2A - Cell Structure And Division Flashcards

Question

What is an **example** of using a graticule and micrometer to find cell size?

Answer 1

1. Line up eyepiece graticule and stage micrometer —> each division on stage micrometer is **0.1 mm** long .. 2. (**no. 3**) At this magnification, 1 division on *stage micrometer* Is same as 4.5 divisions on eyepiece graticule 3. To work out size for 1 division on *eyepiece graticule* Divide 0.1by 4.5 1 division on EG = 0.022mm 4. If you look at a cell under a microscope at this magnification And it’s 4 divisions long, it measures 4 x 0.022= 0.088

Answer 2

In multicellular eukaryotic organisms, cells are specialised to do specific functions A cell’s struc (shape, organelles) helps carry out its function So depending on its job, they can look different to regular animal cells Eg. Epithelial cells… - walls of small intestine have finger like projections called villi - this increases SA for absorption - epithelial cells on surface of villi have folds in cell membrane called micro villi - microvilli increase SA even more - also have lot of mitochondria, to provide energy to transport digested food molecules into cell

Answer 3

They are things you can see down the microscope That aren’t part of the specimen you’re looking at —> can be anything from dust, air bubbles and fingerprints —> to inaccuracies caused by squashing/staining samples Artefacts are usually made during preparation of slides (shdnt be there) You must tprpare specimen on slides carefully (to avoid this) .. Are common in electron micrographs; specimens needs lots of preparation before you can see them First scientists could only distinguish between artefacts and organelles by repeatedly preparing specimens in different ways —> in an objects is seen with one preparation technique but not another - it’s more likely to be an artefact than an organelle

Answer 4

where mitosis starts - the cell doesnt divide here. - interphase is a period of lots of cellular activity - involving DNA replication (chromatin state) - the two copies of DNA (after replication) remain joined at the centromere - - also organelles are replicated G1 (growth phase) - organelles replicated, cell grows back to original size, S (synthesis phase) - DNA and histones replicated G2 - spindle proteins synthesised ready for mitosis

Answer 5

- two daughter cells (same number of chromosomes as each other and parent cell) - genetically identical - diploid cells

Answer 6

chromosomes start to become visible (from short thin threads = later shorten and thicken / condense) - nucleolus disappears; nuclear envelope breaks down - chromosomes drawn to equator of cell by spindle fibres animal cells have two cylindrical organelles called centrioles - move to opposite ends / poles of the cell - from each of the centrioles, spindle fibres develop, attached (span cell from pole to pole) -> spindle fibres=spindle apparatus collectively

Answer 7

plant cells lack centrioles but do develop spindle appartaus (so centrioles arent essential for spindle fibre formation)

Answer 8

the chromosomes are noe seen to be made of two chromatids (each are indentical copies of dna from parent cell) - both joined by centromere Spindle fibres form some microtubules from the poles are attached so pulled along the spindle apparatus to line up across cell equator

Answer 9

centromeres divide and spindle fibres pull individual chromatids apart. as are single. They’re pulled to opposite poles of cell. energy for process from mitochondria (gather round spindle fibres) if cells treated with chemicals that destroy spindle, the remain at equator, not dividing

Answer 10

chromosomes, wch are at the poles, become longer and thinner, leaving wide spread chromatin - spindle fibre disintegrates - nuclear envelope and nucleolus reform

Answer 11

cytoplasmic division occurs, making two daughter cells

Answer 12

- growth (mitosis ensures every body cell has the same dna. Involved in development of tissues) - repair (if cells are damaged or die, the new cells have an identical structure and function) - reproduction (single celled organisms divide by mitosis to give two new organisms) - differentiation (cells change to give rise to specialised cells)

Answer 13

Group of diseases caused by a growth disorder in cells (Result of damage to the genes that regulate mitosis and cell cycle) This leads to uncontrolled division of cells. A group of these cells produced from uncontrolled division Form a tumour - wch can be benign or malignant (cancerous) Cancerous tumours invade surrounding tissue

