3.2 cells Flashcards

Question

function of smooth and rough er

Answer 1

synthesis, storage and transport of proteins

Answer 2

allows passages of large molecules e.g RNA

Answer 3

- folded membranes making cisternae - secretary vesicles pinch off from the cisternae

Answer 4

controls entry and exit of materials in and out of nucleus and reactions taking place within it

Answer 5

stores lipids and proteins made by golgi apparatus and transports them out of the cell

Answer 6

- adds carbohydrates to proteins to form glycoproteins - produce secretory enzymes - secrete carbohydrtes - transport, modify and store lipids - form lysosomes - molecules are 'labelled' with their destination - finished products are transported to cell surface in Golgi vesicles where they fuse with the membrane and the contents in released

Answer 7

tiny bag of digestive enzymes, surrounded by single membrane

Answer 8

- hydrolyse phagocytic cells - completely breaks down dead cells - exocytosis - releases enxymes to outside of cell to destroy material - digests worn out organelles for reuse of materials

Answer 9

small loops of DNA which only carry a few genes

Answer 10

slimy layer made up of protein

Answer 11

prevents bacteria from desiccating (drying out) and protects the bacteria against the host's immune system

Answer 12

length of time in stage= (observed number of cells in this stage/total number of cells) x total length of cell cycle

Answer 13

interphase

Answer 14

when a eukaryotic cell divides to produce two daughter cells, each with identical copies of DNA produced by the parent cell during DNA replication

Answer 15

interphase prophase metaphase anaphase telophase (cytokinesis)

Answer 16

- cell grows - DNA replicates - prepares for cell division

Answer 17

- chromosomes become visible by shortening and thickening - centrioles replicate and move to opposite ends of cells (called poles) - spindle fibres develop and collectively they're called spindle apparatus - nucleolus disappears -nuclear envelope breaks down - chromosomes now free in cytoplasm - chromosomes drawn towards equator by spindle fibres that are attached to the centromere

Answer 18

- chromosomes made up of two chromatids - each chromatid is an identical copy of DNA from the parent cell - chromatids joined by centromere - spindle fibres (microtubules) from poles attach to the centromere - chromosomes pulled along spindle apparatus and arrange themselves across the equator of the cell

Answer 19

- centromeres divide into 2 and spindle fibres pull individual chromatids apart - chromatids move to their respective sides of the cell - now referred to as 'chromosomes' - energy to separate them comes from ATP (respiration)

Answer 20

- chromosomes reach their respective poles and become longer and thinner - this makes them invisible again - the spindle fibres disintegrate - nuclear envelope and nucleolus reform

Answer 21

- cytoplasm divides forming two identical cells - parent cell separate into two genetically identical daughter cells

Answer 22

- growth - repair: if cells become damaged or die, it's important for the new cells produced to have an identical structure and function to those that have been lost - reproduction: single celled organisms divide by mitosis to give two new organisms. each new organism is genetically identical to parent organism

Answer 23

- mitosis: produces 2 daughter cells that have the same number of chromosomes as the parent cell - meiosis: produces 4 daughter cells, each with half the number of chromosomes of the parent cell.

Answer 24

- mitosis is a controlled process - if the cell division becomes uncontrolled then it can lead to formation of tumours and cancers. many cancer treatments are directed at controlling the rate of cell division

Answer 25

binary fission: - circular DNA replicates and both copies attach to the cell membrane - plasmids also replicate - cell membrane begins to grow between the 2 DNA molecules and begin to pinch inward, which divides the cytoplasm into 2 - new cell wall forms between the molecules of DNA, which divides the original cell wall into two identical daughter cells - each have a single copy of the circular DNA and variable number of copies of the plasmids

Answer 26

- viruses don't undergo cell division because they're non living. - if the viruses inject a host cell with their infected nucleic acid, the host cell becomes infected and replicates the virus particles

Answer 27

- transport proteins - phospholipid heads - glycolipids - cholesterol - cytoskeleton filaments

