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Biology A LEVEL > Cell Structure, Magnification and Mitosis > Flashcards

Cell Structure, Magnification and Mitosis Flashcards

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1
Q

What are the two main types of organisms?

A

Eukaryotes and Prokaryotes

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2
Q

What are prokaryotic cells?

A

single- celled organisms that are small and simple eg bacteria

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3
Q

What are eukaryote?

A

Any organism consisting of one or more cells that contain DNA in a membrane bound nucleus – separate from the cytoplasm. ​

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4
Q

What are example of eukaryotes?

A

Animals, Plants, Fungi, Protists​

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5
Q

What is the structure of an animal cell?

A
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6
Q

What is the structure of plant cell (practice on white board)

A
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7
Q

What makes a fungal cell different from a plant cell?

A
  • Their cell walls are made of chitin
  • They don’t have chloroplasts (they don’t photosynthesize)
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8
Q

Where is the cell surface membrane found? (description)

A
  • Surface of animal cells
  • Inside cell wall of other cells
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9
Q

What is the cell surface membrane made of?

A

Mainly lipids and protein

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10
Q

What is the function of the cell surface membrane?

A
  • Regulates movement of substances in and out of the cell.
  • Has receptor molecules - Allows it to respond to chemicals like hormones
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11
Q

What is the description of a nucleus?

A
  • Surrounded by nuclear envelope (double membrane) - contains many pores
  • Contains chromatin to form chromosomes
  • contains nucleolus which is the site of ribosome synthesis
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12
Q

What is the function of a nucleus?

A
  • Controls cell’s activities
  • Pores allow substances to move between nucleus and cytoplasm
  • Nucleolus makes ribosomes
  • Contains DNA in form of chromosomes
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13
Q

Describe a Mitochondrion

A
  • Usually oval - shaped
  • Double membrane - inner one folded to form cristae
  • Inside is the matrix - contains enzymes involved in respiration
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14
Q

What is the function of mitochondrion?

A
  • Site of aerobic respiration where ATP is produced.
  • Found in large numbers in cells that are very active and require a lot of energy
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15
Q

Describe Chloroplasts

A
  • Small and flattened - found in plant and algal cells
  • surrounded by double membrane
  • Membranes inside - Thykaloid membranes
  • Membranes stacked up in parts of chloroplasts to form grana
  • Grana linked together by lamellae
  • Lamellae - thin, flat, pieces of thylakoid membrane
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16
Q

What is the function of chloroplasts?

A
  • Site of photosynthesis
  • 1st stage of photosynthesis happens in the grana (light photosynthesis)
  • 2nd stage happens in stroma- sugar photosynthesis (thick fluid found in chloroplasts)
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17
Q

What is the description of Golgi Apparatus?

A
  • Group of fluid-filled membrane-bound flattened sacs.
  • Vesicles often seen at the edges of the sacs.
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18
Q

What is the function of Golgi apparatus?

A
  • Processes and packages new lipids and proteins
  • Makes lysosomes
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19
Q

What is the description of Golgi vesicle?

A
  • Small fluid-filled sac in the cytoplasm
  • Surrounded by a membrane
  • Produced by Golgi Apparatus
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20
Q

What is the function of Golgi vesicle?

A
  • Stores lipids and proteins made By Golgi Apparatus
  • Transports them out of the cell (via cell-surface membrane)
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21
Q

What is the description of Lysosome?

A
  • Round organelle surrounded by a membrane
  • Type of Golgi vesicle
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22
Q

What is the function of Lysosomes?

A
  • Contains digestive enzymes called lysozymes - kept separate from cytoplasm by surrounding the membrane
  • Lysozymes can be used to digest invading cells or break down worn out components of the cell
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23
Q

What is the description of ribosome?

A
  • Very Small
  • Floats free in cytoplasm or attached to rough endoplasmic rectum
  • Made up of proteins and RNA
  • NOT SURROUNDED BY MEMBRANE
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24
Q

What is the function of Ribosomes?

A
  • Site where proteins are made
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25
Q

What are the two types of ribosomes?

A

70S - found in prokaryotes
80S - found in eukaryotes

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26
Q

What is the description of Rough Endoplasmic Rectum?

A
  • A system of membranes enclosing a fluid-filled space.
  • The surface is covered with ribosomes.
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27
Q

What is the function of rough endoplasmic rectum?

A

Folds and processes proteins that have been made at the ribosomes

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28
Q

What is the structure of smooth endoplasmic rectum?

