Lecture 2

Question 1

Visualizing cells became possible following the invention of the _________?

Answer 1

Light microscope

Question 2

What did Robert Hooke do?

Answer 2

• described the appearance of plants and insects underneath a microscope
• coined the term “cell”

Question 3

What is the most common type of light microscope used today?

Answer 3

• a compound microscope that is a microscope with multiple lenses

Question 4

How does a light microscope show an image of a cell?

Answer 4

light passes through an unstained, living cell undergoes very little changes in amplitude, but the phase of light is changed and small phase differences can be made visual by using special lenses

Question 5

What is the advantage of staining a sample under a light microscope?

Answer 5

• The stained portions of a cell reduce the amplitude of light waves of particular wavelength passing through them and a coloured image of the cell is obtained
• some stains can localize different cellular compartments

Question 6

what is fluorescence microscopy

Answer 6

• can be used to localize and quantify specific molecules in fixed and live cells
• light is absorbed at one wavelength and emitted at a longer wavelength (example: DAPI has an absorption maximum of 358 and an emission maximum of 461nm)
• fluorescent dyes are used for staining cells

Question 7

Fluorescence microscopes have two filters

Answer 7

1. filters lights before hitting the specimen, allowing only the wavelength of light that excites the fluorescent dye
2. blocks all light except the wavelength of light emitted by the excited fluorescent dye

Question 8

DAPI

Answer 8

visualizes nuclear DNA in both fixed and living cells by forming complexes with double stranded DNA to enhance fluorescence

Question 9

Conjugation of Fluorochromes to antibodies

Answer 9

• fluorochromes (fluorescent dyes) can attach to specific antibodies to perform immunofluorescent microscopy
• these antibodies will only bind to your target of interest

Question 10

What is confocal microscopy

Answer 10

• a specialized type of fluorescence microscopy. Preventing blurry images resulting from the presence of fluorescent structure above and below the plane of focus
  A few key features:
  –> a beam is focused on a single point
  –> a small hole allows light from the in focus point through to hit the detector
  –> out of focus light is excluded from the detector

Question 11

Can confocal microscopes produce 3D images?

Answer 11

not directly 3D confocal images can be constructed using multiple 2D confocal images taken at different planes of focus

Question 12

Define resolving power

Answer 12

• the ability of an imaging device to separate points of an object located at a small angular distance

Question 13

Compare transmission electron microscopy and scanning electron microscopy.

Answer 13

Transmission electron microscopy (TEM): operates under similar principle light microscopy except uses a beam of electrons intends of light (2D image)

Sanning electron microscopy (SEM): scatters electrons off the surface of the sample (3D image)

Question 14

what are the 3 main features of a cell

Answer 14

• Nucleus
• Cytoplasm
• Plasma membrane

Question 15

Nucleoid

Answer 15

• region of the cell which contains most of the cells genetic material
• it is not surrounded by a membrane

Question 16

Nucleus

Answer 16

• membrane-enclosed organelle which contains the cells genetic material

Question 17

What does the presence or absence of a nucleus define?

Answer 17

• it defines which organisms are prokaryotes and which are eukaryotes

Question 18

Compare prokaryotes and eukaryotes.

Answer 18

Prokaryotes –> no membrane bound organelle, nucleoid, smaller, singular circular chromosome, cytoplasm bound by plasma membrane

Eukaryotes–> membrane bound organelles, nucleus, larger, multiple linear chromosome, cytoplasm bound by plasma membrane and nuclear membrane

Question 19

Name 3 prokaryotes

Answer 19

• archaea
• photosynthetic bacteria
• non photosynthetic bacteria

Question 20

Outline the main features of the nucleus

Answer 20

1. Nuclear envelop has 2 membranes:
   - inner nuclear membrane and outer nuclear membrane (note that the outer membrane in contact w/ the ER)
2. Nucleolus: large structure in nucleus where ribosomal RNA is transcribed and and ribosomal subunits are assembled
3. Had nuclear pores

Question 21

Why do we have nuclear pores?

Answer 21

to allow passage of molecules in and out of nucleus (transport of proteins)

Question 22

Outline the main features of the mitochondria

Answer 22

• contain there own DNA and reproduce by division
• contains an inner and outer membrane
• contribute to cellular respiration (generates the energy currency of the cell) –> electron transport from oxidation of food, oxidative phosphorylation

Question 23

What are the most probable origins of mitochondria and chloroplasts?

Answer 23

• chloroplast (most certainly) and mitochondria (most likely) evolved from engulfed bacteria

Question 24

Endoplasmic reticulum

Answer 24

• major site of proteins, membrane lipid and oblisaccaride synthesis
• ribosomes attached to the ER translate RNA into proteins

Question 25

Golgi apparatus

Answer 25

- stacks of flattened membrane enclosed sacs that modifies and packages molecules made in the ER destined to be secreted or sent to another compartment - exchange is mediated by secretory vesicles

Question 26

secretory vesicles

Answer 26

membrane vesicles that transport materials to and from compartments

Question 27

Lysosomes

Answer 27

- contain hydrolytic enzyme which are activated by proteolytic cleavage in an acidic environment

Question 28

What do lysosome membranes contain?

Answer 28

- they contain transport molecules which carry the products of macromolecules (sugars, nucleotides, amino acids) to the cytosine for reuse (or excretion)

Question 29

Peroximes

Answer 29

- membrane enclosed vesicle where carry out oxidation reaction leading to the production of hydrogen peroxide (H2O2) - H2O2 is used to inactivate toxic molecules - found in all animal cells except RBCs and in many plant cell - used to breakdown non toxic molecules (fatty acids into acetyl coA) Or biosynthetic reactions (production of plasmalogen)

Question 30

Does cytosol = cytoplasm

Answer 30

No cytosol is the aqueous portion of the cytoplasm. The cytoplasm include the aqueous portion, the suspended particle and the organelles

Question 31

The cytoplasm of a cell is ___________

Answer 31

Crowded

Question 32

What is the cytoskeleton?

Answer 32

network of protein filaments in the cytoplasm involved in strength, movement, shape, cell division and organization --> involves actin filaments, microtubules and intermediate filaments

Question 33

What are the major components of the cell membrane

Answer 33

- lipids - carbohydrates - proteins

Question 34

What are the membrane functions

Answer 34

- maintain the integrity of cells and organelles - provides a highly selective permeability barrier - control flow of information between organelles and surrounding environment: contain receptors for chemical stimuli, some membranes generate electrical and chemical signals - sites of energy transformation: mitochondrial membrane performs oxidative phosphorylation