? (9)

A
  • Plasma membrane
  • Nucleus (+ Nucleolus + Nuclear envelope)
  • Ribosome
  • Mitochondria
  • Cytoplasm
  • Rough endoplasmic reticulum
  • Smooth endoplasmic reticulum
  • Golgi apparatus
  • Lysosome
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11
Q

What are the organelles of a plant cell? (12)

A
  • Plasma membrane
  • Nucleus (+ Nucleolus + Nuclear envelope)
  • Ribosome
  • Mitochondria
  • Cytoplasm
  • Rough endoplasmic reticulum
  • Smooth endoplasmic reticulum
  • Golgi apparatus
  • Lysosome
  • Chloroplast
  • Cell wall (+ Plasmodesmata)
  • Vacuole
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12
Q

Remember to revise labelling an animal and plant cell.

A

Pg 24 of revision guide

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13
Q

What are the extra features of plant cells compared to animal cells?

A
  • Cellulose cell wall (with plasmodesmata)
  • Vacuole
  • Chloroplasts
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14
Q

What might you also find in plant cells that is not an organelle?

A

Starch grains - these are just used for storage.

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15
Q

What is the difference between plant and animal cells?

A

Plant cells have all the same organelles as animals cells as well as:
• Cellulose cell wall
• Vacuole
• Chloroplasts

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16
Q

Are algae single-felled or multicellular?

A

They can be both.

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17
Q

How do algal cells compare to plant cells?

A

They are very similar and have all the same organelles.

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18
Q

How do fungal cells compared to plant cells?

A

They have all the same organelles as plant cells except:
• Cell wall is made of chitin, not cellulose
• Don’t have chloroplasts

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19
Q

Do organelles have membranes?

A

Yes, mostly - this can make them easy to confuse with entire cells.

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20
Q

Remember to revise labelling cell organelles.

A

Pg 25 of revision guide.

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21
Q

What is the cell-surface membrane and what is it made of?

A
  • Membrane found on the surface of animal cells and just inside the cell wall of other cells
  • Mad of lipids and proteins
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22
Q

What is the function of the cell surface membrane?

A
  • Controls movement of substances in and out of cell

* Has receptor molecules to respond to chemicals (e.g. hormones)

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23
Q

What are the parts of the nucleus?

A
  • Nuclear envelope
  • Nucleolus
  • Chromatin
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24
Q

What is the function of the nucleus?

A
  • Control’s the cell’s activities
  • Stores DNA which contains instructions for protein synthesis
  • Nucleolus makes ribosomes
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25
Q

What is the nuclear envelope (and its pores) and what do they do?

A
  • Double membrane which surrounds the nucleus

* Pores control movement of substances between the nucleus and the cytoplasm

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26
Q

What is the nucleolus and what does it do?

A
  • Found in the nucleus

* Produces ribosomes (by producing ribosomal DNA and putting the ribosomes together)

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27
Q

What is chromatin and what does it do?

A
  • The chromosomes found in the nucleus

* DNA stories instructions to make proteins

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28
Q

What are chromosomes in the nucleus made from?

A

Protein-bound linear DNA

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29
Q

What are the parts of a mitochondrion?

A
  • Inner membrane
  • Outer membrane
  • Cristae
  • Matrix
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30
Q

What is the function of a mitochondrion?

A

• Site of aerobic respiration, where ATP is produced

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31
Q

What are cristae and what do they do?

A
  • Folds in the inner membrane of mitochondria

* They increase the surface area for the attachment of proteins and enzymes

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32
Q

What is the matrix and what does it do?

A
  • The fluid in mitochondria which contains proteins, lipids, ribosomes and DNA
  • This allows protein synthesis to happen
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33
Q

What is the function of the membranes of mitochondria?

A

They control what goes in and out of the mitochondrion

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34
Q

Do mitochondria produce proteins?

A

Yes, they make some of their own proteins, which is why they have small amounts of DNA inside.

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35
Q

What are the parts of a chloroplast?

