2: Cells Flashcards

Question

What are electron microscopes?

Answer 1

- uses beam of electrons to form image - maximum resolution= 0.0002µm (for organelles) - maximum magnification= ×1500000 - 2 types: transmission and scanning

Answer 2

- electromagnet focuses electron beam to transmit through the specimen - denser parts absorbs more electrons so they appear darker - image appears 2D in black and white (you can add colour with false colour imaging) - higher resolution to see internal structure

Answer 3

- scans beam of electrons, knocks electrons on surface that gather in a cathode ray tube - only shows cell outer surface - 3D image in black and white - lower resolution than TEMs

Answer 4

**homogenisation-**break down cell by grinding in blender, pistel and pellet, homogeniser or vibrating cells to break down plasma membrane and release organelles. **filtration-**filter the solution with gauze to seperate the large debris (e.g. connective tissue). organelles pass through gauze **ultracentifugation-**spin for pellets in a centifuge machine, spin at increasing speeds. pour solution into next tube. | solution must be cold, isotonic (even concentration) and with a buffer

Answer 5

animal- nuclei, mitochondria, lysosomes, endoplasmic reticulum, ribosomes plant- nuclei, chloroplast, mitochondria, endoplasmic reticulum, ribosomes

Answer 6

1. **Interphase-**cell prepares to divide as cell grows to make proteins and organelles (G1), DNA unravels and replicates (S), genes double and cell grows (G2) 2. **Prophase-**chromosomes (2 sister chromatids joined at the centromere) condense and become shorter. the nuclear envelope breaks down, freeing chromosomes in the cytoplasm (early prophase). centrioles ove to opposite cell poles producing spindle/ protein fibres (late prophase). 3. **Metaphase-**chromosomes meet at the centre, spindle fibres attatch to each centromere 4. **Anaphase-**centromere divides and spindle fibres contract pulling V-shaped chromatids to opposite cell poles. 5. **Telophase-**chromatids reach opposite sides, uncoil and thin again, 2 new nuclear envelopes form around chromosomes and cytokenesis occurs (cytoplasm pinches inwards). 2 genetically identical daughter cells form. This process repeats | **I P**eed on the **MAT**

Answer 7

**mitosis time**= (no. cells in certain stage÷ no. cells observed)× total time **mittoc index**= no. cells with visible chromosomes÷ no. cells observed

Answer 8

**Interphase-** chromosomes invisible in nucleus **Prophase-** chromosomes visible **Metaphase-** chromosomes at equator of cell **Anaphase-** chromosomes pulling apart/ V-shaped **Telophase-** 2 nuclei and cell walls begin to form

Answer 9

- mitosis and cell cycle caused by genes - when our cell cycle divides enough, they tend to stop dividing - a **mutation** in a gene causes cells to grow out of control if it controls cell division - the cell keeps dividing to make more cells - this forms a tumour

Answer 10

- if a tumor can invade other tissues, it's a **cancer**(malignant) - some cancer treatments are designed to control the rate of cell division in the tumor by disrupting the cell cycle, killing cells - these treatments can kill positive and bad cells (tumour cells) - they are more likely to kill tumour cells though as they divide more rapidly - this is why chemo-therapy is spread out

Answer 11

- disrupt G1 phase of the cell cycle/ organelle synthesis (chemo therapy) - they prevent synthesis of enzymes needed for DNA replication - if not produced, the cell can't enter the synthesis phase, disrupting the cell cycle, forcing the cell to kill itself

Answer 12

- radiation therapy and some drugs can cause damage to the cell's DNA - at several points during the cell cycle, the DNA is checked for damage - if severe damage is detected, the cell will kill itself, oreventing any further tumour growth

Answer 13

- surrounds cell, barrier between cell and external environment - controls substances leaving and entering the cell - partially permeable mebrane (only some molecules pass through) - substances enter cell through transport (4 types)

Answer 14

- all partially permeable to seperate cells from the cytoplasm - RNA can leave the nuclear envelope, the DNA can't as it's too large - made of lipids (mainly phospholipids), carbohydrates and proteins - these phospholipids form a continuous bilayer around the cell - bilayer is 'fluid' (can move) as phospholipids are constantly moving | fluid mosaic model- describes all basic cell membrane characteristics

