Studied by 27 people
Looks like no one added any tags here yet for you.
What is common and what is different between enzymes and inorganic catalysts?
Common
Increases reaction rate by lowering the activation energy
Not Consumed in the Reaction
Do Not Affect Equilibrium
Differences
Enzymes are specific protein molecules with complex 3-dimensional structure
Where inorganic catalysts are small inorganic molecules, usually metal ions
Regulation - Enzyme activity can be regulated by inhibitors, activators, or feedback inhibition. Inorganic catalysts not regulated in the same way generally lack sophisticated control mechanisms
What are the advantages of the enzymes over inorganic catalysts?
High specificity, Mild reaction conditions, High reaction rates, Biodegradability, Stereospecificity, Compatibility with biological systems
What are the cofactors that can help enzymes catalyze their reactions?
Metal ions, coenzymes, prosthetic groups
You are expected to understand the following concepts - Apoenzyme, coenzyme, holoenzyme, prosthetic group.
Aponenzyme - the protein portion of an enzyme that is inactive on its own, requiring a cofactor to become functional
Conenyzme - An organic cofactor that temporarily binds to the enzyme and participates in the reaction. Coenzymes often act as carries for functional groups
Holoenzyme - The complete, active with its aponezyme and its necessary cofactors. Holoenzymes can catalyze reactions effectively
Prosthetic group - a non-protein, organic molecule that is tightly bound to the enzyme and plays a crucial role in its activity
What are the factors that can affect activity of enzymes?
Temperature
Low temperatures - enzymes become less active as molecular motion decreases, which reduces the chances of substrate and enzyme interactions
High temperatures - can denature enzymes, disrupting their three-dimensional structure and rendering them inactive
pH
Extreme pH values can denature the enzyme by breaking ionic and hydrogen bonds, leading to loss of function
Substrate concentration
Increasing substrate concentration increases the rate of reaction up to a point; beyond this, the enzyme becomes saturated, and the reaction rate plateaus
Enzyme concentration
Higher enzyme concentration typically increases the reaction rate if sufficient substrate is available
Presence of inhibitors or activators
Inhibitors - reduce enzyme activity either by blocking the active site or altering the enzyme shape
Activators - increasing enzyme activity by enhancing substrate binding or stabilizing the enzyme’s active form
What happens to enzymes at high and low temperatures? pH?
High temperature - can cause enzyme denaturation, where the enzyme structure is disrupted, leading to the loss of its catalytic properties
Low temperature - leads to a decrease in kinetic energy, reducing the frequency of enzyme-substrate collisions and slowing down the reaction rate
Optimal pH - each enzyme has a specific pH range in which it is most active. Deviations from this range can result in reduced activity or denaturation
You are expected to understand the following concepts – Substrate, product, enzyme’s active site,activation energy, transition state
Substrate (S) - molecule that binds to active site and is modified in a reaction
Product (P) - altered form of substrate that is generated by a reaction
Transition state - transient higher-energy configuration that can decay to S or P
Active site - pocket on enzyme where reactions occur
Activation Energy- This is the minimum amount of energy required to initiate a chemical reaction. Enzymes lower the activation energy, making it easier for the reaction to occur
Is the chemical equilibrium affected during enzyme-catalyzed reaction?
No, an enzyme-catalyzed reaction does not affect the chemical equilibrium of a reaction
What happens with the rates of forward and reverse reactions during enzyme catalysis?
Forward Reaction: When the substrate binds to the enzyme, the enzyme facilitates the conversion of the substrate into the product, typically increasing the rate of the forward reaction.
Reverse Reaction: Once the product is formed, it can also revert to the substrate. The enzyme also catalyzes this reverse reaction, though the rate may differ based on the concentration of substrate and product.
Equilibrium: At equilibrium, the rates of the forward and reverse reactions become equal. This means that the concentration of substrate and product remains constant over time, even though both reactions continue to occur.
Impact of Enzymes: Enzymes do not change the equilibrium position; they simply accelerate the rate at which equilibrium is reached by lowering the activation energy for both the forward and reverse reactions.
What happens with the activation energy during enzyme-catalyzed reaction?
The activation energy is lowered, this can occur by
Lowering Activation Energy: Enzymes provide an alternative reaction pathway with a lower activation energy compared to the uncatalyzed reaction. This means that less energy is required to reach the transition state.
Mechanism: Enzymes stabilize the transition state, often by forming temporary interactions with the substrate. This stabilization reduces the energy barrier that must be overcome for the reaction to proceed.
