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AQA A Level Biology > 3.2.1 Cell Structure > Flashcards

3.2.1 Cell Structure Flashcards

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1
Q

What is a tissue?

A

A group of specialised cells

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2
Q

What is an organ?

A

A combination of different tissues that are co-ordinated to perform a variety of functions

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3
Q

What is an organ system?

A

Many organs working together to perform a function

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4
Q

Give an example of a organ system?

A

Digestive, respiratory or circulatory

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5
Q

A group of abnormal cells is….

A

A tumor

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6
Q

What is the adaptation of the sperm cell?

A

Organelles

Acrosome in head has digestive enzymes (break down egg)
Mid-piece packed with mitochondria to release energy for movement

Movement
Tail rotates so it can swim

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7
Q

What is the adaptation of the xylem and pholem?

A

XYLEM
No top/bottom wallas
Ligin = supports tubes
Cells w/o organelles so free movement of water

PHOLEM
Cells have few subcelluar structures
Made of living cells
Cells joined end to end = flow is easier

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8
Q

What are the adaptations of the root hair cell?

A

Increased surface area (uptake of H20 is greater)
Thinner walls = shorter diffusion pathway

Organelle
Mitochondria = active transport for mineral ions
Permanent vacuole = water potential is maintained

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9
Q

When do eukaryotes get specialised?

A

In multicelluar organisms

Eukaryotes have become specialised to specific functions

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10
Q

What is the adaption for the muscle cells?

A

Shape
Layers of protein filaments = cause contraction as they slide over each other

Organelles
High density of mitochondria = provide energy for contraction

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11
Q

What is the adaptation of the red blood cell?

A

Biconcave shape
No nucleus
= more space so more 02 can be transported

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12
Q

Give an example of a tissue?

A

Epithelial tissue, xylem and muscle

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13
Q

What are the adaptations of neurons?

A

Dendrites + axons → receive and transmit signals

Axons covered in fatty sheats

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14
Q

What is an Animal Cell made of?

A

Organelles (nucleus, endoplasmic reticulum, golgi body, lysosomes, mitochondria, ribosomes) – all have membrane except the ribosomes

Cytoplasm (site of chemical reaction)

Cell Membrane (holds cell contents together, controls what enters/leaves cell, cell signalling)

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15
Q

What two things can change with adaptation to a eukaryotic cell?

A

The shape of the cell

The organelles

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16
Q

Instead of a single membrane, the mitochondria is what?

A

Double membrane organelle

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17
Q

What is the cell surface membrane made out of?

A

Phospholipid bilayer

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18
Q

What does the cristae in the mitochondria provide?

A

A high surface area

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19
Q

What is the function of the chloroplasts?

A

The site of photosynthesis

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20
Q

What is the structure of the nucleus?

A 
DNA
(DNA wrapped in histones to make) chromatin 
Nuclear Envelope (double membrane)
Nuclear pores 
Nucleolus 
Nucleoplasm
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21
Q

What are the functions of the nucleus?

A

Site of DNA replication and transcription

Contains the genetic code for a single cell

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22
Q

Describe the structure of the endoplasmic reticulum

A

Folded membranes
Fluid filled
RER AND SER

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23
Q

Function of the RER

A

Synthesize and transport proteins throughout the cell

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24
Q

Function of the SER

A

Synthesise, store and transport lipids and carbohydrates

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25
Q

What is the difference between the RER and SER?

A

RER has ribsomes on surfaces

SER has NO ribsomes

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26
Q

What is the function of the golgi apparatus?

A

Modify and package proteins
Packages into vesicles for transport
Digestive enzymes are placed into lysosomes

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27
Q

What is the function of the ribsomes?

A

Site of protein synthesis

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28
Q

Name all the organelles in a Eukaryotic Cell?

A 
Cell surface membrane 
Nucleues 
Mitochondria 
Chlorplasts 
Golgi apparatus 
Lysosomes 
Ribosomes 
RER
SER
Cell wall 
Cell Vacoule
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29
Q

What is a plant cell made of?