Answer 15

- phospholipids form barriers to dissolved substances (water soluble) - phospolipids automatically arrange into the bilayer (hydrophillic head outwards, hydrophobic tail inwards) - canter of layer is hydrophobic and can move - water soluble substances (e.g. ions, polar molecules, glucose) can't diffuse through the membrane - though water is small, it can diffuse through by mitosis (as it's small) - has many proteins scattered through bilayer (e.g. channel/ carrier) - allows molecule to pass through the membrane - molecules/ ions can pass through channel proteins, simple diffusion and carriers by **active transport** and **facilitated diffusion**

Answer 16

- receptor proteins help the cell to detect chemicals - these chemicals help the cell to respond in certain way (e.g. insulin binding to complementary liver receptors) - proteins and lipids may have carbohydrates attatched to them (glyco-) - these are invlolved in cell signalling and recognition - the bilayer also has cholesterol to privide stability found between phospholipids, binding to their tails packing it tightly. - this can restict movement in the bilayer, allowing the membrane to be more rigid - this maintains the shape of animal cells (as they don't have a cell wall) - important in places like the red blood cells, aren't suported by other cells and flow freely

Answer 17

**0°C- phospholipid bilayer has little energy:** - doesn't move as much, close together keeping cell rigid - proteins can denature increasing permeability - ice crystals can puncture ppm - larger molecules can pass through **0-40°C- phospholipids have most efficient energy:** - phospholipids can move around, aren't as packed closely together - membrane is partially permeable - as temp. increases, phosphopid molecules move around more and have more energy, increasing permeability **45+°C- phospholipid layer breaks down** - membrane becomes more permeable - water in the cell expands putting pressure on the plasma membrane - channel and carrier proteing begin to denature and remaine open increasing cell permeability

Answer 18

WHAT?: the overall movement of particles in a gas or liquid from a region of high concentration to regions of low concentration, down the concentraion gradient - particles continue to diffuse until there's an even distribution of particles - when particles are able to diffuse directly across the membrane, this is simple diffusion (without help) | this is a passive process (doesn't rquire energy)

Answer 19

-** concentration gradient:** steeper concentration gradient, faster diffusion rate. as particles diffuse across the membrane, the difference in concentration gradient decreases until partciles reach equilibrium - **thickness in exchange surfaces:** thinner, shorter diffuion pathway, faster rate, less distance needs to be travelled - **surface area:** larger surface area/ exchange surface, faster rate of diffusion

Answer 20

larger molecules (e.g. glucose/ amino acids) diffuse slowly across the phospholipid bilayer, so to increase the diffusion rate, carrier proteins are needed **CARRIER PROTEINS:** protein changes shape to release molecule, each carrier protein is complementary to moving a certain substrate **CHANNEL PROTEINS:** pores in the cell membrane allow diffusion, charged particles diffuse for facilitated diffusion complementary to them | a passive process as it still goes down the concentration gradient

Answer 21

- concentration gradient - **no. carrier/ channel proteins on surface membrane: **more proteins, faster diffusion rate but if all proteins are occupied, rate of diffusion remains constant

Answer 22

the movement of molecules against the concentration gradient, requiring energy in the form of ATP from mitochondria and channel proteins

Answer 23

- speed of carrier proteins - no. carrier proteins, limited by when they're occupied - rate of respiration is dependend on ATP availability which controls the rate of active transport

Answer 24

- move against the concentration gradient, requiring energy - ATP (adenosine triphosphate breaks down with hydrolysis (water) to form ADP (adenosine diphosphate) and pi (inorganic phosphate) - energy is released and used to transport substances and solutes

Answer 25

- binds to 2 molecules at once - if one substance goes down the conc. gradient, other substance can move with it, against it **e.g. glucose and sodium** - sodium diffuses out of the cell down conc. gradient (high-low) - steep conc. gradient of sodium also moves glucose across the membrane against its conc. gradient | a type of carrier protein (symport- same direction, antiport- different)

