Topic 2 Flashcards

1
Q

Cell membrane structure

A

Phospholipid bilayer with embedded intrinsic & extrinsic proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Cell membrane function

A

Selectively permeable barrier controls passage of substances in and out the cell
barrier between internal and external cell environments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Nucleus Structure

A

Nuclear pores, nucleolus, DNA and nuclear envelope
Nuclear envelope is inner and outer membrane and nuclear pores

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Nucleus Function(4)

A

Site of transcription & pre- mRNA splicing - mRNA production
site of DNA replication
nucleolus makes ribosomes
nuclear pore allows movement of substances to/from cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Mitochondria Structure

A

Double membrane with inner membrane folded into cristae
70S ribosomes in matrix
small circular DNA
enzymes in matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Mitochondria Function

A

Site of aerobic respiration
produces ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Chloroplast structure

A

Thylakoid membranes stacked to form grana, linked by lamellae
stroma contains enzymes
contains starch granules, small circular DNA and 70S ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Chloroplast function

A

Chlorophyll absorbs light for photosynthesis to produce organic molecules (glucose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Organisms containing chloroplasts

A

Plants
Algae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Golgi apparatus stucture

A

Fluid-filled, membrane-bound sacs (horseshoe shaped)
vesicles at edge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Golgi apparatus function

A

Modifies proteins received from RER
packages them into vesicles to transport to cell membrane for exocytosis
makes lysosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Lysosome structure

A

Type of Golgi vesicle containing digestive enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Lysosome function

A

Contains digestive enzymes
e.g lysozymes to hydrolyse pathogens/cell waste products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Rough endoplasmic reticulum function(3)

A

Site of protein synthesis
folds polypeptides to secondary & tertiary structures
packaging into vesicles to transport to Golgi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Smooth endoplasmic reticulum function

A

Synthesises and processes lipids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Cell wall function

A

Provides structural strength, rigidity and support to cell
helps resist osmotic pressures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Ribosome structure

A

Small and large subunit
made of protein and rRNA
free floating in cytoplasm & bound to RER
70S in prokaryotes, mitochondria and chloroplasts
80S in eukaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Ribosome function

A

Site of translation in protein synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Rough endoplasmic reticulum structure

A

System of membranes with bound ribosomes
continuous with nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Smooth endoplasmic reticulum structure

A

System of membranes with no bound ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Cell wall structure

A

In plant, fungal and bacterial cells
plants - made of microfibrils of cellulose
fungi - made of chitin
bacteria - murein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Cell vacuole structure

A

Fluid-filled
surrounded by a single membrane called a tonoplast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Contrast prokaryotic & eukaryotic cells(5)

A

Prokaryotic cells are smaller
prokaryotes have no membrane bound organelles
prokaryotes have smaller 70S ribosomes
prokaryotes have no nucleus - circular DNA not associated with histones
prokaryotic cell wall made of murein instead of cellulose/chitin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Occasional features of prokaryotes