Increased Reaction Rate: By lowering the activation energy, enzymes increase the rate of both the forward and reverse reactions, allowing the system to reach equilibrium more quickly.
What are the ways to lower the activation energy in chemical reactions?
Catalysts: Substances that increase the rate of a reaction without being consumed. Catalysts provide an alternative pathway with a lower activation energy.
Enzymes: Biological catalysts that speed up reactions by stabilizing the transition state, lowering the energy required to reach it.
Increasing Temperature: Raising the temperature increases the kinetic energy of the molecules, which can lead to more frequent and energetic collisions, helping to overcome the activation energy barrier.
Pressure: For reactions involving gases, increasing pressure can bring reactant molecules closer together, enhancing the likelihood of effective collisions.
Concentration: Increasing the concentration of reactants can also lead to more frequent collisions, thereby increasing the rate of reaction and effectively lowering the activation energy needed for some reactions.
Surface Area: For solid reactants, increasing the surface area (e.g., by grinding into a powder) allows more collisions to occur, which can facilitate the reaction.
Role of binding energy in catalysis?
Stabilization of Transition State: When a substrate binds to an enzyme, the interactions formed (such as hydrogen bonds, ionic bonds, and van der Waals forces) release energy. This binding energy stabilizes the transition state of the reaction, lowering the activation energy required to reach it.
Specificity: The binding energy also contributes to the specificity of enzymes. The precise interactions between the enzyme and its substrate ensure that only the correct substrate is bound, which is essential for effective catalysis.
Induced Fit: The concept of induced fit describes how the binding of the substrate can change the shape of the enzyme, enhancing the interactions and further lowering the energy barrier for the reaction.
Formation of the Enzyme-Substrate Complex: The energy released during the formation of the enzyme-substrate complex helps to drive the reaction forward, making it more favorable.
Transition State Stabilization: By lowering the energy of the transition state through binding interactions, enzymes accelerate the conversion of substrate to product, increasing the reaction rate.
Acid-Base Catalysis
a proton is either donated or accepted to stabilize a reaction intermediate or transition state. Enzymes with this type of mechanism often use side chains of amino acids like histidine, aspartic acid, or glutamic acid to transfer protons
Example: The enzyme ribonuclease A uses histidine residues as both a general acid and a general base to catalyze the cleavage of RNA.
Covalent Catalysis
a transient covalent bond forms between the enzyme and the substrate. This intermediate can then undergo additional chemical transformations that lower the activation energy of the reaction.
Example: Chymotrypsin, a protease, uses a serine residue to form a covalent acyl-enzyme intermediate during peptide bond cleavage.
Metal-Ion Catalysis
This type of catalysis involves metal ions such as Zn²⁺, Mg²⁺, or Fe³⁺, which can stabilize charged intermediates, participate in oxidation-reduction reactions, or help orient substrates correctly within the active site.
Example: Carbonic anhydrase uses a Zn²⁺ ion to facilitate the conversion of carbon dioxide and water into bicarbonate and protons.
Electrostatic Catalysis
the enzyme stabilizes charged transition states through non-covalent interactions, such as hydrogen bonds, dipole-dipole interactions, or salt bridges. This reduces the energy barrier for the reaction.
Example: The enzyme lysozyme stabilizes its transition state through electrostatic interactions between negatively charged residues and positively charged groups in the substrate.
Chymotrypsin and Transpeptidase mechanisms – do not need to know detailed exact mechanisms, only the key concepts: What is nucleophilic attack? What is the nucleophile in the reaction and what is the leaving group?
Nucleophile: In transpeptidase, the nucleophile is often a serine or cysteine residue in the active site, similar to chymotrypsin. It attacks the carbonyl carbon of a peptide bond.
Leaving Group: The leaving group is typically the amino acid that is being transferred, breaking off from the original peptide and forming a new bond with another amino acid.
What is the most important catalytic residue in chymotrypsin which gives name to the whole class of proteases?
The most important catalytic residue in chymotrypsin is serine (specifically, serine 195). This residue is critical for the enzyme's catalytic activity and is responsible for the nucleophilic attack on the peptide bond of the substrate. The presence of serine as a catalytic residue is a defining feature of the serine protease class of proteases, which includes other enzymes that use a similar mechanism for protein digestion and processing.
What is initial velocity of the enzyme-catalyzed reaction?
The initial linear portion of the enzyme reaction when less than 10% of substrate has been depleted or less than 10% of the product has formed
What is maximum velocity of the enzyme-catalyzed reaction?
