2.1 - Cell Structure and Microscopes

Question 1

What is the eyepiece graticule?

Answer 1

A measuring device
Placed in the eyepiece of a microscope
Acts as a ruler when viewing object under the microscope

Question 2

What is the stage graticule?

Answer 2

Small scale placed placed on a microscope stage

Used to calibrate the value of eyepiece divisions at different magnifications

Question 3

What is resolution?

Answer 3

The clarity of an image, the higher the resolution the clearer the image

Question 4

What is magnification?

Answer 4

The number of times larger an image appears, compared with the size of the object

Question 5

What is the maximum magnification of a light and electron microscope?

Answer 5

Light: X1500

Electron:

Question 6

What is the maximum resolution of both a light microscope and an electron microscope?

Answer 6

Light:

Electron:

Question 7

How big are typical eukaryotic cells?

Answer 7

20 micrometers

Question 8

How big are typical prokaryotic cells?

Answer 8

0.1 - 5 micrometers

Question 9

What is a photomicrogtaph?

Answer 9

Photograph of an image seen using and optical microscope

Question 10

Advantages of optical microscopes

Answer 10

Relatively cheap
Easy to use
Portable, able to use in the field and laboratories
Able to study living specimens

Question 11

Disadvantages of an optical microscope

Answer 11

Low Resolution
Low Magnification
So cannot see some organelles in a cell

Question 12

Equation for total magnification of a microscope

Answer 12

Total magnification = objective lens x eyepiece lens

Question 13

About laser scanning (confocal) microscopes

Answer 13

Use laser light to scan object and show it on a computer screen
High res and high contrast images
Used mainly in medical profession
Can study living specimens

Question 14

How electron microscopes work

Answer 14

Beam of fast-travelling electrons hit object, focused by magnets
Have much greater magnification and resolution than optical microscopes

Question 15

Details of Transmission Electron Microscopes(TEM)

Answer 15

Form 2D black-and-white images
Magnification: x 2 million
Can study living specimens
Electrons go through specimen

Question 16

Features of Scanning Electron Microscopes

Answer 16

Electrons bounce off the specimen
Max magnification: x 200,000
Gives a 3D image

Question 17

How are specimens for micro graphs prepared?

Answer 17

Specimens are dehydrated
Embedded in wax - reduced distortion when slicing
Cut into thin slices called sections
Preserved in special chemicals

Question 18

Importance of staining specimens

Answer 18

Bind to certain molecules

Makes them easier to see

Question 19

What organelle do animal cells not have that plants do, and what do animal cells have that plants do not?

Answer 19

Plant cells have:
Large Vacuole
Chloroplast
Cell Wall

Animal Cells have:
Centriole
Lysosome

Question 20

Definition of organelles

Answer 20

Small structures within cells, each of which has a specific function

Question 21

Describe the structure of the nucleus?

Answer 21

Surrounded by a double membrane, called the nuclear envelope
There are pores in the nuclear envelope
Contains genetic material of the cell
Genetic material is in form chromatin.

Question 22

Describe the structure of the nucleolus

Answer 22

Does not have a membrane around it

Contains RNA

Question 23

What is the function of the nucleus?

Answer 23

Controls the cell’s activity
Stores the genetic information(genome) of the cell
Transmits genetic information(during mitosis)
Provides instructions to ribosomes for protein synthesis

Question 24

What is the function of the nucleolus?

Answer 24

Assembles ribosomes in the cell

Question 25

Structure of the RER

Answer 25

System of membranes, containing fluid-filled cavities(cisternae) that are continuous with the nuclear membrane It is coated with ribosomes

Question 26

What is the function of the RER?

Answer 26

Processes proteins from ribosomes Proteins actively pass through membrane Sent to the Golgi apparatus

Question 27

Structure of the SER

Answer 27

System of membranes, containing fluid-filled cavities(cisternae) that are continuous with the nuclear envelope No ribosomes on its surface

Question 29

Function of the SER

Answer 29

Involved with absorption, synthesis and transport of lipids(from the gut)

Question 29

Structure of the Golgi apparatus

Answer 29

A stack of membrane-bound flattened stacks. | Secretory vesicles bring material to and from the Golgi apparatus

Question 29

Function of the Golgi apparatus

Answer 29

Synthesis proteins from the RER Packages them into vesicles (Then stored in the cell or moved to plasma membrane) - modifies and repackages proteins from the RER - repackaged back into secretory vesicles - modified - add a protein/carb group

Question 31

Structure of the mitochondria

Answer 31

Spherical, or rod-shaped Surrounded by two membranes with a fluid-filled space between them Inner membrane highly folded into cristae Inner part of mitochondrion is a fluid-filled matrix

Question 32

Function of the mitochondria

Answer 32

Site of ATP production during aerobic respiration | Abundant in cells where much metabolic activity takes place, e.g muscles

Question 33

Structure of the chloroplasts

Answer 33

Surrounded by a double membrane or envelope Inner membrane contains flattened membrane stacks called thylakoids Each stack of thylakoids is called a granum Fluid filled matrix called the stroma Chloroplasts contain loops of DNA and starch grains

Question 34

Function of the chloroplasts

Answer 34

Site of photosynthesis Create ATP in the plant, occurs in grana Hydrogen reduces carbon dioxide Uses energy form ATP to make carbohydrates Occurs the stroma

Question 35

Structure of the vacuole

Answer 35

Surrounded by a membrane called the tonoplast, and contains fluid

Question 36

Function of the vacuole

Answer 36

Only found in plants Contains cell sap(water and solutes) Maintains cell stability as pushes against cell wall makes cell turgid Helps support the plant