A

Plasmids - loops of DNA
capsule surrounding cell wall - helps agglutination + adds protection
flagella for movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Cell vacuole function
Makes cells turgid - structural support temporary store of sugars, amino acids coloured pigments attract pollinators
26
Protein carriers
Bind with a molecule, e.g. glucose, which causes a change in the shape of the protein this change in shape enables the molecule to be released to the other side of the membrane
27
Protein channels
Tubes filled with water enabling water-soluble ions to pass through the membrane, selective, channel proteins only open in the presence of certain ions when they bind to the protein
28
Features of viruses(3)
Non living and acellular contain genetic material, capsid and attachment proteins some (HIV) contain a lipid envelope + enzymes (reverse transcriptase)
29
3 types of microscopes
Optical (light) microscopes Scanning electron microscopes (SEM) Transmission electron microscopes (TEM)
30
Magnification
How many times larger the image is compared to the object calculated by equation: Image size/actual size
31
Resolution
The minimum distance between two objects in which they can still be viewed as separate determined by wavelength of light (for optical microscopes) or electrons (for electron microcopes)
32
Optical microscopes
Beam of light used to create image glass lens used for focusing 2D coloured image produced
33
Evaluate optical microscopes(5)
Poorer resolution as long wavelength of light - small organelles not visible Lower magnification Can view living samples Simple staining method Vacuum not required
34
Transmission electron microscopes(5)
Beam of electrons passes through the sample used to create an image Focused using electromagnets 2D, black & white image produced Can see internal ultrastructure of cell Structures absorb electrons and appear dark Produces photomicrograph
35
Evaluation TEMs(6) - limitations and advantages
Highest resolving power high magnification extremely thin specimens required complex staining method specimen must be dead vaccum required Artefacts present in final photomicrgraph. Hard to differentiate between natural specimen and artefacts. They are things that result from preparation of specimen
36
Scanning electron microscopes (4)
Beam of electrons pass across sample used to create image focused using electromagnets 3D, black and white image produced electrons scattered across specimen producing image
37
Evaluation SEMs(6)
High resolving power high magnification thick specimens usable complex staining method specimen must be dead vaccum required
38
Why calibrate eyepiece graticule?
Calibration of the eyepiece is required each time the objective lens is changed Calibrate to work out the distance between each division at that magnification
39
Purpose of cell fractionation
Break open cells & remove cell debris so organelles can be studied
40
Homogenisation
Process by which cells are broken open so organelles are free to be separated done using homogeniser (blender)
41
Homogenisation conditions
Cold reduces enzyme activity preventing organelle digestion Isotonic prevents movement of water by osmosis - no bursting / shrivelling of organelles Buffered resists pH changes preventing organelle + enzyme damage
42
Ultra- centrifugation
Homogenate solution filtered to remove cell debris solution placed in a centrifuge which spins at a low speed initially then increasingly faster speeds to separate organelles according to their density
43
Differential centrifugation
Supernatant first out (spun at lowest speed) is most dense = nuclei spun at higher speeds chloroplasts -> mitochondria -> lysosomes -> RER/SER -> ribosomes (least dense)
44
Binary Fission
Involves circular DNA & plasmids replicating cytokinesis creates two daughter nuclei each daughter cell has one copy of circular DNA and a variable number of plasmids
45
Cell cycle
1) Interphase (G1, S, G2) 2) nuclear division - mitosis or meiosis 3) cytokinesis
46
Interphase
Longest stage in the cell cycle G0 phase - resting phase in which the cell is neither replicating or preparing to divide. G1 phase - cells grows in size and synthesizes mRNA and protein required orDNA synthesis. S phase - DNA replication and much of DNA repair activity occurs in cell DNA replicates and appears as two sister chromatids held by centromere G2 phase - cell prepares for mitosis Also has checkpoints
47
Mitosis
One round of cell division two diploid, genetically identical daughter cells growth and repair (e.g. clonal expansion) comprised of prophase, metaphase, anaphase and telophase
48
Prophase
Chromosomes condense and become visible nuclear envelope disintegrates in animals - centrioles separate & spindle fibre structure forms
49
Metaphase
