Cells Flashcards

Question

What is the function of the cell wall?

Answer 1

Provides mechanical strength to the plant cell (to prevent bursting from osmotic pressure) Enables water to move through the plant

Answer 2

Composed of strong, cellulose microfibrils embedded in a matrix Middle lamella cements neighbouring cells together

Answer 3

Cellulose or glycoprotein (or both)

Answer 4

Chitin and glycan (polysaccharides), as well as glycoproteins

Answer 5

'Fluid mosaic' phospholipid bilayer with extrinsic and intrinsic proteins embedded

Answer 6

Isolates cytoplasm for extracellular environment Selectively permeable to regulate transport of substances Involved in cell signalling/cell recognition

Answer 7

Steroid molecule connects phospholipids and reduces fluidity

Answer 8

Cell signalling/Cell recognition (antigens) and binding cells together

Answer 9

Cell signalling and Cell recognition

Answer 10

Small ring of DNA that carries non-essential genes Can be exhanged between bacterial cells via conjugation

Answer 11

Rotating tail propels (usually unicellular) organism Locomotion Sensory

Answer 12

Sticks cells together Acts as a food reserve Protects cells from digestive enzymes (such as during phagocytosis) and external chemicals

Answer 13

DNA is enclosed in a nucleus, contains membrane-bound specialised organelles

Answer 14

DNA is free in cytoplasm, no membrane-bound organelles

Answer 15

Murein (peptidoglycan) cell wall, slime capsule, loose (circular) DNA, plasmids, may have a flagellum

Answer 16

Not a living cell (acellular) Small (20-300nm) Don't reproduce but replicate (inside host cells) Attachment proteins on capsid enable virus to identify and attach to host cell

Answer 17

1. Recognise and attach to host cell 2. Infect (enter) host cell 3. Embed DNA into host cell's DNA 4. Force cell organelles to manufacture virus components 5. Form new viruses 6. New viruses exit the host cell

Answer 18

mm: 10-³ m μm: 10-⁶ m nm: 10-⁹ m

Answer 19

The amount by which an object has been enlarged to view as an image Dependent upon the lenses used

Answer 20

The ability to distinguish between two points that lie close together Dependent upon the wavelength of radiation used

Answer 21

Magnification = Image size/Actual size

Answer 22

Light and Electron microscopes

Answer 23

They use a pair of convex glass lenses that can resolve images that are 0.2μm apart

Answer 24

The wavelength of light is shorter so it restricts the resolution

Answer 25

They use a beam of electrons, that are focused by electronagnets inside a vacuum environment

Answer 26

So that particles in the air don't deflect the electrons out of the beam alignment

Answer 27

Transmission Electron Microscopes and Scanning Electron Microscopes

Answer 28

Objects that are closer than 0.2μm apart

Answer 29

A beam of electrons passes through a thin section of a specimen Areas that absorb the electrons appear darker on the electron micrograph that is produced

Answer 30

A beam of electrons passes across the surface and scatter The pattern of scattering builds up a 3D image depending on the contours of the specimen

Answer 31

•Whole system must be in a vacuum so living specimens cant be observed •Complex staining process required which may introduce artefacts into the image •Specimens have to be very thin, particularly for TEM so electrons can pass through

Answer 32

A glass disc with an etched scale placed in the eyepiece of a microscope

Answer 33

To mesasure size of object under objective lens

Answer 34

•Cell is very active: Growing and carrying out metabolic functions •Cell is preparing for next phase •Cellular checks are made to ensure DNA is in a good enough condition to be replicated •If DNA damaged cell division terminated at this stage

Answer 35

•The cell continues to grow •DNA is replicated •Chromosomes are therefore duplicated

Answer 36

•The cell continues to grow •Organelles (such as mitochondria) are copied •Components of microtubules (which will move chromosomes during mitosis) are synthesised

Answer 37

The nucleus divides The chromatids (containing replicated DNA) seperate from each other and are redistributed as chromosomes in the nuclei of the 2 daughter cells

Answer 38

Interphase Prophase Metaphase Anaphase Telophase

Answer 39

The cell grows and then prepares to divide Chromosomes and some organelles are replicated Chromosomes also begin to condense

Answer 40

1. Chromosomes become more visible, thicken 2. Centrioles move to opposite ends of the cell (poles) 3. Spindle fibres develop from each of the centrioles (spindle apparatus) 4. Nucleolus disappears and the nuclear envelope breaks down, leaving the chromosomes free in cell cytoplasm

Answer 41

1. Chromosomes seen to be made up of two chromatids 2. Microtubules attatch to centromere - chromosomes pulled to the cell equator where they line up

Answer 42

1. Centromeres divide, seperating each pair of sister chromatids 2. Chromatids pulled to their respective poles as spindles contract