A
  • Two membranes
  • Stroma
  • Grana (stacks of thylakoid membranes)
  • Lamellae
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36
Q

What is the function of a chloroplast?

A

• The site where photosynthesis happens

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37
Q

What does the double membrane in chloroplasts do?

A
  • Collectively known as the chloroplast envelope

* Control what goes in and out of the chloroplast

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38
Q

What is the stroma and what does it do?

A
  • A fluid-filled area of a chloroplast

* Some parts of photosynthesis happen here

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39
Q

What is a granum and what does it do?

A
  • A stack of thylakoids membranes found in chloroplasts

* First stage of photosynthesis happens here

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40
Q

What is a thylakoid membrane?

A

It is a part of the chloroplast. Many of these membranes can be stacked on top of each other to form a GRANUM. Intergranal lamella are also made from thylakoid membrane.

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41
Q

What is a lamella and what does it do?

A

• A thin piece of thylakoid membrane which links grana together in chloroplasts

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42
Q

What is the Golgi apparatus and what are its functions?

A

• Group of fluid-filled, membrane-bound flattened sacs
• Processes and packages new lipids and proteins
• Produces vesicles, including lysosomes
(• Produces secretory enzymes)
(• Secretes carbohydrates)

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43
Q

What produces vesicles?

A

The Golgi apparatus

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44
Q

What is the function of a vesicle?

A
  • Stores lipids and proteins (made by the Golgi apparatus)

* Transports these out of the cell (through the cell membrane)

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45
Q

What is a vesicle?

A
  • A small, fluid-filled sac in the cytoplasm, surrounded by a membrane and made by the Golgi apparatus
  • Used to stores proteins and lipids from the Golgi and transport these out of the cell
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46
Q

What is a lysosome?

A

• A type of Golgi vesicle which contains lysozymes to digest invading cells and break down old cell components

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47
Q

What is the function of a lysosome?

A

Contains lysozymes (digestive enzymes) to:
• Digest invading cells
• Break down old cell components
• Release enzymes outside of cell to destroy material

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48
Q

What is a lysozyme and where is it found?

A
  • Digestive enzyme found in lysosomes.

* Used to break down old cell components and digest invading cells.

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49
Q

Where are ribosomes found?

A

Either floating freely in the cytoplasm or attached to the rough endoplasmic reticulum.

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50
Q

Which cell components have no membrane?

A

• Ribosomes

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51
Q

What are the parts of a ribosome?

A
  • Large sub-unit

* Small sub-unit

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52
Q

What is the function of a ribosome?

A

• The site where proteins are synthesised.

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53
Q

What is a ribosome made of?

A

Proteins and RNA

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54
Q

What is the relative size of a ribosome?

A

Very small

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55
Q

What are the different sites of synthesis and modification of proteins, carbohydrates and lipids?

A
  • RER - Protein folding and processing (+ synthesis by ribosomes)
  • SER - Lipid and carbohydrate synthesis and processing
  • Golgi apparatus - Protein and lipid modification
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56
Q

What is the rough endoplasmic reticulum?

A
  • System of membranes enclosing a fluid-filled space

* Surface is covered with ribosomes

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57
Q

What is the function of the rough endoplasmic reticulum?

A
  • Providing a large SA for ribosomes
  • Folding and processing of proteins
  • Pathway for transport of proteins around cell
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58
Q

What is the smooth endoplasmic reticulum?

A
  • System of membrane enclosing a fluid-filled space

* No ribosomes on the surface

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59
Q

What are the flattened sacs in the Golgi apparatus called?

A

Cisternae

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60
Q

What is the function of the smooth endoplasmic reticulum?

A

• Synthesis, storage and transport of lipids and carbohydrates

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61
Q

What is the function of the Golgi apparatus?

A

• Processes and packages new lipids and proteins
• Produces vesicles, including lysosomes
(• Produces secretory enzymes)
(• Secretes carbohydrates)

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62
Q

Describe the process and organelles involved in creating different proteins, lipids and carbohydrates.