A

Organelles w/ chloroplasts + vacuole
Cytoplasm
Cell membrane
Cell wall

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30
Q

What is the structure of the chloroplast?

A 
Double membrane 
Contains thylakoids 
Thylakoids contain chlorophyll
Stack of thylakoids is Granum
Stroma is fluid surrounding
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31
Q

What is the role of the permanent vacuole?

A

Providing support = turgid
Stores sugars + amino acids
Pigments help attract pollinators

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32
Q

What is the function of the cell wall?

A

Provides stability

Prevents the bursting of the cell from osmosis pressure of water

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33
Q

What three things have a cell wall?

A

Fungi
Plants
Algae

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34
Q

What is the cell wall made of in plants?

A

Cellulose

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35
Q

What is the role of the cell surface membrane?

A

To control the movement of substances in and out of the cell

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36
Q

What are lysomes?

A

Relatively small organelles formed when the vesicles made by the golgi contain digestive enzymes

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37
Q

What are the four functions of the lysosomes?

A

Hydrolse phagocytotic cells

Break down dead cells

Break down old organelles

Release enzymes outside the cell to destory material around the cell (exocytosis)

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38
Q

What is the cell wall made of in fungi?

A

Chitin

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39
Q

What is the cell wall made of in Algae?

A

Cellulose or glycoprotiens

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40
Q

What organelles does a prokaryotic cell have?

A 
Cell wall 
Capsule 
Cell surface membrane 
Cytoplasm 
Circular strand of DNA 
Plasmids 
Flagellum 
Ribsomes
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41
Q

What is the cell wall made of in Prokayotic cell?

A

Muerin (glycoprotien)

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42
Q

What is the role of plasmids?

A

Contains gene that aid survival of prokaryotes

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43
Q

Describe the structure of virueses

A

Nucleic acid (dna/rna)
a caspid
Attachment protien

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44
Q

Why are viruses described as acellular and non-living

A
  • Acellular → not made of or able to be divided into cells

- Non-living → unable to exist/reproduce without a host cell

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45
Q

How does an optical microscope work?

A

Use light to form 2d images

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46
Q

What are limitations of light microscopes?

A

Low resolution so cant view smaller organisms

Only used on thin specimens

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47
Q

What are the advantages of optical microscope?

A

Can see living organisms

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48
Q

How does a Scanning electron microscope work?

A

Breams of electrons scan surface
Knocking off electrons from specimen
Gathered in a cathode ray tube to form a 3D image

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49
Q

What are the advantages of a SEM?

A

3D image
High resolution ( can see internal structures)
High magnification
Used on thick specimen

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50
Q

What are the disadvantages of the SEM?

A

Lower resolution than TEM
Cannot be used on living specimens
No colour images

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51
Q

What are the principles of TEM?

A

Beam of Electrons pass through specimen
Denser parts absorb more electrons
Denser parts are darker in appearance
Electrons have a short wavelength

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52
Q

What are the limitations/disadvantages of TEM?

A

Cannot be living
Specimen must be thin
2D image

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53
Q

What are the advantages of TEM?

A

High resolution; see internal structures

High magnification

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54
Q

Define ‘Magnification’

A

How much bigger the image of a sample is compared to the real size

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55
Q

What is the formula for magnification?

A

by Magnification =

size of image /size of the real object

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56
Q

Define ‘resolution’

A

How well distinguished an image is between 2 points;

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57
Q

Describe how you would measure size of an object viewed with an optical microscope

A
  • Line up eyepiece graticule with stage
    micrometer
  • Use stage micrometer to calculate the size
    of divisions on eyepiece graticule at a
    particular magnification
  • Take the micrometer away and use the
    graticule to measure how many divisions
    make up the object
  • Calculate the size of the object by multiplying the number of divisions by the size of divisions counted
  • Recalibrate eyepiece graticule at different magnifications
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58
Q

In required practical 2, what are the limitations?

A

Squash and staining increase artefacts
An optical microscope has a low magnification power
Cut differently at root = inconsistent size of cells

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59
Q

How to convert μm → nm

A

x1000

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60
Q

How to convert μm → mm

A

divide by 1000

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61
Q

How were people testing for artefacts before modern technology?

