Prokaryotic Cells

Question 1

what is a prokaryote

Answer 1

a single celled organism whose DNA is free floating in the cytoplasm without a nucleus

Question 2

what does prokaryote mean and what does this suggest

Answer 2

prokaryotic means before nucleus. this suggests they were around before eukaryotes

Question 3

what are the two types of prokaryotes

Answer 3

bacteria and archaea

Question 4

what is archaea

Answer 4

they are found in extreme environments

Question 5

what are the similarities between eukaryotic and prokaryotic cells

Answer 5

they have a plasma membrane, cytoplasm, ribosomes for assembling amino acids into proteins and genetic material (DNA & RNA)

Question 6

what are the differences between eukaryotic and prokaryotic cells

Answer 6

• prokaryotes lack a nucleus and membrane bound organelles while eukaryotic cells have a nucleus and membrane bound organelles
• eukaryotes are more complex and larger than prokaryotes
• prokaryotes have a much less well developed cytoskeleton with no centrioles, smaller ribosomes and have a cell wall made of peptidoglycan and not cellulose
• have naked DNA that’s not wound around histone proteins but floats in the cytoplasm in a loop (not a linear chromosome

Question 7

what are the structures that are always present in prokaryotic cells

Answer 7

• RNA and ribosomes
• cell wall
• plasma membrane
• circular DNA
• cytoplasm
• nucleoid

Question 8

what are the additional structures that are always present in prokaryotic cells

Answer 8

• pilli
• plasmid
• capsule
• mesosome
• flagellum

Question 9

describe the RNA and ribosomes

Answer 9

ribosomes in prokaryotic cells (70S) are smaller than those in eukaryotic cells (80S). they are essential for protein synthesis with 70S ribosomes forming simpler proteins

Question 10

how is ribosomal structure similar in prokaryotic and eukaryotic cells

Answer 10

• organised into large and small subunit (prokaryotic ribosomes contain over 50 different types of protein and those of eukaryotic cells contain more than 80 different types of protein)
• large subunit contains two different ribosomal RNAs in prokaryotes and 3 in eukaryotes while the small subunit contain one ribosomal RNA
• the larger 80S eukaryotic ribosome settles out at a faster rate in a solution or first in sedimentation. the 80S ribosomes are possibly involved in the production of more complex proteins

Question 11

describe the cell wall

Answer 11

made of peptidoglycan - a cross linked polymer made of amino acids and sugars

Question 12

how does the cell wall of prokaryotes differ from plant cells

Answer 12

prokaryotic cells have a cell wall made from peptidoglycan also known as murein. it is a complex polymer formed from amino acids and sugars.
in eukaryotes, the cell wall is made from cellulos

Question 13

describe the plasma membrane

Answer 13

encloses the cell, regulating the movement of substances in and out

Question 14

describe the DNA

Answer 14

it is circular. a single supercoiled loop of DNA, located in the nucleoid region

Question 15

how does the DNA differ from eukaryotic cells

Answer 15

the structure of the DNA contained within prokaryotes but is packaged differently.
prokaryotes generally only have one molecules of DNA - a chromosome which is supercoiled to make it more compact. the genes on the chromosome are often grouped into operons meaning a number of genes are switched on or off at the same time

Question 16

describe the cytoplasm

Answer 16

the gel-like substance filling the cell where various cellular processes occur

Question 17

describe the nucleoid

Answer 17

the region within the cytoplasm where the DNA is positioned

Question 18

what are pilli

Answer 18

small hair like projections that enable attachment to surfaces or other cells involved in sexual reproduction by transferring plasmid DNA

Question 19

what is a plasmid

Answer 19

small, circular DNA molecules that replicate independantly and can carry advantageous genes like antibiotic resistance

Question 20

what are plasmids used for

Answer 20

they are replicated independantly of a bacteriums genophore (during bacterial conjugation) and may confer an advantage such as antibiotic resistance.
used in genetic engineering to make copies of genes or large quantities of proteins or hormones

Question 21

what is a capsule

Answer 21

a protective, waxy layer surrounding the cell wall, shielding bacteria from immune attacks and dessication. they are composed of polysaccharides and have water to protect from dessication

Question 22

what is a mesosome

Answer 22

an infolding of the plasma membrane associated with DNA during cell division aiding in cell wall formation.

Question 23

what are flagellum

Answer 23

a long, whip-like structure used for movement powered by protein motors allowing bacteria to move efficiently

Question 24

how does the flagella differ from eukaryotic cells

Answer 24

prokaryotic flagellum have a thinner structure, rotated by a molecular motor, anchored by a basal body, the filament moves in a whip like movement which propels the cell and the energy to rotate is from chemiosmosis
eukaryotic flagellum have a 9+2 structural arrangement, each microtubule is composed at the protein tubulin, the energy to rotate is from ATP, anchored to a cell by a basal body, and the coordinated sliding of microtubules confers movement

Question 25

why can’t prokaryotic cells carry out mitosis

Answer 25

they do not have linear chromosomes so cannot carry out mitosis.

Question 26

how do prokaryotic cells divide

Answer 26

by binary fission and not by mitosis.

Question 27

how does binary fission occur

Answer 27

before they divide, their DNA is copied so that each new cell recieves the large loop of DNA and only smaller plasmids

Question 28

why are bacteria classed as microorganisms and prokaryotes

Answer 28

microorganisms because they are very small
prokaryotes because fo their cell structure

Question 29

are all microorganisms prokaryotes

Answer 29

no

Question 30

what organelles do prokaryotes lack

Answer 30

the nucleus, ER and Golgi