cells Flashcards

Question

What is a tissue

Answer 1

Group of specialised cells with a similar structure working together to perform a specific function, often with the same origin

Answer 2

Aggregations of tissues performing specific functions

Answer 3

Group of organs working together to perform specific functions

Answer 4

● Cytoplasm lacking membrane-bound organelles ● So genetic material not enclosed in a nucleus

Answer 5

Always present - cell surface mem - cell wall (Murein glycoprotein) - cytoplasm - small 70s ribosomes - circ dna (free in cytoplasm - not associated with proteins)

Answer 6

Has membrane-bound organelles eg. mitochondria, endoplasmic reticulum Vs No membrane-bound organelles eg. no mitochondria, endoplasmic reticulum Has a nucleus Containing DNa Vs No nucleus DNA is is free in cytoplasm v2 DNA is long & linear & associated with histone proteins DNA is short & circular & not associated with proteins Larger (80S) ribosomes (in cytoplasm) vs Smaller (70S) ribosomes Cell wall only in plants, algae and fungi Containing cellulose or chitin Vs Cell wall in all prokaryotic cells Containing murein, a glycoprotein Plasmids / capsule never present (sometimes flagella) Vs Plasmids, flagella and a capsule sometimes present Larger overall size vs Much smaller overall size

Answer 7

● Acellular- not made of cells, no cell membrane / cytoplasm / organelles ● Non-living- have no metabolism, cannot independently move / respire / replicate / excrete

Answer 8

1. Nucleic acids surrounded by a capsid (protein coat) 2. Attachment proteins allow attachment to specific host cells 3. No cytoplasm, ribosomes, cell wall, cell-surface membrane etc. 4. Some also surrounded by a lipid envelope eg. HIV

Answer 9

● Magnification = number of times greater image is than size of the real (actual) object ○ Magnification = size of image / size of real object ● Resolution = minimum distance apart 2 objects can be to be distinguished as separate objects

Answer 10

Light focused through glass lenses vs electrons focused through electromagnets in tem and sem

Answer 11

Light passes through specimen diff struc absorb diff amounts and wavelengths In tem electrons pass through specimen and denser parts absorb more so appear darker In sem electrons are deflected/bounce off of specimens surface

Answer 12

Sem - 3D image of a surface Optical and tem - 2d image of a cross section

Answer 13

Low resolution in optical mic due to long wavelength of light Very high resolution in tem - short wavelength of e- High res in sem - short wavelength of e-

Answer 14

Can’t see internal struc in optical or sem, can see in tem

Answer 15

Very thin specimens in tem Doesn’t matter in sem Thin in optical

Answer 16

Low mag x1500 in light High mag x1000000 in tem and sem

Answer 17

Optical - can view living Tem/sem - has to be dead/dehydrated specimens in vacuum

Answer 18

Simple prep in light mic Complex preparation so artefacts often present in tem and sem

Answer 19

Colour in optical no colour in sem or tem

Answer 20

● Scientists prepared specimens in different ways ● If an object was seen with one technique but not another, it was more likely to be an artefact than an organelle

Answer 21

Metre Milimetre Micrometer Nanometre Going down x1000 Going up divide by 1000

Answer 22

1. Line up (scale of) eyepiece graticule with (scale of) stage micrometre 2. Calibrate eyepiece graticule - use stage micrometre to calculate size of divisions on eyepiece graticule 3. Take micrometre away and use graticule to measure how many divisions make up the object 4. Calculate size of object by multiplying number of divisions by size of division 5. Recalibrate eyepiece graticule at different magnifications

Answer 23

1. Homogenise tissue / use a blender ● Disrupts the cell membrane, breaking open cells to release contents / organelles 2. Place in a cold, isotonic, buffered solution ● Cold to reduce enzyme activity ○ So organelles not broken down / damaged ● Isotonic so water doesn’t move in or out of organelles by osmosis ○ So they don’t burst ● Buffered to keep pH constant ○ So enzymes don’t denature 3. Filter homogenate ● Remove large, unwanted debris eg. whole cells, connective tissue 4. Ultracentrifugation- separates organelles in order of density / mass ● Centrifuge homogenate in a tube at a low speed ● Remove pellet of heaviest organelle and respin supernatant at a higher speed ● Repeat at increasing speeds until separated out, each time the pellet is made of lighter organelles (nuclei → chloroplasts / mitochondria → lysosomes → ER → ribosomes)

Answer 24

Interphase - dna replicates semi conservatively (s phase) - 2 chromatids (identical copies) joined at centromere - number of organelles and volume of cytoplasm increases, protein synthesis (g1/g2) Mitosis - nucleus divides - 2 nuclei produced with identical copies of DNA produced by parent cell Cytokinesis - cytoplasm and cell mem divide to form 2 genetically identical daughter cells

Answer 25

Stage 1 Prophase • Chromosomes condense, becoming shorter / thicker so visible Appear as 2 sister chromatids joined by a centromere • Nuclear envelope breaks down • Centrioles move to opposite poles forming spindle network • Spindle fibres start to attach to chromosomes by their centromeres Stage 2 Metaphase • Spindle fibres attach to chromosomes by their centromeres • Chromosomes align along equator Stage 3 Anaphase • Spindle fibres shorten / contract • Centromere divides Pulling chromatids (from each pair) to opposite poles of cell Stage 4 Telophase Chromosomes uncoil, becoming longer / thinner Nuclear envelopes reform = 2 nuclei Spindle fibres / centrioles break down

Answer 26

● Within multicellular organisms, not all cells retain the ability to divide (eg. neurons) ● Only cells that do retain this ability go through a cell cycle

