Lecture 5

Question 1

In prokaryotes where does DNA replication, transcription and translation occur?

Answer 1

cytoplasm

Question 2

Most prokaryotes have how many chromosomes and what shape?

Answer 2

single circular chromosome

Question 3

Why do prokaryotes have a circular chromosome?

Answer 3

protection from exonuclease which chew up naked linear DNA

Question 4

If a bacteria has linear chromosomes how can it protect itself?

Answer 4

hairpins or covalently bound proteins protect it from exonucleases

Question 5

how is DNA packed in prokaryotes?

Answer 5

supercoiled loops around a central core, looks like a bottlebrush

Question 6

How does DNA alleviate torsion?

Answer 6

right-handed supercoils = negatively supercoiled

Question 7

What two enzymes regulate supercoiling?

Answer 7

gyrase and topoisomerase 1

Question 8

What does gyrase do?

Answer 8

cuts DNA and introduces negative supercoils

Question 9

What does topoisomerase 1 do?

Answer 9

creates positive supercoils (left handed supercoiling) by making single strand breaks that relax supercoils

Question 10

What state is the DNA usually in? why?

Answer 10

slightly negatively supercoiled, causes slight strand separation

Question 11

where does transcription occur in prokaryotes? where doesn’t it occur and why?

Answer 11

nucleoid/cytoplasm interface, doesn’t occur in middle of nucleoid bc enzymes can’t get there and DNA can’t relax

Question 12

Is transcription and translation coupled in prokaryotes?

Answer 12

yes

Question 13

Is the cytoplasm crowded? what is the benefit?

Answer 13

yes, helps in protein folding and in coupling cellular processes

Question 14

What is the purpose of gas vesicles?

Answer 14

increase a cells buoyancy which helps aquatic prokaryotes receive the most light

Question 15

What is the structure of gas vesicles?

Answer 15

protein shell that is permeable to gases and repels water
—-no lipid membrane that would hinder gas diffusion

Question 16

What is the purpose of thylakoids?

Answer 16

increase SA membranes that house the photosynthetic machinery. contain necessary pigments, proteins, and cofactors needed to capture light energy

Question 17

Do cyanobacteria have thylakoids?

Answer 17

yes

Question 18

What is the purpose of carboxysomes? structure?

Answer 18

confines the special enzymes needed for carbon fixation

made of a proteins shell

Question 19

Where are carboxysomes found?

Answer 19

autotrophic bacteria that fix CO2

Question 20

Where are enterosomes found?

Answer 20

heterotrophic bacteria, found in the gut

Question 21

What is the purpose of enterosomes?

Answer 21

contain enzymes that metabolize propanediol and ethanolamine.
help bacteria cope with toxic propanaldehyde

Question 22

What is fucose?

Answer 22

metabolie of propendiol and is a common sugar in the mammalian intestine

Question 23

What is polyhydroxyalkanoate (PHA)?

Answer 23

carbon polymers that can be used when carbon becomes limiting —can be stored in a storage granule

Question 24

What are magnetosomes composed of?

Answer 24

membrane-bound iron containing crystals

Question 25

What is the purpose of magnetosome?

Answer 25

allow bacteria to align themselves with the earth’s magnetic field and provides them with a sense of direction

–can swim towards lower o2 concentrations which they prefer