BIO 171 Exam 1 - Membranes, Junctions, Transport, Tonicity of Solutions, Genes, & Protein Synthesis

Plasma Membrane

made up of 2 lipids: phospholipids & cholesterol; *FLUID MOSACIC* (very flexible; plasma membrane is an example of this)

Phospholipids

have a head and tail; polar heads (hydrophilic) on outside and non polar tails (hydrophobic) on the inside

Membrane proteins

Integral: go all the way through membrane

Peripheral: sit on the outside of the membrane

Gap Junctions

allow selected molecules to pass (ex: bone marrow)

Tight Junctions

Impermeable junctions; ex: brain and stomach

Desmosomes

very flexible

Passive Transport

goes across a concentration gradient (concentration moves high to low); simple diffusion, facilitated diffusion, osmosis

Simple Diffusion

Easy; high to low concentration; lipid-soluble molecules and gases; ex: O2 in lungs diffuses into blood

Facilitated Diffusion

mediated by membrane protein carriers or channels; how impermeable substances cross the membrane; MUST USE TRANSPORT PROTEIN but still goes across a concentration gradient

Osmosis

semi-impermeable; movement of water across a concentration gradient

Active Transport

requires ATP because the energy is pumping AGAINST a concentration gradient; ex: sodium-potassium pump

Cystic Fibrosis

results from a dysfunctioning chloride pump (mucus builds up)

water follows

solute

Isotonic

Normal; equal fluid moving in and out

Hypotonic

water follows solute into cell which causes swelling; less solute (more room for water)

Hypertonic

water moves out of the cell which causes shrinking; a lot of solute (less room for water)

Protein Synthesis

DNA codes to make RNA and then RNA makes proteins

Transcription

DNA is copied onto a strand of MRNA

Translation

reads MRNA and determines protein sequence; then becomes TRNA (transfer RNA)

codones

code for amino acids; 3 condones = 1 amino acid and 3 nucleotides = 1 codon