Cell Biology - Evolution of the cell

Question 1

What happened 4.5 billion years ago?

Answer 1

Formation of the solar system

Question 2

What happened 4.0 billion years ago?

Answer 2

• Water condensation as Earth cools down
• Formation of Earth crust
• Formation of organic molecules

Question 3

What happened 3.5 billion years ago?

Answer 3

Stromatolites indicate first life

Question 4

What happened 3.0 billion years ago?

Answer 4

• Photosynthesis developed in cyanobacteria-like microbes

- Oxygen in the atmosphere

Question 5

What happened 2.0 billion years ago?

Answer 5

Development of eukaryotic cell that contain symbiotic prokaryotes

Question 6

What happened 1.5 billion years ago?

Answer 6

Appearance if multi-cellularity

Question 7

What happened 0.5 billion years ago?

Answer 7

Cambrian explosion of multi-cellular life forms symmetrical with antenna and segmented

Question 8

What happened 0.25 billion years ago?

Answer 8

Dinosaurs dominate the Earth

Question 9

What happened 0.0004 billion years ago?

Answer 9

Homo sapiens developed

Question 10

What can be formed under “Early Earth conditions”?

Answer 10

Building blocks of RNA

Question 11

What can ribonucleotides be formed from?

Answer 11

Cyanamide, cyanoacetylene, glycolaldhyde, glyceraldehyde and inorganic phosphate

Question 12

What is crucial to establish a working protein?

Answer 12

Ribosomes

Question 13

What do ribosomes consist of?

Answer 13

Protein and RNA

Question 14

What do ribosomes do?

Answer 14

Translate mRNA into protein

Question 15

What are ribosomes considered to be?

Answer 15

Riboenzymes

Question 16

What does the riboenzymes of ribosome depend on?

Answer 16

Enzymatic activating of ribosomes depend in RNA part of ribosomes

Question 17

What is the RNA world hypothesis?

Answer 17

RNA was at the origin of life

• stored genetic information
• catalyse chemical reactions

Question 18

Who proposed the RNA world hypothesis?

Answer 18

Alexander Rich in 1962

Question 19

How does RNA have enzymatic activity?

Answer 19

Single stranded RNA can fold and form molecules that catalyse chemical reactions

Question 20

What is a catalytic RNA molecule called?

Answer 20

Ribozyme

Question 21

What are examples of ribozymes?

Answer 21

• Class I RNA ligase

- RNA-degrading riboszyme

Question 22

What can ribonucleotides spontaneously do on clay surfaces?

Answer 22

Polymerise

Question 23

How does replicase ribozymes produce new replicases?

Answer 23

• Ribozyme replicates an un-folded RNA stand of another replicase molecule
• High temperature, both stands separate; one folds into a new replicase, one serves as template for further synthesis

Question 24

What do some minerals catalyse from hydrogen and carbon monoxide gases?

Answer 24

Fatty acids

Question 25

What do polar fatty acids self-organise into?

Answer 25

Micelles

Question 26

What happens in water to fatty acids?

Answer 26

Hydrophobic chains turn towards each other exposing hydrophilic head

Question 27

What forms vesicles?

Answer 27

Micelles

Question 28

What is required to form vesicles?

Answer 28

Acidic pH | Micelles

Question 29

Where can vesicles be formed?

Answer 29

Clay surfaces

Question 30

What can cause vesicles to grow?

Answer 30

Fusion with micelles

Question 31

Are lipids in vesicles membrane rigid or dynamic?

Answer 31

Dynamic

Question 32

What is an advantage of lipids in vesicle membranes being dynamic?

Answer 32

Flipping of lipids can transport molecules over the membrane

Question 33

What can accumulate with in vesicles?

Answer 33

Molecules such as ribonucleotides, ribozymes etc.

Question 34

What results in a protocell?

Answer 34

Combining RNA replicase and vesicles

Question 35

Describe the combination of RNA replicase and vesicles to form a protocell:

Answer 35

- RNA replicase use ribonuceotides to make a copy of anther RNA replicase - Micelles fuse with the vesicle and enlarge it until it becomes unstable and divides - Random mistakes form better replicates, uptake of new RNAs incorporate new ribozymes, make protocell grow and divide faster - Protocells compete for resources and faster growing protocols are more competitive

Question 36

What is symbiosis?

Answer 36

Interaction between two different organisms, living in close physical association, advantages to both

Question 37

What is cellular endosymbiosis?

Answer 37

When a single cell organism lives in host cell

Question 38

What explains cellular complexity?

Answer 38

Endosymbiosis theory

Question 39

Who proposed the endosymbiosis theory?

Answer 39

Lynn Margulis

Question 40

Overall summary of endosymbiosis theory:

Answer 40

Three fundamental organelles: mitochondria, photosynthetic plastids, basal bodies of flagella Mechanisms

Question 41

What is the mechanism proposed by endosymbiosis theory?

Answer 41

1) Phagocytosis of a prokaryote 2) Host cell and endosymbiont reproduce 3) Development of an interdependence

Question 42

What do mitochondria and chloroplast derive from?

Answer 42

Engulfed prokaryotes

Question 43

How is the eukaryotic cell established?

Answer 43

- prokaryote - Infolding of membrane forms nucleus and endoplasmic reticulum - early eukaryote - Engulfing of heterotrophic prokaryote results in mitochondria (=fungi/ animal) - Engulfing of photosynthetic prokaryote results in chloroplasts (plant cells)

Question 44

What are the arguments that support endosymbiosis theory (chloroplasts and mitochondria derive from prokaryote)?

Answer 44

- They have their own circular genome - Contain 70s ribosome - Chloroplast use tubulin-like FtsZ for division - Chloroplasts and cyanobacteria have thylakoid membrane - Both surrounded by double membrane - Bacteria and mitochondria share specific membrane lipid - Share organisation similarities

Question 45

Explain how the evidence they have their own circular genome support the endosymbiosis theory?

Answer 45

Genome of human mitochondria: -16000 nucleotides encode for: 13 polypeptides, 22 tRNAs, 2 rRNAs Genome of plant chloroplasts: -70,000 to 200,000 nucleotides encode for: 120-130 polypeptides, 54 RNAs

Question 46

Explain how the evidence chloroplasts and cyanobacteria have thylakoid membranes support the endosymbiosis theory?

Answer 46

- Contain chlorophyll | - Share cellulose as main component of the cell wall

Question 47

Explain how the evidence both surrounded by a double membrane support the endosymbiosis theory?

Answer 47

Derived from incomplete phagocytosis

Question 48

Explain how the evidence bacteria and mitochondria share a specific membrane lipid support the endosymbiosis theory?

Answer 48

Cardiolipin | 20% of all lipids

Question 49

Explain how the evidence chloroplasts and mitochondria share organisation similarities support the endosymbiosis theory?

Answer 49

- Inner and outer membrane - 70S ribosomes - Circular DNA - Import of nuclear proteins - Endogenous membranes that enlarge the surfaces - Not part of cellar endomembrane system

Question 50

What do unicellular marine alga Bigelowiella nations contain derived from establishment of a secondary endosymbiosis?

Answer 50

Plastids

Question 51

What is a nucleomorph?

Answer 51

DNA-containing relict of an engulfed eukaryote

Question 52

What are lichens a symbiosis of?

Answer 52

Fungi and uni-cellular algae

Question 53

Where are coral reefs found?

Answer 53

Only in clear shallow water

Question 54

What are corals a symbiosis of?

Answer 54

Algae and polyp

Question 55

What doe coral polyps and zooxanthellae form?

Answer 55

Mutualistic cellular endosymbiosis