Involves hydrogen bonds, hydrophobic interactions, and ionic bonds.
Hemoglobin Formation
The interaction of two α and two β subunits to form a functional hemoglobin molecule exemplifies quaternary structure.
Cell Membrane Composition
Cell membranes are principally composed of phospholipids.
Amphipathic Molecules
An amphipathic molecule is part water-soluble and part water-insoluble.
Fundamental Building Block of Cellular Membranes
The fundamental building block is the phospholipid.
Mitochondrial Inner Membrane In-foldings
The in-foldings of the inner mitochondrial membrane are called cristae.
Inner Compartment of Mitochondria
The inner compartment of mitochondria is called the matrix.
Electron Transport Location
Electron transport occurs in the mitochondrial inner membrane.
Plasma Membrane Function
The plasma membrane functions as a selective barrier to the passage of molecules.
It also serves as a site for the uptake of macromolecules into the cell and a site for cell-cell interactions.
Plasma Membrane Barrier
The plasma membrane's barrier to passive diffusion is primarily a function of the membrane's phospholipids.
Plasma Membrane Phospholipid Distribution
Plasma membrane phospholipids are asymmetrically distributed between the two membrane halves.
Mammalian Erythrocytes
Mammalian erythrocytes (red blood cells) are particularly useful for studies of the plasma membrane because they have only one membrane, the plasma membrane.
Erythrocyte Proteins
The two erythrocyte proteins glycophorin and band 3 are transmembrane proteins.
Membrane Protein Clusters
Clusters of transmembrane α helices in membrane proteins such as RBC band 3 define segments through which ions can be transported.
Passive Diffusion Across Plasma Membrane
Molecules that diffuse passively across the plasma membrane most rapidly are small and hydrophobic.
Facilitated Diffusion
Facilitated diffusion differs from passive diffusion in that facilitated diffusion is mediated by a protein carrier or channel.
Phospholipid Movement in Membrane
Phospholipids in a membrane commonly move laterally in the plane of the bilayer and rotate within the bilayer.
Membrane Structure Model
The currently accepted model of membrane structure is called the fluid mosaic model.
Membrane Function
The unique functions of different membranes are primarily due to their proteins.
Transmembrane Proteins
Transmembrane proteins that span the membrane are integral membrane proteins.
Transmembrane Protein Spanning
Transmembrane proteins can span the lipid bilayer as α helices.
Estrogen Signaling
Signaling by the steroid hormone estrogen is an example of endocrine signaling.
Neurotransmitter Signaling
Signaling by neurotransmitters is an example of paracrine signaling.
Signal Molecule Diffusing Through Plasma Membrane
Estrogen is the signal molecule that diffuses through the plasma membrane to ultimately bind nuclear receptors and influence transcription.
Steroid Hormone Receptors
Steroid hormones usually act via receptors that bind directly to DNA.
Nitric Oxide as a Signal Molecule
Nitric oxide diffuses across cell membranes and directly alters the activity of intracellular enzymes.
Molecule Stimulating Fibroblast Proliferation
EGF stimulates fibroblasts to proliferate and thus heal a wound.
G Protein Activating Adenylyl Cyclase
The G protein that activates adenylyl cyclase is a heterotrimeric G protein that separates into α and βγ subunits.
GTP on G Protein
The GTP on the G protein that is linked to adenylyl cyclase is split to GDP and Pi upon activation by the receptor.
Cholera Toxin
Cholera toxin inhibits the ability of the α subunit of Gs to split GTP. The toxin causes stimulation.
Alpha Subunit of G Protein
The alpha subunit of the G protein that is associated with the epinephrine receptor, Gs, activates adenylate cyclase.
Major Function of cAMP
A major function of cAMP in animal cells is to activate protein kinase A.
First Step in Growth Factor Pathway Activation
The first step in growth factor pathway activation is receptor dimerization.
Hydrolysis of PIP2 by Phospholipase C
Hydrolysis of PIP2 by phospholipase C is stimulated by both GPCR and tyrosine kinase receptors.
Second Messenger PIP3
The second messenger, PIP3 is generated by the action of the enzyme phosphatidylinositide (PI) 3-kinase on phosphatidylinositol 4,5-bisphosphate (PIP2).
Molecular Basis of Cystic Fibrosis
The molecular basis of cystic fibrosis is the production of a defective chloride channel.
Gene Therapy for Cystic Fibrosis
Gene Therapy for cystic fibrosis involves transfer of the CFTR gene into bronchial epithelia.
Calcium Levels in Cytosol
Calcium levels remain low in the cytosol thus Ca2+ increase can be used as intracellular signals.
Permeability of Phospholipid Bilayers
Phospholipid bilayers are permeable only to molecules that are small and uncharged.
Passive Transport Molecules
Passive transport molecules allow small molecules across membranes.
Molecules Traversing Membrane Against Concentration Gradient
Molecules that traverse a membrane against their concentration gradient do so by active transport.
Steroid Hormones
Steroid hormones are derivatives of cholesterol.
Enzymes as Catalysts
Like other catalysts, enzymes increase the reaction rates without being consumed and do not alter the chemical equilibrium.
Enzyme Action
Enzymes act by decreasing activation energy.
Reaction Mechanism
A reaction in which the substrate binds to the enzyme and the configuration of both molecules changes is an example of an induced fit mechanism.
Trypsin and Chymotrypsin Enzymes
Trypsin and chymotrypsin enzymes are called proteases.
Coenzymes
Coenzymes are all molecules that work with an enzyme.
ΔG for ATP Hydrolysis
The ΔG for hydrolysis of ATP to ADP and Pi is −7.3 kcal/mol.
Electron Transport and Oxidative Phosphorylation Location
Electron transport and oxidative phosphorylation are performed by protein complexes in the mitochondrial inner membrane.
Hypothesis of Oxidative Phosphorylation
The hypothesis of oxidative phosphorylation is called the chemiosmotic hypothesis.