Chromosomes align along equator of cell spindle fibres released from poles now attach to centromere and chromatid
50
Anaphase
Spindle fibre contracts (using ATP) to pull chromatids, centromere first, towards opposite poles of cell centromere divides in two
51
Telophase
Chromosomes at each pole become longer and thinner again spindle fibres disintegrate + nucleus reforms
52
Mitotic index
Used to determine proportion of cells undergoing mitosis Calculated as a percentage OR decimal Mitotic index = the total no. of cells in mitosis/ the total no. of cells x100 for percentage
53
Fluid mosaic model
Describes the lateral movement of membranes - gives fluid structure with scattered embedded intrinsic and extrinsic proteins membrane contains glycoproteins, glycolipids, phospholipids and cholesterol
54
Phospholipids in membranes
Phospholipids align as a bilayer hydrophilic heads are attracted to water hydrophobic tails repelled by water
55
Cholesterol
Present in eukaryotic organisms to restrict lateral movement of the membranes adds rigidity to membrane- resistant to high temperatures & prevents water + dissolved ions leaking out
56
Selectively permeable membrane
Molecules must have specific properties to pass through plasma membrane lipid soluble (hormones e.g. oestrogen) very small molecules non-polar molecules (oxygen)
57
Simple diffusion
Net movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached passive
58
Facilitated diffusion
Passive process using protein channels/carriers down the concentration gradient used for ions and polar molecules e.e sodium ions and large molecules e.g. glucose
59
Osmosis
Net movement of water from an area of higher water potential to an area of lower (more negative) water potential across a partially permeable membrane
60
Water potential
The pressure created by water molecules measured in kPa and represented by symbol ψ pure water has a water potential of 0kPa the more negative the water potential, the more solute must be dissolved
61
Hypertonic solution
When the water potential of a solution is more negative than the cell water moves out of the cell by osmosis both animal and plant cells will shrink and shrivel
62
Hypotonic solution
When the water potential of a solution is more positive (closer to zero) than the cell water moves into the cell by osmosis animal cells will lyse (burst) plant cells will become turgid
63
Isotonic
When the water potential of the surrounding solution is the same as the water potential inside the cell no net movement in water cells would remain the same mass
64
Active transport
The movement of ions and molecules from an area of lower concentration to an area of higher concentration using ATP and carrier proteins carrier proteins act as selective pumps to move substances
65
Role of carrier protein in active transport
When molecules bind to the receptor - ATP will bind to protein on inside of membrane and is hydrolysed to ADP/ Pi protein changes shape and opens inside membrane
66
Co-transport
The movement of two substances across a membrane together, when one is unable to cross the membrane itself involves a cotransport protein involves active transport e.g. absorption of glucose/amino acids from lumen of intestines
67
Molecules lymphocytes identify
Pathogens (bacteria, fungi, viruses) cells from other organisms of same species (transplants) abnormal body cells (tumour cells) toxins (released from bacteria)
68
Antigens
Proteins on the cell-surface membrane trigger an immune response when detected by lymphocytes
69
Antigenic variability
When pathogenic DNA mutates causing a change in shape of antigen previous immunity is no longer effective as memory cells don't recognise new shape of antigen. Specific antibody no longer binds to new antigen
70
Physical barriers
Anatomical barriers to pathogens- skin stomach acid lysozymes in tears
71
Phagocytes
Non-specific immune response phagocytes become antigen- presenting cells after destroying pathogen
72
T lymphocytes
Made in bone marrow and mature in thymus gland Involved in cell-mediated immune response Only respond to antigen-presenting cells(own body cells)
73
Antigen- presenting cells. 4 types of
Any cell that presents a non-self antigen on their surface infected body cells macrophage after phagocytosis cells of transplanted organ cancer cells
74
Role of T helper cells
Have receptors on their surface that attach to antigens on APCs become activated - clonal selection
75
Role of cloned T helper cells (4)
Some remain as helper T cells & activate B lymphocytes stimulate macrophages for phagocytosis become memory cells for that shaped antigen become cytotoxic killer T cells
76
Cytotoxic T cells
Destroy abnormal / infected cells by releasing perforin (membrane permeable) so that any substances can enter or leave the cell and this causes cell death
77
B lymphocytes