Answer 28

- hydrophillic heads of both layers point to the outside of the membrane as it's attracted to the water on both sides - hydrophillic tails point to centre of membrane, repelled by water on both sides

Answer 29

- allow lipid soluble substances to enter and leave the cell - prevents water-soluble substances entering and leaving the cell - makes the cell flexible and self sealing

Answer 30

- interspersed throughout the cell-surface membrane - some proteins occur in the surface of the bilayer, they act as mechanical support to the membrane - other proteins completely span the phospholipid bilayer from one side to the other. some are protein channels, which form water-filled tubes to allow water-soluble ions to diffuse across the membrane. - others are carrier proteins that bind to ions or molecules like glucose etc, then change shape in order to move these molecules across the membrane.

Answer 31

- provides structural support - acts as channels transporting water-soluble substances across the membrane - allow active transport across the membrane through carrier proteins - form cell-surface receptors for identifying cells - helps cells adhere together

Answer 32

-occur within the phospholipid bilayer of the cell-surface membrane -they add strength to the membranes - cholesterol molecules are very hydrophobic- play a role in preventing loss of water and dissolved ions from the cell - also pull together fatty acid tails of the phospholipid molecules, limiting their movement and that of other molecules without making the membrane too rigid

Answer 33

- reduce lateral movement of other molecules including phospholipids - make the membrane less fluid at high temperatures - prevent leakage of water and dissolved ions from the cell

Answer 34

- extends from the phospholipid bilayer into the watery environment outside the cell.

Answer 35

- acts as recognition sites - help maintain the stability of the membrane - helps cells to attach to one another and so form tissues

Answer 36

- outer surface of membrane - acts as cell surface receptors for more specifically hormones and neurotransmitters

Answer 37

- acts as cell-cell recognition sites - helps cells to attach to one another and so form tissues - allows cells to recognise one another, e.g lymphocytes can recognise an organism's own cells

Answer 38

- 'fluid' cause the molecules move around each other in the membrane and gives it a flexible structure that is constantly changing in shape - 'mosaic' cause the molecules of different shapes and sizes fit together to form a pattern like a mosaic

Answer 39

- control entry and exit of materials in discrete organelles e.g mitochondria - separate organelles from cytoplasm so that specific metabolic reactions can take place within them - provide an internal transport system e.g E.R - isolate enzymes that might damage the cell e.g lysosomes - provide surfaces on which reactions can occur e.g protein synthesis on ribosomes on rough E.R

Answer 40

- not soluble in lipids and therefore cannot pass though the phospholipid layer - too large to pass through the channels in membrane - are the same charge as the charge on the protein channels so they are repelled - electrically charged (polar) and therefore have difficulty passing through the non-polar tails in the phospholipid bilayer

Answer 41

the net movement of molecules or ions from a region of high concentration to a region of lower concentration until a dynamic equilibrium is achieved. (down a concentration gradient)

Answer 42

- cell doesn't use its ATP to move molecules or ions - they move due to kinetic energy

Answer 43

- small, uncharged molecules e.g oxygen, carbon dioxide exception = water

Answer 44

- they aren't lipid soluble - too large - have a charge e.g ions and polar molecules

Answer 45

- they will only pass across the membrane if there is a complementary shaped protein to facilitate its transport e,g channel proteins and carrier proteins

Answer 46

- carrier proteins - channel proteins

Answer 47

- have a water filled hydrophilic channel through which ions can pass - allow specific water-soluble ions to pass through, if specific ion isn't present, the channel remains closed.