Vmax is the rate of the reaction at which the enzyme shows the highest turnover
Effect of substrate concentration on initial velocity of the enzyme-catalyzed reactions
Low Substrate Concentration: At low substrate concentrations, the initial velocity increases linearly with an increase in substrate concentration. This is because more substrate molecules are available to bind to the enzyme, leading to more enzyme-substrate complexes and a higher reaction rate.
Intermediate Substrate Concentration: As substrate concentration continues to increase, the rate of reaction begins to slow down. The enzyme active sites become more occupied, and there are fewer available enzymes to bind additional substrate molecules. The increase in initial velocity starts to plateau.
Saturation Point: Eventually, a point is reached where all active sites of the enzyme molecules are saturated with substrate. At this point, the reaction velocity reaches its maximum (Vmax). Further increases in substrate concentration do not lead to an increase in the initial velocity, as the enzyme is working at full capacity.
Michaelis Constant (Km): The substrate concentration at which the reaction velocity is half of Vmax is known as the Michaelis constant (Km). Km provides insight into the enzyme's affinity for the substrate: a lower Km indicates a higher affinity.
Michaelis-Menten equation: you are expected to know two forms of this equation V=Vmax*[S]/(Km+[S]) and V=kcat*[Etot]*[S]/(Km+[S]) in which Vmax is expressed as Vmax=kcat*[Etot].
The first form of the equation highlights how initial velocity depends on substrate concentration relative to Km and Vmax.
The second form incorporates the turnover number and total enzyme concentration, providing insight into the enzyme's efficiency.
Both forms illustrate the relationship between substrate concentration, enzyme activity, and reaction velocity in enzyme kinetics
You are expected to understand the following concepts – Michaelis constant Km, turnover number kcat, initial reaction velocity Vo, maximum reaction velocity Vmax.
Km: Reflects substrate affinity.
kcat: Indicates catalytic efficiency.
V₀: Measures initial reaction speed.
Vmax: Represents the maximum reaction rate at saturation.
What happens to reaction velocity at [S]>>Km? At [S]<<Km? At [S]=Km?
[S] >> Km: V approaches Vmax (enzyme saturation).
[S] << Km: V is directly proportional to [S] (linear increase).
[S] = Km: V is half of Vmax.
What are enzyme inhibitors?
Enzyme inhibitors are molecules that decrease enzyme activity, reducing the rate of enzymatic reactions.
Types of Enzyme Inhibitors
Competitive Inhibitors: Compete with the substrate for the active site. They increase Km but do not change Vmax.
Non-competitive Inhibitors: Bind to an allosteric site, affecting enzyme shape. They decrease Vmax without changing Km.
Uncompetitive Inhibitors: Bind only to the enzyme-substrate complex, lowering both Km and Vmax.
What are reversible and irreversible enzyme inhibitors?
Reversible Inhibition: Non-covalent binding, allowing effects to be reversed.
Irreversible Inhibition: Covalent bonding permanently inactivates the enzyme.
What happens with Km and Vmax upon inhibition by each of the above inhibitors?
Competitive: ↑ Km, unchanged Vmax.
Uncompetitive: ↓ Km, ↓ Vmax.
Mixed: Km may ↑ or ↓, ↓ Vmax.
Allosteric regulation of enzymes.
Is a mechanism by which enzymes are controlled through the binding of regulatory molecules at sites other than the active site.
Allosteric Sites: Locations on the enzyme where effectors bind, inducing conformational changes that affect enzyme activity.
Types of Effectors:
Activators: Increase enzyme activity.
Inhibitors: Decrease enzyme activity.
Cooperativity: Allosteric enzymes often show cooperative binding, leading to a sigmoidal reaction velocity versus substrate concentration curve.
Feedback Inhibition: The end product of a pathway inhibits an earlier step, preventing overproduction.
Regulatory Role: Allows fine-tuning of enzyme activity in response to cellular conditions.
What are carbohydrates?
Definition - organic compounds made up of carbon, hydrogen, and oxygen in a ratio of 1:2:1
Composition - monosaccharides, oligosaccharides, polysaccharides
Biological roles - energy source, structural components, cell recognition, cell recognition and signaling, storage
3 main classes of carbohydrates based on the number of saccharide units
Monosaccharides(simple sugars)–one unit only
Oligosaccharides– short chains of monosaccharide units joined by glycosidic bonds(disaccharides are the most abundant)
Polysaccharides– sugar polymers containing more than 20 monosaccharide units(can be linear or branched)
What are aldoses and ketoses?