Made in bone marrow and mature in bone marrow involved in humoral immune response involves antibodies
78
Humoral response
B cells have antibodies and receptors on their surface and so when they come in contact with complementary antigen they engulf the pathogen by endocytosis. Process antigens and presents it on its surface. This B cell acts as APC and if it comes in contact with a T helper cell with complementary receptor. This stimulates B cells to undergo clonal selection and expansion - rapid division by mitosis. differentiate into plasma cells / memory B cells plasma cells make antibodies
79
B memory cells
Derived from B lymphocytes Remember specific antibody for particular antigen Will rapidly divide by mitosis and differentiate into plasma cells upon secondary encounter Resulting in large numbers of antibodies rapidly
80
Antibodies
Quaternary structure proteins made of four polypeptide chains different shaped binding site = variable region complementary to a specific antigen
81
Antibody structure. Draw it
Labels - 2 heavy and light chain Constant and variable region Antigen binding sites
82
Agglutination
Antibodies have two binding sites and are flexible - clumps pathogens together makes it easier for phagocytes to locate and destroy pathogen
83
Passive immunity
Antibodies introduced into body plasma and memory cells not made as no interaction with antigen short-term immunity fast acting
84
Active immunity
Immunity created by own immune system - antibodies made exposure to antigen plasma and memory cells made long term immunity slower acting
85
Natural active immunity
After direct contact with pathogen through infection body creates antibodies and memory cells
86
Artificial active immunity
Creation of antibodies and memory cells following introduction of an attenuated pathogen or antigens vaccination (oral or injection)
87
Vaccinations
Small amounts of dead or attenuated pathogens injected / ingested humoral response activated memory cells are able to divide rapidly into plasma cells when re-infected
88
Primary vs Secondary response
Primary = first exposure to the pathogen longer time for plasma cell secretion & memory cell production for the secondary response, memory cells divide rapidly into plasma cells so a large number of antibodies made rapidly upon reinfection
89
Herd immunity
When enough of the population is vaccinated so pathogen is not transmitted and spread easily Provides protection for those without vaccine - vulnerable ones
90
Monoclonal antibodies
A single type of antibody that can be isolated and cloned antibodies that are identical - from one type of B lymphocyte complementary to only one antigen
91
Uses of monoclonal antibodies
Medical treatment - targeting drugs by attaching antibody complementary to tumour cell antigen. Direct and indirect monoclonal antibody. medical diagnosis - pregnancy tests
92
Pregnancy test
ELISA test which uses 3 monoclonal antibodies and enzymes to test for hCG Explain in detail
93
Purpose of ELISA test
Detect the presence and quantity of an antigen used for medical diagnosis. Eg., HIV
94
Ethical issues with monoclonal antibodies
Requires mice to produce antibodies and tumour cells requires a full cost-benefit analysis
95
HIV structure
Core = RNA and reverse transcriptase capsid = protein coat lipid envelope taken from hosts cell membrane attachment proteins so it can attach to Helper T cells
96
HIV replication
Attaches to CD4 receptor on helper T cells protein fuses with membrane allowing RNA + enzymes to enter reverse transcriptase makes DNA copy and this is inserted into nucleus nucleus synthesises viral proteins Destroys T helper cells
97
Auto Immunodeficiency Syndrome (AIDs)
When HIV has destroyed too many T helper cells, host is unable to produce adequate immune response to other pathogens host susceptible to opportunistic infections eg TB and cancer
98
Role of antibodies in ELISA
First antibody added is complementary to antigen in well - attaches second antibody with enzyme added which attaches to first antibody as complementary. when substrate solution added enzyme can produce colour change
99
Why vaccines may be unsafe(4)
Inactive virus may become active - viral transformation non-pathogenic virus can mutate and harm cells side effects of immune response people may test positive for disease
100
Why are antibiotics ineffective against viruses?
-Antibiotics work by inhibiting certain enzymes involved in creating peptide cross linkages in cell wall which -makes the cell wall weak and therefore cannot withstand pressure when water enters and cell dies -Viruses are inside host cells where antibiotics cannot reach -antibiotics affect parts of bacteria that viruses do not have (e.g the cell wall) -Virus lack their own metabolic pathway and cell structures and they contain protein coat rather than peptidoglycan or murien cell wall
