Euk And Prok Cells

Question 1

Differences between prokaryotic and eukaryotic cells?

Answer 1

Prokaryotic are much smaller with no membrane bound organelles and can survive anywhere. Their DNA is in nucleoids (no chromosome)
Eukaryotes have all membrane bound organelles- dna in chromosome

Question 2

Prokaryotes are divided into 2 domains called..?

Answer 2

Bacteria and archaea

Question 3

What’s the most abundant organism on earth?

Answer 3

Prokaryotes- bc they can survive anywhere

Question 4

Structural adaptations of prokaryotes ?

Answer 4

V small 0.5-5n much smaller than eukaryotic cells.

They have a variety of shapes: spheres (cocci), rods (bacilli) and spirals

Question 5

How do you classify bacteria by cell wall composition ?

Answer 5

Grab stain:
Gram positive bacteria have simpler walls with lots of peptidoglycan

Gram negative gave less peptidoglycan and an outer membrane that contains lipopolysaccharide

Question 6

Explain fimbriae?

Answer 6

Hair like thin appendages

Allows attachment to substrates/surfaces of other cells

Question 7

Pili?

Answer 7

Longer than fimbrae

Allow prokaryotes to exchange DNA (conjugation)

Question 8

Flagella?

Answer 8

Long filamentous appendages consisting of filament, hook and motor
Composed of 42 different types of proteins
Scattered across the surface or concentrated at one/both ends of the cell
Role - movement, attachment and secretory apparatus

Question 9

Ribosomes?

Answer 9

Small in prokaryotes in the cytoplasm (70S ribosomes) consisting of rRNA and protein. For protein synthesis and anyoibiotic target size (can attach to the sub unit and inhibit protein synthesis)

Question 10

Endospores? (Prokaryotes)

Answer 10

Dormant, tough non-reproductive structure
Permits survival of nuclear material for later germination
Ensures survival of bacterium through environmental stress
Resistant to uv and gamma radiation
Found in soil/water (where they can survive for long)

Question 11

Cysts?

Answer 11

Azotobacter species and others form cysts. Dormant cells with thickened cell walls
Permits survival of nuclear material for later germination/ ensures survival of bacterium through stress
Resistant to desiccation and some chemicals but CANNOT Withstand high temps like endospores

Question 12

What do fungi do?

Answer 12

They absorb nutrients from the soil, transfer them to trees and receive sugars in return (some transfer sugars between trees of different species)

Question 13

Why are fungi important ?

Answer 13

Essential for the wellbeing of most terrestrial ecosystems because they break down organic material and recycle vital nutrients
1.5mil species of fungi

Question 14

What are common body structures (prokaryotes)?

Answer 14

Multicellular filaments and single cells (yeasts) some species grow as both

Question 15

How are the body of fungi adapted for absorption?

Answer 15

They form networks of branched hyphae

Hyphae have tubular cell walls strengthened with chitin

Question 16

How is hyphae divided?

Answer 16

Most fungi have hyphae divided into cells by septa (with pores allowing cell to cell movement )

Question 17

What do fungal hyphae form ?

Answer 17

An interwoven mass called a mycelium (the structure of mycelium maximises surface to volume ratio) making feeding very efficient

Question 18

What’s a virus?

Answer 18

An infectious particle consisting of DNA/genes packaged in a protein coat
Much simpler structure than prokaryotes
They can’t reproduce/metabolise outside of their host cell (borrowed life)

Question 19

Explain structure and function of viruses?

Answer 19

Viruses aren’t cells, they are small infectious particles consisting of nucleic acids enclosed in a protein coat
Only replicate within host cell- each virus has a limited no of host cells it can infect
Viruses are classified as DNA virus or RNA virus

Question 20

How many genes do viruses have in their genome ?

Answer 20

Between 3 and 2000 genes in their genomes

Question 21

Capsids ??

Answer 21

A protein shell that encloses the viral genome (can be helical or icosahedral)

Question 22

Viral envelopes?

Answer 22

They are derived from the membrane of host cells
They surround the capsids of influenza viruses and many others
Combo of viral and host cell molecules

Question 23

What viruses infect bacteria ?

Answer 23

Bacteriophages/phages
They have an elongated capsid head that encloses their DNA
A protein tail piece attaches the phage to the host and injects the phage DNA inside

Question 24

Surfaces and microorganisms can be imaged by:

Answer 24

• light microscopy
• epifluorescence microscopy
• electron microscopy (scanning, transition, cryo)

Question 25

What types of light microscopy are there?

Answer 25

• bright field
• dark field
• phase contrast

Question 26

Explain bright field light microscopy?

Answer 26

The sample is illuminated via transmitted white light from below and observed from above

Question 27

Why is dark field used?

Answer 27

For unstained/transparent specimens (get a lot more detail)
-dark field can improve image contrasts (especially if transparent objects) while requiring LITTLE eq setup/prep
Does suffer from low light intensity/resolution

Question 28

Explain phase contrast light microscopy?

Answer 28

Consists of a circlular annulus in the condenser which produces a cone of light
This cone is superimposed on a similar sized ring within the phase objective
Every objective has a different size ring so for every objective another condenser setting has to be chosen

Question 29

Key features when viewing an Image under a microscope are ?

Answer 29

Resolution
Magnification
Objectives
Illumination

Question 30

What is resolution ?

When is resolution best ?

Answer 30

The ability to distinguish 2 very small and closely spaced objects as separate entities
When the distance between the 2 objects is short

Question 31

What is resolution determined by?

Answer 31

Certain physical parameters that include wavelength of light/light gathering power of the objective and condenser lens

Question 32

Human eye is best adapted for ?

Answer 32

Green light and our ability to see detail may be compromised with use of blue or violet
Most manufacturers of microscopes correct their simplest lenses for green light

Question 33

What is magnification/imaging?

Answer 33

Microscopes are knows as compound microscopes..
a magnified image of an object is produced by the objective lens
The imagine is magnified by a second lens system for viewing (ocular)
Final magnification if the microscope depends on the: magnifying power of the objective x magnifying power of ocular

Question 34

What do objective magnification powers range from?

Answer 34

4x to 100x
Ocular magnification ranges: 8x-12x
So a standard microscope will provide u with a mag range of 40x-1000x

Question 35

What is ‘objectives’?

Answer 35

Each objective lens consists of 6 or more pieces of glass that combine to produce a clear imagine of an object
These provide corrections and image clarity

Question 36

FINally whats illimination?

Answer 36

Important factor in producing a good image with the light microscope in obtaining adequate levels of light in the specimen
Light should be uniform across the field of view
Best way to illumine the specimen involves the use of another lens system (condenser)

Question 37

Scanning electron microscope ?

Answer 37

Focuses a high energy beam of electrons onto the surface of the sample to create an image
Detects signals from the interaction of the incident electrons with the sample surface
The type of signals gathered in an SEM vary and can include: secondary electrons