UNIT 1 Cells, Microscopes [memorise]

Question 1

units

Answer 1

1mm = 1000um

1000nm =1um

1m = 1000mm

Question 2

slides produced by …

+ prepare a slide using a…

Answer 2

cutting very thin layers of tissues -

which are then stained

permanently mounted on glass slide for repeated use.

+ liquid specimen, solid specimen & human cells

Question 3

ensure -

Answer 3

preparation method always needs to ensure that

samples are THIN enough to allow LIGHT to pass through

Question 4

preparing a slide using a LIQUID specimen

Answer 4

• add few drops of liquid sample to a CLEAN SLIDE using a pipette

-lower coverslip over specimen
-gently press down to remove air bubbles

Question 5

preparing a slide using a SOLID specimen

Answer 5

-use scissors/scalpel/tweezers to cut a small sample of tissue

-peel away/cut a very thin layer of cells from tissue sample.

-place sample onto a slide.

-drop of water may be added. Place epidermal tissue into water on slide.

apply drop of IODINE stain. so structure within cell can be observed

-lower coverslip over specimen & press down to remove air bubbles

Question 6

preparing a slide using HUMAN CELLS

Answer 6

-brush teeth, remove bacteria from teeth so don’t obscure view of cheek cells.

-sterile cotton swab; swab inside cheek surface of mouth for 5-10 sec

3. smear cotton swab on centre of slide for 2-3 sec

• add drop of METHYLENE SOLUTION

5. place coverslip on top; lay coverslip down at ONE EDGE & gently lower other edge until flat

• reduces bubble formation under coverslip

-absorb any excess solution by allowing paper towel to touch one side of coverslip

Question 7

methylene blue solution works how

Answer 7

methylene blue stains negatively charged molecules in cell, - DNA & RNA

so nucleus & mitochondria appear darker than their surroundings

Question 8

what do coverslips do?

Answer 8

• protect the microscope lens from liquids

-and help to prevent drying out.

Question 9

📍STAINS - what? colour?

1. eosin
2. iodine
3. crystal violet
4. methylene blue
5. congo red

-use small volume of stain to specimen; too much=nothing visible.

Answer 9

1. cell membranes & cytoplasm. pink/red
2. nucleus & plant cell wall pale yellow. starch blue-black
3. cells walls, purple.
4. animal cell nucleus, dark blue.
5. stains background around cells red, provide contrast with cells

Question 10

prokaryotes (6)

rmbr: no nucleus, no ER, no membrane-bound structures.

diagram - always (5): cell wall (containg MUREIN, a peptidoglycan), cytoplasm, cell surface membrane, circular DNA, ribosomes.

sometimes (5):
flagellum (locomotion),
capsule (/slime layer, additional protection),
infolding of cell membrane surface (may form photosynthetic membrane/carry out nitrogen fixation),
plasmid (small circle of DNA, several maybe),
pili (attachment to other cells or surfaces, involved in sexual reproduction)

Answer 10

unicellular, generally 1-5um in diameter, peptidoglycan cell walls, 70S ribosomes, absense of organelles surrounded by double membrane, circular DNA

-free DNA (NOT SURROUNDED by double membrane)
-free ribosomes
-no organelles (separate/membrane-bound)

-some carry out nitrogen fixation

Question 11

eukaryotic (features)

yes nucleus, yes (rough/smooth) ER, yes mitochondria.

Answer 11

• up to 40um diameter, 10-100um. 1000x times volume of bacteria

-DNA linear in nucleus, associated with histone proteins. double-membrane nucleus

-80S ribosomes cytoplasm. 70s mitochondria/chloroplasts
-organelles: single/double/no membrane

-cell walls sometimes - cellulose/lignin in plants. Chitin in fungi.

-none carry out nitrogen fixation

Question 12

flagella prokaryotic vs eukaryotic

Answer 12

pro: flagella SIMPLE & LACK microtubules, EXTRACELLULAR (project outside cell surface membrane)

eu: flagella COMPLEX with a 9+2 arrangement of MICROTUBULES, surrounded by cell surface membrane - INTERCELLULAR

Question 13

cell division pro vs eu

Answer 13

pro (bacteria): binary fission, NO SPINDLE.

eukaryotic (plants, fungi, animal): MITOSIS and MEIOSIS, involves SPINDLE. Chromosomes separated by spindle fibres.

Question 14

plant cells

Answer 14

yes nucleus, cytoplasm, large permamnet vacuole (central), thykaloid inside chloroplast, grana (thylakoid stacks in stroma), tonoplast (membrane surrounding vacuole), chloroplast, cell wall.

MIDDLE lamella: thin layer holding cells tgt

plasmodesmata: connects cytoplasm of neighbouring cells.