Answer 48

- can change shape when a specific molecule binds and the molecule is then released on the other side of the membrane

Answer 49

passage of water from a region of higher water potential to a region of lower water potential through a partially permeable membrane until a dynamic equilibrium is reached

Answer 50

lower its water potential (into negatives)

Answer 51

from a region of higher (less negative) water potential to a region of lower (more negative) water potential e.g -20kPa --> -30kPa

Answer 52

the more pure the solution is (means there is more solute in the solution)

Answer 53

pathogens abnormal body cells toxins cells from other organisms of the same species e.g organ transplant, blood transplant

Answer 54

a molecule that triggers an immune response by lymphocytes

Answer 55

- when a pathogen mutates frequently, so its antigens change suddenly rather than gradually. - this means that new antigens on the pathogen are no longer recognised by the immune system and therefore new strains of pathogens become created

Answer 56

- mutations mean that antigens on the pathogen change suddenly. - this means that vaccines become ineffective because the new antigens on the pathogens are no longer recognised by the immune system - so the immune system cannot produce the antibodies needed to destroy the pathogens

Answer 57

influenza virus (flu) and HIV

Answer 58

- phagocyte moves towards pathogen along a concentration gradient - pathogen engulfed by endocytosis - pathogen now contained within phagosome (phagocytic vacuole) - lysosomes fuse with phagosome to form a phagolysosome -lysozymes break down pathogen - waste products excreted by cell via exocytosis - phagocytes can then present the pathogens antigens by sticking it to its own cell surface becoming an antigen presenting cell.

Answer 59

- lysozymes are present within the lysosome and they destroy ingested bacteria by hydrolysis of their cell walls.

Answer 60

- when a phagocyte engulfs a pathogen, it doesn't always fully digest it -antigen from surface of the pathogen is saved and moved to a special protein complex on surface of cells - cell is now an APC - exposes antigen on surface so that other cells of immune system recognise the antigen - special protein complex ensures that APC isn't mistaken for foreign cell and attacked.

Answer 61

specific or adaptive immune response can target a specific pathogen slower than a non specific response

Answer 62

- involves specialised T-cells and other immune cells that they react with e.g phagocytes - target pathogens inside cells

Answer 63

1. once a pathogen has been engulfed and destroyed by a lysozmes, the antigens get positioned on the cell surface. this is now an APC 2. T helper cells have receptors on their surface which can attach to the antigens on APC 3. once attached, this activates the helper T cells to divide by mitosis to replicate and make large numbers of clones 4. cloned helper t cells differentiate into different cells. some become cytotoxic T cells 5. t helper cells release cytokines to stimulate cytoxic t cells 6. cyotoxic t cells detect antigen on surface of infected cell, and once detected, they release perforin which creates pores in the cell membrane 7. in addition enzymes are also released which get into the cell and destroy the infected cell

Answer 64

to destroy abnormal or infected cells by releasing perforin. this protein creates pores in the cell surface membrane which causes the cell to shrivel or lyse

Answer 65

they divide by mitosis to become more helper T cells which stimulate B cells and phagocytosis, or T memory cells or cytotoxic T cells

Answer 66

- infected body cells will present the viral antigen on their surface - a macrophage which has engulfed and destroyed a pathogen will present the antigen on their surface. - cells fo a transplanted organ will have different shaped antigens on their surface compared to your self-cell antigens - cancer cells will have abnormal shaped self-cell antigens

Answer 67

- consists of 4 polypeptide chains - 2 identical light chains and 2 identical heavy chains - disulphide bonds hold the 4 polypeptide chains of antibody together - constant region is the long part that isn't on the end -antigen binding site enables antibody to bind to specific antigen on a pathogen -quarternary structure protein

Answer 68

- An antigen and its complementary antibody have complementary molecular shapes - when antibody collides with a foreign cell that posesses 'non-self' antigens with a complementary shape, it binds with one of the antigens - therefore, 2 molecules combine (Antigen + antibody) to form an antigen-antibody complex

Answer 69

b cells and antibodies

Answer 70

- b cell binds to specific antigen on antigen presenting cell - t helper cell releases cytokines to stimulate b cells to divide by mitosis ( clonal expansion) - b cells differentiate into plasma cells which secrete antibodies with complementary variable region to the antigen - plasma cells develop memory cells

Answer 71

- can live for decades inside body - memory b cells don't make antibodies, rather they will divide by mitosis and make plasma cells rapidly if they collide with an antigen they have previously encountered. - this results in large numbers of antibodies being produced so rapidly that the pathogen is destroyed before any symptoms can occur.

