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Cells Flashcards

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1
Q

What’s a eukaryotic cell ?

A

A cele with nucleus and membrane bound organelles

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2
Q

What is the nucleus and what does it consist of ?

A

Contains DNA arranged in chromosomes and within chromosomes there’re genes that code for primary structure of polypeptide

Nuclear envelope
Nuclear pores
Chromatin
Nucleolus

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3
Q

What’s the role of nuclear envelope ?

A

Double membrane
Allows entry and exit of substances in and out of nucleus

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4
Q

What’s the role of nuclear pores ?

A

Allow passages of larger molecules out of nucleus
E.g mRNA

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5
Q

What’s chromatin ?

A

Linear DNA which is histone bound that condenses to visible chromosomes during nuclear division

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6
Q

What’s the role of nucleolus ?

A

Manufactures RNA and makes ribosomes

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7
Q

What’s the function of nucleus ?

A

Store genetic info that code for primary structure of polypeptide

Produce rRNA and mRNA

location of semi conservative replication

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8
Q

What’s the mitochondria and what does it consist of ?

A

Site of aerobic respiration and synthesises ATP from aerobic respiration

Double membrane - control entry and exit of substances in and out of mitochondria

Cristae - forms folds of inner membrane, provides large surface area for enzymes and proteins involved in aerobic respiration

Matrix - liquid part, contains 70s ribosomes, mitochondrial (circular) DNA. To make own proteins for respiration

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9
Q

What’s the rough endoplasmic reticulum?

A

Outer surface have ribosomes on
Provide large surface area for protein synthesis
Packages proteins into vesicles and transports them to Golgi to be modified

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10
Q

What’s the smooth endoplasmic reticulum ?

A

Lack ribosomes
Synthesises stores and transports lipids and carbohydrates
Package them into vesicle and send to Golgi apparatus to be modified

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11
Q

What’s the Golgi apparatus ?

A

Modifies proteins by adding lipid or carb to them forming glycoproteins or glycolipids then packaged into vesicles and sent to feel surface where they fuse wi it releasing their content outside of cell via exocytosis

Also produce lysosomes

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12
Q

What are lysosomes ?

A

Contain and release hydrolytic enzymes

Fuse wi foreign materials ingested by phagocytes and release their hydrolytic enzymes

Release enzymes outside of cell in order to hydrolyse and breakdown molecules outside of cell

Breakdown damaged and worn out organelles so useful molecules they are made of can be reused

Completely breakdown cell once it’s died (autolysis)

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13
Q

What are the additional organelles in a plant cell ?

A

Cell wall
Chloroplast
Vacuole

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14
Q

What are chloroplast ?

A

Carry out photosynthesis
Double membraned
Contain granum that consist of disc like structures called thylakoids
Within membrane of thylakoids is pigment chlorophyll
Contain stroma (fluid filled matrix) within it are enzymes , starch grains

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15
Q

What’re the adaptations of chloroplasts ?

A

Thylakoid membrane provides large S.A for more chlorophyll
Contain circular DNA and 70s ribosomes to make proteins for photosynthesis

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16
Q

What’s the cellulose cell wall ?

A

Consist of microfibrils: straight cellulose polymers cross linked by weak hydrogen bonds

Provide strength and contributes to overall rigidity of cell wall

Prevent cell from bursting under pressure created by entry of water by osmosis

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17
Q

What are fungi cell walls made of ?

A

Chitin

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18
Q

What are bacteria cell walls made of ?

A

Murein

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19
Q

What’s a vacuole ?

A

Fluid filled sack bound by single membrane called tonoplast

Contains: mineral salts, amino acids, waste, sometimes pigments

Function: provide support making cell turgid, store sugars and amino acids that could act as temporary food sources

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20
Q

What’s a prokaryotic cell ?

A

No nucleus and membrane bound organelles

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21
Q

What does prokaryotic cell consist of ?

A

Circulars DNA
Plasmid DNA
Cell walls made of murein
Capsule

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22
Q

What makes up a virus ?

A

Acellular
Contain DNA or RNA if RNA it has reverse transcriptase
Has capsid to protect genome
attachment proteins to bind to cells

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23
Q

What are the principles of light microscope ?

A

Use glass lense to focus light on specimens
Samples can be living or dead
Stain is needed to make sample more visible:
- methylene blue (human cheek)
- gram staining (prokaryotes)
- iodine (plant cells)
Image is in colour

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24
Q

What are the limitations of light microscope ?

