Biology Chapter 7

1) seperates cell from its surroundings 2) exhibits selective permeability 3) forms additional compartments in eukaryotic cells

lipids and proteins, although some carbs made up of phospholipids in a bilar

-in phospholipid bilaer, proteins embed in it -switch laterally all the time -flip flop less (maybe once a month) -is fluid until temperatures are very low. Then it solidifies

temperature buffer in cold temperatures, prevents from packing together and freezing warm temperature, reduces membrane fluidity because cholesterol is rigid in the membrane

YES! (think hybrid mouse cell)

integral proteins peripheral proteins

proteins that penetrate hydrophobic core of lipid bilaer some span entire membrane, usually alpha helices, stick out in one part center is hydrophobic, top and bottom hydrophilic

proteins that are inside or outside of membrane, attached to integral proteins on cytoplasmic side, held in place by cytoskeleton on ECM, attached to integrins (fibers)

1) transport - if protein spans across entire membrane, may procide hydrophilic channel that is selective for particular molecule/route 2)catalyze chemical reactions 3) signal transduction 4) recognition 4) intercellular connections - hook into various junctions 5) connections to cytoskeleton and ECM

proteins accept chemical messengers from other cells (i.e. hormones)

identifies the cell as belonging to a specific type (tagged with carbohydrates, distinguises self from non self

-nonpolar molecules -small molecules (oxygen, carbon dioxide, hydrocarbons) -glucose and other sugars pass slowly through a lipid bilaer

somewhat but very slow - get stuck in hydrophobic middle

Very rarely

No

Channel proteins Carrier proteins

integral proteins that have hydrophilic tunnel through membrane that selectively allows certain polar ions to go through i.e. aquaporin

integral proteins that hold on to their passengers and change their shape to shuttle them across the membrane

movement across membrane that requires no energy. It could be simple diffusion or facilitated transport.

Movement of molecules from high concentration gradient to low concentration gradient this happens naturally, the gradient itself is potential energy

tend to equalize solute on both sides of membrane

Diffusion of solvent, in biology, water, across a semipermeable membrane down its concentration gradient. Because its solvent it usually goes to where there is MORE solute (the hypertonic solution).

ability of a solution to cause a cell to gain or lose water, depending on the conentration of the nonpenetrating solute inside and out of the cell and the FREE water in the cell

solute concentration the same inside and out animal cells like this plant cells are flaccid

solute outside is SMALLER than inside, so there is net flow of water in. animal cells lyse plant cells love it - they are turgid. don't burst because of cell wall

solute outside greater than inside, water flows OUT animal cells shrink plant cells plasmolyze

hypertonic

hypotonic

isotonic

solution at left side of U is hypotonic because it hass less solute. Right is hypertonic. Water wil flow from hypotonic to ypertonic, causing water to rise.

Water moves from hypotonic into hypertonic. Concentration of water is greater in hypotonic than in hypertonic (moves down its concentration gradient).

in animal cells with no cell wall, they need to regulate their water internally, hence contractile vacuole

facilitated diffusion

aquaporins - always down a concentration gradient ion channels happens VERY quickly millions/sec

Carrier proteins are also used for active transport but if going down concentration gradient, this is passive (no ATP). happens more slowly, 10/s

the use of ATP to move solutes AGAINST concentration gradient. It is always done by carrier proteins.

Active transport via carrier protiens.

Sodium/Potassium pump: creates electrogradient by moving 3Na+ out of cell and 2Ka+ into cell (net -1 in membrane).

1 - pump first binds to Na+. 2 - ATP comes along, "phosphorylates" pump, pumo changes shape. 3 - pump then releases Na+ to outside 4 - pump now open out, only has configuration to fit K+. Pump binds K+. 5 - Pump reverts back to original conformation (like a spring bottle, no atp needed this way) and releases K+ into cell, ready to start again.

2K+

3Na+

-50 to -200 mV -negative voltage inside cell, positive outside

Negative ions are attracted to positive voltage outside of cell, want to leave positive ions are attracted to negative voltage inside of cell, wnat to enter Hence why ions are affected by electrochemical gradient

-exocytosis - kick out -endocytosis - eat

-cell releases substances to outside, milk, proteins, wastes -happens via versicles

ingest food or liquid for feeding or defense -phagocytosis -pinocytosis -recepter mediated endocytosis

-ingests particles -cell membrane forms pseudopods (from microfilaments) infolds, and engulfs this is NOT specific

ingets liquids much smaller folding in takes liquids and issolved particles

is specific REcepters in ECM/membrane. substances pass, recepter binds them. Cell knows it has to pick them up, so in folds in and brings them in. -this takes a lot of energy so cells do this very little (for example when they see a lot of cholesterol, they take in)