+Golgi apparatus,

Question 15

animal cell

Answer 15

ER, mitochondria

lysosome / vesicle

Golgi apparatus

CENTRIOLE - ALWAYS NEAR NUCLEUS.

Question 16

viruses

Answer 16

non-cellular structures

with a nucleic acid core (RNA/DNA)

capsid made of protein

some viruses have outer envelope made of phospholipids

Question 17

& viruses also

Answer 17

-code viral proteins to replicate. Use attachment proteins on surface to bind to & infect host cells.
-infect living cells, lytic cycle kills, lysogenic cycle lives & divides.
- = particles. ≠cells.

-smaller than bacteria. virus = 20-300NM DIAMETER.

Question 18

drawing cells - RULES

📌 DRAW 2-3.

& tissue -> draw layers (not cells)

Answer 18

📌 title (SPECIMEN, STAIN, MAGNIFICIATION)

📌 magnification recorded (scale bar)

📌sharp pencil
📌plain white paper
📌clear, single lines
📌no sketching
📌no shading
📌as large as possible
📌well-defined structures
📌only draw visible structures
📌should look like specimen
📌proper proportions
📌clearly labelled - lines do NOT cross, NOT have arrowheads. Connect directly to part of drawing, are on one side of drawing, drawn with a RULER.

Question 19

most important general notes on drawing

Answer 19

📌 cells: DRAW 2-3.

& tissue -> draw layers (not cells).

📌 PLAN drawings: tissues viewed under lower mgf; individual cells NEVER drawn.

Question 20

nucleus

Answer 20

nucleolus deeply staining

nuclear envelope

chromatin (DNA & protein) - deeply staining and thread-like

Question 21

-scale bar to calculate mgf

Answer 21

-use scale bar to find both actual size (written on scale bar) &

image size (measured length of bar)

and find mgf.

Question 22

eyepiece graticule (engraved ruler)

Answer 22

-often divided into 100 smaller divisions

-values of divisions vary depending on mgf.

CALIBRATE graticule every time you view an object.

Question 23

CALIBRATION is done using…

Answer 23

STAGE MICROMETER - a slide that contains a small ruler with an accurate known scale.

📌align stage micrometer under graticule at chosen mgf.

choose 2 aligned points on scale. count divisions. calc mgf factor …

Question 24

📍📍 1 graticule division/mgf factor/calibration value =

Answer 24

number of um stage micrometer ÷ number of graticule divisions on epg

Question 25

📍📍 length of object (um) =

Answer 25

[graticule divisions covered by object] ⨯ [mgf factor we just found number of um÷epg graticule divisions)]

Question 26

light microscope - lens mgf? -visible light -max 1500x to 2000x

Answer 26

EYEPIECE lens = x10 mgf. series of OBJECTIVE: each have diff mgf. 📍📍total mgf = eyepiece mgf ⨯ objective lens mgf

Question 27

magnification vs resolution

Answer 27

mgf: number of times a specimen has been enlarged to give a bigger image. resolution: CLARITY, its ability to distinguish 2 separate points on an image as separate objects

Question 28

resolution of light microscope ... also limited by...

Answer 28

-resolution of LM limits mgf usefully achieved; poor resolution = inc. mgf doesn't help! If res. too LOW, 2 separate objects will be observed as ONE point & image blurry/not visible. & it is limited by WAVELENGTH of light; visible light 400-700nm. Resolution can't be smaller than half of wavelength of visible light (max resolution of 200nm); ANY POINTS separated by a distance of LESS than 200nm can't be resolved

Question 29

So why, again, is the phospholipid bilayer & the ribosome UNABLE to be observed?

Answer 29

ANY POINTS separated by a distance of LESS than 200nm can't be resolved by a light microscope. Not distinguishable as separate objects. The specimen is shorter than wl, waves not interrupted, so specimen not detected.

Question 30

ELECTRON microscope 📌 large machines permanently installed 📌 create vacuum for e- to travel thru 📌 complex specimen prep 📌 max mgf x500,000, from x100 minimum 📌 max resolution of 0.5nm 📌 specimen ALWAYS DEAD.

Answer 30

→ HIGHER resolution & mgf than light microscopes; ELECTRONS have a much SMALLER WAVELENGTH than visible light. Can behave as waves. → resolution of 0.5nm, 📍 ~0.1nm. Specimens larger than 0.5nm. e- wl = ~0.005nm? More resolving power = shorter light wl. -fires beam of electron at specimen. Transmission EM fire e- through specimen. Scanning EM bounce e- off surface of specimen. E- picked up by electromagnetic lens; using EM coils bc e- can't pass thru glass lens. -specimen e.g., organelles, viruses, DNA, whole cells (detailed); see exterior & 3D shape.