Answer 26

- the likelihood of water molecules to diffuse/ move into or out of a solution - 'free water' (amount of water molecules free/ not dissolved) - more free water, the more it will move (pure wayer)

Answer 27

- movement of water molecules fron a region of high water potential (less negative) to a region of low water potential (more negative) across a partially permeable membrane, down the water potential gradient

Answer 28

- water potential 0 (100% free water) - if a solute is added to the water, it lowers the water potential and the water potential is negative | lower w.p., less free water, more negative

Answer 29

**if solution has the same w.p. on both sides of the ppm:** - solution is isotonic - cells don't lose or gain water, no net water movement or difference in water potential **if solution has higher w.p. than the inside of the cell:** - cell is hypotonic (too little solutes) - if cell is places into solution with higher w.p., water will move into cell by somsosis so it swells/ bursts (lysis/ turgid) **if solution has a lower w.p. than inside of the cell:** - cell is hypertonic (too much solutes) - if cell is placed into a hypertonic solution with less free water, water will move out of cells by osmosis, so cell shrivels (flaccid) | higher water potential, more free water, less negative

Answer 30

- **water potential/ concentration gradient**: higher w.p. gradient, faster osmosis rate as osmosis continues, difference in w.p. on either side of the membrane decreases, so the rate levels pff - **thickness of exchange surface** (shorter diffusion pathway, faster) - **surface area of exchange surface** (larger) - **temperature** (evaporation of water, less free water, more energy)

Answer 31

- embedded in the cell-sirface membrane are proteins involved in cell recognition and act as antigens. - allow immune cells in the body to recognise the difference between our body cells (self) vs foreign cells (non-self) - this includes pathogens (causing disease), abnormal body mcells, cells from other people of the same species and toxins

Answer 32

- cancerous or pathogen infected body cells have abnormal antigens on their cell surface membrane - toxins and poisons from other cells are antigens themselves - cells from other people will have different blood to your own (e.g. blood transfusion, organ transplants)

Answer 33

**Blood A-** antigen a **Blood B-** antigen b **Blood AB-** antigens a and b **Blood O-** antigen o - if a person needs a blood transfusion, they can only receive blood with the same antigens as there's - a wrong blood type triggers the immune response

Answer 34

- triggered when a foreign antigen is detected in the body; this involves different white blood cells with different roles in the immune system 1. phagocytosis 2. t-cells 3. b-cells 4. antibody production 5. production of memory cells and immunity

Answer 35

- when an invading pathogen enters the body, phagocytes recognise the foreign antigen - cytoplasm of phagocyte engulfs it and surrounds the non-self cell - pathogen's contained in phagocyctic vacuole in cytoplasm (seperate from the cell) - lysosome (witn lysozymes) fuses wit phagocytic vacuole and release digestive enzymes to break down and digest it - phagocyte presents pathogens' antigens on the cell membrane - the phagocyte becomes an antigen presenting cell, activating the other immune system cells

Answer 36

- a type of white blood cell with receptor proteins on the plasma membrane - binds to complementary antigens on the antigen presenting cell (phagocyte), activating the T-cells - helper T cells (**Th**) release chemical signals, activating and stimulating phagocytes and cytotoxic (**Tc**) to kill foreign/ abnormal cells

Answer 37

- Th cells activate the B-cells when they bind to the antigen, secreting antibodies - B cells (B lymphocytes) are covered with antibodies each with different shaped binding sites, so they only form antigen-antibody complexes with antigens with a complementary shape.

