Class Notes (834,721)
Canada (508,692)
Physiology (1,062)

Module 3 Cell Organelle.docx

7 Pages
Unlock Document

Physiology 1021
Tom Stavraky

Cell Organelle Cell Membrane  Proteins, nucleotides, (large molecules, needed for inside cell) cannot penetrate  Other molecules, many ions can, selectively permeable  Waist and nutrients Cell Membrane Structure Phospholipid Molecule  Head: Phosphate (Hydrophilic)  Tail: Lipid (Hydrophobic) Cholesterol Molecule  Inserted into non-polar lipid layer  Helps make membrane impermeable to some H2O Helps keep membrane flexible  Associated Protein: Enzyme  Attached to either intra/extra cellular surf.  Ex. Enzymes: catalysts for rxns inside/outside membrane Carbohydrate Molecule  Found with extracellular membrane proteins/lipids  Form protective layer “glycocalyx”  Key role in immune response  Recognition of other cells in body Membrane Spanning Protein  Can span entire width of membrane  Can act as gates or channels (control subst in/out of cell) Structural Proteins  Usually attached to inside surf.  Can strengthen membrane  Can anchor some cell organs to inside of cell memb. Phospholipids  Form lipid bilayer  Hydrophobic tails are major barrier to water-soluble substances  Ex. ions, glucose, urea  Fat-soluble subst. like2O , 2, steroid hormones can penetrate (can dissolve in lipid region of memb) Membrane Proteins Functions: 1. Receptor: attachment of chem hormones and neurotransmitors 2. Enzyme: catalyst in chem rxns/breakdown molecules 3. Ion channel/Pore: all water-soluble subst (ions) into cell 4. Membrane-transport carriers: transport molec. across membrane (may include gated channels) 5. Cell-identity markers: Glycoproteins/Antigens: foreign particles, can stimulate immune system **Most important fn of proteins: Transport substances across membrane 1. Endocytosis/exocytosis (pinocytosis for small molecules) 2. Diffusion through the lipid bilayer (fat-soluble molecules) 3. Diffusion through protein channels(water-soluble molecules) 4. Facilitated Diffusion 5. Active Transport Diffusion  Movement of molecules of high concentration to low, due to random thermal motion  Moves down chemical concentration gradient  Continues to diffuse until concentration gradient and net movement is zero  Chemical equilibrium Ions  Move toward opposite charge down their electrical gradient  Charged ions: can move down both electrical & chemical gradient  Molecules stop moving after electrochemical equilibrium (force is equal to & in opposite direction) Diffusion of Lipid-Soluble Substances  Can pass thru cell membrane (water-soluble have tougher time)  Include O , CO , fatty acids, steroid hormones 2 2 Diffusion of Water-Soluble Substances  Require special protein channels/pores to cross membrane  Each channel is specific only allows one type of ion through (exceptions) Diffusion Factors  The size of protein channel limits size of molecule (ex. glucose too large)  Charge on molecule will affect rate of movement bc channels have charge (+ will not go thru +)  > Electrochemical gradient of molecule, >rate of movement thru channels  > # of channels in membrane >ions will diffuse across membrane Facilitated Diffusion  Other water-soluble too big (ex. glucose) cannot diffuse thru lipid bilayer & too large to pass thru channels  Molecules attach to protein carries on membrane, cause change in protein’s shape  Change  Opening of protein channel, molecule passes  Protein rotates molecule to inner surface of membrane, released  Does not require energy, powered by concentration gradient of the molecule  Rate of transport= #of available proteins  All carries occupied=saturated, cannot operate any faster  Shows chemical specificity & competitive inhibition (molecules that are similar in shape) Active Transport  Requires protein carriers  Shows chemical specificity & competitive inhibition  Moves molecules up concentration gradients (low to high),thus requires ATP  Inorganic phosphate required, powers carrier movements Osmosis  Cannot diffuse through hydrophobic portion of lipid membra
More Less

Related notes for Physiology 1021

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.