2.1.1g Prokaryotic Cells

Question 1

see showbie slide for diagram of prokaryotic & eukaryotic

Question 2

Prokaryotic cells

Answer 2

• DO NOT have a nucleus
• DO NOT have membrane-bound organelles
• includes all bacterial cells

Question 3

Eukaryotic cells

Answer 3

• DO have a nucleus
• DO have membrane-bound organelles
• includes all animal & plant cells

Question 4

What is a prokaryote

Answer 4

a single celled organism without a nucleus & do not have membrane-bound organelles (eg. bacteria)

Question 5

What is a eukaryote

Answer 5

have membranes around their many complex organelles.
these often have a specific function (eg. muscle fibres) & are part of multicellular organism

Question 6

Prokaryotic cells may also contain…

Answer 6

extra small rings of DNA called PLASMIDS.
- plasmids code for very specific features sa. antibiotic resistance
- plasmids can be shared between bacteria to pass on resistance & also resistance can be passed on through binary fission

Question 7

see showbie for diagram of bacterial cell (prokaryotic)

Question 8

Structures that are ALWAYS PRESENT in Prokaryotic cells

Answer 8

• plasma membrane
• circular DNA sometimes referred to as a chromosome
• cytoplasm
• ribosomes
• cell wall made of cross-linked peptidoglycan

Question 9

Additional structures SOMETIMES present in Prokaryotic cells

Answer 9

• pili
• plasmid
• capsule
• mesosome
• flagellum

Question 10

Additional prokaryotic structures: pili

Answer 10

for attachment to other cells or surfaces, involved in sexual reproduction

Question 11

Additional prokaryotic structures: plasmid

Answer 11

small circular piece of DNA, several may be present

Question 12

Additional prokaryotic structures: capsule

Answer 12

Protective slimy layer which helps the cell to retain moisture & adhere to surfaces. Provides additional protection

Question 13

Additional prokaryotic structures: mesosome

Answer 13

infolding of inner plasma membrane which contains enzymes required for respiration, associated w DNA during cell division, and helps w formation of new cell walls

Question 14

Significance of infolding of plasma membrane

Answer 14

infolding of plasma membrane may form a photosynthetic membrane, or carry out nitrogen fixation

Question 15

Additional prokaryotic structures: flagellum

Answer 15

a tail like structure which rotates to move the cell.
For locomotion, very simple structure

Question 16

Structure of prokaryotic (always present): cell wall

Answer 16

rigid outer covering made of peptidoglycan

Question 17

Features of prokaryotic cells (difference)

Answer 17

• extremely small cells (less than 2μm in diameter)
• no true nucleus
• DNA is circular (only one loop of DNA), not associated w proteins. Some DNA is in the form of plasmids
• very few organelles. No membrane bound organelles
• contains smaller 70S ribosomes (18nm)
• cell wall made of peptidoglycan (aka murein) - complex polymer formed from amino acids & sugars
• may have an outer slime capsule surrounding the cell
• flagella (when present) made of the protein flagellin, arranged in a helix
• divides by binary fission
  eg: E. coli bacterium

Question 18

Features of eukaryotic cells (differences)

Answer 18

• larger cells (10-100μm in dia)
• distinct nucleus is present
• DNA is linear (many chromosomes), is associated w proteins called histone. No plasmids
• many membrane bound organelles
• contains larger 80S ribosomes (22nm), involved in formation of more complex proteins
• plant cell wall made of cellulose. Fungi cell wall made of chitin
• no capsule surrounding the cell
• flagella (when present) made of microtubule proteins arranged in 9+2 arrangement
• divides by mitosis & meiosis

Question 19

What is the theory of Endosymbiosis

Answer 19

That mitochondria & chloroplasts, & possibly other eukaryotic organelles, were formerly free-living bacteria, that is, prokaryotes.
The theory is that these prokaryotes were taken inside another cell as an endosymbiont (an organism that lives within the body or cells of another organism). This eventually led to the evolution of eukaryotic cells