B2.2 Compartmentalization

What is compartmentalization?

Dividing a cell into sections or compartments, each with a specific job, surrounded by membranes.

Why is compartmentalization important

Allows for:

-Increased rate of chemical reactions (higher concentration of enzymes & metabolites)

-Separation of incompatible processes

What are organelles?

Discrete subunits of cells, membrane-bound in eukaryotes, with specific functions.

Which structures are NOT organelles?

Cell wall, cytoskeleton, cytoplasm → Not membrane-bound, lack specific functions.

Are ribosomes considered organelles?

Yes, but they are not membrane-bound.

Function: Synthesize proteins.

What process occurs in the nucleus?

Transcription: DNA → pre-mRNA (contains exons & introns).

What process occurs in the cytoplasm?

Translation: Ribosomes synthesize proteins from mRNA.

What is splicing? (HL Only)

Definition: Removing introns from pre-mRNA to create mature mRNA (only in eukaryotes).

What is the difference between exons and introns?

Exons: Useful genes, expressed as proteins.

Introns: Non-coding sequences, removed during splicing.

What is the function of mitochondria?

Generates ATP by aerobic respiration (only in eukaryotes).

What are the key features of mitochondria?

Outer membrane: Contains transport proteins.

-Inner membrane: Highly folded (cristae) → increases surface area for ATP production.

- Matrix: Contains enzymes for the Krebs cycle.

- Inter membrane space: Small volume, allowing rapid ion gradient formation.

- mDNA: Own mitochondrial DNA → gene expression.

How do cristae enhance cellular respiration?

Increases surface area → More space for proteins involved in ATP production.

What is found in the matrix and why is it important?

Contains enzymes for the Krebs cycle, which produces electron carriers for the electron transport chain.

How does the intermembrane space aid ATP production?

Small volume allows gradients to build up quickly, driving ATP synthesis.

What is the function of chloroplasts?

Photosynthesis (converting light energy into chemical energy).

What are the three membranes in chloroplasts?

Outer membrane

Inner membrane

Thylakoid membranes

What are the structural similarities between mitochondria & chloroplasts?

Mitochondria Chloroplasts

Cristae → Increase SA Thylakoid membranes → Increase SA

Matrix → Contains enzymes Stroma → Contains enzymes

Intermembrane space →Allows ion gradients Thylakoid lumen → Allows ion gradients

How do thylakoid membranes maximize light absorption?

Increased surface area → More space for pigments & enzymes.

-Stacked to reduce self-shading.

What is the difference between the stroma and thylakoid membranes?

Stroma: Contains enzymes for the Calvin cycle.

Thylakoid membranes: Contain pigments & proteins for the light-dependent reactions.

How does stroma compartmentalization assist the Calvin cycle?

Small volume → Higher concentration of enzymes & substrates →Faster reactions.

What is the structure of the nucleus?

Double membrane → Protects DNA.

Outer membrane → Connected to rough ER.

What is the function of ribosomes?

Protein synthesis from mRNA.

What is the difference between free & bound ribosomes?

Free ribosomes →Synthesize proteins for the cell itself.

Bound ribosomes (on rough ER) → Synthesize proteins for secretion or membrane use.

What are vesicles used for?

Transporting proteins & molecules inside the cell.

Steps of protein processing:

1. Protein synthesis (ribosomes).

2. Processing in rough ER.

3. Transport in vesicles to the Golgi apparatus.

4. Modification & sorting in Golgi.

5. Vesicles transport final proteins to destination (inside or outside the cell).