A

Similar to rough endoplasmic reticulum, but with no ribosomes.

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29
Q

What is the function of smooth endoplasmic rectum?

A

Synthesises and processes lipids

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30
Q

What is the structure of a cell wall?

A
  • A rigid structure that surrounds cells in plants, algae and fungi.
  • In plants and algae it’s made mainly of the carbohydrate cellulose.
  • In fungi, it’s made of chitin.
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31
Q

What is the function of Cell wall?

A

Supports cells and prevents them from changing shape.

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32
Q

What is the structure of Cell vacuole?

A
  • A membrane-bound organelle found in the cytoplasm of plant cells.
  • Contains cell sap - a weak solution of sugar and salts.
  • The surrounding membrane is called the tonoplast.
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33
Q

What is the function of a vacuole?

A
  • Helps to maintain pressure inside the cell
  • Keeps cell rigid - stops plant wilting
  • Isolates unwanted chemicals in cell
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34
Q

What is the difference between Plants and animal cells?

A

Plants have a cellulose cell wall with plasmodesmata, vacuole and chloroplasts

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35
Q

What is plasmodesmata?

A

‘channels’ for exchanging substances with adjacent cells

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36
Q

What is the difference between unicellular and multicellular organisms?

A

unicellular - all the functions necessary for life must be carried out in one cell.
multicellular - can delegate jobs to particular group of cells

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37
Q

What is differentiation?

A

The process by which a cell becomes specialized to perform a specific function

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38
Q

Do all cells contain the same DNA?

A

YES but different genes are switched on

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39
Q

What are specialized cells?

A

Cells that have adapted to a specific function

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40
Q

What are the two key types of microscopes?

A

Light and electron

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41
Q

What are the two types of electron microscope?

A

transmission and scanning

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42
Q

What does magnification mean?

A

how many times larger the image is compared to the actual size of the object.

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43
Q

What is resolution?

A

The ability to distinguish between two separate points

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44
Q

How is resolution determined in light and electron microscopes?

A
  • In light microscopes, it’s determined by the wavelength of light
  • in electron microscopes, by the wavelength of the electron beam.
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45
Q

What is the main source of light in a light microscope?

A

A beam of light from a lamp or a mirror.

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46
Q

Why do light microscopes have lower resolution than electron microscopes?

A

light has a longer wavelength compared to electrons.

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47
Q

What type of images can light microscopes provide?

A

Color images and can use living samples.

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48
Q

What must specimens be in for electron microscopes to work?

A

A vacuum.

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49
Q

What is the formula for calculating magnification?

A

Image size = actual size × magnification.

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50
Q

What is the difference between transmission and scanning electron microscopes?

A
  • Transmission passes electrons through the specimen for 2D images
  • scanning reflects electrons off the surface for 3D images.
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51
Q

What is the purpose of an eyepiece graticule?

A

allows for precise measurements and analysis of microscopic specimens.

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52
Q

Why must the eyepiece graticule be calibrated?

A

Because the value of the divisions changes with different magnifications.

53
Q

What is a stage micrometer?

A

A glass slide with a scale used to calibrate the eyepiece graticule.

54
Q

How do you use a stage micrometer to calibrate the eyepiece graticule?

A
  • Line it up with the eyepiece graticule
  • Count how many divisions fit into one division of the stage micrometer.
55
Q

What is an advantage of knowing the actual size of structures in microscopy?

A

It allows for accurate measurements of cells and organelles under the microscope.

56
Q

How do prokaryotic cells replicate compared to eukaryotic cells?

A

by binary fission, not mitosis.

57
Q

How do viruses replicate?

A

by injecting their nucleic acid into host cells.

58
Q

What are the main stages of the cell cycle?

A

interphase G1 (Gap Phase 1), S (Synthesis), and G2 (Gap Phase 2). nuclear division (mitosis or meiosis), and cytokinesis.

59
Q

During which phase does the cell spend most of its cycle?

A

(about 90%) is spent in interphase.

60
Q

What happens during the G1 phase of interphase?

A

organelles double, and the cell grows in preparation for division.

61
Q

What occurs in the S phase of interphase?

A

DNA replication

62
Q

What is checked in the G2 phase of interphase?

A

The cell checks DNA for mutations in G2 and destroys the cell if mutations are found.

63
Q

What are the four key stages of mitosis?

A

prophase
metaphase
anaphase
and telophase.

64
Q

What happens during prophase in mitosis?

