2.1 Cell structure

Question 1

preparation of mounted tissue

Answer 1

1. obtain thin section
2. place plant tissue in drop of water
3. stain tissue
4. add coverslip using mounted needle at 45 degrees to avoid air bubbles

Question 2

how do light microscopes work

Answer 2

1. lenses focus rays of light and magnify
2. different structures absorb different amount of wavelengths of light
3. reflected light is transmitted to the observer via eyepiece

Question 3

how do TEMs work

Answer 3

1. pass high beam of electrons through thin slice of specimen
2. more dense structures appear darker since they absorb more electrons
3. focus image onto fluorescent screen using magnetic lenses

Question 4

how does SEMs work

Answer 4

1. focus beam if electrons onto a specimens surface using electromagnetic lenses
2. reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate

Question 5

how do laser scanning microscopes work

Answer 5

1. focus laser beam onto a small area using objective lens
2. fluorophores in the sample smith photons
3. photomultiplier tube amplifies the signal onto a detector.

Question 6

microscopy equation

Answer 6

image size = actual size x magnification

Question 7

magnification

Answer 7

factor by which the image is larger than the actual specimen

Question 8

resolution

Answer 8

smallest separation distance at which 2 separate structures can be distinguished from one another

Question 9

mag and res of light microscope

Answer 9

mag= x2000
res= 200nm

Question 10

mag and res of TEM

Answer 10

mag= x2 000 000
res= 0.2 nm

Question 11

mag and res of SEM

Answer 11

mag= x200 000
res= 10nm

Question 12

calibrating an eyepiece graticule

Answer 12

1. place micrometer on stage
2. line up scales and count how many graticule divisions are in 1mm of the micrometer
3. calculate the length of 1 eyepiece division= 1mm/ number of divisions

Question 13

nucleus structure

Answer 13

• surrounded by a nuclear envelope, a semipermeable double membrane
• nuclear pores allow substances to enter/exit
• dense nucleolus made of RNA + proteins assembles ribosomes

Question 14

nucleus function

Answer 14

• contains DNA coiled around chromatin into chromosomes
• controls cellular processes:
  site of mRNA transcription
  mitosis

Question 15

RER structure

Answer 15

• system of membranes, containing fluid-filled cavities (cisternae)
• coated with ribosomes

Question 16

RER function

Answer 16

• cisternae: network of tubules and flattened sacs extends from cell membrane + connects to nuclear envelope
• large SA for ribosomes

Question 17

SER structure

Answer 17

-system of membranes, containing fluid-filled cavities (cisternae)
- no ribosomes

Question 18

SER function

Answer 18

• contains enzymes that catalyse reactions involves with lipid metabolism:
  synthesis of cholesterol, lipids, steroid hormones

Question 19

Golgi Apparatus structure

Answer 19

• Planar stacks of membrane-bound, flattened sacs
  (looks like a stack of pancakes)

Question 20

Golgi Apparatus function

Answer 20

-proteins modified by adding: sugar,lipids or folding into 3D shape
- proteins being packaged into vesicles

Question 21

Mitochondrion structure

Answer 21

-surrounded by a double membrane with a fluid filled space between
- inner membrane= highly folded into cristae
- inner layer of mitochondrion= fluid-filled matrix

Question 22

Mitochondrion function

Answer 22

• site of ATP production during aerobic respiration
  -self-replicating so more can be made if more energy is needed

Question 23

Chloroplast structure

Answer 23

-surrounded by a double membrane or envelope
- inner membrane= thylakoids(stacks of flattened membrane sacs) each stack is called a granum
- contains loops of DNA and starch grains

Question 24

Chloroplast function

Answer 24

site of photosynthesis
1. light energy trapped by chlorophyll = used to make ATP, occurs in grana
- water also splits to supply hydrogen ions
2. hydrogen reduces CO2, using energy from ATP
- makes carbohydrates: occurs in stroma

Question 25

Vacuole structure

Answer 25

- surrounded by a membrane: tonoplast - contains fluid

Question 26

Vacuole function

Answer 26

- plants= large, permanent vacuole - filled with water and solutes, maintains cells stability - when full, pushes against cell wall making it turgid

Question 27

Lysosomes structure

Answer 27

- formed from Golgi apparatus: single membrane - contain powerful hydrolytic enzymes

Question 28

lysosomes function

Answer 28

- keeps the enzymes separate from rest of cell - engulf old cell organelles and foreign matter - digest them and return digested components to cell for reuse

Question 29

Cilia and undulipodia structure

Answer 29

- protrusions from the cell: surrounded by the cell surface membrane - contain microtubules and formed from centrioles

Question 30

Cilia and undulipodia Function

Answer 30

- epithelial cells= move band of mucus - act as an antenna: receptors allowing cells to detect signals about the environment - spermatozoon is the only cell with undulipodia

Question 31

Ribosomes structure

Answer 31

- spherical and made of ribosomal DNA - made in nucleus: pass through nuclear envelope into cell cytoplasm as two separate subunits and then combine as it leaves - some remain free in the cytoplasm, some attach to RER

Question 32

Ribosomes Function

Answer 32

- bound to exterior of RER= synthesising proteins that will be exported outside the cell - free in the cytoplasm= site of assembly of proteins - large subunit= joins to amino acids - small subunit= mRNA binding site

Question 33

Centrioles structure

Answer 33

- two bundles of microtubules at right angles - microtubules= made of tubular protein subunits which are arranged to form a cylinder

Question 34

Centrioles Function

Answer 34

- before a cell divides: spindle(made of tubulin) forms from centrioles - chromosomes attach to the middle part of the spindle and motor proteins walk along tubulin threads, pulling chromosomes to opposite ends - cilia and undulipodia: centrioles multiply and line up beneath cell surface membrane, microtubules then sprout outwards

Question 35

cellulose cell wall structure

Answer 35

- made of bundles of cellulose fibres

Question 36

cellulose cell wall function

Answer 36

- provide mechanical strength and support -maintains cell shape - permeable to allow solutions to pass through

Question 37

microfilaments structure

Answer 37

- made up of protein (actin)

Question 38

microfilament function

Answer 38

- gives support and mechanical strength to the cell - keeps the shape of cell stable - allows cell movement

Question 39

microtubules function

Answer 39

-provide shape and support - form the track for motor proteins ( dynein + kinesin) to walk along - form the spindle before a cell divides - makes up cilia + undulipodia + centrioles

Question 40

intermediate filaments function

Answer 40

- anchor the nucleus within the cytoplasm - extends between cells enabling signalling and allowing cells to adhere to a membrane

Question 41

All-purpose stains

Answer 41

- methylene blue

Question 42

Acetic Orcein

Answer 42

binds to DNA and stains purple-red

Question 43

Eosin

Answer 43

stains cytoplasm pink

Question 44

Sudan red

Answer 44

stains lipids red

Question 45

iodine

Answer 45

stains cellulose yellow stains starch blue/black