A

Repeatedly prepared specimens in different ways

Compared each way, if one had a inconsistency when the others didn’t, most likely to be an artefact

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62
Q

How to convert cm → m

A

divide by 100

63
Q

What is the formula for mitotic index?

A

undergoing mitosis/ total number of cells observed

64
Q

What is the role of a stain in microscopy?

A

Used to colour components of the cell

65
Q

What are artefacts?

A

things that arent actually part of the specimen

66
Q

What is cell fractionation?

A

The process of separating cell organelles from each other

67
Q

What is ultracentrifugation?

A

Process by which fragments in filtered homogenate are separated in a centrifuge

68
Q

What are the stages in cell fractionation?

A

→ homogenisation
→ Filtration
→ Ultracentrifugation

69
Q

Describe full process of Cell fractionation

A

Homogenise tissue in blender = break open cell

Place in a cold, isotonic, buffered solution
Reduction of enzyme activity
No water movement by osmosis/water potential
PH constant so enzymes dont nature

Filter homogenate to remove debris

Centrifuge homogenate = spun at low speed

Remove pellet of heavy organelle and spin supernatant at higher speed

Repeat at higher speeds until organelles separated out/or desired organelle

70
Q

What is the supernatant?

A

Rest of organelles suspended after centrifuge

71
Q

State and explain why we need the certain conditions in Homogenisation?

A

Ice cold = reduces enzyme activity
Isotonic solution = there is no osmosis pressure to do water potential ( no shrink/burst)
Buffered solution = PH at a constant level to prevent damage to protien structure

72
Q

Breifly, describe stage of Homogensaiton

A

Cell in sample broken by blender

Must be under specific conditions: ice cold, isotonic and buffered solution

73
Q

What is the order of organlles heaviest to lightest

A 
Nuclei 
Chloroplasts 
Mitochondria 
Lysosomes 
Endoplasmic reticlum 
Ribosmes

(new cats make love even right?)

74
Q

Which cells retain the ability to divide?

A

Eukaryotic Cells

75
Q

What are the stages of Mitosis?

A

Prophase, Metaphase, Anaphase,Telophase and Cytokinesis

76
Q

What occurs in Interphase?

A

S phase = DNA replicates semi-conservatively leading to two sister chromatids
G1 and G2 = no. of organelles and volume of cytoplasm increases; Protein synthesis and ATP content increases

77
Q

Describe what occurs in Mitosis

A

Parent cell divisions
Two genetically identical daughter cells, containing identical/exact copies of DNA
PMAT stages

78
Q

What occurs in Prophase?

A 
Chromosomes condense
Shorter and Thicker
Two sister chromatids joined by a centromere 
Nuclear envelope breaks down 
Centrioles move to opposite poles 
Formation of Spindle fibers
79
Q

What occurs in Metaphase?

A

Chromosomes align along equator

Spindle fibers attach to chromosomes by centromeres

80
Q

What occurs in Anaphase?

A

Centromere divides
Spindle fibres contract
Pull sister chromatids to opposite poles of the cell

81
Q

What occurs in Telophase?

A

Chromosomes decondesne
Longer and thinner
Nuclear envelope reforms = two nuclei
Spindle fibres and centrioles break down

82
Q

What occurs in Cytokinesis?

A

The division of the cytoplasm producing two new cells

83
Q

How many chromosomes do Human Diploid cells have?

A

46

84
Q

Explain the importance of Mitosis

A

Growth of multicellular organisms by increasing cell number
Repairing damages tissues
Asexual Reproduction

85
Q

How would recognise a cell in Interphase?

A

No chromosomes visible

86
Q

How would recognise a cell in Prophase ?

A

Chromosomes visible but randomly arranged

87
Q

How would recognise a cell in Metaphase?

A

Chromosomes lined up on equator

88
Q

How would recognise a cell in Anaphase?

A

Chromatids being separated to opposite poles by spindles

89
Q

How would recognise a cell in Telophase?