A
  • Chromosomes condense and become visible
  • chromosomes consists of sister chromatids (identical)
  • centrioles move to opposite poles
  • the nuclear envelope disintegrates.
65
Q

What happens in metaphase?

A

Chromosomes align along the metaphase plate of the cell, and attach to spindle fibres via centromeres.

66
Q

What happens in anaphase?

A

Spindle fibers retract, pulling chromatids to opposite poles, and this process requires ATP.

67
Q

what happens in telophase?

A
  • Chromosomes reach opposite poles
  • become longer and thinner
    -spindle fibers break down, and the nuclear envelope reforms.
68
Q

What is cytokinesis?

A

the final step where the cytoplasm splits, resulting in two genetically identical cells.

69
Q

What is the mitotic index, and how is it calculated?

A
  • the ratio of cells in mitosis to the total number of cells.
  • It’s calculated by dividing the number of cells in mitosis by the total cells in view.
70
Q

What is the purpose of Mitosis?

A

for growth and repair, such as when replacing old cells or creating new cells.

71
Q

How many daughter cells are produced in mitosis, and how many divisions occur?

A

two daughter cells through one division.

72
Q

How is cancer related to mitosis?

A

Cancer is caused by uncontrolled cell division, leading to excessive cell growth and tumor formation.

73
Q

What role do genes play in cell division?

A

They regulate cell division; mutations in these genes can lead to uncontrolled cell division.

74
Q

How do most cancer treatments work?

A

restricting cell division, targeting rapidly dividing cancer cells more than normal cells.

75
Q

Why do cancer treatments affect cancer cells more than normal cells?

A

Cancer cells divide more frequently

76
Q

Method for measuring cells

A
  • Calibrate eyepiece graticule using stage micrometer
  • Measure cell length
  • Repeat measurements and calculate a mean
77
Q

Method for measuring cells

A
  • Calibrate eyepiece graticule using stage micrometer
  • Measure cell length
  • Repeat measurements and calculate a mean
78
Q

Why should a sample be thin and transparent

A

to allow light pass through

79
Q

why do we use stains ?

A

to see the cells more clearly

80
Q

Why are there lots of different types of stain?

A
  • Some don’t work on other cells
  • Specific stain for different cells
81
Q

What is a plasma membrane, and where is it found?

A

structure surrounding both cells and certain organelles, like mitochondria.

82
Q

What is the “fluid mosaic model”?

A
  • describes the membrane’s structure
  • where “fluid” refers to the mobility of molecules
  • “mosaic” refers to the variety of components.
83
Q

What are the main components of the plasma membrane?

A

phospholipids, proteins, glycoproteins, glycolipids, and cholesterol.

84
Q

What is the phospholipid bilayer, and how is it structured?

A

The bilayer consists of two layers of phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward.

85
Q

Describe the structure of a phospholipid

A
  • hydrophilic head (containing a phosphate group)
  • hydrophobic tails (made of fatty acid chains).
86
Q

What role does cholesterol play in the plasma membrane?

A
  • restricts the lateral movement of molecules, making the membrane less fluid and more stable at high temperatures.
87
Q

Differentiate between peripheral and integral proteins in the membrane.

A
  • Peripheral proteins are on one side of the membrane
  • integral proteins span the entire membrane.
88
Q

What are glycoproteins and glycolipids, and what is their function?

A
  • Glycoproteins (proteins with carbohydrates)
  • glycolipids (lipids with carbohydrates)

function as receptors and help in cell recognition.

89
Q

What is the difference between channel proteins and carrier proteins?

A
  • Channel proteins form a pore for water-soluble ions to pass through
  • carrier proteins bind and transport larger molecules across the membrane.
90
Q

What is meant by the plasma membrane being “partially permeable”?

A
  • Only certain molecules, like lipid-soluble substances and small molecules (e.g., oxygen, CO₂), can diffuse directly through the bilayer.
91
Q

Which molecules cannot pass through the membrane via simple diffusion?

A
  • Large polar substances like glucose and ions
  • water-soluble substances
92
Q

What are the size and structure differences between prokaryotic and eukaryotic cells?

A

Prokaryotic cells are smaller, lack membrane-bound organelles, and have simpler structures

93
Q

Do prokaryotic cells have membrane-bound organelles?

A

NO

94
Q

What kind of ribosomes do prokaryotic cells have?

A

70S ribosomes, while eukaryotic cells have 80S ribosomes.

95
Q

In which eukaryotic organelles might you also find 70S ribosomes?

A

mitochondria and chloroplasts of eukaryotic cells.