Answer 38

- B cells divide by mitosis to form plasma (identical) cells - this is called **clonal selection** when all cells are genetically identical and produce identical (monoclonal) antibodies specific to the pathogen - plasma cells secrete lots of antibodies

Answer 39

- after being exposed to antigen T and B cells, they also produce memory cells - Memory T cells remember the specific antigens and will recognise them if they enter the body again - Memory B cells remember the antibodies that are needed to bind to the antigens - the memory cells remain in the body for a long time, making them **immune**

Answer 40

- when a pathogen first enters the body, the **primary response** is triggered - this response is slow as there aren’t many B-cells for that antigen to make the correct antibody needed to bind to it - the body eventually produces the right antibody - slow recovery, shows symptoms in the person

Answer 41

- if the same pathogen enters the body again, the secondary response is triggered - therefore clonal selection occurs faster and b-cells are activated, divided into plasma cells, producing the correct antibody - this destroyed the antigen before any symptoms show

Answer 42

- **cellular-** t-cells and other immune system cells that they interact with (e.g. phagocytes) forming the cellular response - **humoral-** b-cells, clonal selection and the production of monoclonal antibodies form the humoral response | both responses are needed to remove the pathogen

Answer 43

- have two binding sites to bind to two pathogens at once - y-shaped (stick part is the constant region and two binding sites are the variable region) - variable region controls antibody specificity forming antigen binding site - variable region has a unique tertiary structure (complementary) -> disulphide bridges make constant region - Two binding sites cause pathogens to be clumped together (agglutination) - When the phagocyte binds to the antibodies, they engulf many pathogens at once | made of proteins (amino acid chains)

Answer 44

- when invading pathogens enter the body, antigens trigger the primary immune response, taking time, showing symptoms - when the same pathogen enters again, the secondary response occurs (immunity) - if you get the same virus you had before but it changed its antigens, the immune response has to start again, causing illiness

Answer 45

- this is because memory cells produced won't recognise antigens as they change regularly on surface membrane - e.g. flu vaccines change regularly as antigens change(different strains of flu) - as they're the same pathogen, type but different antigens, they're different **strains of the pathogen** - if memory cells don't recognise the new strain of the same pathogen, the previous vaccine won't work, causing you to show symptoms - new vaccines are developed, the most effective one is distributed | both pathogen strains are **immunologically distinct**

Answer 46

- virus that attacks the immune system (virus aren't living, they have to have host cells) - HIV infects and kills helper T-cells, acting as host cell for the virus STRUCTURE: - spherical with core (containing RNA with proteins+enzymes for reverse transcriptase) - outer coating (capsid) which has an extra outer layer (envelope) - has attatchment proteins for host cell

Answer 47

1. attatchment proteins attatch to receptor molecules on cell membrane of host helper T-cell 2. capsid released into host cell where is uncoats and releases RNA into cytoplasm 3. enzyme reverse transcriptase is used to make complementary DNA strand from viral RNA template 4. double stranded DNA is made and inserted to human DNA 5. host cell enzymes used ti make viral proteins from viral DNA found in human DNA 6. viral proteins are assembled into nre viruses which bud from the cell and go onto infect other cells | when new HIV emerges from the host cell, cell emerges and dies

Answer 48

- When HIV in first infects the body it replicates rapidly and the person may experience symptoms of illness - After initial infection period the replication of HIV drops to a lower level - this is called the **latency period** which can last for years and the person may not experience any more symptoms - as HIV replication continues as results in a decrease in the number of helper t cells in the body so the immune system can't effectively respond - eventually number of helper t cells in body reaches a critically low level developing **AIDS** - When someone's immune system fails or deteriorates making them vulnerable to more infections like pneumonia - They can develop diseases that normally wouldn't cause issues in a healthy immune system

Answer 49

- **initial symptoms:** minor mucus membrane infections and recurring respiratory infections - as the number of immune system cells decreases the person becomes more susceptible to more serious infections (like chronic diarrhoea bacterial infections under tuberculosis) - during later aids stages some people may develop serious infections like toxoplasmosis of the brain (a parasitic infection) - They may also develop a fungal infection called candidiasis in the respiratory system | It's these infections not HIV that kills the AIDS patient

Answer 50

- what: when your own immune system produces antibodies following antigen exposure **natural**- when you catch a disease and also produce antibodies **artificial**- when you catch a disease and also produce antibodies given vaccine with antigen so the body produces antibodies

Answer 51

- what: when the immune system doesn't produce antibodies in your given antibodies from a different organism **natural-** for example babies are immune to diseases as they receive antibodies from their mother through breast milk and placenta **artificial-** inject antibodies from someone else