A

Chromosomes in two sets, one at each pole

90
Q

What is a Malignant Tumor?

A

Cancer that spreads and affects other tissues/organs

91
Q

What is a Benign Tumor?

A

Non-Cancerous

92
Q

How do cancers start?

A

Changes occur in genes that control cell division - mutations

93
Q

What are Carcinogens?

A

Agents that may cause Cancer

94
Q

How do some cancer treatments work?

A

Disrupt cell cycle → Mitosis slows down → Tumour growth slows

95
Q

In what two ways can you disrupt the cell cycle as a cancer treatment?

A

Prevent DNA replication → slows down mitosis
Disrupt spindle formation → chromosomes can’t attach to spindle by their centromere → sister chromatids can’t be pulled to opposite poles of cells = slower mitosis

96
Q

What is the advantage and disadvantage of cancer treatments?

A

😊 - Drugs are more effective cancer cells

😔 - Disrupt cell cycle of normal cells too, especially rapidly dividing ones e.g. cells in hair follicles

97
Q

How do Prokaryotic Cells replicate?

A

Binary Fission

98
Q

Describe the process of Binary Fission

A

Circular DNA and Plasmids replicate

Cytoplasm expands as each DNA molecule moves to opposite poles of cell

Cytoplasm Divides

2 Daughter cells, each with single copy of dna and a variable number of plasmids

99
Q

TRUE OR FALSE: “circular DNA replicates once, plasmids can be
replicated many times”

A

True

100
Q

Why do viruses not undergo cell division?

A

They are non-living

101
Q

Describe the process of viral replication

A

Attachment protein binds to complementary receptor protein on surface of host cell

Inject nucleic acid (DNA/RNA) into host cell

Infected host cell replicates the virus particles
]

102
Q

What is the Fluid-mosaic model of membrane structure?

A
  • Molecules within membrane can move laterally (fluid)

- Mixture of phospholipids, proteins, glycoproteins and glycolipids

103
Q

Describe the structure of the cell membrane

A 
It has a Phospholipid Bilayer 
Hydrophilic heads and Hydrophobic tails 
Channel and Carrier Proteins (intrinsic)
Glycolipids
Glycoproteins 
Cholesterol
104
Q

How does the Phospholipid help adapt the membrane?

A

Maintains a different environment on each side of the cell

Fluidity = can bend to take different shapes

105
Q

How do surface proteins help adapt the membrane?

A

Cell recognition/Act as antigens/receptors

106
Q

How does Cholesterol help adapt the membrane?

A

Regulates Fluidity/Increases stability

106
Q

How does Cholesterol help adapt the membrane?

A

Regulates Fluidity/Increases stability

107
Q

What is the main role of cholesterol in the cell membrane?

A

Make the membrane more rigid by restricting the lateral movement of molecules that make up the membrane

108
Q

What is an example of cholesterol doing its role?

A

Binding to fatty acids causing them to pack more closely together

109
Q

Describe Simple Diffusion

A

Net movement of small (non polar) lipid soluble molecules across a selectively permeable membrane down a concentration gradient
Passive

110
Q

What factors affect Simple Diffusion

A

Surface area, concentration gradient and diffusion pathway distance

111
Q

Describe Facilitated diffusion

A

Net movement of lager polar non-lipid soluble molecules aross a selectively permeable membrane down a concentration gradient
Passive
Through a channel protein/carrier protein

112
Q

What is a Carrier protein?

A

Carrier proteins transport large molecules, the protein changes shape when molecule attaches

113
Q

What is a channel protein?

A

Charged/Polar molecules through its pore

114
Q

Describe Active Transport

A

Net movement of ions against a concentration gradient
Uses carrier proteins
Active
Uses energy to change shape of tertiary structure to push through protein

115
Q

Describe Osmosis

A

Net movement of water molecules across a selectively permeable membrane down a water potential gradient
Passive

116
Q

What factors affect Active transport?

A 
PH
Temp
Speed of carrier protein 
No. of carrier proteins 
Rate of respiration (ATP)
117
Q

What is water potential?

