3.2.1 Cell Structure Flashcards
(154 cards)
1
Q
What is a tissue?
A
A group of specialised cells
2
Q
What is an organ?
A
A combination of different tissues that are co-ordinated to perform a variety of functions
3
Q
What is an organ system?
A
Many organs working together to perform a function
4
Q
Give an example of a organ system?
A
Digestive, respiratory or circulatory
5
Q
A group of abnormal cells is….
A
A tumor
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
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
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
9
Q
When do eukaryotes get specialised?
A
In multicelluar organisms
Eukaryotes have become specialised to specific functions
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
11
Q
What is the adaptation of the red blood cell?
A
Biconcave shape
No nucleus
= more space so more 02 can be transported
12
Q
Give an example of a tissue?
A
Epithelial tissue, xylem and muscle
13
Q
What are the adaptations of neurons?
A
Dendrites + axons → receive and transmit signals
Axons covered in fatty sheats
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)
15
Q
What two things can change with adaptation to a eukaryotic cell?
A
The shape of the cell
The organelles
16
Q
Instead of a single membrane, the mitochondria is what?
A
Double membrane organelle
17
Q
What is the cell surface membrane made out of?
A
Phospholipid bilayer
18
Q
What does the cristae in the mitochondria provide?
A
A high surface area
19
Q
What is the function of the chloroplasts?
A
The site of photosynthesis
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
21
Q
What are the functions of the nucleus?
A
Site of DNA replication and transcription
Contains the genetic code for a single cell
22
Q
Describe the structure of the endoplasmic reticulum
A
Folded membranes
Fluid filled
RER AND SER
23
Q
Function of the RER
A
Synthesize and transport proteins throughout the cell
24
Q
Function of the SER
A
Synthesise, store and transport lipids and carbohydrates
25
What is the difference between the RER and SER?
RER has ribsomes on surfaces
SER has NO ribsomes
26
What is the function of the golgi apparatus?
Modify and package proteins
Packages into vesicles for transport
Digestive enzymes are placed into lysosomes
27
What is the function of the ribsomes?
Site of protein synthesis
28
Name all the organelles in a Eukaryotic Cell?
```
Cell surface membrane
Nucleues
Mitochondria
Chlorplasts
Golgi apparatus
Lysosomes
Ribosomes
RER
SER
Cell wall
Cell Vacoule
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29
What is a plant cell made of?
Organelles w/ chloroplasts + vacuole
Cytoplasm
Cell membrane
Cell wall
30
What is the structure of the chloroplast?
```
Double membrane
Contains thylakoids
Thylakoids contain chlorophyll
Stack of thylakoids is Granum
Stroma is fluid surrounding
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31
What is the role of the permanent vacuole?
Providing support = turgid
Stores sugars + amino acids
Pigments help attract pollinators
32
What is the function of the cell wall?
Provides stability
| Prevents the bursting of the cell from osmosis pressure of water
33
What three things have a cell wall?
Fungi
Plants
Algae
34
What is the cell wall made of in plants?
Cellulose
35
What is the role of the cell surface membrane?
To control the movement of substances in and out of the cell
36
What are lysomes?
Relatively small organelles formed when the vesicles made by the golgi contain digestive enzymes
37
What are the four functions of the lysosomes?
Hydrolse phagocytotic cells
Break down dead cells
Break down old organelles
Release enzymes outside the cell to destory material around the cell (exocytosis)
38
What is the cell wall made of in fungi?
Chitin
39
What is the cell wall made of in Algae?
Cellulose or glycoprotiens
40
What organelles does a prokaryotic cell have?
```
Cell wall
Capsule
Cell surface membrane
Cytoplasm
Circular strand of DNA
Plasmids
Flagellum
Ribsomes
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41
What is the cell wall made of in Prokayotic cell?
Muerin (glycoprotien)
42
What is the role of plasmids?
Contains gene that aid survival of prokaryotes
43
Describe the structure of virueses
Nucleic acid (dna/rna)
a caspid
Attachment protien
44
Why are viruses described as acellular and non-living
- Acellular → not made of or able to be divided into cells
| - Non-living → unable to exist/reproduce without a host cell
45
How does an optical microscope work?
Use light to form 2d images
46
What are limitations of light microscopes?
Low resolution so cant view smaller organisms
| Only used on thin specimens
47
What are the advantages of optical microscope?
Can see living organisms
48
How does a Scanning electron microscope work?
Breams of electrons scan surface
Knocking off electrons from specimen
Gathered in a cathode ray tube to form a 3D image
49
What are the advantages of a SEM?
3D image
High resolution ( can see internal structures)
High magnification
Used on thick specimen
50
What are the disadvantages of the SEM?
Lower resolution than TEM
Cannot be used on living specimens
No colour images
51
What are the principles of TEM?
Beam of Electrons pass through specimen
Denser parts absorb more electrons
Denser parts are darker in appearance
Electrons have a short wavelength
52
What are the limitations/disadvantages of TEM?