An aldose is defined as a monosaccharide whose carbon skeleton has an aldehyde group. They are primarily found in plants.
Ketose is a monosaccharide whose carbon skeleton has a ketone group
What are trioses, tetroses, pentoses and hexoses?
They are monosaccharides with three, four, five, and six carbon atoms
Trioses: Have three carbon atoms
Tetroses: Have four carbon atoms
Pentoses: Have five carbon atoms
Hexoses: Have six carbon atoms
D- and L-stereoisomers of monosaccharides. Which of the two types are the predominant in living organisms?
In living organisms are predominant forms of monosaccharides
E.g. D-glucose is the most common sugar used in metabolism
L-sugars are generally less common and often found in specific biological context or as components of certain glycoproteins and glycolipids
What are diastereomers? Examples? (e.g. mannose and galactose) v. What are epimers? Examples? (e.g. glucose and galactose)
Diastereomers are stereoisomers that are not mirror images of each other and have different configurations at one or more of their chiral centers, they differ in physical properties
E.g. Mannose and Galactose - both are aldohexoses with the same molecular formula but differ in the configuration around specific carbon atoms
Epimers are a specific type of diastereomer that differ at only one chiral center, This small difference can lead to significant variations in their biological properties
E.g. Glucose and Galactose - they are both aldohexose but differ at the C-4 carbon; glucose has the hydroxyl group (-OH) on the right, while galactose has it on the left in a fischer projection
Cyclization of monosaccharides: What is anomeric carbon? What are the α- and β-configurations of the anomeric carbon?
The anomeric carbon is the carbon in a monosaccharide that was part of the carbonyl group before cyclization, forming a new chiral center.
It has two configurations
α-Configuration:The -OH group on the anomeric carbon is opposite the CH₂OH group (e.g., in α-D-glucose, -OH points down).
β-Configuration: The -OH group is on the same side as the CH₂OH group (e.g., in β-D-glucose, -OH points up).
These configurations affect the sugar's properties and reactivity in biological systems.
Interconversion of α- and β-anomers in aqueous solutions.
Undergo mutarotation
The sugar cyclizes to form α and β forms
These forms can revert to an open-chain structure
The open-chain form can then cyclize again, creating both anomers
What are furanose and pyranose forms of monosaccharides? Don’t miss it with pentoses and hexoses!
Furanose - this is a five-membered ring structure formed from pentoses (five-carbon sugars) like ribose
Pyranose - this is a six member ring structure formed from hexoses (six-carbon sugars), like glucose
What are reducing sugars? Which chemical group(s) in monosaccharide make them reducing?
Reducing sugars are that can donate electrons to others molecules, typically because they contain a free aldehyde or ketone group
Aldehyde group - present in aldoses (e.g. glucose), which can be oxidized to a carboxylic acid
Ketone group - present in some ketoses (e.g. fructose), which can be also be converted to a reducing form through tautomerization
What is glycosidic bond? What groups and atoms from monosaccharides are involved in glycosidic bond formation?
Glycosidic bond connects the anomeric carbon of one monosaccharide to a hydroxyl group of another, resulting in the formation of a disaccharide or longer carbohydrate chains
What are the functions on nucleotides in biological systems?
Energy for metabolism (ATP)
Enzyme cofactors (NAD+)
Signal transduction (cAMP)
Building blocks for nucleic acids
What components nucleotides are made of?
Nitrogenous base
Pyrimidines C,U, or T
Purines A or G
Pentose sugar
Ribose or Deoxyribose
Phosphate
Mono-, Di-, or Tri-phosphate
Two main types of nucleobases: purines and pyrimidines. What are the most common nucleobases from each class?
Nucleoside
A molecule composed of a nucleobase attached to a sugar molecule (ribose or deoxyribose)
Nuceleobase
derivatives of Pyrimidine or Purine
N containing heteroaromatic molecules
Planar (almost planar)
Absorb UV light around 250-270 nm
Nomenclature of nucleotides and nucleosides, one-letter and three-letter codes for ribo- and deoxyribo-nucleotides.
Ribonucleotides
Adenosine (A, AMP)
Guanoise (G, GMP)
Uridine (U, UMP)
Cytidine (C, CMP)
Deoxyribonucleotides
Deoxyadenosine (A dAMP)
Deoxyguanosine (G, dGMP)
Deoxythymidine (T, dTMP)
Deoxycytidine (C, dCMP)
What are phosphodiester bonds?