A 
the likelihood (potential) of water molecules to diffuse out of or into a
solution;
118
Q

Describe co-transport (sodium and gluocse)

A

Movement of 2 different molecules
Sodium ions are actively transported out of cell into blood by Soidum potassium pump
Sodium ions and glucose move by facilitated diffusion into cell VIA co-transporter protein
Concentration gradient of glucose created (higher concentration in the cell than blood)
Concentration gradient causes glucose to move out of cell into the blood by facilitated diffusion through channel protein

119
Q

How might cells be adapted for transport across their internal or external
membranes

A
  • By an increase in surface area
  • Increase in number of protein
    channels / carriers
120
Q

Define ‘Antigen’

A

Molecules which, when recognised as foreign by the immune system, can stimulate an immune response and lead to the production of antibodies (often on the cell surface membrane)

121
Q

Why are antigens specific?

A 
To allow the immune system to identify: 
Pathogens 
Cells from other organisms of the same species 
Abnormal Body cells 
Toxins released from bacteria
122
Q

Describe the process of Phagocytosis

A

Phagocyte recognises foreign antigens on the pathogen and binds
Phagocyte engulfs the pathogen by surrounding it with its cytoplasm
Pathogen contained in vesicle/phagosome in the cytoplasm of phagocyte
Lysosome fuses with phagosome and releases lysozymes into vesicle/phagosome
These hydrolyse/digest the pathogen
Phagocyte becomes antigen-presenting and stimulates specific immune response

123
Q

What is cell mediated immunity?

A

The type of response when T lymphocytes respond to antigens that are presented on a body cell

124
Q

Describe the cellular response

A

T lymphocytes recognise APCs after phagocytosis

Specific T helper cells with receptors complementary to antigen binds

Becomes activated and divides rapidly by mitosis to form clones

125
Q

What are clones formed in the cellular response used for?

A

Stimulate B cells for the humoral response
Stimulate cytotoxic T cells to kill infected cells
Stimulate phagocytes to engulf pathogens by Phagocytosis

126
Q

Define a ‘Antibody’

A

A protein with specific binding sites produced by B cells in response to the presence of an appropriate antigen

127
Q

What is Humoral Immunity/Response?

A

The type of response which involves B lymphocytes and antibodies

128
Q

Describe what happens in the Humoral Response

A

Clonal Selection
Some become B plasma cells for the primary immune response - secrete large amounts of monoclonal antibody into blood
Some become B memory cells for the secondary immune response

129
Q

Explain ‘Clonal Selection’

A

The receptor on helper t cell attaches to antigen
Activates t cell to divide rapidly
Forms genetically identical cells
These stimulate B-cells to divide and form clones
All produce the antibody that is specific to the foreign antigen

130
Q

Describe the Primary response in terms of Immunity

A

Produces antibodies slower
Lower concentration of antibodies
T helpers need to activate B plasma cells to make the antibodies
Infected individual will express symptoms

131
Q

Describe the Secondary response in terms of Immunity

A

Faster production of antibodies
Higher concentration
B and T memory cells are present
B memory cells undergo mitosis faster

132
Q

What is the structure of an antibody?

A

Quaternary structure protein

133
Q

What do we call it when a antibody binds specifically to antigens?

A

Antigen-antibody complex

134
Q

Describe and explain how the structure of an antibody relates to its function

A
  • Primary structure of protein = sequence of amino acids in a polypeptide chain
  • Determines the folds in the secondary structure
  • Determines the specific shape of the tertiary structure and position of hydrogen,
    ionic and disulfide bonds
  • Quaternary structure is comprised of 4 polypeptide chains held by bonds
  • Enables the specific shaped variable region (binding site) to form which is a
    complementary shape to a specific antigen
  • Enables antigen-antibody complex to form
135
Q

How do antibodies destroy a Pathogen?

A

Binds to two pathogens at binding site
Forms Antigen-antibody complex
Agglutination - antibodies clump pathogens together
Phagocytes bind to antibody + phagocytose many pathogens

136
Q

What is a Vaccination

A

Injection of antigens from dead/weakened pathogens to induce artificial active immunity

137
Q

How does a vaccine work?

