In liver cell (percent volume and how many):
1. Cytoplasm: 54%, 1
2. Mitochondria: 22%, 1700
3. ER: 12%, 1
4. Nucleus: 6%, 1
5. Golgi: 3%, 1
6. Peroxisomes, 1%, 400
7. Lysosomes, 1%, 300
8. Endosomes, 1%, 200

In ancient eukaryotes, plasma membrane performed all membrane activities

Endomemrane system evolved because of invagination of plasma membrane

Mitochondria and chloroplasts thought to have evolved as endosymbionts

Cytoskeleton important in motility, shape, movement/position of organelles, and movement of materials in the cell (chromosomes during mitosis)

Three ways to import proteins into organelles:
1. Through nuclear pores
2. Across membranes
3. Vesicles

Signal sequence: 15-60 amino acid long stretch that directs proteins to organelles for nucleus, mitochondria, chloroplasts, peroxisomes or ER removed after sorting

Switched signal sequences = protein goes to “wrong address”

Nucleus has double membrane = nuclear envelope

Nuclear pore complex has a highly selective gate

Nuclear pores have a very high traffic (500 molecules/each of 3000-4000 pores) but highly selective

Pores more circular from cytosolic side compared to nuclear

Small molecules & proteins pass freely through nuclear pores spontaneously

Larger proteins is active (requires energy):
Proteins have a nuclear localization sequence to bind to, then bind to nuclear import transporter, then goes through gel-like meshwork of nuclear fibrils, out the nuclear basket then detaches from import transporter and delivered to nucleus
Nuclear export signal tags a protein for export

Proteins pass without unfolding

Mature mRNA and rRNA manufactured in nucleus come out of nucleus

Histones, ribosomal proteins, proteins required for transcription and DNA replication, dNTPs & rNTPs move into nucleus

Mitochondria and chloroplasts have a double membrane, chloroplasts have a third membrane - thylakoids
Most genes encoded by nuclear genome, so they must be imported

Proteins destined for mitochondria/chloroplasts made by free ribosomes in