Answer 72

- APC stimulates helper T cell to produce chemical message. Message activates the B cells - called clonal selection - activated B cells divide to form plasma cells - plasma cells undergo rapid division, called clonal expansion then produces required antibody in large quantities

Answer 73

a single type of antibody that can be isolated and cloned

Answer 74

- when an antigen enters the body for the first time, the immune system is activated (primary response) - primary response is slow and weak cause there aren't many B-cells that can make the antibody needed to bind to the specific antigen - after 1st infection, T and B cells produce memory cells that remain in the body - person is now said to be immune cause immune system has the ability to respond quickly to pathogen

Answer 75

- if the same pathogen enters the body again, the immune system will produce a quicker and stronger immune response (secondary response) - clonal selection happens faster - memory B cells activated, divide into plasma cell to produce specific antibody to antigen - secondary response often gets rid of pathogen before you display any symptoms

Answer 76

produces perforin that causes pathogen infected cells to lyse

Answer 77

generates large quantities of antibodies

Answer 78

when antigens bind to other antigens on surface of several pathogens, clumping them together phagocytes can now easily recognise and easily destroy pathogen by phagocytosis

Answer 79

cellular: - targets pathogens in host cell - involves cytotoxic T cells - perforin causes cell to lyse humoral: - produces antibodies - involves plasma cells - can neutralise pathogens both: - coordinated bt helper t cells - interleukin acts as cell signaller - involves APC

Answer 80

produced by introduction of antibodies into individuals from an outside source

Answer 81

produced by stimulating the production of antibodies by the individual's own immune system

Answer 82

natural active: chicken pox artificial active: vaccinations

Answer 83

natural passive: acquiring antibodies from their mother e.g breast milk and across the placenta artificial passive: injection of rabies antibodies after potential exposure

Answer 84

- same antigens that are found on the surface of a known pathogen and stimulate the primary response, resulting in production of memory B cells - may contain attenuated (less virulent) form of the pathogen

Answer 85

- vaccinations are the introduction of the appropriate disease antigens into the body. - intention is to stimulate an immune response against a particular disease - vaccine contains one or more types of antigen from the pathogen - antigens stimulate immune response - memory cells are then produced and these remain in the blood and allow a quicker and stronger response to a future pathogen of this same pathogen - the result is that there is a rapid production of antibodies and the new infection is rapidly overcome before it can cause any harm and with few symptoms or none at all

Answer 86

if enough people in a population are vaccinated against a disease, it's not possible for the disease to spread amongst the population, so everyone is protected reduced chance of passing it on if more people are vaccinated

Answer 87

it isn't ever possible to vaccinate the entire population e.g babies and very young children aren't vaccinated because their immune system aren't fully functional could also be dangerous to vaccinate those who are ill or have compromised immune systems.

Answer 88

- production of existing vaccines and development of new ones often involving the use of animals. how acceptable is this - on whom should vaccines be tested on

Answer 89

- core of genetic information, RNA, and some proteins - outer coating of protein called a capsid - capsid encloses 2 single strands of RNA and some enzymes (one enzyme is reverse transcriptase - catalyses production of DNA to RNA) - extra outer layer called a (lipid) envelope - attachment proteins on surface

Answer 90

1. Attachment proteins attach to receptors on helper T cell/lymphocyte; 2. Nucleic acid/RNA enters cell; 3. Reverse transcriptase converts RNA to DNA; 4. Viral protein/capsid/enzymes produced; 5. Virus (particles) assembled and released (from cell);

Answer 91

- once infected with HIV, a person is said to be HIV positive. - however, the replication of HIV often goes into dormancy and only recommences leading to AIDS many years later - HIV develops into AIDS when the helper t-cell numbers in their body reach a critically low level

Answer 92

- HIV specifically attacks helper T cells. HIV causes AIDS by killing or interfering with the normal functioning of helper T cells. - without a sufficient number of helper T cells, the immune system cannot stimulate B cells to produce antibodies or the cytotoxic T cells that kill cells infected by pathogens . - memory cells also become infected and destroyed - as a result, the body is unable to produce the adequate immune response and becomes susceptible to other infections or cancers