A

Magnification limit to X1,500
Has longer wavelength so lower resolution

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25
What’s resolution ?
Ability to distinguish between two objects that are close together
26
What’s an eye piece graticule ?
Fits on eyepiece, transparent ruler with numbers but no units
27
What’s a stage micrometre ?
Microscope slide with accurate scale, placed on stage Used to calibrate value of each division on eye piece graticule
28
What’s the equation for magnification ?
Image size / actual size
29
What’re the conversions ?
Cm - mm X10 Mm - um X1000 Um - nm X1000 Then divide if going from nm - cm
30
What’re the principles of electron microscope ?
Use beam of electrons to view sample Shorter wavelength so resolution is higher Sample has to be dead No colour on image Focused by electro magnets
31
What’s a scanning electron microscope ?
Specimen is not sliced Electrons bounce of surface of sample Produce 3D image
32
What’s a transmission electron microscope ?
Specimen placed in resin and sliced Electrons fire through specimen Able to see internal structures of organelles Produce 2D image Light areas of image = electrons transmitted Dark areas of image = electrons absorbed Specimen is placed in vacuum Specimen is stained using heavy metals which is a complex process and can create artifacts
33
What’s cell fractionation and ultracentrifugation and the process of if ?
Process of separating organelles from cell 1. Tissue homogenised in blender in an ice cold, isotonic, buffering solution. This breaks open the cell and releases the organelles in solution 2. Mixture then filtered to remove large pieces of tissue/cell/debris 3. Differential centrifugation carried out on solution. Low speed first to force densest organelles to bottom forming a pellet which is then removed 4 the remaining solution (supernatant) is centrifuged at higher speed then next dense organelle goes to bottom 5. Repeat process
34
What’s the order from high to low density of organelles ?
Nucleus Mitochondria Chloroplast Golgi RER and SER Ribosomes
35
What does the cell cycle consist of ?
Interphase Mitosis Cytokinesis
36
Outline the stages of interphase
G1 phase: cell make RNA, enzymes and other proteins required for growth Signal is sent telling cell to divide (change in size and mass) S phase: DNA in nucleus undergoes semi-conservative replication resulting in each chromosome which consist of two identical sister chromatids G2 phase: cell grow for mitosis, microtubules produce and form mitotic spindle, DNA now synthesised and is checked and any errors are corrected
37
What’s mitosis ?
Nuclear division creating two genetically identicle daughter cells Prophase Metaphase Anaphase Telophase
38
What happens in prophase ?
Chromosome condense and become visible Chromosomes made of sister chromatids that are held by centromere Two centrioles move towards opposite poles of cell Spindle fibres begin to emerge from centrioles Nuclear envelope breaks down into small vesicle
39
What happens in anaphase ?
Spindle fibres contract and centromere splits pulling sister chromatids to opposite poles of cell
40
What happens in metaphase ?
Chromosomes line up at equators of cell Centromere of chromosome attach to spindle fibres begin
41
What happens in telophase ?
Chromosomes arrive at opposite poles of cell and begin to uncoil Spindle fibres breakdown Nuclear envelope reforms around each set of chromosomes
42
What happens in cytokineses ?
In animal cells cleavage furrow forms between separate daughter cells Cytoplasm divide forming two genetically identical daughter cells
43
How to calculate mitotic index ?
Nu of cells in mitosis / total number of cells
44
How to calculate how long mitosis takes ?
Nu of cells in mitosis / total number of cells Then X by time taken for whole cell cycle in minutes
45
What’s the role of cell surface membrane ?
To allow molecules in and out of cell
46
Why is the cell surface membrane described as fluid mosaic model ?
Consist of proteins, glycoproteins, phospholipids, carbohydrates and cholesterol Phospholipids create bilayer and molecules in it are constantly moving around relative to one another giving it its membrane fluid structure Proteins are unevenly distributed forming a mosaic pattern Selective permeability of cell membrane is determined by distribution of transport proteins and phospholipid molecules
47
What’s the role of phospholipids in cell surface membrane ?
Allow lipid soluble molecules to pass through Restrict passage of ions and polar molecules
48
What’s the role of channel and carrier proteins in cell surface membrane ?
- aquaporins allow water to cross membrane via osmosis - allow ions and polar molecules to be transported via facilitated diffusion
