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AQA Biology: A Level > Paper 1 and 3: Cells > Flashcards

Paper 1 and 3: Cells Flashcards

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1
Q

What is the function of the nucleus? [2]:

A
  • contains the genetic material of the cell

- controls the activity of the cell

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2
Q

Nucleus location:

A

It is surrounded by a nuclear envelope which contains nuclear pores and chromosomes

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3
Q

Inside the nucleus [2]:

A
  • Chromatin

- The nucleolus

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4
Q

Chromatin [definition]:

A

DNA wrapped around proteins called histones

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5
Q

What is the nucleolus?

A

The site where ribosomes are made

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6
Q

What are ribosomes and where are they found? [2]:

A
  • Ribosomes are the site of protein synthesis

- They are found floating in the cytoplasm or attached to the RER

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7
Q

Cytoplasm [definition]:

A

A watery liquid where most chemical reactions occur

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8
Q

What does RER stand for?

A

Rough endoplasmic reticulum

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9
Q

What is the rough endoplasmic reticulum?

A

A membrane enclosed, fluid filled, space covered with ribosomes.

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10
Q

What is the function of the RER?

A

It is the site where proteins are processed and folded

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11
Q

Eukaryotic ribosomes =

A

80S- bigger than prokaryotic ribosomes

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12
Q

Prokaryotic ribosomes =

A

70S- smaller than eukaryotic ribosomes

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13
Q

What does SER stand for?

A

Smoothe endoplasmic reticulum

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14
Q

SER [definition]:

A

Membrane enclosed, fluid filled spaces that are NOT covered with ribosomes

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15
Q

SER [function]:

A

It synthesises and processes lipids

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16
Q

Golgi aparatus/body [definition]:

A

A group of fluid filled, flattened sacs, associated with vesicles

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17
Q

Vesicle [defintion]:

A

Small, membrane bound sacs

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18
Q

Golgi apparatus [function]:

A

It processes and packages new lipids and proteins which are then transported else where in the cell by the vesicles

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19
Q

Lysosomes [definition]:

A

Rounded organelles surrounded by a double membrane.

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20
Q

Lysosomes [function]:

A

They contain digestive enzymes called lysozymes which are used to digest pathogens and worn/damaged components of the cell

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21
Q

Mitochondria [description]

[2]:

A
  • It has a double membrane where the inner membrane folds into cristae
  • It contains a matrix similar to cytoplasm, and enzymes that are involved in respiration
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22
Q

Mitochondria [function]:

A

It is the site of aerobic respiration and therefore the production of ATP. It is the energy source of the cell

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23
Q

Cell/ surface membrane [function]:

A

Controls the movement of substances into and out of the cell

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24
Q

Microvilli [definition]:

A

Folds on the cell membrane

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25
Q

Microvilli [function]:

A

Increase surface area. Mostly found on cells that are involved in absorption

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26
Q

Thingies found in a chloroplast [6]:

A
  • Thylakoid/ Granum
  • Double membranes (outer + inner)
  • Lamellae
  • Stroma
  • Lipid droplets
  • Starch granules
    TDLSYLS
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27
Q

What is a granum?

A

A stack of thylakoids

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28
Q

What is the function of the lamallae?

A

It conects granum

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29
Q

Eukaryotic cells [info]

[3]:

A
  • Has a nucleus
  • Has membrane bound organelles
  • 80S ribosomes
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30
Q

Prokaryotic cells [info]

[5]:

A
  • Does NOT have a nucleus
  • Does NOT have any membrane bound organelles
  • Has plasmid loops of DNA instead
  • 70S ribosomes
  • Can have slime capsules
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31
Q

Plasmids:

A

Small loops of DNA that carry a few genes (usually coding for antibiotic resistance)

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32
Q

Flagellum:

A

Helps in locomotion. There can be more than one in a cell

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33
Q

Slime capsule:

A

Acts as protection for the bacteria from the immune system

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34
Q

Pilli:

A

Allow plasmids to go through one bacteria into the next

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35
Q

Animal cells do not have [3]:

A
  • Cell walls
  • Chloroplasts
  • Vacuoles
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36
Q

Plant cell walls are made of…

A

cellulose

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37
Q

Algal cell walls are made of…

A

cellulose

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38
Q

Fungal cell walls are made of…

A

Chitin

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39
Q

What are the 3 different types of microscopes used to study cell structure?

