Topic two Flashcards
(93 cards)
1
Q
Describe structure of the cell-surface membrane
A
-Found on the surface of animal cells
-Found just inside the cell wall of plant cells
-Made of mostly lipids and proteins
2
Q
Describe the function of the cell-surface membrane
A
-Regulates the movement of substances in and out of the cell
-Has receptor cells on its surface that allow for response to chemicals, such as hormones
3
Q
Describe the structure of the nucleus
A
-Large organelle
-Surrounded by nuclear membrane, a double membrane which contains many pores
-Contains chromosomes and the/many nucleolus
4
Q
Describe the function of the nucleus
A
-Controls cell activities by controlling the transcription of DNA
-Pores allow substances, such as RNA, to move between the nucleus and cytoplasm
-Nucleolus makes ribosomes
5
Q
Describe the structure of mitochondria
A
-Oval shaped
-Contain a double membrane, inner membrane is folded to form cristae
-Inside is the matrix, containing enzymes for respiration
6
Q
Describe the function of the mitochondria
A
The site of aerobic respiration, which forms ATP for the cell
7
Q
Describe the structure of chloroplasts
A
-Small flattened structure surrounded by a double membrane
-Has membranes inside called thylakoid membranes that are stacked to form the grana
-Grana are linked by lamellae
-The stroma is a thick fluid
8
Q
Describe the function of chloroplasts
A
-Site of photosynthesis
-Part of the reaction takes place in the grana, and the other part in the stroma
9
Q
Describe the structure of the golgi apparatus
A
A group of fluid-filled, membrane-bound sacks
10
Q
Describe the function of the golgi apparatus
A
-Processes and packages new lipids and proteins
-Makes lysosomes
11
Q
Describe the structure of the golgi vesicles
A
A small fluid-filled sack in the cytoplasm, surrounded by a membrane and produced by the golgi apparatus
12
Q
Describe the function of the golgi vesicles
A
Stores and transports lipids and proteins made by the golgi apparatus
13
Q
Describe the structure of lysosomes
A
-Round organelle surrounded by a membrane with no clear internal structure
-Type of golgi vesicle
14
Q
Describe the function of lysosomes
A
-Contains digestive enzymes called lysozymes, keeping them separate from the cell
-Lysozymes can be used to
digest invading cells, or to break down worn out components of the cell
15
Q
Describe the structure of ribosomes
A
-Small organelle that is free in the cytoplasm, or bound to rough ER
-Made up of proteins and RNA
-Not surrounded by membranes
16
Q
Describe the function of ribosomes
A
The site where proteins are made
17
Q
Describe the structure of the rough ER
A
-System of membranes enclosing a fluid-filled space
-Surface is covered with ribosomes
18
Q
Describe the function of the rough ER
A
Folds and processes proteins that have been made by the ribosomes
19
Q
Describe the structure of the smooth ER
A
System of membranes enclosing a fluid-filled space
20
Q
Describe the function of the smooth ER
A
Synthesises and processes lipids
21
Q
Describe the structure of the cell wall
A
-Rigid structure that surrounds the cell in plants, algae and fungi
-Made of cellulose for plants and algae
-Made of chitin for fungi
22
Q
Describe the function of the cell wall
A
Supports cells and prevents them from changing shape
23
Q
Describe the structure of the vacuole
A
-Membrane-bound organism in the cytoplasm
-Contains cell sap
-Surrounded by a membrane called the tonoplast
24
Q
Describe the function of the vacuole
A
-Helps to maintain pressure in cell and keep it rigid, to prevent wilting
-Involved in isolation of unwanted chemicals in the cell
25
Describe the differences between prokaryotic and eukaryotic cells
-Cytoplasm lacks membrane bound organelles
-Smaller ribosomes
-no nucleus- they have a single circular DNA molecule that is free in the cytoplasm which isn't associated with proteins
-A cell wall which contains murein (glycoprotein)
26
What do many prokaryotic cells contain?
-One or more flagella
-One or more plasmids
-A capsule surrounding the cell
27
Describe binary fission
1) Circular DNA (x1) and plasmids (many times) replicate
2) The cell expands and DNA loops move to opposite poles
3) Cytoplasm begins to divide, new cell walls begin to form
4) Cytoplasm divides to 2 daughter cells, each with one DNA loop and variable copies of plasmids
28
How are viruses non-living?