96
Q

Describe the DNA structure in prokaryotic cells.

A

have circular DNA that is free within the cytoplasm

97
Q

How does the nucleus in eukaryotes compare to prokaryotes?

A

Eukaryotes have a nucleus with a nuclear envelope, nucleoplasm, and linear chromosomes with histones; prokaryotes lack a nucleus.

98
Q

What are prokaryotic cell walls made of?

A

glycoprotein called murein.

99
Q

What are the differences in cell walls among prokaryotes, plants, and fungi?

A
  • Prokaryotes have murein
  • plant cell walls are made of cellulose
  • fungi have chitin-based cell walls.
100
Q

What is a plasmid in a prokaryotic cell?

A

a small loop of additional DNA that may contain genes, like antibiotic resistance genes.

101
Q

What is the capsule, and what are its functions?

A

a slimy protein layer that prevents drying out and helps protect bacteria from the host’s immune system.

102
Q

What is a flagellum, and what does it do in some prokaryotic cells?

A

tail-like structure that rotates to propel the bacterium, allowing it to “swim.”

103
Q

Are capsules and flagella found in all prokaryotic cells?

A

NO

104
Q

What is cell fractionation?

A

a process that isolates different organelles from cells to study them individually.

105
Q

three main steps in cell fractionation?

A

homogenization, filtration, and ultracentrifugation.

106
Q

What occurs during homogenization?

A

Cells are broken open in a solution to release organelles, often using a blender or homogenizer.

107
Q

Why is the solution kept cold, isotonic, and buffered during homogenization?

A

Cold: To reduce enzyme activity and prevent damage.

Isotonic: To prevent organelles from bursting or shrinking.

Buffered: To maintain a stable pH and avoid damage from pH changes.

108
Q

What is the purpose of filtration in cell fractionation?

A

To remove large cell debris, leaving a liquid with organelles.

109
Q

What is ultracentrifugation?

A

A process that separates organelles by spinning them at high speeds.

110
Q

In what order do organelles separate during ultracentrifugation?

A

Organelles separate by density:
- first nucleus, then mitochondria, followed by lysosomes, endoplasmic reticulum and finally ribosomes (from heaviest to lightest)

111
Q

Why are multiple centrifugation speeds used in ultracentrifugation?

A

Each speed allows different organelles to settle out based on their density and size.

112
Q

What forms at the bottom of the tube during ultracentrifugation?

A

A pellet of organelles forms at the bottom, with lighter components remaining in the supernatant.

113
Q

What three properties must the solution have during cell fractionation?

A

cold, isotonic, and buffered.

114
Q

What force does a centrifuge generate to separate organelles?

A

Centrifugal force.

115
Q

What is the supernatant in ultracentrifugation?

A

The liquid remaining above the pellet after centrifugation.

116
Q

What happens to the supernatant in differential centrifugation?

A

It is re-spun at a higher speed to separate the next dense organelle.

117
Q

How are organelles separated in differential centrifugation?

A

By spinning the supernatant at increasing speeds to isolate each type of organelle.

118
Q

In plant cells, what is found in the second pellet during centrifugation?

A

Chloroplasts.

119
Q

If asked to separate chloroplasts from plant cells, what is a key step?

A

Spin once to remove the nucleus, then re-spin to isolate chloroplasts in the second pellet.

120
Q

Are viruses considered living cells?

A

NO

121
Q

Where do viruses replicate?

A

Inside of a host cell

122
Q

Why are viruses challenging to treat with medicine?

A

Destroying the virus would also require destroying the host cell.

123
Q

Why can’t antibiotics destroy viruses?

A

Antibiotics target specific cellular processes like protein synthesis or cell walls, which viruses lack.

124
Q

What does the structure of a virus lack compared to bacterial cells?

A

membrane-bound organelles and certain chemical reactions found in bacteria.

125
Q

What are the main structural components of viruses?

A

protein envelope, a capsid, and genetic material (DNA or RNA).

126
Q

Describe Binary fission in bacteria

A
  • Replication of DNA
  • Replication of plasmids
  • Division of cytoplasm to produce daughter cells
127
Q

during cell fractionation a detergent can be used - why?

A

Cell membranes made of phospholipids

Detergent dissolves membranes

Releasing cell contents

128
Q

In an investigation about diffusion and plasma membranes (beetroot discs) why would you ensure the beetroot discs were shaken?

A
  • To ensure all the discs exposed to water/ all discs fully submerged
  • maintain concentration/diffusion gradient

Biology A LEVEL (6 decks)

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