A
  • The light/optical microscope
  • The scanning electron microscope (SEM)
  • The transmission electron microscope (TEM)
40
Q

The light microscope [3]:

A
  • Use light to form an image
  • Has the lowest magnification and resolution
  • Has a maximum magnification of x1500
41
Q

Why do specimens for a light microscope need to be stained?

A

The stain provides a greater contrast which allows us to see in more detail

42
Q

Why do light microscope specimens have to be thin?

A

So that light can pass through

43
Q

Why do light microscopes have the lowest resolution?

A

cus visible light has a long wave length

44
Q

The scanning electron microscope (SER)

[4]:

A
  • Allows you to see in 3D/ produces 3D images
  • Can be used on thick specimens
  • Has a lower resolution than TER but higher than light microscope
  • Cannot be used on living specimens
45
Q

How do scanning electron microscopes work? [3]:

A
  • The image is produced when a beam of electrons is scanned across the specimen.
  • This knocks electrons off the specimen
  • The electrons are collected in a cathode ray to form an image
46
Q

Transmission electron microscopes (TEM)

[4]:

A
  • Gives the highest resolution
  • Cannot be used on living specimens
  • Specimens must be thin
  • Allows internal structures in a cell to be seen in detail
47
Q

How do TEM microscopes work? [2]:

A
  • Uses electromagnets to focus a beam of electrons which is transmitted through the specimen
  • The denser parts of the specimen absorb more elctrons which makes them look darker
48
Q

Artefacts:

A

Debris floating around in a cell

49
Q

Resolution vs magnification [2]:

A
  • Resolution= how clear the image is

- Magnification= how zoomed in it is lol

50
Q

Image size =

A

magnification x actual size

51
Q

mm → μm =

A

x 1000

52
Q

μm → mm

A

÷ 1000

53
Q

How to make a slide [3]:

A
  • Place a drop of water on the slide (to wash it)
  • Place a thin specimen on the slide and apply a stain
  • Place a cover slip over the specimen at 45 º using a mounted needle
54
Q

Obtaining organelles from cells/ Cell fractionation [7]:

A
  • Tissue put in ice cold isotonic solution containing a buffer
  • Tissue is homogenised using a homogeniser or blender
  • Homogenised cell solution is filtered to remove large cell debris
  • Cell solution is poured into a centrifuge tube to go through ultracentrifugation
  • A pellet of the heaviest organelles forms at the bottom of the tube
  • The liquid above the pellet (supernatant) contains the lighter organelles and is drained into a different tube
  • Process repeated at higher speeds until all the organelles are separated out
55
Q

Why is the tissue homogenised?

A

To beak up the cell membrane of the tissue cells, releasing the organelles into the solution

56
Q

Why are the tissues placed in an ice cold solution?

A

To slow down enzyme activity so that the organelles are not damaged

57
Q

Why is the solution buffered?

A

Buffers maintain the pH of a solution so that proteins are not denatured and that organelles are not damaged

58
Q

Why are the tissues placed in an isotonic solution?

A

To prevent osmosis and water entering the organelles, causing them to burst

59
Q

In what order do the organelles sediment out? [5]:

A
  1. Nucleus
  2. Mitochondria + chloroplasts
  3. Lysosomes
  4. SER + RER
  5. Ribosomes
    NMLSER
60
Q

What are the 4 stages of mitosis?

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
61
Q

Cell cycle [4]:

A
  1. Mitosis
  2. Gap phase (G1)
  3. Synthesis (s/ DNA replication)
  4. Gap phase (G2)
62
Q

Common parts of prokaryotic cells [3]:

A
  • plasmid(s)
  • Capsule surrounding the cell
  • One or more flagella
63
Q

Viruses [4]:

A
  • Are acellular and non-living
  • Have genetic material,
  • capsid,
  • attachment protein
64
Q

What are the stages of mitosis? [4]:

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase (&and cytokinesis)
65
Q

Prophase [3]:

A
  • The nuclear envelope breaks down
  • Chromosomes condense, shorten and fatten
  • Centrioles move to opposite poles to form spindle fibres
66
Q

Metaphase [3]:

A
  • The chromosomes are seen to be made out of two chromatids
  • Spindle fibres attach to the centromere of the chromosomes
  • Chromosomes line up along the equator
67
Q

What is the order of the stages in mitosis?