49
What the role of cholesterol in cell surface membrane ?
Decrease permeability and increases stability of membrane Restrict movement of molecules Cause fatty acid chains to pack close together
50
What’s Fick’s law ?
Diffusion rate = (surface area X conc gradient) /. Diffusion pathway
51
What’s diffusion ?
Net movement of molecules from high to low concentration until evenly distributed
52
What’re the factors that affect diffusion ?
Temperature Surface area Conc gradient Diffusion distance
53
What’s facilitated diffusion ?
The use of carrier and channel proteins to allow polar molecules pass through cell surface membrane F.D levels of when all carrier proteins are saturated
54
What’s osmosis ?
Net movement of water molecules from high to low water potential through selectively permeable membrane Water is polar so requires Aquaporin to move down water potential gradient
55
What’s water potential ?
Measured in kPa Highest water potential is 0 Adding a solute to pure water lowers water potential as water is dipole so it attracts to charge of molecules of solute
56
What does hypotonic mean ?
Less water potential in cell than solution so water moves from solution to cell
57
What’s hypertonic ?
More water potential in cell than solution so water moves from cell to solution
58
What’s isotonic ?
Same water potential in cell and solution
59
Why is the tissue placed in an ice cold, isotonic buffer solution ?
Ice cold : reduce kinetic energy and action of enzymes that’s damage organelle Isotonic: prevents osmosis so organelle doesn’t burst or shrivel Buffered: Martian constant pH and prevents proteins from denaturing
60
What’s active transport ?
Transport polar molecules against their conc gradient Low to high concentration Use only carrier protiens Requires ATP ATP gives carrier small amount of energy causing it to change shape which ‘pushes’ molecule through membrane
61
How does cancer arise ?
Uncontrolled mitosis Forming tumour Starts when changes occur in genes that control cell division
62
What is the germ called if it causes cancer ?
Oncogene
63
What’s a benign tumour ?
Non cancerous as they don’t spread from original site L
64
what’s a malignant tumour ?
can cause cancer as they spread in body invading and destroying other tissues
65
What is the process of developing cancer ?
1. Production of Oncogenes: mutated genes caused by carcinogens 2. Cancerous cells ignore signals from other cells and continues to divide 3. Mitosis happens 4. Cancerous cells not removed by immune system 5. Rapid mitosis 6. Tumour gets bigger 7. Tumour is supplied with blood and lymph vessels 8. If malignant it’ll spread to other parts of body 9. Metastasis occurs this is were tumour cells invade other tissues, secondary cancers form
66
What does methotrexate do ?
Inhibit synthesis of DNA nucleotides in cells Controls rate of mitosis
67
What does vincristine and taxol do ?
Prevent formation of mitotic spindles Control rate of mitosis
68
What does adraimycin do ?
Stop DNA from uncoiling so interfere with DNA replication
69
What’s the process of binary fission ?
Happens in prokaryotic cells 1. Circular DNA and plasmid DNA replicate 2. Parent cells divide into two cells on
70
What do antigens detect ?
Self cells Non self cells (pathogens, cells from similar organisms that’ve been transplanted, abnormal cells, toxins)
71
What’s an antigen ?
Foreign molecule usually a protein that stimulates an immune response resulting in production of specific antibody if the antigen does recognise a cell They have specific shape and tertiary structure complimentary to antibody or receptor of immune cell
72
What is phagocytosis ?
1. Phagocyte engulfs pathogen and forms vesicle called phagosome 2. Lysosomes fuse with phagosome 3. Lysosomes release hydrolytic enzymes which breaks down pathogen 4. Debris of pathogen is released from phagocyte via exocytosis 5. Then parts of phagocyte display on cell surface membrane of phagocyte turning it into an antigen presenting cell
73
What do antigen rearing cells activate ?
T and B cells which produce specific immune responds to help remove pathogen more effectively
74
What is cellular response ?
Occurs when there’s a presence of antigen presenting cells Th cells bind to antigen and become activated and divided by mitosis to create many clones
75
What do activated Th cells release and stimulate ?
Releases cytokines which stimulates - B cells to divide by mitosis (needed for humoral response) - phagocytes (allow more phagocytosis to occur) - cytotoxic T cells
76
What’re cytotoxic T cells ?
Bind to antigen of virally infected or cancerous cells Once binded they release perforin which makes holes in cell surface membrane of cell causing the cell to undergo apoptosis and being destroyed