A

Lipids and carbohydrates are synthesised in the SER. The SER modifies these and transports them. Proteins are synthesised by ribosomes (on the RER). The RER processes and transports them.
The Golgi apparatus then modifies these. This includes creating glycoproteins (carbohydrates added to proteins) and secretory enzymes (like those in the pancreas). Finally, these products are transported away using the Golgi vesicles which are pinched off the end cisternae.

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63
Q

What is the cell wall made of in plants, algae and fungi?

A
  • Plants and algae ->Cellulose

* Fungi -> Chitin

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64
Q

What is the function of the cell wall?

A
  • Provide strength -> Prevent damage due to osmotic movement
  • Mechanical strength
  • Allows water to pass along it
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65
Q

What structures are found in-between cell walls?

A

Middle lamella -> This is a thin layer found at the boundary between two cells, which cements cell walls together.

66
Q

What is more outer, the cell membrane or the cell wall?

A

The cell wall

67
Q

What does a vacuole contain?

A

Cell sap - a weak solution of sugars and salts.

68
Q

What are the functions of a vacuole?

A
  • Supports plants by making cells turgid
  • Sugars and amino acids may serve as temporary food store
  • Isolation of unwanted chemicals inside the cell
  • Pigment may be colourful, which attracts insects
69
Q

Describe the successive grouping of specialised cells.

A

Cells -> Tissues -> Organs -> Organ systems

70
Q

What is a tissue?

A

A group of specialised cells working towards a particular function.

71
Q

What are the different organelles found in prokaryotic (bacteria) cells? (8)

A
  • Cell wall
  • Cell-surface membrane
  • Capsule
  • Plasmid
  • Ribosome
  • Cytoplasm
  • Genetic material
  • Flagellum
72
Q

What is different about organelles in the cytoplasm of prokaryotic cells compared to eukaryotic cells?

A

They are not membrane-bound, like in eukaryotic cells.

73
Q

Which organelles in prokaryotic cells are only found in certain species?

A
  • Flagellum
  • Capsule
  • Plasmid
74
Q

What is the difference between ribosomes in eukaryotic and prokaryotic cells?

A
  • Eukaryotic -> 80s ribosomes -> Larger

* Prokaryotic -> 70s ribosomes -> Smaller

75
Q

What is the cell wall made of in prokaryotic (bacteria) cells?

A

Murein - A glycoprotein

76
Q

What is the capsule made from?

A

Secreted slime

77
Q

What is the function of the capsule?

A

• Protects the bacteria from attacks by cells of the immune system

78
Q

How many plasmids are in a bacterial cell?

A

There may be none, one or several.

79
Q

What is a plasmid?

A

A small loop of DNA that isn’t part of the main circular DNA molecule in a bacterial cell.

80
Q

What is the function of a plasmid?

A

• It contains genes for things such as antibiotic resistance and can be passed between bacterial cells.

81
Q

What organelles are prokaryotic cells lacking compared to eukaryotic cells?

A
  • Nucleus
  • RER and SER
  • Golgi apparatus
82
Q

What is the function of the flagellum?

A

• Rotates to make the cell move

83
Q

Describe the genetic material in a prokaryotic cell.

A
  • Circular DNA, as a long coiled-up strand.

* Not attached to any histone proteins.

84
Q

Are viruses cells?

A

No - they are acellular. They are simply nucleic acids surrounded by protein. They’re not even alive.

85
Q

What is the relative size of viruses?

A

They are very small - much smaller than bacteria.

86
Q

How do virus organelles different from bacteria?

A

Viruses have no plasma membrane, cytoplasm or ribosomes.

87
Q

Remember to revise the structure of a virus.

A

Pg 28 of revision guide.

88
Q

What are the parts of a virus?

A
  • Genetic material -> RNA or DNA
  • Capsid
  • Attachment proteins
89
Q

What is the capsid in viruses?

A

A protein coat which surrounds the genetic material core.

90
Q

What is the function of attachment proteins on viruses?