-Non-cellular
-Cannot reproduce independently and require a host
-Do not respond to stimuli
-Have no metabolic activity
-Do not carry out protein synthesis
29
Describe the general structure of a virus
-Genetic material
-Capsid
-Attachment protein
30
Describe how optical microscopes work
-Lense focuses the ray of light, and magnifies the thin slice of specimen
-Different structures will absorb different amounts and wavelengths of light
-Reflected light is transmitted to the observer via the objective lense and eyepiece
31
Describe how a student would prepare a slide for an optical microscope
-Obtain a thin sample of the specimen (one cell thick)
-Add a drop of water to the glass slide, place the sample on top
-Stain to make the structures visible
-Add a coverslip, using a mounting needle at 45º to avoid air bubbles
32
Advantages of an optical microscope
-Colour images
-Can show living structures
-Affordable apparatus
33
Limitations of an optical microscope
-2D images
-Lower resolution than electron microscopes, so can't see ultrastructure
34
Describe how a transmission electron microscope works
-Passes a high energy beam of electrons through a thin slice of specimen
-More dense structures appear darker as they absorb more electrons
-Focus image onto fluorescent screen or photographic plate using magnetic lenses
35
Advantages of a transmission electron microscope
-Electrons have a shorter wavelength than light, giving a higher resolution so ultrastructure can be seen
-High magnification
36
Limitations of a transmission electron microscope
-2D image
-Requires a vacuum, so cannot look at living structures
-Extensive preparation may introduce artefacts
-No colour image
37
Describe how a scanning electron microscope works
-Focus a beam of electrons onto a specimens surface using electromagnetic lenses
-Reflected electrons hit a collecting device
-Amplified to produce an image on a photographic plate
38
Advantages of a scanning electron microscope
-3D image
-Electrons have a shorter wavelength than light, giving a higher resolution
39
Limitations of a scanning electron microscope
-Requires a vacuum, so cannot observe living specimens
-No colour image
-Only shows outer surface
40
Define artefact
Structures or features that appear in a microscopic image but are not actually part of the biological sample being studied
41
Describe cell fractionation
-Done in an ice cold, isotonic buffer solution
-Homogenization-by vibrating or a blender, this breaks up the plasma membrane and releases the organelles into solution
-Filtration-through gauze to separate large cell or tissue debris
-Ultracentrifugation
42
Describe ultracentrifugation
-Using a centrifuge, cell fragments are in a tube and are spun at low speeds to separate into the pellet and supernatant
-Supernatant is drained and poured into another test tube, then spun at a higher speed
-Process is repeated at increasing speeds until all organelles are separated
43
Pellet
Thick sediment at the bottom of the test tube, formed by the heaviest organelle
44
Supernatant
Lighter organelles suspended in fluid above the pellet
45
Order of organelles from most to least dense
Nucleus->mitochondria->lysosomes->RER->plasma membrane->SER->ribosomes
46
Why are fractionated cells kept in an ice-cold, isotonic buffer solution
-Cold-slows hydrolase enzyme action
-Buffered-maintains constant pH
-Isotonic-prevents osmotic lysis/shrinking of organelles
47
Describe semi-conservative DNA replication
-DNA helicase 'unzips' hydrogen bonds, forming two template strands
-Free nucleotides align along the template strands by complementary base pairing (A-T, C-G)
-DNA polymerase synthesises phosphodiester bonds between adjacent nucleotides
48
Describe the cell cycle
-Mitosis-start and end
-GAP phase 1-cell grows, new organelles and proteins are made
-Synthesis-cell replicates DNA, ready to divide by mitosis
-GAP phase 2-cell keeps growing, and proteins needed for division are made
49
Interphase
-Includes GAP 1, synthesis and GAP 2
-Cell carries out normal function, whilst also preparing for mitosis with DNA replication
50
Prophase
-Chromosomes condense to be visible
-Centrioles move to opposite poles, forming protein spindle fibres
-Nuclear membrane breaks down so chromosomes are free in the cytoplasm
51
Metaphase
-Chromosomes align along cell equator
-Attach to spindle fibres by centromere
52
Anaphase
-Centromeres divide, separating sister chromatids
-Spindles contract to pull chromatids to opposite poles
53
Telophase
-Chromatids uncoil and are now chromosomes
-Nuclear membrane forms around each group of chromosomes
-Cytokinesis, forming two genetically identical daughter cells
54
Describe the fluid mosaic model, for cell membranes
-The membrane is composed of lipids, proteins and carbohydrates (attached to lipids and proteins)
-Proteins (carrier and channel) are scattered throughout the membrane, like tiles in a mosaic
55
Phospholipid bilayer
-Hydrophilic heads attract water
-Hydrophobic tails prevent water-soluble substances, such as ions and polar molecules to diffuse through it
-Small, non-polar molecules, such as CO2 and water can diffuse throuh
56
Cholesterol in the cell membrane