Question 31

light microscope -small & portable. no vacuum. can be simple specimen prep. source: incandescent tungsten-based lamps, light bulbs, LEDs, lasers. -real, inverted.

Answer 31

-specimens larger than 200nm (max resolution 200nm) -eg., whole cells, small plant/animal organisms, tissues with organs (leaves/skin) -max mgf x2,000, x40 minimum -living OR dead specimen. glass lens. stained.

Question 32

📌 FUNCTIONS - 1. cell surface membrane [4]

Answer 32

1. controls exchange of materials between internal & external cell environments, separating them. 2. thin, partially permeable, cell membrane formed from phospholipid bilayer. 3. spans diameter of ~10nm. 4. ROLE: regulate nutrient & waste transport in and out of cell.

Question 33

2. nucleus [3]

Answer 33

1. double-layered membrane with pores. 2. contains chromosomes (DNA) & proteins [chromatin] as well as the NUCLEOLI. 3. 10% cell volume, ~1um. in ALL eukaryotic cells.

Question 34

3. nuclear envelope [4]

Answer 34

1. contains many pores 2. thin lipid layers 3. forms part of endoplasmic reticulum (ER). 4. ROLE: nuclear pores regulate passage between nucleus & cytoplasm. RNA travel through to reach ribosomes, transcription =>translation, allowing mRNA & ribosomes to travel out of nucleus & allowing enzymes & signalling molecules to move in.

Question 35

4. nucleolus [3]

Answer 35

1. site of ribosome synthesis 2. made of proteins, RNA, DNA. 3. rRNA (ribosomal RNA) genes make ribosomal subunits that exit the nucleus; then combine with proteins in cytoplasm to form functional ribosomes.

Question 36

5. endoplasmic reticulum [3]

Answer 36

1. around nucleus 2. made up of a series of membranes that form flattened sacs & branching tubules within cytoplasm. 3. ER linked with nuclear envelope.

Question 37

6. rough ER [3]

Answer 37

1. contains folds of membrane linked with nuclear envelope 2. surface of rough ER covered in ribosomes. 3. ROLE: process proteins produced on ribosomes. Involved in producing proteins to be secreted.

Question 38

7. smooth ER [5] TIP: use full name of SER & RER in exam.

Answer 38

1. no ribosomes. 2. ROLE: 📍 involved in production of lipids and steroid hormones (oestrogen, testosterone). 📍carbohydrate metabolism 📍drug/poison detoxification 📍store calcium & its metabolism

Question 39

8. Golgi body [4]

Answer 39

1. near nucleus. Wifi symbol. 2. a SERIES of FLATTENED SACS of membrane filled with liquid & NUTRIENTS, single membrane (not connected) 3. ROLE: modify proteins & lipids, & package them into vesicles for their distribution and transportation 4. lumen (inside), cisternae (top part), cis face (top), trans face (bottom).

Question 40

9. mitochondria [5] numbers depend on tissue and energy needs.

Answer 40

1. double-membraned organelle with embedded proteins. Smaller than chloroplast. 2. Centre filled with nutrient-rich matrix liquid, containing ribosomes, enzymes, & mitochondrial DNA 3. Ribosomes - allowing production of proteins required for respiration ;; Enzymes - aerobic respiration ;; Mitochondrial DNA - small circular DNA coding FUNCTIONAL proteins. 4. INNER MEMBRANE FOLDED to form cristae, providing LARGE SURFACE AREA for embedded proteins involved with aerobic respiration. 5. ROLE: site of aerobic respiration, glucose to ATP

Question 41

10. ribosomes [5]

Answer 41

1. formed in nucleolus. 2. found in cytoplasm of all cells OR as part of rough ER in eukaryotic. 3. each ribosome is a complex of RIBOSOMAL RNA & PROTEINS. 4. 80S ribosomes (60s&40s subunits) -> eukaryotic. Smaller 70s ribosomes (50s and 30s subunits) -> prokaryotes, mitochondria, chloroplasts. 5. ROLE: site of translation during protein synthesis (RNA to proteins)

Question 42

11. vesicles [3] golgi vesicles (pinched off ends of Golgi body) ;;;;;; vesicle surface, bilayer, internal water.

Answer 42

1. small, membrane-bound sacs 2. ROLE: for transport & storage of substances 3. Can fuse with cell surface membrane to allow EXOCYTOSIS, or bud from membrane during ENDOCYTOSIS.

Question 43

12. lysosomes [3] membrane, enzymes, transport proteins. ;;;; autophagy (self-consume), exo/endocytosis.

Answer 43

1. specialised vesicles containing digestive hydrolytic enzymes - worn-out organelles, engulfed pathogens during phagocytosis, cell debris during apoptosis/autolysis 2. ROLE: lysosomes contain enzymes to break down pathogens and to break down non-functioning organelles using hydrolytic enzymes (protease, lipase, lysozyme). Membrane-bound to protect rest of cell (from hydrolytic enzymes). 3. single membrane.