Answer 43

May occur during or after mitosis However, may not occur at all such as in muscle cells which replicate their nuclei but dont seperate to form new cells

Answer 44

Cytoplasm divides to form 2 daughter cells, each surrounded by a plasma membrane

Answer 45

Uncontrolled mitosis leads to rapid cell division Tumours form May be benign or malignant

Answer 46

Number of cells undergoing mitosis ÷ Total number of cells ×100

Answer 47

Uncontrolled mitosis: Genes that control mitosis and cell cycle are faulty or damaged Tumour (mass of cells) forms Benign tumours (harmless) may become malignant (cancerous)

Answer 48

A proto-oncogene tells a cell when to divide A tumour suppressor gene tells cell to stop dividing If either of the above genes are damaged then cells will divide to frequently

Answer 49

Cells can be destroyed by blocking cell cycle Chemo drugs can prevent replication of DNA or interfere with spindle formation to halt metaphase All cells affected but cancer cells divide more rapidly and so more affected Normal cells that divide rapidly also affected e.g hair cells by the drugs so hair loss during treatment

Answer 50

•Circular DNA (and plasmids) copied and move towards cell membrane •Membrane moves inwards, between the two DNA pieces, and divides the cytoplasm •Cell wall forms and creates two new cells, each containing one circular DNA strand and a variable number of plasmids

Answer 51

The tendency of molecules to move from an area of higher concentration to an area of lower concentration Movement down concentration gradient

Answer 52

Rate = surface area×difference in concentration / length of diffusion path

Answer 53

Bigger surface area = faster rate Bigger difference in concentration = faster rate Long path = lower rate

Answer 54

Assisted diffusion, from high to low concentration But only at specific points along a membrane Carrier proteins 'help' the process

Answer 55

Movement of water through a membrane from higher to lower concentration

Answer 56

Substance being dissolved in a liquid e.g salt

Answer 57

Substance doing the dissolving (e.g water)

Answer 58

The extent to which a membrane will allow molecules to pass

Answer 59

Allows some molecules to pass but not others

Answer 60

Highest water potential is 0 Pure water = 0 All other solutions have negative water potentials More negative = more solute

Answer 61

A solution that causes a cell to shrink because of osmosis. Meaning water leaves the cell.

Answer 62

A solution that causes a cell to swell because of osmosis meaning water rushes into the cell.

Answer 63

A solution that causes no change in cell size. Meaning there is no movement of water.

Answer 64

•The movement of a substance against the concentration gradient •Requires the cell to use energy in the form of ATP

Answer 65

The movement of a substance into the cell by a vesicle. A vesicle is a form of packaging that is used by cells.

Answer 66

The movement of a substance out of the cell by a vesicle

Answer 67

Cytoplasm of cell surrounds and engulfs particle (Eg. amoeba and white blood cell)

Answer 68

1.Cytoplasmic Na+ binds to the Na/K pump. 2.Na+ binding stimulates phosphorylation by ATP 3.Phosphorylation causes the protein to change its conformation, expelling Na+ to the outside. 4.Extracellular K+ binds to the protein, triggering release of the phosphate group 5. Loss of the phosphate restores the protein's original conformation. 6.K+ is released and Na+ sites are receptive again; the cycle repeats.

Answer 69

Cell fractionation is the process by which organelles can be obtained

Answer 70

Homogenation Ultracentrifuguation

Answer 71

Cells must be placed in a cold, isotonic, buffered solution:

Answer 72

To prevent or reduce enzyme activity that might otherwise damage organelles

Answer 73

To prevent osmosis which would cause organelles to swell, burst or shrink

Answer 74

To maintain a constant pH in order to avoid chemical damage

Answer 75

• Cells are broken up by a homogeniser (mini blender) •Organelles are released from the cell •Homogenate is filtered to remove debris and unbroken cells

Answer 76

•Cell fragments are separated using an ultracentrifuge •Homogenate is spun at varying speeds generating a centrifugal force •Organelles are deposited into a pellet at the bottom of the tube depending on size •At slower speeds, heavier organelles are deposited as a pellet. E.g. Nuclei •As speed increases, organelles of smaller sizes are deposited from the supernatant. E.g. Chloroplasts (in plant cells) then mitochondria

Answer 77

A microorganism that can cause disease

Answer 78

1) A phagocyte recognises the antigens on a pathogen 2) The cytoplasm of the phagocyte moves round the pathogen, engulfing it. 3) The pathogen is now contained in a vacuole or a vesicle in the cytoplasm of the phagocyte. 4) A lysosome fuses with the phagocytic vacuole and the lytic enzymes break down with the pathogen 5) The phagocyte presents the pathogens antigens, it sticks the antigens on its surface to activate other immune system cells.