Answer 27

Parent cell divides to produce 2 genetically identical daughter cells for: ● Growth of multicellular organisms by increasing cell number ● Replacing cells to repair damaged tissues ● Asexual reproduction

Answer 28

Mitosis is a controlled process so: ● Mutations in DNA / genes controlling mitosis can lead to uncontrolled cell division ● Tumour formed if this results in mass of abnormal cells ○ Malignant tumour = cancerous, can spread (metastasis) ○ Benign tumour = non-cancerous

Answer 29

● Some disrupt spindle fibre activity / formation ○ So chromosomes can’t attach to spindle by their centromere ○ So chromatids can’t be separated to opposite poles (no anaphase) ○ So prevents / slows mitosis ● Some prevent DNA replication during interphase ○ So can’t make 2 copies of each chromosome (chromatids) ○ So prevents / slows mitosis

Answer 30

Binary fission: 1. Replication of circular DNA 2. Replication of plasmids 3. Division of cytoplasm to produce 2 daughter cells ○ Single copy of circular DNA ○ Variable number of copies of plasmids

Answer 31

Being non-living, viruses do not undergo cell division 1. 2. 3. Attachment proteins attach to complementary receptors on host cell Inject viral nucleic acid (DNA/RNA) into host cell Infected host cell replicates virus particles: a. Nucleic acid replicated b. Cell produces viral protein / capsid / enzymes c. Virus assembled then released

Answer 32

● Molecules free to move laterally in phospholipid bilayer ● Many components - phospholipids, proteins, glycoproteins and glycolipids

Answer 33

● Phospholipids form a bilayer- fatty acid tails face inwards, phosphate heads face outwards ● Proteins ○ Intrinsic / integral proteins span bilayer eg. channel and carrier proteins ○ Extrinsic / peripheral proteins on surface of membrane ● Glycolipids (lipids with polysaccharide chains attached) found on exterior surface ● Glycoproteins (proteins with polysaccharide chains attached) found on exterior surface ● Cholesterol (sometimes present) bonds to phospholipid hydrophobic fatty acid tails

Answer 34

● Bilayer, with water present on either side ● Hydrophobic fatty acid tails repelled from water so point away from water / to interior ● Hydrophilic phosphate heads attracted to water so point to water

Answer 35

● Restricts movement of other molecules making up membrane ● So decreases fluidity (and permeability) / increases rigidity

Answer 36

● Phospholipid bilayer is fluid → membrane can bend for vesicle formation / phagocytosis ● Glycoproteins / glycolipids act as receptors / antigens → involved in cell signalling / recognition

Answer 37

● Lipid-soluble (non-polar) or very small substances eg. O2, steroid hormones ● Move from an area of higher concentration to an area of lower conc., down a conc. gradient ● Across phospholipid bilayer ● Passive - doesn’t require energy from ATP / respiration (only kinetic energy of substances)

Answer 38

● Restricts movement of water soluble (polar) & larger substances eg. Na + / glucose ● Due to hydrophobic fatty acid tails in interior of bilayer

Answer 39

● Water-soluble / polar / charged (or slightly larger) substances eg. glucose, amino acids ● Move down a concentration gradient ● Through specific channel / carrier proteins ● Passive - doesn’t require energy from ATP / respiration (only kinetic energy of substances

Answer 40

● Shape / charge of protein determines which substances move ● Channel proteins facilitate diffusion of water-soluble substances ○ Hydrophilic pore filled with water ○ May be gated- can open / close ● Carrier proteins facilitate diffusion of (slightly larger) substances ○ Complementary substance attaches to binding site ○ Protein changes shape to transport substance

Answer 41

● Water diffuses / moves ● From an area of high to low water potential (ψ) / down a water potential gradient ● Through a partially permeable membrane ● Passive - doesn’t require energy from ATP / respiration (only kinetic energy of substances)

Answer 42

Water potential is a measure of how likely water molecules are to move out of a solution - pure (distilled) water has the maximum possible ψ (0 kPA), increasing solute concentration decreases ψ

Answer 43

● Substances move from area of lower to higher concentration / against a concentration gradient ● Requiring hydrolysis of ATP and specific carrier proteins

Answer 44

1.Complementary substance binds to specific carrier protein 2. ATP binds, hydrolysed into ADP + Pi, releasing energy 3. Carrier protein changes shape, releasing substance on side of higher concentration 4. Pi released → protein returns to original shape

Answer 45

● Two different substances bind to and move simultaneously via a co-transporter protein (type of carrier protein) ● Movement of one substance against its concentration gradient is often coupled with the movement of another down its concentration gradient

Answer 46

1 ● Na+ actively transported from epithelial cells to blood (by Na +/K+pump) ● Establishing a conc. gradient of Na+ (higher in lumen than epithelial cell) 2 ● Na+ enters epithelial cell down its concentration gradient with glucose against its concentration gradient ● Via a co-transporter protein 3 ● Glucose moves down a conc. gradient into blood via facilitated diffusio

Answer 47

Describe how surface area, number of channel or carrier proteins and differences in gradients of concentration or water potential affect the rate of movement across cell membranes ● Increasing surface area of membrane increases rate of movement ● Increasing number of channel / carrier proteins increases rate of facilitated diffusion / active transport ● Increasing concentration gradient increases rate of simple diffusion ● Increasing concentration gradient increases rate of facilitated diffusion ○ Until number of channel / carrier proteins becomes a limiting factor as all in use / saturated ● Increasing water potential gradient increases rate of osmosis

Answer 48

● Cell membrane folded eg. microvilli in ileum → increase in surface area ● More protein channels / carriers → for facilitated diffusion (or active transport - carrier proteins only) ● Large number of mitochondria → make more ATP by aerobic respiration for active transport