Chapter 5 - Cellular Function Flashcards
6 basic functions of proteins
- maintain cell shape
- coordinate changes inside and outside the cell via attachments to the cytoskeleton and extracellular matrix
- receptors for chemical messengers from other cells (cellular communication via signal transduction)
- enzymes that catalyze reactions
- glycoproteins are involved in cellular recognition (help to recognize self as self and alert the immune system to intruders)
- transport of substances across the membrane
Passive transport
Involves either Diffusion or osmosis.
Diffusion - net movement of molecules from area of high [ ] to low [ ] until equilibrium is reached.
2 types of diffusion:
1) Simple
2) Facilitated
Osmosis - same as diffusion but with water.
Facilitated diffusion
Polar and charged molecules require transmembrane proteins as carriers, or use ion channels to move through the lipid bilayer.
The molecules are attracted to the polar phospholipid head so they need to be carried across, or go through the protein channel.
Ex. Glucose, ions
Simple diffusion
Non-polar and lipid soluble substances diffuse directly through the lipid bilayer.
Shouldn’t interact with the phospholipid polar heads since there is no charge to be attracted to.
Ex. Oxygen, O2
Active transport
Substances cross the membrane moving against the concentration gradient and energy is required.
3 types:
- primary active transport
- secondary active transport
- vesicle transport
Isotonic
The concentration of dissolved particles (solutes) is the same inside and outside of the cell
Hypotonic
The concentration of dissolved particles is less than the concentration of water.
(Water rapidly flows in faster than it leaves-> cell may burst, aka hemolysis)
Hypertonic
The concentration of dissolved particles is greater than the concentration of water in the cell.
(Water rapidly leaves faster than it enters-> cell may shrivel, aka crenation)
Exocytosis
A way for large molecules to leave the cell
Endocytosis
A way for large molecules to get inside of the cell.
3 types:
a) Phagocytosis - cell eating
b) Pinocytosis - cell drinking
c) Receptor mediated
Energy
The capacity to cause change or perform work.
2 basic kinds:
- potential
- kinetic
Potential energy
The energy that matter possesses as a
result of its location or structure (a compressed spring, an archery bow pulled back.
Chemical energy is the potential energy available for release in a chemical reaction – most important
energy for life.
Kinetic energy
Energy associated with matter in motion.
Ex. The archery bow being released and the arrow shoots
Exergonic reaction
An energy-releasing reaction.
The products of the reaction have less energy than the reactants do.
Ex. Respiration
Endergonic reaction
An energy-requiring reaction.
The products of the reaction have more energy than the reactants
Ex. Photosynthesis
Law of Energy Conservation
(The first law of thermodynamics)
The energy in the universe is constant. It can be transformed, but cannot be created or destroyed.
The Entropy Law
(The second law of thermodynamics)
The entropy (randomness) of the universe is constantly increasing.
Energy coupling
Then use of energy from exergonic reactions to drive endergonic reactions
Ex. Na+/K+ pump - energy used to pump 3Na+ out of the cell is also used to bring 2K+ into the cell
Activation energy
The energy required to start a reaction.
Lowered by enzyme catalysts
How do membranes form?
When mixed with water phospholipids will automatically form bilayers. This will surround areas of water, resulting in water filled bubbles, surrounded by lipid bilayers.
Aquaporin
A protein associated with facilitated diffusion that creates a channel for water that can allow up to 3 billion water molecules to pass per second.
Tonicity
The ability of a solution surrounding a cell which causes that cell to lose or gain water
3 kinds:
- isotonic
- hypotonic
- hypertonic
Osmoregation
Describes a cells control their water balance to maintain homeostasis.
Ex. Fish gills are a form of osmoregulation
Metabolism
All the thousands of exergonic and endergonic reactions on the body
Metabolic pathway
A series of chemical reactions that builds or breaks down complex molecules.
Substrate
A specific substance on which an enzyme acts on
Active site
Where the substrate binds into a pocket of the enzyme.
Associated with R groups
Cofactors
Non-protein molecules / ions that are required for proper functioning of the enzyme. They will bind to the active site and aid the enzyme.
Ex. Zn, Cu, Fe
If it is organic = coenzyme
Vitamins
Substances that are necessary for life, but that we have lost the ability to synthesize.
Help in making coenzymes
Competitive inhibitors
When the inhibitor binds to the active site of the enzyme, and competes with a substrate for that active site.
Noncompetitive inhibitors
Binds to the enzyme at another location (aka an allosteric site), and changes the shape of the enzyme so the active site no longer fits the substrate.
Feedback inhibition
Sometimes inhibitors are good things:
Feedback inhibition will shut off a metabolic pathway once there is enough product produced (it acts as an inhibitor of the enzyme to stop it from wasting too much energy)
Examples: antidepressants, blood pressure meds, advil
System
Refers to what you are studying
Surroundings
Refers to everything that exists outside of the system that you are studying
Proenzyme
Enzymes in the body that are produced in an inactive form. (Usually these come before the actual enzyme: precursor of the enzyme)
Ex. Pepsin is inactive at first to protect cells from being digested, but will eventually activate to digest proteins in the stomach
When two aqueous solutions that differ in solute concentration are placed on either side of a semi permeable membrane and osmosis is allowed to take place, the water will…
Exhibit a net movement to the side with lower free water concentration.