Phosphodiester bonds link successive nucleotides in lines at polymers - nucleic acids (2 types)
DNA - deoxyribose
RNA - ribose
What is backbone of nucleic acid? What nucleotide components it is made of?
Phosphate + sugar = backbone
Directionality of DNA/RNA backbone.
5’ to 3’
We read the sequence from 5’ to 3’
What makes DNA more stable under physiological conditions compared to RNA?
RNA is prone to autohydrolysis and has a 2 prime wage making it unstable (ph>7)
How many strands are usually in DNA? In RNA?
DNA consist of two strands
RNA consist of one strands
What are Watson-Crick base pairs?
AT/GC are also called Waston-Crick base pairs
How many H-bonds are there between A and T? G and C?
A & T = 2 H bonds
G & C = 3 H bonds
What is Chargaff’s rule?
Purines pair with pyrimidines
A pair with T/U
G pair with C
The main features of DNA double helix
two strands are wound around the same axis, backbone is outside, nucleobases are inside, nucleobases from one strand base-pair with nucleobases from the other one based on Chargaff’s rule, two strands are antiparallel.
What is complementarity of DNA strands? You are expected to be able to draw complementary sequences of the given ones obeying Watson-Crick base-pairing rule and 5’-3’ directionality.
A forms base pair with T
G forms base pair with C
What is in common and what is different between DNA and RNA?
DNA is a double-stranded, forming a double helix
RNA is usually single-stranded
What are the main types of RNA in living organisms?
mRNA , rRNA, tTRNA
Versatility of RNA structures.
Ability to fold into complex three-dimensional shapes allowing them to perform diverse functions by interaction with other molecules including proteins and small molecules through specific binding sites
Participates in gene regulation, catalysis, and viral replication
What is denaturation of DNA?
The process where H-bond holding the two strands of DNA double helix together are broken, causing the strands to separate and unwind into single strands
What is the reverse process?
The process of converting RNA into DNA, essentially going from the “RNA to DNA” direction instead of the typical DNA to RNA transcription pathway.
What can cause DNA denaturation?
Heat
pH changes
Chemical agents
Ionic strength
Mechanical forces
What factors affect DNA denaturation?
Temperature (high)
pH levels
Salt concentration
Chemical agents
DNA sequence
Length of DNA
Mechanical stress
What happens to the UV absorbance by DNA upon denaturation? What is hyperchromic effect?
UV absorbance increases due to the hyperchromic effect, this occurs because the nitrogenous bases become more accessible to UV light when the double-stranded DNA separates, leading to higher absorbance at around 260 nm. This change is used to monitor DNA stability and melting temperature in laboratory techniques
Why it is harder to melt DNA with higher GC content?
It is harder to melt DNA with higher GC content because GC base pairs have three hydrogen bonds. This makes the GC pairing significantly stronger and requires more energy (higher temperature) to separate the strands and "melt" the DNA. In comparison, AT base pairs only have two
Storage lipids
Biological roles and composition
Biological roles
Define cells boundaries
Allow important and export
Retain metabolites and ions within the cell
Sense external signals and transmit information into the cell
Provide compartmentalization within the cell
Produce and transmit nerve signals
Store energy as a proton gradient
Support synthesis of ATP
Composition
Lipid composition of bio membranes is different various organisms, various tissue of the same organism, various organelles of the same cell
Ratio of lipid to protein varies in different biomembranes
Type of phospholipid varies in different biomembranes
Abundance and type of sterols varies
Cholesterol is predominant in the plasma membrane, but is virtually absent in mitochondria
Galactolipids are abundant in the membrane of plants chloroplast, but are almost absent in animals
Standard nomenclature of fatty acids? What does 18:1(delta9) mean?
18 carbons and delta 9 means there is one double bond at the 9th carbon position
What are glycerophospholipids?
Also called phosphoglycerides, are membrane lipids in which two fatty acids are attached in ester linkage to the first and second carbons of glycerol, and a highly polar or charged group is attached through a phosphodiester linkage to the third carbon.
What components they are composed of? (structural lipids)
they contain two fatty acids that are attached to L-glycerol-3-phosphate via ester linkages with hydroxyls on 1st and 2nd carbons (diacylglycerol)
How many fatty acids typical glycerophospholipids contain?
two
Are these fatty acids saturated or unsaturated? What are head groups?
In general, glycerophospholipids contain a C16 or C18 saturated fatty acid at C-1 and a C18 or C20 unsaturated fatty acid at C-2.
Can be either?
