IB Bio Topic A: Unity and Diversity

What does it mean for a cell to be living?

able to maintain conditions neesed for exsistance; self-sustaining

What is cell theory?

cell is the smallest unit capable fo self-sustaining life

What is abiogenesis?

the theory that life originated from non-living matter

what is the evidence of abiogenisis?

1. Catalysis

2. Self-Assembly

3. Self-Replication

4. Compartmentalization

What is catalysis?

simple organic molecules synthesised from primordial inorganic material

What is self-assembly?

more complex polymers constructed from simple molecules

What is self-replication?

Polymers formed ability to duplicate (inheritance)

What is compartmentalization?

Molecules become packaged into membranes with unique internal chemistry

How did organic molecules come about?

Specific pre-biotic conditions for spontaneous formation

What were the specific pre-biotic conditions that allowed for the formation of organic molecules?

1. reducing atmosphere; lack of free oxygen and ozone

2. High temperatures; due to high levels of ultra violent light (penetration) and greenhouse effect due to lack of ozone

3. High Methane and carbon dioxide; due to volcanic eruptions

What evidence is there for the theory of the creation of organic molecules?

The Miller-Urey Experiment

What was the Miller-Urey Experiment?

Recreation of hypothesized pre-biotic conditions of Earth

1. Water boiled to vapor

2. Water mixed with gases to reduce atmosphere (CH4, NH3, H2)

3. Mixture exposed to electrial discharge

4. Mixture then cooled and left for about week

Found traces of amino acids and fatty acids (primordial soup)

What is the first step in monomers (amino acids) evolving into protcells/polymers?

Catalysis that allows for self assembly

What do scientist belive acted as a catalyst?

RNA

What is the evidence for RNA existing in early monomer?

1. single stranded and small = easy assemble

2. can act as a catalyst; ribozymes

3. can be used to make protein + DNA

How are protocells/polymers formed?

In water, non-polar fatty acids arrange to form a ring

Why do non-polar fatty acids form a ring in water?

Hydrophobic tails avoid contact with polar solution (water)

How is a spontaneous membrane formed?

Polar monomers attract to the hyrophilic glycerol head of the fatty acid circle to form a spherical bylayer; inner and outer chemistry can differ

What is believed to be the origin of water?

Asteroids cool the atmosphere to allow water the condense from vapor form

what are the requirements for life?

1. homeostasis

2. metabolism (cell respiration)

3. excretion

4. movement

5. nutrition

6. growth

7. response to stimuli

8. reproducation

What is LUCA?

the last univerasl common ancestor; found in hydrothermal vents

What is the evidence for LUCA?

1. universal genetic code

2. 300 shared genes; related to anaerobic processes

3. same biomolecules

4. same metabolism

What are the two ways to data fossils?

Relative and absolute

what is relative dating?

Comparative rock position

what is absolute dating?

Using half-life of carbon to date

What were the first cells?

Prokaryotic; unicellular and lack compartmentalisation

How did cells evolve into eukayotic cells?

Endosymbiosis

What is endosymbiosis?

one cell engulded by another and assimilated

What is the evidence for endosymbiosis?

1. Membranes- double membrane structure

2. Antibiotics- suseptible to

3. DNA- DNA circular and naked

4. Division- reproduce via fission-like process

5. Ribosomes- both have own

What is the advantage of being multicellular?

1. can exceed size limit (SA:Vol ratio)

2. longer life span

3. allows for specialization

What are organelles?

sub-cellular structures adapted to carry out specific functions

What is the nucleous and what does it do?

stores genetic material of the cell (chromatin)

Control center by coordinating expression of genes

What is the nuclear envelope and what is its purpose?

Double membrane surrounding the nucleous

• Seperate transcription and translation

• pores control rate of t and t

• allows the evelope to disassembel and break down into vesicles

What is are the ribosomes?

site of protein synthesis in the cell; made of protein and RNA with two subunits (70s in procaryotes and 80s in eukaryotic)

What are the subunits of RNA

1. Small subunit bind to mRNA

2. large subunit bind to tRNA

3. Subunits form a complex that allow translation to occur

What are the different ribosomes in eukaryotes?

1. Free ribosomes- within the cytosol; synthesise protein used interacellular

2. Embeded ribosomes- within the endoplasmic reticulum (rough) proteins produced to be packaged into vesicles for transport and secretion

3. 80s

What is the mitochondria?

site of aerobic respiration in eukaryotic cells

What are the parts of the chloroplast?

• thylakoid

• grana

• photosystems

• stroma

• lamellae

What is the thylakoid?

flat disc w/ a small internal volume to maximise the gradient upon protein accumulation

What is the grand?

thylakoids arranged into stacks to increase SA:Vol ration of thylakoid membrane

what are photosystems?

pigments organised into clusters w/in thylakoids to optimize light absorption

what is the stroma?

the central cavity contains appropriate enzymes and suitable pH for the calvin cycle to occur

what is the lamellae?

connects and separates the thylakoid stacks (grant) to maximise photosynthetic efficiency

what is the golgi complex?

flat sacs of cisternae that sort, modify, store, and export cellular material located between the endoplasmic reticulum and the cell membrane

How does the golgi complex function?

1. proteins from the rough ER and lipids from the smooth ER arrive at the golgi body in vesicles

2. modified into functional molecules; different sacs responsible for specific modifications

3. Molecules for secretion packaged into vesticles for extracellular release

What are vesicles?

membrane-wrapped container involved in shuttling materials between cellular compartments

What are the types of vesicles?

1. lysosome

2. peroxisome

3. vacuoles

What are lysomes?

vesicles that break down cellular waste and dibris

what are peroxisomes?

vesicles that digest toxic metabolites

What are vacuoles?

vesicles that store excess fluid and regulate pH

What is clathrin and what does it do?

triskelion-shaped molecule recruted to a membrane by adaptor proteins to help form some vesicles

How does clathrin help form vesicles?

1. linked together to form a round lattice that pulls the membrane into a bud

2. bud cleaved by dynamin (protein) to form a vesticle

How does surface area affect the cell?

cells that are specilized for material exchange are adapted for increased surface area (flat and long (squamous)); allow faster exchange as do not have to go outside the cell