A

PMAT

68
Q

Anaphase [2]:

A
  • Spindle fibres contract to pull sister chromatids to opposite poles of the cell
  • Sister fibres look v-shaped
69
Q

Telophase [4]:

A
  • Sister chromatids at opposite poles of the cell
  • The nuclear envelope reforms around the chromosomes
  • The are 2 nuclei now
  • The cytoplasm splits and there are now 2 genetically identical daughter cells
70
Q

What is cytokinesis?

A

When the cytoplasm splits

71
Q

What is the process in which prokaryotic cells divide?

A

Binary fission

72
Q

Binary fission [4]:

A
  • The circular DNA molecule replicates and both copies attach to the cell membrane
  • Plasmid replicates
  • The cell membrane begins to grow between the 2 DNA molecules, dividing the cytoplasm in 2
  • A new cell wall forms between the 2 molecules of DNA, dividing the original cell into 2 identical daughter cells
73
Q

What does each daughter cell have in binary fission? [2]:

A
  • A copy of circular DNA

- variable number of copies of plasmids

74
Q

Virus cell division [2]:

A
  • They do not undergo cell division

- Following the injection of their nucleic acid, the infected host cell replicates the virus particles

75
Q

Required practical 2

A

Preparation of stained, squashed cells from plant root tips; set up and use an optical microscope to identify the stages of mitosis in these stained squashes and calculation of a mitotic index

76
Q

Why is the tip of the root cell used in required practical 2?

A

It is where the most meristematic tissue can be found

lots of meristem tissue

77
Q

Mitotic index =

A

Number if cells in mitosis
————————————- x 100
Total number of cells

78
Q

Interphase [2]:

A
  • Occupies the most of the cell cycle (G1 & G2)

- Also known as the resting stage because no division takes place

79
Q

Nuclear division:

A

Mitosis or meiosis

80
Q

Mitosis is a…

A

controlled process

81
Q

What does uncontrolled cell division lead to?

A

Tumours/ cancer

82
Q

Cancer treatments [2]:

A
  • Preventing the DNA from replicating

- Inhibiting the metaphase stage of mitosis by interfering with spindle formation

83
Q

Issue with cancer treatment drugs [2]:

A
  • They also disrupt the cell cycle of normal cells and not just cancerous ones
  • However the drugs are very effective against rapidly dividing cells
84
Q

Cell surface membrane [2]:

A

The plasma membrane that surrounds the cell and forms the boundary between the cell cytoplasm and the environment
- Allows substances in and out of the cell

85
Q

Why is it called the fluid mosaic model? [2]:

A
  • Mosaic- because proteins of different shapes and sizes are embedded within the phospholipid bilayer
  • Fluid- because it can move and is flexible. It is not rigid.
86
Q

Cell membrane components [7]:

A
  • Phospholipid Bilayer
  • Extrinsic Proteins
  • Carrier Proteins
  • Protein channels/ Channel protein
  • Glycoproteins
  • Glycolipids
  • Cholesterol
87
Q

Phospholipid Bilayer [3]:

A
  • This forms a double layer and is the main part of the membrane
  • It forms a barrier between the internal and external environment.
  • It prevents water soluble molecules from entering the cell.
88
Q

Carrier Proteins [function]:

A

These proteins allow large molecules to enter and leave the cell by changing shape

89
Q

Protein channels/ Channel protein [2]:

A
  • These proteins have smaller water filled pores running through the middle
  • They allow some large molecules, water soluble and charged molecules to enter and leave the cell
90
Q

Extrinsic Proteins [function]:

A

These are proteins that are partly embedded in the phospholipid bilayer and provide mechanical support

91
Q

Glycoproteins [2]:

A
  • They are protein molecules embedded in the phospholipid bilayer with a carbohydrate molecule attached
  • Their function is as receptors and they are also involved in cell recognition
92
Q

Cholesterol molecule [function]:

A

These molecules are randomly found throughout the phospholipid bilayer, adding strength and rigidity

93
Q

Glycolipids [2]:

A
  • These are phospholipid molecules in the bilayer with a carbohydrate chain attached
  • Its function is also reception and recognition
94
Q

What is a thylakoid?

A

Flattened sacs inside a chloroplast, bound by pigmented membranes where photosynthesis take place

95
Q

What happens during interphase that prepares cells for mitosis? [3]:

A
  • Build-up of energy stores
  • Increase in cytoplasm
  • Synthesis of proteins

AQA Biology: A Level (18 decks)

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