Question 44

13. centrioles [3]

Answer 44

1. NOT in flowering plants or fungi. EUKARYOTIC ONLY. & NEAR nucleus. 2. centrioles are hollow fibres made of microtubules - tubulin protein. 9 groups of 3 microtubules each for each centriole. 3. 2 centrioles at right angles to each other form a centrosome; CENTROSOME organises spindle fibres during cell division.

Question 45

14. microtubules [5]

Answer 45

1. hollow tubes made of tubulin protein. 2. a and B tubulin proteins combine to form dimers that are then JOINED into protofilaments. 3. 13 protofilaments in a cylinder make a microtubule. 4. microtubules make up CYTOSKELETON of cell. 5. ROLE: provide SUPPORT & movement of cell.

Question 46

15. cilia HAIR [3]

Answer 46

1. NOT in plant cells. Found in animal & protists cells. Thin, ~10nm. 2. hair-like projections made from MICROTUBULES. 3. ROLE: move cell/s, transport fluid & materials past cilia.

Question 47

16. microvilli FINGER [2] note: microvilli ≠ villi

Answer 47

1. finger-like cell membrane projections that 2. ROLE: that increase SURFACE AREA for absorption. 3. eg. lining of small intestine. Kidney tubules.

Question 48

17. cell wall [2.5]

Answer 48

1. permeable. Outside cell surface membrane. 1.5. Cellulose fibres crisscross in plants so strong & elastic. 2.5. ROLE: supports structure, protects cell.

Question 49

18. chloroplasts [5] NOTE: chloroplast = larger than mitochondria.

Answer 49

1. double-membrane, lipid membrane 2. contains chlorophyll, found in membranes of thylakoids, ROLE: absorb light energy for photosynthesis 3. Thylakoids STACK to form GRANA in stroma. 4. Grana joined together by LAMELLAE. 5. Chloroplast contains small circular pieces of DNA & ribosomes, ROLE: used to synthesise proteins needed in chloroplast REPLICATION & photosynthesis.

Question 50

19. plasmodesmata [2]

Answer 50

1. bridges of cytoplasm between neighbouring plant cells. Cytoplasm continues, so substances move easily. 2. ROLE: material transport and communication between plant cells.

Question 51

20. vacuole [6]

Answer 51

1. ANIMAL: several small temporary vacuoles/none, ROLE: STORAGE, can contain nutrients, water or waste. 2. PLANT: 1 large permanent vacuole, partially permeable tonoplast membrane, ROLE: to store water & cell sap, & push against cell to keep plant cell turgid, providing more structural support.

Question 52

21. cytoplasm [3]

Answer 52

1. jelly-like matrix MADE OF dissolved nutrients & salts. 2. contains organelles, sugars, amino acids, & proteins for GROWTH & REPRODUCTION. 3. GENERAL ROLE: aid material movement, cell shape & organelle network

Question 53

micrographs use (3): Shape, Location, Size relative to other organelles.

Answer 53

📌 nucleus largest. 📌 mitochondria second largest. (Often cylindrical with folded inner membrane/circular.) 📌 rough ER near nucleus (sometimes with ribosomes) 📌lysosomes & vesicles smaller than mitochondria.

Question 54

electron micrographs: plant cells

Answer 54

vacuole is large & empty. nucleus = largest DARK region in cell. chloroplasts next largest, grana sometimes visible

Question 55

animal vs plant cells common structures (9)

Answer 55

cell surface membrane, cytoplasm, nucleus mitochondria, RER & SER, Golgi body, Vesicles & lysosomes, ribosomes, microtubules

Question 56

plant cells - differences 1. external 2. internal (4) - ONLY plant cells 3. internal (2) - ONLY animal cells

Answer 56

1. larger, more regular in shape than animal cells. 2. cellulose cell wall ;; large permanent vacuole ;; chloroplasts ;; plasmodesmata 3. ANIMAL: centrioles, microvilli

Question 57

vital role of ATP describe cycle.

Answer 57

ATP → [active transport, muscle contraction, anabolic reactions] → ADP (Adenosine diphosphate) + inorganic P (phosphate) → respiration → back to ATP. -energy released. Process reversed during respiration to make ATP, maintaining constant supply of energy.

Question 58

describe, in simple terms, the vital role of ATP (adenosine triphosphate)

Answer 58

- cells use ATP, a nucleotide, from respiration for energy-requiring processes. e.g., in anabolic reactions to build larger molecules from smaller molecules; to move substances across cell membrane in active transport; move substance within cell. & IN animals, muscle contraction; conduction of nerve impulses.