Lecture 7

Question 1

cellular organelle characteristics

Answer 1

• membrane structures
• specialised function
• within cytosol of eukaryote cell
• held within the plasma membrane
  -self replicating

Question 2

Perioxisomes

Answer 2

organelle for oxidation
- peroxisomes are specialised metabolic compartments bounded by a membrane
- they often have a crystalline core of enzymes
- they are self-replicating but do not contain DNA or ribosomes

Question 3

Functions of peroxisomes

Answer 3

• break down fatty acids and other organic molecules using molecular oxygen
• hydrogen peroxide generated, is used to oxidise ethanol
• this oxidation can also be used to produce useful compounds, including phospholipids for nerve cells

Question 4

Mitochondria

Answer 4

chemical energy conversion
- outer membrane smooth with an inner membrane folded into cristae
- two compartments: inter membrane space and mitochondrial matrix
- some metabolic steps of cellular respiration are catalysed in the mitochondrial matrix
- large surface area of cristae for enzymes that synthesise ATP

Question 5

Chloroplasts

Answer 5

found in leaves and other green organs of plants
transducing organelle- transformed sunlight into sugar
contain chlorophyll as well as enzymes/ other molecules
site of photosynthesis
organised to optimise light harvesting and photosynthesis

Question 6

Function of chloroplasts

Answer 6

photosynthesis
- thylakoids are membranous sacs
- stacked sacs are the grana
- they absorb light
- stroma (internal fluid)
- site where carbohydrates are made second stage of photosynthesis

Question 7

Mitochondria and chloroplasts

Answer 7

enveloped by a double membrane

contain free ribosomes and circular DNA

their DNA is related to that of bacteria

grow and reproduce somewhat independently

complex organelle

Question 8

Symbiosis

Answer 8

relations/ interactions between organisms

Question 9

Hypothesis of endosymbiotic theory

Answer 9

eukaryotic cells have benefited from engulfing different prokaryotes
- outputs from prokaryotes benefit eukaryotes
- engulfed prokaryotes are replicated and transferred when cells divide

Question 10

Stages of endosymbiosis

Answer 10

1. original eukaryote cell: anaerobe with an infolding plasma membrane forming cell with nucleus
2. heterophic bacteria (prokaryote) engulfed and became endosymbiont
3. 1.8 billion Yeats ago ancestral eukaryote formed
4. formation of plants when cyanobacteria engulfed by ancestral eukaryote and became and endosymbiont

Question 11

four pieces of evidence for endosymbiosis

Answer 11

cellular organelle: different DNA to the host cell resembles prokaryotic DNA

membrane composition of the organelle: closer to prokaryote

presence of double membranes of these organelle

protein synthesis apparatus similar to those seen in prokaryotes

Question 13

Where does the double membrane come from?

Answer 13

the double membrane found in mitochondria and chloroplasts is a relic of the absorption of prokaryotic bacteria by the eukaryotic host cell

the inner membrane which now contains numerous folds came from the bacterial membrane, while the outer membrane came from the host cell itself

Question 14

Important step in endosymbiosis

Answer 14

linking the metabolism of the host and endosymbiont
- allows regulatory pathways to evolve that maximise the connection and host fitness

Question 15

Aromatic amino acid synthesis

Answer 15

• the essential amino acids are a necessary part of the animal diet because we lack a pathway to synthesis them
• tryptophan, phenylalanine and tyrosine
• there are 2 ways to synthesis these amino acids: prokaryotic or fungal
• autotrophs lack a diet and must synthesise these and all 17 other AA
• chloroplasts have retained their prokaryotic pathway and bear sole responsibility for this task in plants and algae