-A lipid that fits between phospholipids to give the membrane stability
-Binds to the tails, packing them closer together and restricting the movement
-Helps to maintain shape of animal cells, especially unsupported ones such as red blood cells
-Also hydrophobic, helping to reinforce barrier
57
Simple diffusion
-The net movement of molecules down a concentration gradient until equilibrium is reached
-ATP isn't required, but the molecules have kinetic energy
-Only small, lipid soluble molecules can diffuse across the membrane
58
Facilitated diffusion
-The net movement of molecules down a concentration gradient until equilibrium is reached
-However it uses channel proteins to allow larger molecules, ions, and polar molecules to pass through
-Tubes filled with water allow polar and water soluble molecules to pass through
-Specific carrier proteins allow molecules such as glucose to pass through
59
Osmosis
The net movement of water molecules through a partially permeable membrane, down a water potential gradient
60
Active transport
-Uses an ATP and carrier proteins ( or protein pumps) for the movement of molecules against a concentration gradient
-Selective as only certain molecules can bind to the carrier protein
61
Explain co-transport
-Na+ is actively transported out of the epithelial cells in the ileum into the blood to create a concentration gradient, with more Na+ in the lumen
-Causes Na+ to diffuse into the ileum via Na-glucose pump, causing there to be a higher concentration of glucose
-Glucose diffuses out of the cell into the blood through a protein channel, via facilitated diffusion
62
Five factors that affect the rate of diffusion
-Temperature
-Diffusion distance
-Surface area
-Size of molecule
-Difference in concentration
63
Antigen
-Molecules, typically proteins, that cause an immune response when detected in the body
-Foreign antigens are antigens that aren't typically found in the body, and allow the immune system to identify: toxins, pathogens, abnormal body cells and cells from other individuals
64
Pathogens
-Organisms that cause disease, such as bacteria, viruses and fungi
65
Abnormal body cells
Cancer cells and pathogen infected cells have different antigens on their cell surface
66
Toxins
Molecules that are poisonous, can be from bacteria
67
Cells from other individuals of the same species
When recieving cells from another person, such as blood transfusions or organ donation, some antigens will be different, causing an immune response
68
Describe phagocytosis
-Phagocyte recognises foreign antigens and engulfs the pathogen to form a phagocytic vesicle
-Lysosomes fuse to the vesicle and release lysozymes
-The hydrolytic enzymes break down the pathogen
-Phagocyte displays the foreign antigens on its surface to activate other immune system cells
69
T-cell/T-lymphocyte
A type of white blood cell with receptor cells on its surface that bind to the foreign antigens presented by pathogens
70
T-helper cells
Release chemical signals that activate and stimulate phagocytes, as well as B-cells
71
Cytotoxic T cells
Kill abnormal and foreign cells
72
B cells
A type of white blood cell, covered with antibodies on its surface. Each B cell has different shaped antibodies to bind to different antigens
73
Clonal selection
-Antigen-antibody complex formed with B cells
-This, and substances released from helper T cells activate the B cell
-B cell divides into plasma cells
74
Antibody production
-Plasma cells identical to B cells secrete many specific antibodies
-These are monoclonal antibodies, and bind to the antigens on the pathogen surface
75
Agglutination
-Antibodies have two binding sites, so can bind to two pathogens at once to clump them together
-Phagocytes bind to the antibodies and phagocytose many pathogens at once
76
General antibody structure
-A Y-shaped protein
-Has two variable regions that have a unique tertiary structure, making it complementary to a specific antigen
-All antibodies have the same constant regions
77
Cellular response
T-cells and other immune system cells they interact with, such as phagocytes
78
Humoral response
B cells, clonal selection, and the production of monoclonal antibodies
79
Secondary immune response
-When the pathogen enters the body a second time, the immune system produces a stronger and faster immune response
-Memory B cells are activated and divide into plasma cells that can produce the antibody specific to the antigen/pathogen
-Memory T cells are activated, and divide to the correct type of T cell to kill the cell carrying the antigen
-This response often gets rid of the pathogen before the person shows symptoms
80
Active immunity
-When your immune system makes its own antibodies after being stimulated by an antigen
-Natural-immunity after having the disease
-Artificial-immunity after receiving a vaccine that contains a harmless dose of the antigen
81
Passive immunity
-When your immune system doesn't make any antibodies of its own, and is given them from another organism
-Natural-a baby is immune due to the antibodies from its mother, in the breast milk and placenta
-Artificial-immunity after being injected with the antibodies from someone else
82
How is active immunity different from passive immunity?