A

• Allow the virus to identify and attach to cells

91
Q

What is the process by which prokaryotic cells divide called?

A

Binary fission

92
Q

Describe binary fission.

A

1) Circular DNA and plasmids replicate. DNA loop replicates only once, but but plasmids can be replicated several times.
2) Cell gets bigger and DNA loops move to opposite poles of the cell
3) Cytoplasm divides.
4) Two daughter cells are produced.

93
Q

Describe how viruses replicate.

A

1) Use attachment proteins to bind to complementary receptor proteins on surface of host cell
2) Most viruses can only infect one type of cell due to the fact that the proteins and receptors must be complementary
3) Viruses inject their DNA or RNA into the host cell, which forces it to replicate the virus

94
Q

What is the formula for magnification?

A

Magnification = Size of Image / Size of Object

95
Q

What is resolution?

A

How well a microscope distinguishes between two points that are close together.

96
Q

What are the main types of microscope?

A
  • Light microscopes

* Electron microscopes -> Transmission and Scanning

97
Q

What are the types of electron microscope?

A
  • Transmission electron microscope (TEM)

* Scanning electron microscope (SEM)

98
Q

How does a light microscope work?

A

Light is passed upwards through the specimen. Thinner, less dense parts absorb less light and appear brighter. Most LM are compound, so they use two lenses to magnify the image.

99
Q

Compare the resolution of light microscopes, TEMs and SEMs.

A

Light: 200nm
TEM: 0.1 nm
SEM: 20nm

100
Q

Which organelles would you not be able to make out using a light microscope?

A
  • Ribosomes
  • Endoplasmic reticulum
  • Lysosomes
101
Q

Compare the magnification of light microscopes, TEMs and SEMs.

A

Light: x1,500
TEM: x1,500,000
SEM: x1,500,000

102
Q

How does a transmission electron microscope work?

A
  • Electron gun fires a beam of electrons from below, which is focused using an electromagnet
  • More electrons pass through thinner, less dense parts of the specimen, making them appear brighter
  • An image forms on a screen
103
Q

How does a scanning electron microscope work?

A
  • Beam of electrons from above is passed forwards and backwards over the specimen in a regular pattern.
  • The contours on the specimen scatter electrons and the pattern in which this happens can be used by a computer to generate a 3D image
104
Q

What are the advantages and disadvantages of electron microscopes over light microscopes?

A 
ADV
• Better resolution
• Beam can be focused by electromagnets
• SEMs can produce 3D images
DIS
• Expensive
• Large
• Vacuum must be maintained
• Only thin specimen can be observed by TEM
• Specimen must be stained -> Image is not in colour
• Artefacts -> Preparation of specimen may alter finished photomicrograph
• Training is required
105
Q

What are the advantages of TEMs and SEMs?

A

TEMs
• Give higher resolution images than SEMs
SEMs
• Can be used on thicker specimen than TEMs

106
Q

What are plasmodesmata?

A

“Channels” in the cell wall for exchanging substances between adjacent cells.

107
Q

How can a specimen be prepared for viewing under an optical microscope?

A
  • Pipette a small drop of water onto the slide
  • Place a thin section of your specimen on top using tweezers
  • Add a drop of a stain
  • Add the cover slip, standing it upright and then carefully lowering it down
108
Q

What are the 3 main steps of cell fractionation?

A
  • Homogenisation - breaking up cells
  • Filtration - getting rid of the big bits
  • Ultracentrifugation - separating the organelles
109
Q

What is homogenisation?

A

Breaking up cells to release the organelles into a solution.

110
Q

Give some ways in which homogenisation can be done.

A
  • Vibrating the cells

* Grinding the cells up in a blender

111
Q

What are the conditions for homogenisation?

A
  • Ice-cold
  • Isotonic solution
  • Buffer solution
112
Q

During homogenisation, why must the solution be kept ice-cold?

A

To reduce the activity of enzymes that break down the cell organelles.

113
Q

During homogenisation, why must the solution be isotonic?

