BS101: Lecutre 7 - Endosymbiosis & Organelle Diversity

Describe Organelles

Specialised functions, w/in cytosol of eukaryote cell

Where are Organelles held?

Within plasma membrane

Are some organelles self-replicating?

Yes

What parts of the cell are Plant-only Compartments?

Cell wall, central vacuole, chloroplasts

What parts of the cell are Plant and Animal Compartments?

Ribosomes, ER, Plasma Membrane, Golgi, Mitochondria, Nucleus

What parts of the cell are Animal-only Compartments?

Small/no vacuole, centrioles, centrosomes, flagella

What are Peroxisomes?

Specialised metabolic compartments bound by single membrane

What do Peroxisomes often have?

Crystalline core of enzymes

Describe the Enzyme Core of Peroxisomes

Dense packing of enzymes so appear crystalline

Are Peroxisomes self-replicating?

Yes but don’t contain DNA/Ribosomes

What is the role of Peroxisomes in breaking down molecules?

Break down FAs and other organic molecules (eg alcohol) using molecular O2

What can Oxidation also be used for?

To produce useful compounds, including phospholipids for nerve cells

Describe Oxidation in plants?

Essential to metabolise compounds that are more toxic in minute quantities in chloroplast

How are peroxisomes related to other organelles?

Unknown

Describe Mitochondria

Smooth outer membrane & inner membrane folded into cristae

What is the role of the Inner Membrane in the Mitochondria?

Creates 2 compartments, intermembrane space & mitochondrial matrix

What is the role of the Mitochondrial Matrix in catalysis?

Some metabolic steps of cell respiration are catalysed there

What is the purpose of Cristae in the Mitochondria?

Present large SA for enzymes that synthesise ATP

What is the main role of Chloroplasts?

Convert sunlight into fuel

What do Chloroplasts contain?

Chlorophyll pigment + enzymes & other molecules that function in photosynthesis

What is a Transducing Organelle?

Transforms sunlight into sugar (potential to chemical energy)

What are Thylakoids?

Membranous sacs which stack to form granum

What is the role of Thylakoids/Granum?

Absorb light

What is the Stroma?

Internal fluid where carbon fixation occurs

Why are Chloroplasts green?

Chlorophyll only absorb red & blue light, transmist and reflects green light

What is the role of the Thylakoid Membrane?

Site of electron transport and ATP Production

• What are Glyoxysomes?

• FAs

• Seeds

• Plants’ peroxisomes

• Convert FAs to carbs

• Important during seed germination

What is the role of the Mitochondria in Respiration?

Sites of cellular respiration, uses O2 to generate ATP

What is the role of the Chloroplast in Photosynthesis?

Site of photosynthesis, uses sunlight to produce ATP and fix CO2

How are the structures of Mitochondria and Chloroplasts similar?

Double membrane, free ribosomes, circular DNA molecules

How are Mitochondria and Chloroplasts related to bacteria?

DNA is related

How do Mitochondria and Chloroplasts grow?

Grow and reproduce somewhat independently to cells

What is the Endosymbiotic Theory?

Eukaryotes are hypothesised to have benefited form engulfing prokaryotes

What is the importance of Nutrients and Oxygen in Endosymbiotic Theory?

Nutrients/O2 released from prokaryotes can be beneficial to host eukaryotes

What happens to Organelles when cells divide?

Also replicated and transferred

What is the Host Cell in Endosymbiotic Theory?

Ancestor of Eukaryote

What is the original eukaryote in Serial Endosymbiosis?

Anaerobe w/ infolding plasma membrane forming cell w/ nucleus

How is the Endosymbiont formed?

Heterotrophic bacteria engulfed

What about DNA provides evidence for Endosymbiosis?

Cellular organelles’ DNA resemble prokaryotes

What about membranes provides evidence for Endosymbiosis?

Membrane composition of organelles are closer to prokaryotes + presence of double membrane

What about Protein Synthesis provides evidence for Endosymbiosis?

Similar to prokaryotes, 70S Ribosomes

What is the Double Membrane a relic of?

Absorption of prokaryotic bacteria by eukaryotic host cells

Where do the parts of the double membrane come from?

Inner - bacterial membrane, outer - host

Describe Primary Plastid Capture

Occured once in a single common ancestor of all land plants + green/red algae

Why are essential Amino Acids a necessary part of animal diet?

We lack a pathway to synthesise tryptophan, phenylalanine, tyrosine

What are the 2 ways to synthesise Amino Acids?

Prokaryotic/fungal

What are Paulinella Chromatophora?

Freshwater amoeba that hosts a cyanobacterium like cyanelle

What is significant about cyanelle numbers?

Tightly regulated, implies host over symbion

Can cyanelle grow independently in lab settings?

No

What is the Elysiachlorotica?

Sea slug that can salvage plastids from an alga and maintain them in special diverticulae of slug gut

What is the relationship between Plastids and Genes?

Plastids express genes and synthesise proteins for up to 9 months

Do plastids survive?

Plastids don’t survive and aren’t passed to next gen, not permanent

Early work on signal transduction and glycogen metabolism by Sutherland indicated that

the signal molecule did not interact directly with the cytosolic enzyme but required an intact plasma membrane before the enzyme could be activated

Certain yeast cells secrete a molecule called the α factor. The purpose of this molecule is to

stimulate cells of the opposite mating type, a yeast cells, to grow toward the α cell

Cells use different signaling strategies to achieve different goals. In hormonal signaling,

specialized cells release hormone molecules into the circulatory system, permitting distant cells to be affected

What did Sutherland discover about glycogen metabolism in liver cells?

The hormone epinephrine binds to a specific receptor on the plasma membrane of the liver cell.

Receptors for signal molecules

may be found embedded in the plasma membrane or found within the cytoplasm or nucleus

The general name for an enzyme that transfers phosphate groups from ATP to a protein is

protein kinase