Answer 79

Cell mediated Immunity: T lymphocytes Humoral immunity: B lymphocytes

Answer 80

•Doesnt require antibodies •Cells with foreign antigens on their surface are “antigen-presenting cells” •Only responds to antigens on cell surfaces (not in body fluid) •Antigen presenting cells can be phagocytes displaying foreign antigens, invaded body cells, cancer cells, transplanted cells or foreign cells

Answer 81

•Foreign cells in body fluids present antigens •A B-lymphocyte will have a complementary antibody which attaches to the antigen •The antigen is taken into the B-lymphocyte, by endocytosis, and is presented on the B-lymphocytes membrane •TH cells bind to the antigen and stimulate B-cells to divide to form identical clones (clonal selection) which produce antibodies that are complementary to the foreign antigen •As each B-cell produces one specific type of antibody they are called monoclonal antibodies

Answer 82

Involved in the primary immune response. •Secrete antibodies directly into body fluids •Only survive for a few days but produce 2000 antibodies per second •Response is slow and person will get ill before pathogen is destroyed

Answer 83

Involved in the secondary immune response •Circulate in the blood and tissue fluid •Remain in body fluids for decades •When they encounter the antigen from the primary response they divide rapidly. •Response is rapid and person will not get ill.

Answer 84

•Attach to specific antigen to form antigen-antibody complex • Cause bacterial cells to clump together • Act as marker for phagocytes to bind

Answer 85

•Targeted medication Eg. Cancer treatment •Medical diagnosis •Pregnancy testing •Transplant surgery

Answer 86

•Direct monoclonal antibody therapy: produces monoclonal antibodies to match receptors on cancer cells. Once bound to the cancer cells, the antibodies prevent the attachment of chemical signals that cause the cells divide • Indirect monoclonal antibody therapy: attaches cytotoxic drugs to monoclonal antibodies. Once bound to the cancer cells, cause cells to die

Answer 87

Monoclonal antibodies can be used to detect the amount of certain substances in the blood by binding to them

Answer 88

•Monoclonal antibodies (and colour particles) are attached to the test strip of home pregnancy testing kits • Pregnant women produce high levels of hCG in urine • The hCG attaches to the antibodies and as the hCG-antibody-colour complex moves along the testing strip they become trapped to form a coloured line

Answer 89

1.Mouse (or rabbit) exposed to antigen. 2.B cells in mouse make antibodies which are extracted. 3.B cells are mixed and fused with cancer cells. 4.Single fused (hybrid) cells are selected and grown. 5.All antibodies produced from each hybrid will be identical - monoclonal

Answer 90

•Use of mice (or rabbits) to produce monoclonal antibodies and tumours however guidelines written to minimise suffering • Successful in treating cancers but caused deaths in MS sufferers however informed consent is required before treatment • Drugs trials can potentially cause harm to healthy volunteers

Answer 91

A common test used to detect is someone has been exposed to a virus such as HIV

Answer 92

1.Virus proteins (antigens) are added to wells of a 96-well plate 2.The antigens bind to the plastic, coating the bottom of the wells 3.The primary antibody is added to the well.The primary antibodies (IgM) are from the patient’s serum sample. 4.Excess antibody is washed away, leaving only antibodies bound to the antigens behind. This wash removes excess antibodies that are unbound and prevents non-specific binding. 5.A secondary antibody is added to the wells. This antibody recognizes the patient IgM antibodies, bound to the antigens.The secondary antibody also has a colorimetric tag attached 6.Excess secondary antibody is washed away, leaving only secondary antibodies, bound to the patient IgM antibodies.This wash removes excess antibodies that are unbound. 7.A substrate is added to the wells. 8.Bound secondary antibody containing a colorimetric tag will cause a color change when exposed to the substrate. A color change indicates a positive reaction

Answer 93

• Lipid envelope with embedded attachment proteins • Capsid surrounds 2 strands of RNA and enzymes (including reverse transcriptase)

Answer 94

•T-helper cells stimulate B cells (to produce antibodies) or cytotoxic T-cells (to kill pathogens) • Without the correct number of T-helper cells, the body is unable to effectively produce an immune response and thereby becomes susceptible to disease • Death of the patient may result due to a disease that would not normally affect them significantly

Answer 95

•Antibiotics are only effective against bacteria: They work by disrupting the production of murein which forms bacterial cells walls • Viruses do not have murein cell walls and they do not have organelles to replicate; viruses used host cells and their organelles

Answer 96

• HIV enters the body and circulates in blood until it binds to CD4 protein on cells (usually T-helper cells) • Capsid fuses with cell membrane & contents are released into host cell • Reverse transcriptase converts viral RNA to DNA which then enters the host nucleus and is embedded into the DNA • Messenger RNA is created and provides the code for viral proteins; the host cell produces viral components and the newly formed virus breaks from the cell taking part of the membrane as it’s lipid envelope

Answer 97

Vaccines are a way of introducing a pathogen into the body in order to produce an immune response. The pathogen may be dead of inactivated, but the antigens on its surface will still produce an immune response. This is active immunity and results in the creation of memory B cells which will be able trigger a rapid secondary immune response should the same pathogen ever be detected again.