Answer 52

- active has a slow response to protection and passive has an immediate response to protection - in active you need to be exposed to the antigen whereas in passive you don't need exposure - In active memory cells are produced however in passive no memory cells are produced - Active provides long-term protection as antibodies are produced and response to complementary antigens in the body however in passive short-term protection is provided and antibodies eventually break down

Answer 53

- contains antigen stimulating our immune system to produce antibodies, plasma cells and memory cells against a particular pathogen without causing disease - against a particular pathogen without causing disease either contain free antigens or antigens attached to dead (attenuated/ weak living) pathogens so no symptoms or diseases are caused -Can be taken orally or injected

Answer 54

ADVANTAGES: - **herd immunity-** protect others from disease, reducing ocurrences of disease in the population so those aren't vaccinated are less likely to catch the disease DISADVANTAGES: - orally: Maybe broken down by enzymes as its digested - vaccine: hard to absorb into the bloodstream if they're large molecules - **ethical issues-** all Vaccines tested on animals before tested on humans - Testing Vaccines on humans can be risky as volunteers put themselves at risk of gaining the disease - Some people don't take vaccine due to the side effects - Difficult to decide who to give Vaccines too first it in risk of disease

Answer 55

- an enzyme linked to an immunosorbant assay, using enzymes linked to antibodies to detect presence of antigens abd antibodies in a persons blood - test to see if personhas certain illness or antigena

Answer 56

**used to test patient's sample for presence of an antigen using only 1 type of antibody** 1. take patient's blood sample and remove plasmids/ antigens 2. bind all antigens to wall of test plate 3. detection antibody (with enzymes) with complementary binding site to the antigen is added to the wells 4. well is washed out to remove unbound antibodies 5. substrate is added to the wells 6. enzyme on antibody will react with substate causing it to change colour as it's broken down 7. the colour chage means the patient has tested antigens | colour change intensity -> concentration of antigens

Answer 57

**used to test a patient's sample for the presence of an antibody with a secondary antibody** 1. take patient's blood sample, removing plasmids and COMPLEMENTARY antigens 2. antigens complemetary to antibody is binded to the wall of the plate 3. antibodies from the patient's blood plasma is added to the wells. if antibodies are present, they bind to antigens 4. well is washed out to remove unbound antibodies 5. secondary antibodies (with enzyme) complementary to antibody are tested for is added to the well 6. wash out well secons time to remove unbound secondary antibodies 7. add substrate and observe for colour change | colour change intensity -> concentration of antibodies

Answer 58

- used to detect the preence of hormones (in pregnancy) and antigens (in covid) in a patient's sample - these use antibodies (mobile or immobile) with a complementary binding side to the antigen or hormone being detected - antibodie have a coloured bead attatched to them

Answer 59

- application area contains antibodies with comp. binding site to hormone/ antigens being detected - mobile antibodies have coloured bead attatched - in display window, there's the same antibodies (no coloured beads) that are immobiised - further up the window, there's a control zone

Answer 60

- when patient's sample is applied to the application area, if hormone/ antigen is present, it will bind to the binding site on the anbtibody forming - sample contains fluid (urine/ buffer) causing sample to move up absorbent strip, carrying antibodies with them

Answer 61

- first strip in the display window contains immobilised antibodies - Antigen antibody complexes that form bind to immobilised antibodies as they move up the test strip - Accumulation of antigen antibody complexes with coloured bead attaches to them causing a coloured strip to appear - If no antigen antibody complexes form, antibodies with coloured bead attached continue to move up the strip and no colored line forms - Any antibodies with coloured beads attached to them form antigen antibody complexes continue to move up the test immobilised on the second strip - Accumulation of antibodies with colored bead attached to them cause coloured strip to appear showing the test worked immobile antibodies- strip mobile antibodies- application zone

Answer 62

**Antibody:** A protein found in the blood that is produced by plasma cells which binds to antigens as a part of the immune response. **Antigen:** a foreign cell that can be detected by antibodies and trigger an immune response.

2: Cells Flashcards

(86 cards)