Organelles & compartmentalization

What is an organelle

Discrete structure within a cell adapted to perform a specific function

Which organelles have NO membrane

• Ribosomes

• Centrioles

• Nucleolus

Which organelles have a SINGLE membrane

• Vesicles

• Vacuoles

• Rough ER

• Smooth ER

• Golgi apparatus

• Lysosomes

Whihc organelles have DOUBLE membrane

• Nucleus

• Mitochondria

• Chloroplast

Which cellular structures are not considered to be organelles?

• Cell wall

• Cytoplasm

• Cytoskeleton

Why is cell wall not an organelle

It is outside of the cell membrane

It is “extracellular”

Why is cytoplasm not an organelle

Although many reactions occur in it, it is not specialized to perform a specific function

Why is cytoskeleton not an organelle

Composed of many diff types of filaments and tubules

Not a discrete structure

Function of Golgi apparatus

Package and ships materials within cell

Function of lysosomes

Break down waste

Function of vesicles

Transport materials within cell

What is ultracentrifugation in studying organelles?

It separates organelles based on density for biochemical studies

Transcription and translation in eukaryotes vs prokaryotes

• Prokaryote—>no nucleus—>DNA immediately transcribed bc everything is tg—>efficient

• Eukaryote—>DNA inside nucleus—>ribosomes cannot enter—>mRNA leaving nucleus gives time for mRNA modification to make specific proteins needed

What is compartmentalisation

When the cytoplasm is divided into compartments by membrane bound organelles

Advantages of compartmentalisation

• Enzymes can be concentrated in a small space, increasing chance of collision between active site and substrate

• Damaging substances can be isolated within a membrane

• Conditions such as pH can be maintained to be optimum

• Organelles can move within cytoplasm to meet cell’s needs

Benefit of lysosomes being compartmentalised

They require an acidic environment to function(pH 5)

Which isn’t compatible for the neutral(pH7)cytoplasm

Digestive enzymes of lysosomes could break down useful materials if left free in cytoplasm

Phagocytic vacuole

• Cell intakes external material via phagocytosis

• It places the content in a vacuole with its own membrane

• Separates it from cytoplasm

• pH in vacuole can be altered to satisfy enzyme needs

What are parts of the mitochondria

• Outer&inner membrane

• Intermembrane space

• Matrix

• Ribosomes

• Cristae

• DNA

Function of outer membrane

• Selectively permeable

• Helps maintain suitable environment for complex reactions

Function of intermembrane space

• Protons(H+)are pumped into this space during electron transport chain—>creates steep conc gradient

• The small volume ensures even small entry of protons quickly raises proton conc, crucial for ATP synthesis

Function of inner membrane

• Hosts ETC(electron transport chain)and ATP synthase

• Its folded structure increases surface area, maximizing number of ETC proteins and boosting ATP output

Cristae function

Increases surface area for greater ATP production

What is ETC(electron transport chain)

It passes electrons and pumps protons into inter membrane space, setting proton gradient (Bus releases people into a public bathroom where they pump their shit, setting a gradient)

What is ATP synthase

Uses proton gradient to convert ADP and inorganic phosphate into ATP

What is oxidative phosphorylation

Process where most ATP is generated

Function of matrix

• Contains enzymes and substrates for Krebs cycle and link reaction generating electron carrier(NADH and FADH2)

• These electron carriers fuel ETC, leading to further ATP production

• Also holds mitochondrial DNA and 70s ribosomes, enabling quick protein synthesis in mitochondrion

What are the parts of a chloroplast

Double membrane, thylakoid membrane, photosystems, thylakoid lumen, stroma, ribosome, DNA

Function of thylakoid membrane

Provides vast surface area for light absorption and electron transport

Function of thylakoid lumen

It’s small volume allows rapid establishment of a proton gradient for efficient ATP prod

Function of photosystems

Absorb light energy

Function of stroma

Houses all components for calvin cycle to function

Why does the nucleus double membrane have pores

• It creates relatively large pores via fusion of inner and outer layers of phospholipids

• allow enzymes for transcription to enter

• Allow mRNA to exit

• Larger than protein channels

• Have proteins to control which substances move through it

Versatility of nucleus membrane during mitosis

• Nuclear membrane breaks down and forms small vesicles during division

• After mitosis, these vesicles fuse back to create 2 new membranes

Difference between free and bound ribosomes

• Free is floating in cytoplasm produces protein to use within cell

• Bound is attached to rough ER and send protein out of cell. The protein will be pushed into lumen of ER and placed into vesicle to be transported

What does Golgi apparatus do

• Modifies and packages protein to send to specific location

• Modification function of golgi can alter protein from rough ER before packaging

Flow of protein in golgi

Protein makes its way to folded membranes of golgi and emerges down the other end in a separate vessel

How is vesicle made

• Piece of membrane of organelles pinched off to form a cage

• Multiple clathrin proteins bind together to initiate the indenting of membrane

• These proteins form a lattice of hexagons and pentagons to cage membrane of vesicle

• Clathrin then breaks off and uncoats vesicle to connect to final location to deliver content inside

• Or pieces of membrane of cells needs additional phospholipid to grow