unit 2 - Cell structure and function

Nucleus

structure:

• double membrane (nuclear envelope) with pores

functions:

• stores genetic information (DNA)

• synthesis of RNA

• ribosome subunit assembly

Rough ER

structure:

• studded with ribosomes attached to nuclear envelope

functions:

• site of membrane-bound protein and secreted protein synthesis

• cell compartmentalization

• mechanical support

• role in intracellular transport (transport vesicles to the golgi)

smooth ER

structure:

• folded, tubelike structure (cisternae)

functions:

• detoxification

• calcium storage

• lipid synthesis

Golgi complex

structure:

• membrane-bound structure composed on flattened sacs (cisternae)

functions:

• folding and chemical modification of synthesized proteins

• packaging protein traffic

• “mail center” — different glycoproteins on outside

• ex. if trying to make lysosome it comes from Golgi, synthesize hydrolytic enzyme in rough ER → goes to Golgi —> releases it out as transport vesicle that becomes a lysosome

  • issue in hydrolytic enzymes = issue in rough ER or golgi

ribosomes

structure:

• composed of rRNA and protein

• large and small subunits

• types: bound or free (cytoplasmic)

Functions:

• protein synthesis

mitochondria

structure:

• double membrane

  • outer: smooth; inner: highly folded

  • more fold = more ETC

Functions:

• site of oxidative phosphorylation (cristae/inner membrane)

• site of Krebs cycle (matrix)

chloroplast

structure

• double outer membrane (thylakoid sac stacked: grana and fluid: stroma)

function

• site of photosynthesis

• thylakoid: light reactions

• stroma: Calvin-benson cycle

lysosome

structure:

• membrane-enclosed sacs that contain hydrolytic enzymes

functions:

• intracellular digestion (recycle cell organic materials + programmed cell death apoptosis)

vacuole

structure:

• membrane bound sac

functions

• storage and release of macromolecules and cellular waste products

• central: water retention — turgor pressure

  • when plant is in hypotonic environment

• contractile: osmoregulation (protists)

  • live in freshwater/hypertonic environments + pushes water out

• food: phagocytosis, fuse with lysosome

  • cellular eating

SA:V

• smaller cells typically have a higher area to volume ratio and more efficient exchange of materials with the environment

• large surface area + small volume!

simple diffusion

• passive transport, no NRG

• down concentration gradient

  • goes straight through w no assistance

• small, nonpolar

• no transport protein needed

• examples: CO2, O2, N2

• small amount of H2O leak through membrane

facilitated diffusion

• passive transport, no NRG

• down concentration gradient

• small molecules

• requires transport protein

  • channel vs. carrier protein

    • channel + passageway straight through, carrier = binding to pass through (changes shape)

• ex. water, NA+, K+, Ca+

Active transport

• requires input of NRG

• against concentration gradient

• requires transport protein (carrier protein)

• example NA+, K+, Ca+, H+