Cannot be living
Specimen must be thin
2D image
53
What are the advantages of TEM?
High resolution; see internal structures
High magnification
54
Define ‘Magnification’
How much bigger the image of a sample is compared to the real size
55
What is the formula for magnification?
by Magnification =
size of image /size of the real object
56
Define ‘resolution’
How well distinguished an image is between 2 points;
57
Describe how you would measure size of an object viewed with an optical microscope
- 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
58
In required practical 2, what are the limitations?
Squash and staining increase artefacts
An optical microscope has a low magnification power
Cut differently at root = inconsistent size of cells
59
How to convert μm → nm
x1000
60
How to convert μm → mm
divide by 1000
61
How were people testing for artefacts before modern technology?
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
62
How to convert cm → m
divide by 100
63
What is the formula for mitotic index?
undergoing mitosis/ total number of cells observed
64
What is the role of a stain in microscopy?
Used to colour components of the cell
65
What are artefacts?
things that arent actually part of the specimen
66
What is cell fractionation?
The process of separating cell organelles from each other
67
What is ultracentrifugation?
Process by which fragments in filtered homogenate are separated in a centrifuge
68
What are the stages in cell fractionation?
→ homogenisation
→ Filtration
→ Ultracentrifugation
69
Describe full process of Cell fractionation
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
What is the supernatant?
Rest of organelles suspended after centrifuge
71
State and explain why we need the certain conditions in Homogenisation?
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
Breifly, describe stage of Homogensaiton
Cell in sample broken by blender
| Must be under specific conditions: ice cold, isotonic and buffered solution
73
What is the order of organlles heaviest to lightest
```
Nuclei
Chloroplasts
Mitochondria
Lysosomes
Endoplasmic reticlum
Ribosmes
```
(new cats make love even right?)
74
Which cells retain the ability to divide?
Eukaryotic Cells
75
What are the stages of Mitosis?
Prophase, Metaphase, Anaphase,Telophase and Cytokinesis
76
What occurs in Interphase?
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
Describe what occurs in Mitosis
Parent cell divisions
Two genetically identical daughter cells, containing identical/exact copies of DNA
PMAT stages
78
What occurs in Prophase?
```
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
What occurs in Metaphase?
Chromosomes align along equator
| Spindle fibers attach to chromosomes by centromeres
80
What occurs in Anaphase?
Centromere divides
Spindle fibres contract
Pull sister chromatids to opposite poles of the cell
81
What occurs in Telophase?
Chromosomes decondesne
Longer and thinner
Nuclear envelope reforms = two nuclei
Spindle fibres and centrioles break down
82
What occurs in Cytokinesis?
The division of the cytoplasm producing two new cells
83
How many chromosomes do Human Diploid cells have?
46
84
Explain the importance of Mitosis
Growth of multicellular organisms by increasing cell number
Repairing damages tissues
Asexual Reproduction
85
How would recognise a cell in Interphase?
No chromosomes visible
86
How would recognise a cell in Prophase ?
Chromosomes visible but randomly arranged
87
How would recognise a cell in Metaphase?
Chromosomes lined up on equator
88
How would recognise a cell in Anaphase?
Chromatids being separated to opposite poles by spindles
89
How would recognise a cell in Telophase?
Chromosomes in two sets, one at each pole
90
What is a Malignant Tumor?
Cancer that spreads and affects other tissues/organs
91
What is a Benign Tumor?
Non-Cancerous
92
How do cancers start?
Changes occur in genes that control cell division - mutations
93
What are Carcinogens?
Agents that may cause Cancer
94
How do some cancer treatments work?
Disrupt cell cycle → Mitosis slows down → Tumour growth slows
95
In what two ways can you disrupt the cell cycle as a cancer treatment?
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
What is the advantage and disadvantage of cancer treatments?
😊 - Drugs are more effective cancer cells
😔 - Disrupt cell cycle of normal cells too, especially rapidly dividing ones e.g. cells in hair follicles
97
How do Prokaryotic Cells replicate?
Binary Fission
98
Describe the process of Binary Fission
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
TRUE OR FALSE: “circular DNA replicates once, plasmids can be
replicated many times”
True
100
Why do viruses not undergo cell division?
They are non-living
101
Describe the process of viral replication
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
What is the Fluid-mosaic model of membrane structure?
- Molecules within membrane can move laterally (fluid)
| - Mixture of phospholipids, proteins, glycoproteins and glycolipids
103
Describe the structure of the cell membrane
```
It has a Phospholipid Bilayer
Hydrophilic heads and Hydrophobic tails
Channel and Carrier Proteins (intrinsic)
Glycolipids
Glycoproteins
Cholesterol
```
104
How does the Phospholipid help adapt the membrane?
Maintains a different environment on each side of the cell
| Fluidity = can bend to take different shapes
105
How do surface proteins help adapt the membrane?