Are they charged or not? Are they polar or not? (structural lipids)
Yes, the phosphate group is negatively charged at physiological pH
What is the backbone of sphingolipids?
NOT glycerol, the backbone is along-chain amino alcohol sphingosine
How many fatty acids are attached to sphingosine in sphingolipids?
one
What are steroid hormones? What are they synthesized from?
Steroids are oxidized derivatives of sterols; they have the sterol nucleus but lack the alkyl chain attached to ring D of cholesterol, and they are more polar than cholesterol. Steroid hormones move through the bloodstream (on protein carriers) from their site of production to target tissues, where they enter cells, bind to highly specific receptor proteins in the nucleus, and trigger changes in gene expression and thus metabolism
What are the main components of the biomembranes?
Biomembranes separate interior parts of the cell from its surrounding. Eukaryotic cells also have various internal membranes that divide the internal space of the cell into compartments. They are composed of a variety of lipids and proteins.
What are the functions of biomembranes? iii. What are the sources of asymmetry in biomembranes?
Functions include defining cell boundaries, allowing import/export,
What forces keep the lipids together in a biomembrane?
Hydrophobic interactions between the hydrophilic head and hydrophobic tail of the molecules keep lipids together
What are the sources of membrane asymmetry? vii. Membrane dynamics: What is lateral diffusion of lipids?
Biomembranes are usually asymmetric due to these reasons:
Some lipids are found preferably “inside”
Some lipids are found preferably “outside”
Carbohydrate moieties are always outside the cell
Electrically polarized (inside negative ~ –60mV)
What is fluid mosaic model of membrane organization?
Proposed in 1972 by Singer and Nicholson (UCSD). Lipids form a viscous two-dimensional solvent into which proteins are inserted and integrated more or less deeply. Integral proteins are firmly associated with the membrane, often spanning the bilayer. Peripheral proteins are weakly associated and can be removed easily.
Functions of proteins biomembranes
Receptors: detecting signals from outside
Channels, gates, pumps
Enzymes
What are the 3 main types of membrane proteins? What are the main features of the each class?
Peripheral, Integral, and Anchored (Amphitropic).
Peripheral:
Associate with the polar head groups of membrane lipids.
Loosely associated with membrane.
Can be removed from a membrane by disrupting ionic interactions either with high salt wash or change in pH.
Integral:
Span the entire membrane
Asymmetric (different domains in different compartments)
Tightly associated with membrane
Stretches of hydrophobic amino acids in the protein interact with the hydrophobic regions of the membrane
Can be removed from a membrane by detergents that disrupt the membrane
Purified integral membrane proteins still retain phospholipids associated with them
Anchored:
Some membrane proteins are lipoproteins and contain a covalently linked lipid molecule
Anchoring of proteins to the membrane
What are the main three types of transport across the membranes?
Uniport, Symport, and Antiport (sym and anti are co-transports)
What is the active transport? What is required for the active transport to occur?
Primary active transport: hydrolysis of ATP is directly coupled to movement of the substrate.
Secondary active transport: hydrolysis of ATP drives transport of a substrate to create a concentration gradient. Movement of this substrate down concentration gradient drives symport or antiport of second substrate.
BOTH require ATP for active transport to occur.
ATPase-synthase complex.
Energy of ATP hydrolysis can be used to drive protons through the membrane
Proton driven ATP-Synthases can function in both directions
Energy of the proton gradient can be used to synthesize ATP
What are GPCRs
Epinephrine (adrenaline) receptor, interacts with G-proteins and active enzymes that generate intracellular second messengers. Illustrated by the B-adrenergic receptor system that detects epinephrine.
Gs - Stimulates production of cAMP
What are G-protiens?
Mediate signal transduction from GPCRs to other target proteins
Epinephrine: “Fight or Flight” hormone
Hormone made in adrenal glands (pair of organs on top of kidneys)
Mediates stress response: mobilization of energy
Binding to receptors in muscle or liver cells induce breakdown of glycogen
Binding to receptors in adipose cells induces lipid hydrolysis
Binding to receptors in heart cells increases heart rate
Which organisms can digest cellulose?
Bacteria, fungi, protozoa
What factors affect solubility and melting points of fatty acids?
The longer the chain, the higher the melting point of the fatty acid
More double bonds (unsaturated) = lower melting point and higher solubility
What happens with the melting points of fatty acids as the number of double bonds in them increases (assuming that the number of carbons is the same)?
More double bonds (unsaturated) = lower melting point and higher solubility
Note
Flashcard