Signal Transduction, ECM, Mitochondria (Lecture 17) Flashcards
What do integral membrane proteins have?
Molecules move across membranes through what mechanisms?
Ion channels are what?
Tetrodotoxin and Curare are what?
What is the Na+ glucose symporter?
How do active transporters move molecules from lower to higher concentrations?
- Integral membrane proteins have transmembrane domains (𝛼 helices) made of hydrophobic amino acids
- Molecules move across membranes through passive and active mechanisms
- Ion channels are gated and can be activated by voltage (charge) or ligands
- Tetrodotoxin and Curare are toxins that interfere with movement through ion channels
- The Na+ glucose symporter uses the higher concentration of Na+ to drive glucose against a concentration gradient
- Active Transporters use energy (ATP) to move molecules from lower to higher concentrations
Integral Membrane proteins ( Transmembrane proteins) have many important roles in cell function
What type of transmembrane proteins has been discussed thus far?
- ACh nicotinic receptor (ligand-gated channel)
- Na+ channels Glucose transporter Na+-glucose symporter
- Na+/K+ ATPase pump
What are membrane proteins important for?
How do signals from outside the cell get “into” the cell?
- Membrane proteins are important for signal transduction
- How do signals from outside the cell get “into” the cell?
- Ligand (a small molecule that binds to a receptor)
-
Ligand binding changes the conformation of the receptor protein
- (Note: the ligand does not enter the cell)
- The cytosolic side of the receptor protein is affected by the conformation change
- These conformational changes cause other proteins (in the cytosol or membrane-bound) to become activated
How epinephrine activates the conversion of glycogen to glucose is an example of what?
How epinephrine activates the conversion of glycogen to glucose is an example of a signal transduction
Epinephrine is made in adrenal glands (FLight or fight response/acute stress response) → Blood → Liver
How epinephrine activates the conversion of glycogen to glucose is an example of a signal transduction
How is epinephrine (adrenalin) made?
epinephrine (adrenalin) is made in the adrenal gland → blood → liver
epinephrine (Ligand) → binds to a receptor on liver cell → conformation change on the cytosolic side
When the G-protein is “off” it has GDP, the GDP gets converted to GTP and the G-protein is now “on”, this signal cascade breaks down glycogen to glucose
Why are membrane proteins important?
What are multicellular organisms composed of?
What does ECM =?
- Membrane proteins are important for interacting with components in the extracellular matrix (ECM)
- Multicellular organisms are composed of tissues and organs consisting of communities of cells. These cells work together to perform a function; e.g., skin, liver, leaves, etc.
- ECM = organized network of material produced and secreted by cells
What cells have walls?
Plant cell walls = ECM
Are composed of…
Provide…
Protect…
- Cells of bacteria, plants, and fungi have walls
- Plant cell walls = ECM
- composed of cellulose, hemicellulose, pectin, and proteins
- provide structural support to the cell and to the whole organism (‘skeleton’)
- protect the cell from mechanical damage and pathogen attack
What are the main functions of these intracellular compartments?
Cytosol
Nucleus
Endoplasmic Reticulum
Golgi apparatus
Lysosomes
Endosomes
Mitochondria
Chloroplasts
Peroxisomes
Cytosol - Protein synthesis, many metabolic pathways
Nucleus - Contains genome, DNA, RNA synthesis, ribosome assembly
Endoplasmic Reticulum - Synthesis of lipids, synthesis of proteins
Golgi Apparatus - Protein modification, packaging of proteins and lipids
Lysosomes - Degradation of cellular material
Endosomes - Sorting, recycling
Mitochondria - ATP synthesis, apoptosis
Chloroplasts - Photosynthesis, ATP synthesis
Peroxisomes - Oxidation of toxic molecules
Origin of the Eukaryotic Cells:
What is the Endosymbiont Theory?
Theory: Double-membraned organelles present in eukaryotic cells (i.e., mitochondria & chloroplasts) are derived from formerly free-living prokaryotes that were engulfed by an ancestral cell for endosymbiosis
What is the respiration equation?
(CH2O) + O2 → CO2 + H2O + ATP
What is the photosynthesis equation?
CO2 + H2O →sunlight→ (CH2O) + O2
Mitochondria: Structure and Function?
Mitochondria have a double membrane, consisting of an inner and outer membrane and an aqueous compartment in between
Mitochondria have two membranes: What is the first?
-
Outer Mitochondrial Membrane (OMM)
* contains many enzymes with diverse metabolic functions
* Porins- large channels
- when open, the membrane is freely permeable (e.g. to ATP)
Mitochondria have two membranes: What is the second?
- Inner Mitochondrial Membrane (IMM)
- high protein: lipid ratio (3:1)
- double-layered folds = cristae
-
cristae:
- increase the membrane surface area
- contain machinery for aerobic respiration and ATP formation
- rich in a phospholipid called cardiolipin (characteristic of bacterial membranes)
Aqueous compartments of mitochondria
What are the two compartments?
1. intermembrane space
2. matrix
- high [protein] - gel-like consistency
- mitochondrial ribosomes
- mitochondrial DNA (mtDNA)
- encodes polypeptides that are integrated into the IMM, ribosomes, tRNA
Oxidative Phosphorylation:
ATP Synthesis in the Mitochondria
What are the two steps in brief?
ATP Synthesis in the Mitochondria
Step 1
- electron transport and proton pumping
- generates an electrochemical gradient
Step 2
- proton (H+) movement down electrochemical gradient powers ATP synthesis
Oxidative Phosphorylation: Explain step 1
Oxidative Phosphorylation: Step 1
- high-energy electrons (e-) pass from coenzymes (NADH and FADH2) in the matrix to electron carriers in IMM
- series of e- carriers
- (respiratory enzyme complexes I, II, III, IV)
- = electron-transport chain (ETC)
- energy transfer at each complex used to pump protons (H+) from the matrix into intermembrane space
- ultimately, low energy e- is transferred to a terminal e- acceptor (O2)
- H2O produced
Oxidative Phosphorylation: Explain step 2
- Controlled movement of protons back across IMM
- via ATP synthase
- the potential energy in an electrochemical gradient across IMM converted to ATP in the matrix