101
Why do you wash well in ELISA
Removes unbound 2nd antibodies otherwise enzyme may be present→ colour change → false positive
102
Pathogens
Microorganisms that cause a disease by releasing toxins or killing cells / tissues
103
Cytokinesis
Final stage in the cell cycle when the cytoplasm splits in two creates two new cells
104
Uncontrolled mitosis
Uncontrolled cell division can lead to the formation of tumours and of cancers many cancer treatments are directed at controlling the rate of cell division
105
Viral replication
Following injection of their nucleic acid the infected host cell replicates the virus particles
106
Cell adaptations for rapid transport across membranes?
Increase in surface area or membrane increases in the number of protein channels and carrier molecules in the membranes
107
Antigen- antibody complex
When a complementary antibody binds to an antigen this clumps pathogens together (agglutination)
108
Why is the high resolution of TEM not always achieved?
-difficulties preparing specimen will limit resolution that can be achieved -higher energy beam is required which may destroy the specimen
109
Osmosis and plant cells
When water enters plant cell by osmosis - it enters protoplast and protoplast pushes against the cell wall and plant cell becomes turgid. When water leaves plant cell it moves out of protoplast and it stops pushing against cell wall and this is called incipient plasmolysis. When more water leaves the protoplast pulls away from cell wall and the cell structures start to shrink and this is called plasmolysis
110
Why is high concentration of glucose ORS for people with diarrhoea not good
As glucose increases solute concentration in lumen causing more water to leave epithelial cells which worsens dehydration
111
How is monoclonal antibodies produced outside body and modified for use in humans (7)
-Mice exposed to non self cell antigen for which antibody is required -mice produces mixture is antibodies which is extracted from the spleen of the mice -its then mixed with cells that divide readily outside body - cancer tumour cell -detergent is added to this mixture to break down the cell membrane so both structure can join and this produces HYBRIDOMA cell -theses cells are then separated under microscope and each cell grown in culture to see if they process the desired antibody - the ones which produces the desired antibody is grown in large scale and these antibodies are called monoclonal antibody as its produced from a single B cell -As it’s made of mice cells its modified to make it like human cells before being used on humans and this process is called Humanisation
112
Features of successful vaccination programs
-economically viable and sufficient vaccine available to vaccinate the vulnerable population - herd immunity -Means of administering it at an appropriate time eg trained staffs -Means of storing, transporting and production available eg hygienic conditions -few side effects as this may make people opt out
113
How do drugs used in chemotherapy work
They prevent DNA replication Inhibition metaphase stage by interfering with spindle formation
114
Indirect active transport for absorption of amino acids and glucose in ileum
1-Na+ actively transported out of epithelial cells by sodium potassium pump. Takes place in a different type of carrier protein. 2-Thus maintains concentration gradient between lumen and epithelial cells as there is high concentration of Na+ in the ileum compared to epithelial cells 3-So Na+ moves down the concentration gradient into epithelial cells using co transport protein as it carries either amino acids or glucose into the epithelial cells. 4- the glucose or amino acid moves into blood plasma by facilitated diffusion using different type of carrier protein 5-Na+ is down the concentration gradient while glucose/amino acid is against. It’s the movement of Na+ down the concentration gradient rather than ATP which drives this process
115
Why is active transport required in the ileum along with diffusion for absorption of glucose and amino acid
-Carbohydrates and amino acids continuously being digested so high concentration in the lumen always. And in the blood glucose always used up as it’s transported around and used in respiration. -Therefore concentration gradient established and glucose and amino acids can diffuse by facilitated diffusion into blood. -But diffusion is only till equilibrium is reached, so for moving and absorbing of all the glucose and amino acids is done using active transport against the concentration gradient
116
How is rate of absorption in ileum increases
-Epithelial cells contains villi which contains micro villi which increases the surface area for absorption -Increasing surface area increases no. of carrier proteins and channels therefore increasing absorption