A

Stimulates the formation of memory cells, forcing a faster and stronger secondary response

138
Q

Describe the second exposure to a antigen after Vaccination against it

A 
Faster secondary response 
Antibodies produced faster 
Higher concentration 
Destruction of pathogen (agglutination and phagocytosis) 
Immunity
139
Q

What are the disadvantages of Vaccines?

A

Poor response
Antigenic Variation (mutate frequency is high so antigens change) causes it to be ineffective
Antigenic concealment

140
Q

A vaccine that would eradicate a disease what should it not be?

A

Mutating
Having a life cycle w/ other organisms
Have symptoms that make it hard to diagnose or trace

141
Q

What is Herd Immunity?

A

When a large proportion of the population has been vaccinated it makes it difficult for a pathogen to spread within that population.

142
Q

How does Herd Immunity make it difficult to spread pathogens?

A

More people are immune so fewer people carry pathogen

Less likely that a non vaccinated individual will come in contact with an infected person and pass on the disease

143
Q

What is active immunity?

A

Resistance to disease from an individual’s own immune system where an antigen induces plasma cells to make antibodies

144
Q

What is passive immunity?

A

(Resistance to disease results from the) introduction of antibodies from another individual’s such as placenta/mother’s milk. Short lived

145
Q

What are the differences between active and passive immunity?

A 
Active Immunity 
Exposure to antigen 
Memory cells involved 
Antibody produced and secreted by B plasma cells 
Slower
Long term immunity 
Passive Immunity 
No exposure 
No memory cells 
Antibody introduced into body from another organism 
Fast acting 
Short term immunity
146
Q

What are the ethical issues of vaccines?

A 
Tested on animals before use on humans  
Tested on humans
Vaccine may not work 
Expensive - less money spent of research and treatments of other diseases 
Can have side effects
147
Q

What can antigenic variability be responsible for?

A

May experience a disease more than once
Vaccines against a disease may be hard
More frequent making of diseases

148
Q

Explain the effect of antigen variability on disease

A
  • Change in antigen shape (due to a genetic mutation)
  • Not recognised by B memory cell → no plasma cells / antibodies
  • Not immune
  • Must re-undergo primary immune response → slower / releases lower concentration of
    antibodies
  • Disease symptoms felt
149
Q

What is a monoclonal antibody?

A

Antibody produced from a single group of genetically identical B cells/plasma cells

150
Q

What are the use of monoclonal antibodies

A

Bind to specific complementary antigen

  • Have a variable region with a specific tertiary structure/shape
  • Only one complementary antigen will fit
151
Q

Explain the replication of HIV in helper T cells

A
  1. HIV attachment protein attaches to a receptor on the helper T-cell membrane
  2. Virus lipid envelope fuses with cell surface membrane and capsid released into cell which uncoats, releasing RNA and reverse transcriptase into cytoplasm
  3. Viral DNA is made from viral RNA
    - Reverse transcriptase produces a complementary viral DNA strand from viral RNA template
    - Double stranded DNA is made from this (DNA polymerase)
  4. Viral DNA integrated into host cell’s DNA (by enzyme integrase)
  5. Host cell enzymes used to make viral proteins from viral DNA (within human DNA) → viral proteins assembled with viral RNA to make a new virus
  6. New virus bud from cell (taking some of cell surface membrane as envelope)
152
Q

How does HIV cause the symptoms of AIDS

A

Infects and kills helper T cells as it multiplies rapidly → cannot stimulate cytotoxic t cells, b cells and phagocytes
Immune system deteriorates = more likely to catch infections
Normal diseases can be more deadly

153
Q

Why antibiotics are ineffective against viruses

A

Antibiotics can’t enter human cells - the virus exists in the host cell (acellular)
Viruses don’t have their own metabolic reactions
A resistant strain of bacteria via natural selection → reducing the effectiveness of antibiotics and waste of money

AQA A Level Biology (9 decks)

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