-Requires exposure to the pathogen
-Takes a while to develop
-Memory cells are produced
-Protection is long term because antibody is produced in response to exposure to antigen
83
How is passive immunity different from active immunity?
-Doesn't require exposure to antigen
-Protection is immediate
-Memory cells aren't produced
-Short term protected as antibodies break down
84
Herd immunity
Vaccines protect the individuals that receive them, but also reduce the occurrence of the disease, protecting everyone even if they don't have the vaccine, if enough people are vaccinated
85
Vaccines
-Contain a harmless amount of a pathogen, or a dead pathogen
-This allows for an individual to build up immunity without actually getting the disease
86
Describe the structure of HIV cells
-Spherical structure
-Has a core containing RNA and other proteins, such as reverse transcriptase
-Capsid-outer coating of protein
-Envelope-a membrane made from the membrane of a previous host cell
-Attachment proteins that allow it to attach to T cells
87
How does HIV result in AIDs symptoms
-Attachment proteins bind to complementary CD4 on helper T cells
-HIV particles replicate, damaging/killing the T cell
-AIDs develops when there aren't enough helper T cells for the immune system to function
-Patients then cannot destroy other pathogens, so suffer from infections
88
Describe how HIV cells replicate in helper T cells
-HIV attachment protein binds to a receptor molecule on the host T cell
-The capsid is released into the cell, it uncoats and releases RNA into the cytoplasm
-Reverse transcriptase makes a DNA strand that is complementary to the viral RNA
-A double-stranded DNA is made, and inserted into the host cell DNA
-Host cell enzymes make viral proteins from the inserted viral DNA
-Viral proteins assemble to form new proteins, which then go on to infect other T helper cells
89
Why don't antibiotics work to cure viruses?
-Antibiotics target metabolic and reproductive systems in bacteria cells
-These differ to human cells, so antibiotics wouldn't be able to target the virus
90
Direct monoclonal antibody therapy (Eg herceptin for breast cancer)
-Antibodies are produced that are specific to the antigens on cancer cells
-Monoclonal antibodies are given to the patient
-They bind to antigens on the cancer cells, preventing uncontrolled growth
91
Indirect monoclonal antibody therapy
-A cytotoxic drug is attached to monoclonal antibodies
-The antibodies are given to the patient
-The antibodies attach to antigens/receptors on the cell surface, killing it
92
Describe an ELISA test
-Add the patients test sample to the base of a beaker
-Wash to remove any unbound sample
-Add an antibody that is complementary to the antigen you are testing for
-Wash to remove any unbound antibody
-Add a second antibody that is attached to an enzyme, this antibody is complementary to the first
-Add a colourless enzyme substrate that will produce coloured products after forming an E-S complex
-If there is colour, the antigen is present. The intensity of this colour indicates the quantity of antigens present
93
Ethical issues of using monoclonal antibodies
-Requires mice to make the antibodies and tumour cells
-They have their spleens removed to get them, killing the mice