Answer 14

Some treatments are designed to control cell division rate in tumours By disrupting the cell cycle, killing tumours cells Also can kill normal body cells dividing too rapidly, but more likely to kill tumour cells - some cell cycle targets of cancer treatments.. 1. G1 (cell growth/protein production) - some chemical drugs (chemotherapy) prevent - synthesis of enzymes needed in DNA replication - if not produced the cell is unable to enter synthesis (S) phase - disrupting cell cycle, forcing it to kill itself 2. S phase (dna replication) - radiation and some drugs damage DNA - at several points in cell cycle (including just before and during S phase) - dna in cell is checked for damage - if severe damage detected, the cell will kill itself Both stopping further tumour growth

Answer 15

Before a cell divides , dna is checked to ensure it has been replicated correctly Chemical signals then tell a cell to stop or start division Neighbouring cells communicate with dividing cells to regulate growth too If any of these don’t happen, a cell will divide uncontrollably Leading to cancer

Answer 16

Precautions - wear gloves and lab coat when handling stains - use safety goggles when handling acid 1. Cut 1cm from tip of a growing root like onion It’s too as that’s where growth occurs/mitosis takes place 2. Prepare boiling tube 1M HCl; put in water bath 60°C 3. Transfer root tip into boiling tube (incubate 5 mins) 4. Use pipette to rinse rinse root tip with cold water; dry with paper towel 5. Place root tip on slide; cut 2mm from its tip 6. Use mounted needle to break root tip open, spreading out cells so specimen’s thin 7. Add a few drops of toluidine blue stain (makes chromosomes easy to see under microscope) 8. Place cover slip over cells squash tissue by pushing firmly Making tissue thinner so light can pass; don’t smear slip - chromosomes will damage 9. Now you can see stages of mitosis under optical microscope (**DIAGRAM NO,4**)

Answer 17

1. Clip slide you’ve prepared under the stage; turn light on 2. Select lowest magnification objective lens 3. Use the coarse adjustment knob to bring up stage (just below lens) 4. Look down eyepiece (ocular lens); turn coarse adjustment knob away from objective lens until image is roughly in focus 5. Adjust focus with fine adjustment knob until image is clear 6. Upon increasing magnification, swap to higher power objective lens and refocus If asked to draw cells undergoing mitosis - write magnification of specimen - also label drawing

Answer 18

= number of cells with visible chromosomes/undergoing mitosis /total number cells observed Let’s you find how quick tissue is growing - a plant root tip is constantly growing, so you’d find a high mitotic index - in other samples, a high mitotic index indicates tissue is repairing or cancerous growth

Answer 19

Are nucleic acids surrounded by a protein coat (acellular; not alive) - smaller than bacterial cels = 0.1micrometre across - All viruses invade and reproduce inside cells of other organisms (these cells are host cells) Structure.. - attachment protein - lipid envelope - matrix - capsid - reverse transcriptase (enzyme) - genetic material RNA **DIAGRAM No.5**

Answer 20

1. Use attachment proteins to bind To complimentary receptor proteins (on host’s surface) 2. Different viruses= diff attachement proteins hence require diff receptor proteins On host cells. As a result some viruses can only infect one cell type 3. As not alive , viruses dont undergo cell division.. - attachment to specific receptors on host - fuse with host cell membrane - inject nucleic acid (can be RNA or DNA) - (genetic info gives instructions for host cell to start producing viral components — hijacking) - new virus particles made (new viruses) - infect more cells LYCTIC CYCLE

Answer 21

It’s binary fission, the cell replicates its genetic material Before physically splitting into two daughters cells 1. The circular dna and plasmids replicate - main dna loop is replicated once; plasmids can be replicated lots of times 2. Cell gets bigger (cytoplasmic membrane elongates) and DNA loops move to opposite cell poles 3. Cytoplasm begins dividing (new cell walls start forming) 4. Cytoplasm divides and two daughter cells produced Each daughter cell has one copy of the circular DNA but can have a variable number of copies of the plasmids . Ideal conditions are warm, moist and rich in oxygen

Answer 22

2n (n = number of divisions)

Answer 23

1. Lag phase A flat line as getting used to pétri dish food 2. Rapid growth Due to food, water, growth and space 3. Stationary phase 4. Death phase Growth rate=death rate (run out of food) More dying than growling