77
How are B cells stimulated ?
Antigen burning to receptors / antibodies of another surface Release of cytokines from Th cells
78
What happens after B cells are stimulated v
- B cells divide by mitosis to produce clones - these then differentiate into either plasma cells (produce monoclonal antibodies) for primary response or memory cells which can help mount faster immune response upon re infection (secondary response)
79
What’re monoclonal antibodies ?
Same tertiary structure provided by identical or cloned plasma cells. Quaternary protein 4 polypeptide chains (2 short 2 long) Joined together by disulphide bridges Has 2 antigen binding sites that’re complimentary to 1 antigen
80
What is the function of a monoclonal antibody ?
Bind to antigen to form antigen-antibody complex 2 antigen binding sites allow antibody to bind to antigens and ‘clump’ them together (agglutination) Which attracts phagocytes leading to destruction of antigen via phagocytosis
81
How’re monoclonal antibodies made in lab ?
1.Mouse injected with chosen antigen 2. B lymphocytes take from mouse and fuses with tumour cells 3. Making hybridoma 4. Which divides quickly to produce lots of clones that produce monoclonal antibodies
82
How is the ELISA tests ran ?
1. 1st monoclonal antibody fixed to bottom of well 2. Sample is added that may contain antigen and will bind to 1st M.A 3. 2nd M.A is added to well that contains an enzyme which binds to antigens 4. Substrate is added and enzyme will convert it to diff colour if antigen is present
83
What does it mean if the test says you don’t have it and you really don’t have it ?
True negative
84
What does it mean if the test says you don’t have it but you do you ?
False negative
85
What does it mean if the test says you have it but you don’t really have it ?
False positive
86
What does it mean if the test says you do have it and you actually do have it ?
True positive
87
How do vaccines work ?
1.Antigen taken of C.S.M of pathogen 2. mRNA of it is formed and placed in vaccine 3. This is injected into person 4. Goes to ribosome of cell 5. Antigen is produced now becoming antigen presenting cell 6. Stimulates humoral response producing memory and plasma cells
88
What is herd immunity ?
Both vaccinated and unvaccinated are protected because vaccinated recover quicker and less likely to spreads pathogen to unvaccinated
89
What’re the ethics for vaccines ?
They may have side effects Testing on animals may not work on humans
90
What is active immunity ?
One’s body produces antibodies and memory cells upon exposure to antibody It’s a slow immune response but provides long term immunity
91
What is passive immunity ?
Prepare antibodies received from elsewhere Its a rapid immune response but only provides short term immunity
92
What’re the characteristics of a virus ?
1.Non living / acellular (need host to replicate) 2. Lipid/viral envelope made of phospholipid 3. Attachment proteins to allow virus to infect host cell 4. Genome can be DNA or RNA (if RNA it has reverse transcriptase) 5. Capsid to protect genome
93
What does HIV stand for ?
Human immunodeficiency virus which causes AIDS
94
What is the structure of HIV ?
Acellular No cell surface membrane Cannot replicate immediately RNA is its genome Contains reverse transcriptase to produce cDNA from viral RNA Capsid to protect genome Lipid envelope and attachment proteins ti enable virus to specifically bind to and infect Th cells
95
How does HIV replicate ?
1. HIV bind to CD4 receptors on Th cell 2. Viral RNA and reverse transcriptase enter cell 3. Reverse transcriptase converts viral RNA into DNA 4. Viral DNA moves into nucleus and into hosts genome using intergrase 5. HIV DNA transcripts into HIV mRNA which is then translated to produce HIV proteins 6. Infected Th cells produce virions 7. Virions released from Th cells Overtime this reduced the amount of Th cells leading to AIDS
96
What is AIDS ?
Acquired immune deficiency syndrome which is caused by the over time number of Th cells decreasing due to HIV infection Someone with AIDS typically has few as 200 Th cells/mm^3 of blood compared to someone who hasn’t had 800-1200 Th cells/mm^3 of blood
97
Can antigens or antibodies detect AIDS ?
No
98
How is AIDS checked for ?
Screened for by checking number of Th cells or by ELISAs to measure concentration of HIV antibodies
99
How do antibiotics work ?
Prevent bacteria murein cell walls from synthesising or by directly damaging cell wall Lead to bacteria destruction due to osmotic damage Some antibiotics can inhibit binary fission, preventing DNA replication and protein synthesis

Biology Revision (7 decks)

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