week 5

Question 1

There are two kinds of cells:.

Answer 1

prokaryotic and eukaryotic.

Question 2

There are two main lineages of prokaryotes

Answer 2

Bacteria and Archaea.

Question 3

Prokaryotes tend to be structurally _____, but are _______ and ______ very diverse.

Answer 3

simple
genetically
metabolically

Question 4

Eukaryotic cells tend to be much _____ than prokaryotic cells and contain many internal compartments (organelles)

Answer 4

larger

Question 5

Some of those compartments have an

Answer 5

endosymbiotic origin

Question 6

What is an endosymbiotic origin?

Answer 6

they are derived from once free-living Bacteria. The key evidence is ultrastructural (the detailed cell structure of bacteria compared to the endosymbiotic organelles) and genetic (mitochondria and chloroplasts have bacteria-like genomes).
Endosymbiosis is a powerful evolutionary force.

Question 7

Mitochondria are related to

Answer 7

Alphaproteobacteria, chloroplasts to Cyanobacteria.

Question 8

Molecular phylogenetics suggests that

Answer 8

the host cell for the mitochondrial endosymbiont was a member of the Asgard archaea.

Question 9

There are various interesting scenarios for how interactions between Asgard archaea and Alphaproteobacteria

Answer 9

gave rise to the first eukaryotic cells, although testing these scenarios is difficult.

Question 10

What are the differences between prokaryotic and eukaryotic cells?

Answer 10

Prokaryotes:
–Relatively undifferentiated.
— Small; a few micrometres (0.5-5 μm) in length (e.g. Escherichia coli, 1-2μm).
- (Relatively) simple structure: a cytoplasm containing a circular DNA chromosome (the genome),
surrounded by a cell membrane and cell wall.
- Limited structural organisation of cytoplasm.
–Most (but not all) prokaryotes have simple shapes, and are a few microns
(millionths of a metre, thousanths of a milimetre) long.

Eukaryotic 
---Euglena gracilis, a single-celled eukaryote (~35-80μm long, or longer)
---Large, many internal compartments.
Compartments:
- Nucleus (containing DNA
genome on
chromosomes)
- Mitochondria (for
oxidative
phosphorylation)
- Chloroplasts
(photosynthesis)
- Vacuoles
Often other compartments,
complex cell behaviours

Question 11

What are the three prokaryote cell shapes?

Answer 11

Bacillus
Coccus
Spirillum

Question 12

What are three types of harmful bacteria?

Answer 12

Escherichia coli: mostly friendly gut bacterium.
Staphylococcus aureus: skin and mouth bacterium.
Borellia burgdoferi: nasty spiral-shaped bacterium that causes Lyme’s disease.

Question 13

What is the function of the nucleus in eukaryotic cells?

Answer 13

• contains the genome.
• Site of transcription (DNA
  to RNA).

Question 14

What is the function of the endoplasmic reticulum in eukaryotic cells?

Answer 14

is continuous with the
nucleus:
- Translation (synthesis of
proteins)
- Lipids
- Carbohydrates

Question 15

Together what is the function of the nucleus and ER in eukaryotic cells?

Answer 15

a membrane-bound complex for controlling the cell.

Question 16

What are eukaryotes?

Answer 16

organisms made of eukaryotic cells.
● Most eukaryotes are single-celled; these are called protists (e.g. Euglena).
● Eukaryotes have evolved to become multicellular many times, giving rise to
animals, plants, fungi, brown algae, slime moulds, and other groups.
● Eukaryotes evolved once: all eukaryotic cells share a common ancestor.

Question 17

What is symbiosis?

Answer 17

Symbiosis: two organisms living
together for mutual benefit.
Common in nature, and familiar from
natural history, e.g. clownfish and
anemones.
The most striking cases involve
co-evolution, where the partners
gradually evolve to work together more
effectively (clownfish-anemone host
specificity).
What starts off as a loose interaction between partners can evolve to become much more specific and intimate.

Question 18

Symbioses among prokaryotes are

Answer 18

ubiquitous

Question 19

How does symbioses occur in prokaryotes?

Answer 19

Archaea-Bacteria symbioses
involve the exchange of electrons
or hydrogen molecules (H2
) over
very short distances between cells.
Very short distances needed for
efficient exchange (vs. diffusion).

Question 20

What is endosymbiosis?

Answer 20

one organism living inside another
In endosymbiosis, the association between the partners evolves to become so
intimate that one ends up entirely inside the other.
The endosymbiotic theory: the structural complexity of eukaryotic cells arose
from one (or more) organisms living inside another.
Those 2 organisms co-evolving for such a long time leads to a super organism thats completely integrated and where you cant really tell apart the original partners anymore.
So its a symbiosis thats evolved to such a state that you cant separate the organisms.