Answer 93

- viruses don't have their own enzymes and ribosomes - they use the ones in the host cells - antibiotics disrupt cell structures and metabolic mechanisms so because viruses use human enzymes, ribosomes etc to replicate, antibiotics can't inhibit them - viruses also have a protein coat rather than a murein cell wall and so do not have the sites where antibiotics can work. - most antiviral drugs are designed to target the few virus specific enzymes that exist e.g HIV uses reverse transcriptase to replicate. Human cells don't have this enzyme so drugs can be designed to inhibit it without affecting human cells - reverse transcriptase inhibitors

Answer 94

cancer drug delivery: - cancer cells have antigens called tumour markers that aren't on normal body cells - monoclonal antibodies can be made that are specific to the antigens on the cancer cells (tumour markers) and will bind to them - these antibodies are given to a patient and attach themselves to the receptors on their cancer cells - attach to the surface of their cancel cells and block the chemical signals that stimulate their uncontrolled growth

Answer 95

- this test detects the hormone hCG that is found in urine of pregnant women - application area contains antibodies that are complementary to the hCG protein, which are bound to the coloured bead - when urine is applied to the application area, hCG will bind to the antibodies on the beads, forming an antigen- antibody complex - urine moves up the test strip, carrying any beads with it - test strip contains antibodies to hCG that are immobilised - if theres hCG present, strip turns blue, immobilised antibody binds to any hCG concentrating the hCG - antibody complex with the blue beads attached

Answer 96

- allows you to see if a patient has any antibodies to a certain antigen or any antigen to a certain antibody - can be used in medical diagnosis to test for pathogenic infection e.g HIV or for allergies and anything else - if a colour change is present in an ELISA test, it demonstrates that the antigen or antibody of interest is present

Answer 97

- HIV antigen bound to the bottom of the well - plasma sample is added - if any HIV specific antibodies in plasma, these will bind to the HIV antigen stuck to the bottom of the well - well is then washed to remove unbound antibodies - secondary antibody is added - secondary antibody can bind to the HIV specific antibody - well washed again which removes secondary unbound antibody - if no primary antibody is present, all of the secondary antibody is washed away - substrate added - this is able to react with the enzyme attached to the secondary antibody and produce a coloured product - if solution changes colour, it indicates patient has HIV specific antibodies in blood

Answer 98

- monoclonal antibody therapy, animal rights issue - animals used to produce cells from which monoclonal antibodies are produced

Answer 99

electron beam passed through specimen: absorption/transmission of light creates dark/light sections. Photomicrograph taken of image

Answer 100

electron beam passed back & forth across specimen: electrons scattered and pattern used to generate 3D image by computer analysis

Answer 101

uses light and several lenses to magnify a sample

Answer 102

poor resolution: organelle ultrastructure can't be studied

Answer 103

- Not in colour - Artefacts - System in vacuum so living specimens can't be studied

Answer 104

- 2D image - Specimens must be very thin (to allow electrons to pass through)

Answer 105

1) The cytoplasm has no membrane bound organelles. 2)The ribosomes are smaller than those in a eukaryotic cell 3)Some prokaryotes have a flagellum, a long hair-like structure that rotates to help the cell move. 4)A prokaryote lacks a nucleus. The DNA floats free in the cytoplasm. It is circular DNA, one long coiled up strand 5)Some prokaryotes have plasmids- small loops of DNA that aren't part of the main circular DNA molecule. They contain genes for antibiotic resistance. 6)Some prokaryotes have a capsule made up of secreted slime to help protect bacteria from attacks from the immune system. 7)The cell wall supports the cell and is made from a polymer called murein.

Answer 106

because they are not cells. They are just nucleic acids surrounded by protein and are not even alive.

Answer 107

attachment proteins on edge of capsid

Answer 108

use attachment proteins to bind to complimentary receptors proteins on the surface of the host cell

Answer 109

cause the receptor proteins have to be complimentary to the attachment proteins on the surface of the virus