2.1 CELL STRUCTURE

Question 1

Four types of microscopes

Answer 1

1) light
2) scanning electron
3) transmission electron
4) laser scanning confocal

Question 2

Define resolution

Answer 2

• minimum distance between two objects in which they can still be seen as separate

Question 3

Define magnification

Answer 3

• how many times larger the image is compared to the actual object

Question 4

Formula for magnification

Answer 4

Image = Actual x Magnification

Question 5

State the 3 steps to calibrate an eye piece graticule

Answer 5

1) line up the stage micrometer and eyepiece graticule whilst looking through the eyepeice
2) count how many divisions on the eyepiece graticule (ruler below) fit into one division of the micrometer scale (ruler above)
3) length of one division on the micrometer (ruler above) DIVIDED BY how many divisions of the eyepiece graticule (ruler below) fit into it

Question 6

Name the four types of slides/mounts used in light microscopy

Answer 6

1) Dry mount
2) Wet mount
3) Squash slides
4) Smear slides

Question 7

Describe how dry mounts are prepared

Answer 7

• Place a cover slip on top of specimen

Question 8

Describe how wet mounts are prepared

Answer 8

• Add water to specimen
• Lower cover slip with mounted needle to prevent air bubble formation

Question 9

Describe how squash slides are prepared

Answer 9

• Add water to specimen
• Lower cover slip with mounted needle to prevent air bubble formation
• Squash cover slip down to ensure thin enough layer of specimen formed

Question 10

Describe how smear slides are prepared

Answer 10

• Use edge of another slide to smear sample across the slide to produce even, thin coat
• Place a cover slip on top

Question 11

Define differential staining

Answer 11

• using many chemical stains to stain different parts of a cell different colours in light microscopy

Question 12

Why is differential staining important? (2)

Answer 12

• provides increased contrast for differentiation
• to make cells/cell organelles visible

Question 13

State the relative magnification of all the microscopes

Answer 13

(lowest magnification) Light < LSCM < SEM < TEM (highest magnification)

Question 14

State the relative resolutions of all the microscopes

Answer 14

(lowest resolution) TEM < SEM < Light < LSCM (highest resolution)

Question 15

Describe the type of image produced by a Light microscope

Answer 15

• 2D
• Coloured

Question 16

Describe the type of image produced by a Laser Scanning Confocal microscope

Answer 16

• 2D OR 3D
• Coloured

Question 17

Describe the type of image produced by a Scanning Electron microscope

Answer 17

• 3D
• Black and white

Question 18

Describe the type of image produced by a Transmission Electron microscope

Answer 18

• 2D
• Black and white

Question 19

What do Light microscopes observe?

Answer 19

• Alive, thin
• Whole cells/tissues

Question 20

What do Laser Scanning Confocal microscopes observe?

Answer 20

• Alive, thick or thin
• Objects within certain depths of cells

Question 21

What do Transmission Electron microscopes observe?

Answer 21

• Dead, thin
• Organelles

Question 22

What do Scanning Electron microscopes observe?

Answer 22

• Dead, thick or thin
• Cell surfaces

Question 23

4 key rules of drawing images from microscopes

Answer 23

1) state the magnification
2) no overlapping lines
3) annotations of components
4) title the specimen

Question 24

Why are eukaryotic organelles membrane bound and which one isnt?

Answer 24

• separates organelle from cytoplasm
• ribosomes arent membrane bound

Question 25

Nucleus structure and function

Answer 25

- Nuclear envelope with pores to separate nucleus from rest of cell and so mRNA can leave and hormones can enter - Nucleolus containing RNA, where ribosomes produced - Chromatin as the genetic material consisting of DNA wrapped around histone protein

Question 26

Rough Endoplasmic Reticulum (RER) structure and function

Answer 26

- ribosome coated membrane system - synthesising proteins

Question 27

Smooth Endoplasmic Reticulum (SER) structure and function

Answer 27

- membrane system - synthesising lipids

Question 28

Golgi Apparatus structure and function

Answer 28

- flattened membrane sacs - modifying proteins

Question 29

Mitochondria structure and function

Answer 29

- surrounded by inner and outer membrane and a fluid-filled inner matrix with highly folded cristae membrane - site of ATP production during aerobic respiration

Question 30

Chloroplast structure and function

Answer 30

- surrounded by inner and outer membrane and a fluid-filled matrix (stroma) with stacks of thylakoids (grana) connected by intergranal lamallae - site of photosynthesis

Question 31

Ribosome structure and function

Answer 31

- made of rRNA and proteins - site of translation during protein synthesis

Question 32

Lysosome structure and function

Answer 32

- contain digestive enzymes that are separate from rest of cell - can engulf old cell organelles and digest foreign material

Question 33

Plasma cell surface membrane structure and function

Answer 33

- phospholipid bilayer embedded with protein, cholestrol, glycolipids and glycolipids - partially permeable to control what enters and leaves cell

Question 34

Centriol structure and function

Answer 34

- small microtubules made of tubulin -produces spindle fibres for mitosis

Question 35

Cellulose cell wall structure and function

Answer 35

- made of cellulose in plants and surrounds plasma cell surface membrane - prevents lysis, provides strength/support

Question 36

Flagella/Cilia structure and function

Answer 36

- small hairlike extentions of plasma cell surface membrane - wafts/moves things or moves the cell

Question 37

Uses of the cytoskeleton (5)

Answer 37

- provides stability/mechanical strength - forms a track for motor proteins to drag along/transport organelles - enables cell movement - form spindle fibres for mitosis - extends between cells to enable cell signalling

Question 38

Steps of secretion of **proteins** by **organelles**

Answer 38

1) **Genes** on **chromatin** in **nucleus** is **transcribed** into **mRNA** and leave via **nuclear envelope pores** to **RER's ribosomes** 2)**Polypeptide** chains are **translated** at the **ribsomes** on **RER** then **packaged** in **transport** **vesicles** to **Golgi Apparatus** 3) In **Golgi apparatus**, **protein** is **modified** then **packaged** into **secretory vesicles** which move along **cytoskeleton** 4) **Secretory vesicle** containing **protein** fuses with **plasma cell surface membrane** and secreted via **exocytosis**

Question 39

Similarities between prokaryotes and eukaryotes (4)

Answer 39

- Plasma cell surface membrane - Cytoplasm - Ribosome - DNA and RNA

Question 40

Differences of prokaryotes against eukaryotes (5)

Answer 40

- much smaller - no nucleus - no membrane bound organelles - peptidoglycan cell wall - less developed cytoskeleton