Cell recognition/Act as antigens/receptors
106
How does Cholesterol help adapt the membrane?
Regulates Fluidity/Increases stability
106
How does Cholesterol help adapt the membrane?
Regulates Fluidity/Increases stability
107
What is the main role of cholesterol in the cell membrane?
Make the membrane more rigid by restricting the lateral movement of molecules that make up the membrane
108
What is an example of cholesterol doing its role?
Binding to fatty acids causing them to pack more closely together
109
Describe Simple Diffusion
Net movement of small (non polar) lipid soluble molecules across a selectively permeable membrane down a concentration gradient
Passive
110
What factors affect Simple Diffusion
Surface area, concentration gradient and diffusion pathway distance
111
Describe Facilitated diffusion
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
What is a Carrier protein?
Carrier proteins transport large molecules, the protein changes shape when molecule attaches
113
What is a channel protein?
Charged/Polar molecules through its pore
114
Describe Active Transport
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
Describe Osmosis
Net movement of water molecules across a selectively permeable membrane down a water potential gradient
Passive
116
What factors affect Active transport?
```
PH
Temp
Speed of carrier protein
No. of carrier proteins
Rate of respiration (ATP)
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117
What is water potential?
```
the likelihood (potential) of water molecules to diffuse out of or into a
solution;
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118
Describe co-transport (sodium and gluocse)
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
How might cells be adapted for transport across their internal or external
membranes
- By an increase in surface area
- Increase in number of protein
channels / carriers
120
Define ‘Antigen’
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
Why are antigens specific?
```
To allow the immune system to identify:
Pathogens
Cells from other organisms of the same species
Abnormal Body cells
Toxins released from bacteria
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122
Describe the process of Phagocytosis
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
What is cell mediated immunity?
The type of response when T lymphocytes respond to antigens that are presented on a body cell
124
Describe the cellular response
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
What are clones formed in the cellular response used for?
Stimulate B cells for the humoral response
Stimulate cytotoxic T cells to kill infected cells
Stimulate phagocytes to engulf pathogens by Phagocytosis
126
Define a ‘Antibody’
A protein with specific binding sites produced by B cells in response to the presence of an appropriate antigen
127
What is Humoral Immunity/Response?
The type of response which involves B lymphocytes and antibodies
128
Describe what happens in the Humoral Response
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
Explain ‘Clonal Selection’
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
Describe the Primary response in terms of Immunity
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
Describe the Secondary response in terms of Immunity
Faster production of antibodies
Higher concentration
B and T memory cells are present
B memory cells undergo mitosis faster
132
What is the structure of an antibody?
Quaternary structure protein
133
What do we call it when a antibody binds specifically to antigens?
Antigen-antibody complex
134
Describe and explain how the structure of an antibody relates to its function
- 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
How do antibodies destroy a Pathogen?
Binds to two pathogens at binding site
Forms Antigen-antibody complex
Agglutination - antibodies clump pathogens together
Phagocytes bind to antibody + phagocytose many pathogens
136
What is a Vaccination
Injection of antigens from dead/weakened pathogens to induce artificial active immunity
137
How does a vaccine work?
Stimulates the formation of memory cells, forcing a faster and stronger secondary response
138
Describe the second exposure to a antigen after Vaccination against it
```
Faster secondary response
Antibodies produced faster
Higher concentration
Destruction of pathogen (agglutination and phagocytosis)
Immunity
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139
What are the disadvantages of Vaccines?
Poor response
Antigenic Variation (mutate frequency is high so antigens change) causes it to be ineffective
Antigenic concealment
140
A vaccine that would eradicate a disease what should it not be?
Mutating
Having a life cycle w/ other organisms
Have symptoms that make it hard to diagnose or trace
141
What is Herd Immunity?
When a large proportion of the population has been vaccinated it makes it difficult for a pathogen to spread within that population.
142
How does Herd Immunity make it difficult to spread pathogens?
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
What is active immunity?
Resistance to disease from an individual's own immune system where an antigen induces plasma cells to make antibodies
144
What is passive immunity?
(Resistance to disease results from the) introduction of antibodies from another individual’s such as placenta/mother’s milk. Short lived
145
What are the differences between active and passive immunity?
```
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
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146
What are the ethical issues of vaccines?
```
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
What can antigenic variability be responsible for?
May experience a disease more than once
Vaccines against a disease may be hard
More frequent making of diseases
148
Explain the effect of antigen variability on disease
- 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
What is a monoclonal antibody?
Antibody produced from a single group of genetically identical B cells/plasma cells
150
What are the use of monoclonal antibodies
Bind to specific complementary antigen
- Have a variable region with a specific tertiary structure/shape
- Only one complementary antigen will fit
151
Explain the replication of HIV in helper T cells
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
How does HIV cause the symptoms of AIDS
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
Why antibiotics are ineffective against viruses
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
