Prokaryotic Cells

Question 1

What makes prokaryotic cells different to eukaryotic cells in terms of its organelles?

Answer 1

• doesn’t have a nucleus

- has no membrane-bound organelles

Question 2

What structures are absent in prokaryotic cells which are found in eukaryotic cells?

Answer 2

• nucleus
• mitochondria
• chloroplast
• Rough endoplasmic reticulum
• smooth endoplasmic reticulum
• golgi apparatus

Question 3

How are prokaryotic cells different to eukaryotic cells in terms of size?

Answer 3

Bacteria cells are smaller then eukaryotic cells; they are about 1/10th of the size. They range from 1-10 micrometers long

Question 4

What does it mean if bacteria are pathogenic?

Answer 4

Harmful to human health

Question 5

What is the prokaryotic cell wall?

What is this parts function?

Answer 5

• made of a substance called peptidoglycan (this contains carbohydrates and amino acids)
• function is to keep some substances out of cell. Stops the cell bursting if it takes in water by osmosis. And holds the cells shape

Question 6

What is the prokaryotic cell surface membrane?

What is this parts function?

Answer 6

• (only membrane in the whole cell) made of a phospholipid bilayer and proteins just like in eukaryotic cell membrane
• it is selectively permeable, meaning it controls which molecules may enter or leave the cell

Question 7

What are the 2 different types of genetic material found in a prokaryotic cell?
What are their functions?

Answer 7

• Chromosome-made uno of long circular DNA molecules with no histones, found in a part of the cytoplasm called the nucleoid
• contains the genes needed for the bacterial cell to grow and reproduce
• Plasmid-a small circular piece of DNA found in some bacterial cells
• function is to carry genes in addition to those in the main chromosome E.g carries genes that code for enzymes to destroy antibiotics

Question 8

What is the prokaryotic capsule?

What is this parts function?

Answer 8

• a slimy and waxy layer found outside the cell wall of some bacteria
• it’s function is to protect the cell from drying out and makes the cell slippery so it is harder for white blood cells to engulf them (phagocytosis)

Question 9

What is the prokaryotic ribosome?

What is this parts function?

Answer 9

• made of RNA and proteins, much smaller then in eukaryotic cells (70S) in prokaryotic, (80S) in eukaryotic
• it carries out protein synthesis

Question 10

What is the prokaryotic flagellum?

What is this parts function?

Answer 10

• found only in some bacterial cells, it’s a simple structure made from the protein flagellin giving rigid and corkscrew shape, different to the undulipodia found in eukaryotic cells
• rotates from the base allowing the bacterium to move through fluids

Question 11

What is the prokaryotic pili?

What is this parts function?

Answer 11

• small, hair-like, rod structures

- used for cell to cell attachment, sex pili are used for conjugation, the passing of plasmids between prokaryotic cells

Question 12

Compare prokaryotes with eukaryotes in terms of their size and organelles.

Answer 12

Prokaryotes: Eukaryotes:
-Extremely small (2 micrometers). -Larger cells 10-100 micro m
-DNA is circular. -DNA is linear
-No nucleus=free DNA. -Nucleus present=DNA inside
-Cell wall made of polysaccharide -Cellulose/chitin cell wall
-Few organelles and no membrane. -many membrane bound organelles
bound organelles e.g no mitochondria. E.g mitochondria
-Flagella made of protein flagellin -Flagella made of microtubules
arranged in a helix. arranged in a 9+2 formation
-Small ribosomes (70S) -Larger ribosomes (80S)

Question 13

How do bacteria cells reproduce?

Briefly describe the steps in this process and any extra details regarding this process

Answer 13

• Binary fission (term mitosis refers to division of nucleus)
  1. DNA replication (chromosomes and plasmids replicate)
  2. Cell elongation
  3. Septum formation
  4. Cell separation- each daughter cell receives one copy of the chromosome

-much faster then the cell cycle, meaning that bacteria are able to reproduce much quicker (optimum conditions=every 20 minutes)

Question 14

What diseases can prokaryotic cells cause?

Answer 14

• Cholera
• TB
• Whooping cough
• Food poisoning (campylobacter)

Question 15

What does it mean if strains of bacteria are resistant to antibiotics?

Answer 15

Means that antibiotics do not work to destroy the strain of bacteria . It is coded for by genes within the plasmids

Question 16

MRSA is one type of bacteria strain. What sort of problems can resistant strains cause?

Answer 16

• resistance is coded on plasmid DNA, bacteria can share plasmids with each other, resistance can pass between cells, resistance can also therefore be passed to daughter cells during binary fission
• new antibiotics have to be developed to make sure the resistant strains are controlled and to which the bacteria is more susceptible.

Question 17

Give examples of ways prokaryotic species can be useful to humans

Answer 17

• In the intestines= vitamin K production
• Surface of the skin=“normal flora” help to prevent harmful microorganisms getting into the body
• Food industry= cheese and yoghurt production
• Sewage treatment= digestion of waste material

Question 18

Explain what is meant by the endosymbiont theory

Answer 18

Theory to explain the origin of chloroplast and mitochondria from bacteria that became engulfed by another cell. According to the theory, both cells benefited from the association

Question 19

What features of chloroplast and mitochondrial structures supports the theory of the origin of eukaryotic cells?

Answer 19

• divide by fission
• have loops of DNA
• have smaller ribosomes
• same size as bacteria roughly

Question 20

What evidence is there to support the endosymbiont theory?

Answer 20

• both have double membrane
• both contain DNA
• mitochondria/chloroplast are about same size as prokaryotes
• necessary for protein synthesis