Question 38

Structure of lysosome

Answer 38

Small bags formed from Golgi Apparatus surrounded by a single membrane Contain digestive enzymes Abundant in phagocytic cells(white blood cell)

Question 39

Function of lysosome

Answer 39

Separates digestive enzymes from rest of cell | Engulf old cell material to digest and reuse them

Question 40

Structure of cilia

Answer 40

Hair like structures protruding from cells Each contain microtubules Formed from centrioles

Question 41

Function of cilia

Answer 41

Line airways to move mucus

Question 42

What does the undolipodia do? | Flagella

Answer 42

Allows the sperm cell in humans to move | Propels it forward

Question 43

Structure of ribosomes

Answer 43

``` Made of ribosomal DNA Made in the nucleolus Pass through nuclear envelope into cytoplasm Some remain free in cytoplasm Some attach to RER ```

Question 44

Function of Ribosomes

Answer 44

Site of Protein Synthesis

Question 45

Structure of centrioles

Answer 45

Two bundles of microtubules Made of tubulin protein subunits Arranged to form a cylinder

Question 46

Function of centrioles

Answer 46

Involved in formation of cilia and undulipodia(sperm flagella)

Question 47

Structure of cytoskeleton

Answer 47

- consists of rod-like microfilaments made of subunits of actin - polymers of actin - straight, cylindrical microtubules- made of tubular subunits

Question 48

Function of cytoskeleton | 3 Marks

Answer 48

- Change shape of cell - E.g. exocytosis, requires ATP - Provide support and structural integrity to cell - Movement of organelles within cell - E.g. movement of vesicles towards plasma membrane - Movement of undulipodia to move cell - requires ATP - Formation of spindle - for movement of chromosomes in mitosis

Question 49

Structure of cell wall(cellulose)

Answer 49

Made form bundles of cellulose fibres | Outside of plasma membrane

Question 50

Function of cell wall

Answer 50

Provides strength and support Maintains cells shape Contribute to strength and support of plant Permeable - allow solutions to pass through (Fungi have cell wall of chitin)

Question 51

Process of making and secreting a protein(simple)

Answer 51

1. mRNA copy of the instructions (gene) for insulin is made in the nucleus. 2. mRNA leaves the nucleus through a nuclear pore. 3. mRNA attaches to a ribosome 4. Ribosome reads the instructions to assemble the protein (insulin). 5. Insulin molecules are ‘pinched off’ in vesicles and travel towards Golgi apparatus. 6. Vesicle fuses with Golgi apparatus. 7. Golgi apparatus processes and packages insulin molecules ready for release. 8. Packaged insulin molecules are ‘pinched off’ in vesicles from Golgi apparatus and move towards plasma membrane. 9. Vesicle fuses with plasma membrane. Protein leaves plasma membrane by exocytosis - requires ATP

Question 52

Prokaryotic and eukaryotic cells similarities

Answer 52

A plasma membrane Cytoplasm Ribosomes DNA and RNA

Question 53

Differences between eukaryotes and prokaryotes

Answer 53

``` Much smaller No nucleus No membrane-bound organelle(mitochondria) Cell wall made of peptidocglycan Smaller ribosomes DNA floats free in cytoplasm ```

Question 54

What different organelles do prokaryotes have?

Answer 54

Protective waxy capsule Plasmid DNA Flagella - allows cell to move Pili - small hair like projections that enable bacteria to adhere to host cell

Question 55

Resolution def

Answer 55

The ability to distinguish between two objects as separate in an image - it is the ability to see detail in an image

Question 56

Suggest two processes inside cells that rely on the cytoskeleton for movement.

Answer 56

- Movement of chromosomes/chromatids in cell division - movement of cytoplasm in cytokinesis - vesicles are moved/shuttled across the cytoplasm by the cytoskeleton (to RER) in protein synthesis - RNA/proteins are moved by microtubules in protein synthesis

Question 57

Structures C and E are both examples of mitochondria. Suggest why E looks so different to C. (2 Marks)

Answer 57

- cut in different planes / angles - mitochondria may naturally vary in shape - longer than wide etc. - artefact / deformed during preparation of section

Question 58

Membranes are a fundamental part of the cell. They are found both at the surface of a cell and inside a cell. (a) State three roles of membranes inside cells. (3 Marks)

Answer 58

- make compartments within cell organelles - e.g. vesicles - isolation of organelle contents from substances or metabolic pathways outside the cell, e.g. hydrolytic enzymes in lysosomes - site of attachment for enzymes on organelle membranes, e.g. ribosomes and tRNA - provide selective permeability - creation of concentration gradients

Question 59

Outline how the vesicles are moved from one organelle to another. (3 Marks)

Answer 59

- cytoskeleton - provides pathways for movement - vesicles move along microtubules - microtubules extend - this requires ATP

Question 60

Units of measurement in terms of metres

Answer 60

``` Km - 1x10^3 metres Metres - 1x10^1 metres Dm - 1x10^-1 metres Cm - 1x10^-2 metres Mm - 1x10^-3 metres Micrometre- 1x10^-6 metres Nanometer- 1x10^-9 metres ```

Question 61

Describe the advantages of staining specimens to be viewed under a microscope. (2 Marks)

Answer 61

- Easier to view different organelles - (staining) provides / increases, contrast ; - identify / recognise, cell types / organelles / parts of cell ; - identify / recognise, different (named), compounds / molecules