A

To prevent movement of water and thus the damage of organelles by osmosis.

114
Q

During homogenisation, why must a buffer solution be used?

A

To maintain the pH.

115
Q

What is a buffer solution?

A

A solution which keeps the pH almost constant.

116
Q

Why must the homogenised cell solution be filtered during cell fractionation?

A

To separate any large cell debris or tissue debris, like connective tissue, from the solution.

117
Q

What is the process by which different organelles in a solution are separated called?

A

Ultracentrifugation

118
Q

Describe the process of ultracentrifugation.

A

1) Cell fragments are poured into a tube, which is put into a centrifuge. The centrifuge spins at a low speed. The most dense organelles (e.g. nuclei) are flung to the end of the test tube. They form a thick sediment called a pellet. The rest remains as a fluid above, called the supernatant.
2) Supernatant is drained off and poured into another tube. This time it is spun at a higher speed. Once again, the most dense organelles form a pellet and the supernatant is separated out.
3) The process is repeated several times, with the pellet being made out of gradually lighter organelles each time.

119
Q

What are the two types of cell division in eukaryotes?

A

Mitosis and meiosis

120
Q

What is mitosis?

A

When a parent cell divides to produce two genetically identical daughter cells.

121
Q

What is mitosis needed for?

A
  • Growth

* Repairing damaged tissues

122
Q

What is the process of cells dividing by mitosis called?

A

The cell cycle.

123
Q

What are the two MAIN parts of the cell cycle?

A
  • Interphase

* Mitosis

124
Q

What is interphase?

A

The period of cell growth and DNA replication, when mitosis isn’t happening.

125
Q

What are the three parts of interphase?

A
  • Gap phase 1
  • Synthesis
  • Gap phase 2
126
Q

What happens in gap phase 1 of interphase?

A

Cell grows and new organelles and proteins are made.

127
Q

What happens in the synthesis phase of interphase?

A

Cell replicates its DNA, ready to divide by mitosis.

128
Q

What happens in gap phase 2 of interphase?

A

Cell keeps growing and proteins needed for cell division are made.

129
Q

Describe the order of the cell cycle stages.

A
  • Mitosis
  • Gap phase 1
  • Synthesis
  • Gap phase 2
130
Q

What abbreviations are used in the cell cycle?

A
  • Mitosis = M
  • Gap phase 1 = G1
  • Synthesis = S
  • Gap phase 2 = G2
131
Q

What is the order of the stages of mitosis?

A 
(• Interphase)
• Prophase
• Metaphase
• Anaphase
• Telophase
132
Q

What abbreviation can be used to remember the stages of mitosis?

A

PMAT

133
Q

What happens in interphase?

A
  • Cell carries out normal function
  • DNA is unravelled and duplicated
  • Organelles are also replicated
  • ATP content is increased

(See diagram pg 32)

134
Q

Describe the chromosomes at the start of mitosis and how they end up after mitosis.

A
  • Two separate strands called chromatids
  • Joined in the middle by a centromere
  • This is because each chromosome has made a copy of itself already during interphase
  • After mitosis, chromatids end up as one-strand chromosomes
135
Q

Describe prophase.

A
  • Chromosomes condense, getting shorter and fatter
  • Centrioles start moving to opposite ends of the cells, forming a spindle
  • Nuclear envelope breaks down and chromosomes lie free in the cytoplasm
136
Q

What is a centromere?

A

The part that joins the two chromatids in a chromosome (when the DNA has been duplicated).

137
Q

What is a chromatid?

A

A single strand of DNA in a chromosome (when the DNA has been duplicated).

138
Q

What are centrioles?

A

Tiny bundles of protein that hold the ends of the spindle in mitosis.

139
Q

What is the spindle?

A

A network of fibres across the cell in mitosis which help pull the chromosomes to opposite sides.

140
Q

Describe metaphase.

A
  • Chromosomes line up along the middle of the cell

* Centromeres attach to the spindle

141
Q

Describe anaphase.

