Microscopy and Cell structure

Question 1

What are the symbols for ‘millimeter’, ‘micrometer’ and ‘nanometer’?

Answer 1

mm
μm
nm

Question 2

Cell theory states that…

Answer 2

Cells are the basic unit of life
Cells are made from other cells
All living things are composed of a cell or cells

Question 3

What are the two types of microscopes?

Answer 3

Light microscope

Electron microscope

Question 4

Magnification=

Answer 4

Image/Actual

Question 5

What is magnification?

Answer 5

Magnification is how many times bigger the image is than the actual size of the object.

Question 6

What is resolution?

Answer 6

This is the ability to distinguish to different points as separate entities

Question 7

Why cant light microscopes see ribosomes

Answer 7

Light waves have a wavelength of 400nm and ribosomes are 25nm, so they don’t interfere with the waves and making them impossible to see in a light microscope.

Question 8

Why must some biological molecules be stained?

Answer 8

They are transparent so they let light pass through them and won’t be visible.

Question 9

Why were electron microscopes made?

Answer 9

So that scientists could see things that were smaller than 200nm

Question 10

What are the advantages of using an electron microscope?

Answer 10

Very short wavelength (0.01 to 10nm)
Negatively charged (can be focused using an electromagnet)
Have a resolution of 0.5nm (400x better than light microscope)

Question 11

What is the resolution of light microscopes?

Answer 11

200nm

Question 12

What are the two types of electron microscope?

Answer 12

Transmitting electron microscope (TEM)

Scanning electron microscope (SEM)

Question 13

Describe the TEM

Answer 13

Beams pass through the specimen 
Only transmitted (that pass through) electrons are seen 
Specimen must be dead

Question 14

Describe the SEM

Answer 14

Beams of electrons scan the surface of specimen
Only reflected beams are observed
Produces a 3D image
Specimen must be dead

Question 15

What organelles do we find in animal cells?

Answer 15

Cell membrane
Nuclear envelope
Nucleoplasm
Nucleolus 
Ribosomes
Mitochondria
RER
SER
Golgi apparatus
Lysosomes
Cytoplasm

Question 16

What organelles do we find in plant cells?

Answer 16

Cell wall 
Cell membrane
Nucleus 
Nucleolus
Nuclear envelope
Mitochondria
Ribosomes
RER 
SER
Cytoplasm
Vacuole
Chloroplast
Cytoplasm
Amyloplast

Question 17

What are the 2 types of cells

Answer 17

Eukaryotes

Prokaryotes

Question 18

Features of Eukaryotic cells

Answer 18

Have a nucleus
Have membrane bound organelles
Found in all organisms except bacteria and some algae

Question 19

Features of Prokaryotic cells

Answer 19

Have loose DNA
Much simpler that eukaryotic cells
Found in bacteria and blue-green algae

Question 20

The nucleus

Answer 20

Surrounded by double membrane and is (4-6μm)
Made of:
1) Nuclear envelope (is porous to allow transportation in and out the nucleus)
2) Nucleolus (site of ribosomal RNA production)
3) Nucleoplasm (contains chromatin which is uncoiled chromosomes)
Contains genetic material
Chromatin consists of DNA and proteins
During cell division chromatin condenses into chromosomes
Largest organelle

Question 21

ER

Answer 21

Made of flattened membrane bound sacs (cisternae)

Used for manufacture and transportation

Question 22

RER

Answer 22

Has ribosomes attached to it

Used for manufacture and transportation of proteins to the Golgi apparatus.

Question 23

SER

Answer 23

Has no ribosomes attached to it

Produces lipids and steroids (cholesterol, testosterone)

Question 24

Golgi apparatus

Answer 24

Flattened single membrane bound vesicles (cisternae)
Modifies and packages products
Has many small vesicles due to budding
Receives proteins from ER
Packages proteins into vesicles to be transported within or outside the cell
Modifies proteins (adds sugars)

Question 25

What is endocytosis?

Answer 25

It is the cellular process in which cells are brought into the cell

Question 26

What is exocytosis?

Answer 26

It is a form of active transport where molecules are transported out of the cell

Question 27

Lysosomes

Answer 27

Spherical sacs surrounded by a single membrane 0.1-0.5μm in diameter Contains hydrolytic enzymes to break down materials Specialized lysosome (acrosome) in head of the sperm

Question 28

Mitochondria

Answer 28

``` Powerhouse of the cell 2-4μm Double membrane filled with fluid Inner membrane is folded to form cristae Central part is called matrix Matrix has its own DNA Site where ATP is produced during aerobic respiration ```

Question 29

Chloroplast

Answer 29

Double membrane filled with fluid Inner membrane connected to thylakoids (stacks of thylakoids is called grana) Contains chlorophyll Size varies Site of photosynthesis to produce ATP Light energy is used to derive carbohydrate molecules from CO2

Question 30

Vacuole

Answer 30

Maintains stability in cell Creates turgor pressure by pushing cytoplasm against cell wall Large and permanent in plants

Question 31

Cell surface membrane

Answer 31

7nm wide Can be seen as 2 lines separated lighter layer (trilaminar appearance) Middle layer made of phospholipid bilayer Phospholipid bilayer contains 3 proteins: 1) Carrier proteins (found all throughout the bilayer) 2) Extrinsic (found on the outside may be attached to carbohydrates) 3) Intrinsic (found inside on cytoplasm) Partially permeable

Question 32

Microvilli

Answer 32

Finger like extension of cell membrane Common in epithelial cells Increases surface area Used in absorption

Question 33

Ribosomes

Answer 33

``` Not membrane bound 25nm Can be found attached to RER or lose in cytoplasm Has 2 subunits Made of RNA and protein Synthesizes proteins ```

Question 34

Microtubules

Answer 34

``` Long, hollow, rigid tubes found in cytoplasm No membrane 25nm in diameter Makes up the cytoskeleton Made of tubulin (alpha and beta) Alpha and beta tubulin join to form dimer And the dimers form protofilaments 13 protofilaments make a microtubule Supports the cell Is part of the intracellular transportation system Forms spindles in cell division. Use ATP for energy ```

Question 35

Microtubule Organizing Centers (MTOCs)

Answer 35

Specialised areas where microtubules are made from tubulin. 1) Centrosomes Only found in animal cells Used for construction if spindles Made of 2 centrioles crossing each other 2) Centrioles Made on 9 triplets of microtubules Function remains a mystery Found at the base of flagella and cilia to helps with movement.

Question 36

Cilia and Flagella

Answer 36

``` Structurally the same in eukaryotes Hair like extensions of the cell surface Use ATP for energy Flagella occurs in 1 or 2s Cilia comes in large numbers ```

Question 37

Cell wall and plasmodesmata

Answer 37

Rigid and contains cellulose to strengthen it Linked to neighboring cell wall by plasmodesmata Prevents cell from bursting (osmosis) Freely permeable to allow movement of ions to cell surface membrane Plasmodesmata controls movement between cells and controlled by structure of pores

Question 38

Uses of energy

Answer 38

``` Synthesis of complex substances Active transport Mechanical work (peristalsis, cilia movement) Bioluminescence Maintaining body temperature ```

Question 39

Role of ATP

Answer 39

``` Known as universal energy carrier because it is a link between anabolic and catalytic reactions Energy is released when ATP is hydrolysed This energy can be used in the cell for: Muscle contraction Active transport Spindle formation Vesicle formation Anabolism (protein synthesis) Activation of chemicals ```