Answer 98

•Cost of the vaccine •Severity of the side effects •Ease of production, transportation and administration

Answer 99

•Folded membrane or microvilli increase surface area e.g for diffusion •Many mitochondria = large amounts of ATP for active transport •Walls one cell thick to reduce distance of diffusion pathway

Answer 100

They're acellular and non living: no cytoplasm, cannot self-produce, no metabolism

Answer 101

•Linear genetic material (DNA or rNA) & viral enzymes e.g reverse transcriptase •Surrounded by capsid •No cytoplasm

Answer 102

•Simple virus surrounded by matrix protein •Matrix protein surrounded by envelope derived from cell membrane of host cell •Attachment proteins on surface

Answer 103

1) rupturing them to release nutrients inside them 2) breaking down nutrients inside the cell for their own use. This starves and eventually kills the cell. 3) replicating inside the cells and bursting them when they're released

Answer 104

•Production of toxins •Cell damage

Answer 105

•Smoking •Excessive exposure to sunlight •Excessive alcohol intake

Answer 106

•Gas-exchange system: if you breathe in air that contains pathogens, most of them will be trapped in mucus lining the lung epithelium. Some pathogens are able to reach the alveoli where they can invade cells and cause damage. •Skin: if you damage your skin, pathogens on the surface can enter your bloodstream. Blood clots prevent pathogens from entering. •Digestive system: if you eat or drink food that contains pathogens. Some will survive from the acidic conditions of the stomach, and invade cells of the gut wall and cause disease.

Answer 107

•Cellular: The T-cells and other immune system cells that they interact with e.g phagocytes , form the cellular response •Humoral: B cells and the production of antibodies form the humoral response.

Answer 108

•The primary response is slow because there aren't many B-cells that can make the antibody needed to bind to it. •The infected person will show symptoms of the disease while the body produces enough of the right antibody to overcome the infection. •T-cells and B-cells produce memory cells. Memory T-cells remember the specific antigen and will recognise it second time round. Memory B-cells record the specific antibodies needed to bind the antigen. •The body is now immune

Answer 109

•If the same pathogen enters the body again, the immune system will produce a quicker, stronger immune response. •Memory B-cells divide into plasma cells that produce the right antibody to the antigen. Memory T-cells divide into the correct type of T cells to kill the cell carrying the antigen. •The secondary response often gets rid of the pathogen before you begin to show any symptoms.

Answer 110

1. Nuclei 2. Mitochondria 3. Lysosome 4. Endoplasmic reticulum 5. Ribosomes

Answer 111

Acellular, non-living particles Smaller than bacteria

Answer 112

Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease. This means you become immune without getting the symptoms. Vaccines protect individuals because they reduce the occurance of the disease. Those not vaccinated are less likely to catch the diease because there are fewer people to catch it from - this is called herd immunity.

Answer 113

Their hydrophilic/hydrophobic interactions lead to the formation of a phospholipid bilayer. 1. Allow lipid-soluble substances to enter/exit cell. 2. Prevent water-soluble substances entering and leaving cell. 3. Make the membrane flexible and self-sealing.

Answer 114

Some in surface of bilayer: 1. Act to provide mechanical support to membrane. 2. Along with glycolipids, act as cell receptors for molecules such as hormones. Some span the entire membrane: 3. Protein channels - water filled tubes allowing water-soluble ions to diffuse across the membrane. 4. Protein carriers - bind to ions or molecules like glucose/amino acids - then change shape to move these molecules across the membrane. 5. Help cells adhere together. 6. Form cell-surface receptors for identifying cells.

Answer 115

1. Reduce lateral movement of other molecules (including phospholipids) - pulls together the fatty acid tails, limiting movement without making the membrane too rigid. 2. Make the membrane less fluid at high temperatures. 3. Prevent leakage of water and dissolved ions from the cell, as cholesterol molecules are very hydrophobic.

Answer 116

The arangement of all the various molecules combined into the structure. ●Fluid: Membrane is flexible and can constantly change in shape as individual phospholipid molecules can move relative to one another. ●Mosaic: Proteins embedded in the phospholipid bilayer vary in shape, size + pattern like tiles in a mosaic.