A
  • Centromeres divide, separating each pair of sister chromatids
  • Spindles contract, pulling chromatids to opposite poles of the spindle by the centromeres -> Chromatids appear v-shaped
142
Q

Describe telophase.

A
  • Chromatids reach opposite poles, uncoil, and become long and thin -> Now called chromosomes again
  • Nuclear envelope forms around each group of chromosomes
  • Cytoplasm divides and two daughter cells are formed
143
Q

What is the cytoplasm dividing called?

A

Cytokinesis

144
Q

In which stage of mitosis do the chromatids appear v-shaped?

A

Anaphase

145
Q

Revise mitosis diagrams.

A

See pg 32 of revision guide.

146
Q

Describe how a cancer can form.

A
  • Mitosis and the cell cycle are controlled by genes
  • Usually, after dividing enough times, the cell stops
  • A mutation in the genes can cause cell growth to get out of control
  • A tumour forms
147
Q

Describe how some cancer treatments work and the drawback of this.

A
  • The treatment disrupts the cell cycle -> This kills the cell
  • However, this also affects healthy tissue
148
Q

What are two examples of cell cycle targets for cancer treatments?

A
  • Gap phase 1

* Synthesis

149
Q

Describe how cancer drugs target G1.

A

Mostly chemotherapy drugs:
• Prevent the synthesis of enzymes needed for DNA replication
• Without these, the cell can’t enter synthesis and is forced to kill itself

150
Q

Describe how cancer drugs target the synthesis stage.

A

Mostly radiation and some drugs:
• Damage DNA
• The cell checks its DNA for damage before and during the S phase
• If severe damage is detected, the cell will kill itself.

151
Q

Describe how a root tip can be prepared for observation under a microscope.

A

1) Cut 1cm from the tip of a growing root
2) Prepare a boiling tube containing 1M HCl and put it in a water bath at 60*C
3) Put the root tip into the water and incubate for 5 minutes
4) Use a pipette to rinse the root tip well with cold water. Leave to dry on a paper towel.
5) Place the tip on a microscope slide and cut 2mm from the end. Remove the rest.
6) Use a mounted needle to break the tip open and spread the cells out thinly.
7) Add a few drops of stain and leave for a few minutes.
8) Place a cover slip over the cells and press down to squash the tissue.
9) Observe under a microscope.

152
Q

How can cells on a slide be observed using an optical microscope?

A

1) Clip the slide onto the stage
2) Select the low-powered objective lens
3) Use the coarse adjustment knob to bring the stage up to just below the lens.
4) Looking down the eyepiece, use the coarse adjustment knob to move the stage downwards until it is roughly in focus
5) Adjust the focus with the fine adjustment knob
6) Repeat with higher magnification if necessary

153
Q

What is true formula for mitosis index?

A

Mitotic index = No. of cells in mitosis / Total no. of cells

154
Q

What does the mitotic index tell us?

A
  • How quickly the tissue is growing

* High mitotic index might suggest cancerous growth or that tissue repair is happening

155
Q

What is an eyepiece graticule?

A

A transparent ruler without units that is fitted onto the

156
Q

What is a stage micrometers and what is it used for?

A
  • A microscope slide with a an accurate scale (with units).

* Used to work out the value of the divisions on the eyepiece graticule at a particular magnification.

157
Q

Describe how a stage micrometer and eyepiece graticule work together.

A

A stage micrometer is used to calculate what length each division on the eyepiece graticule represents.

158
Q

What formula relates the actual size of a cell, the size of the image and the magnification?

A

Actual size = Size of Image / Magnification

159
Q

What are artefacts?

A

Things that you can see down the microscope that aren’t part of the cell or specimen.

160
Q

Give some examples of artefacts.

A
  • Dust
  • Air bubbles
  • Fingerprints
161
Q

When are artefacts especially common and why?

A

• In electron micrographs • Because the specimen requires a lot of preparation before viewing under an electron microscope

A LEVEL - Biology (P2) (19 decks)

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