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Question 1

Elements

Answer 1

Pure substances consisting of one atom type

Question 2

Molecules

Answer 2

Combinations of two or more elements joined by covalent bonds.

Question 3

Origins of Elements

Answer 3

All the elements that form our bodies—such as carbon, nitrogen, and oxygen—came from the stars.

Question 4

Origins of Life on Earth

Answer 4

Simple gaseous molecules were present in the early Earth’s atmosphere.
Water: Condensation in oceans was necessary for life to form.
Reducing atmosphere: The lack of free oxygen prevented oxidation, which helped in bond formation.
Energy sources: Electrical discharges (e.g., lightning) provided the necessary energy for chemical reactions.

Question 5

Key Points

Answer 5

Primordial Universe: Hydrogen and helium condensed to form the first generation of stars.

+7 billion years: Fusion in stars produces heavier elements, including carbon, nitrogen, and oxygen.

Supernova: Large unstable stars exploded, dispersing these heavier elements.

Second-generation stars: Form solar systems incorporating heavier elements.

Carbon’s central role: Carbon, along with hydrogen, nitrogen, and oxygen, favors bond formation and is essential for forming complex molecules.

Carbon’s ability to form covalent bonds (single, double, or triple bonds) with other atoms provides versatility and diversity in molecular chemistry.

Question 6

Biology is Modular

Answer 6

Life molecules are made from biological subunits (monomers) that form large and complex macromolecules.
Efficiency: Monomers like sugars, amino acids, and nucleotides form biopolymers (e.g., DNA, proteins) efficiently.
Assembly: These monomers are joined together to form large biopolymers that constitute the essential molecules of life.

Question 7

Miller-Urey experiment

Answer 7

Key aspects of the experiment:
Water vapor (H₂O) was heated to simulate evaporation from ancient oceans.
A mixture of gases (CH₄, NH₃, H₂) was circulated through the apparatus to mimic early atmospheric conditions.
Electric sparks acted as a stand-in for lightning, providing energy to drive chemical reactions.
The water vapor was cooled and condensed, allowing any newly formed organic compounds to collect in the water below.
The result: amino acids such as glycine, alanine, beta alanine, and aspartic acid were synthesized, demonstrating that organic molecules essential to life could have been formed under prebiotic Earth conditions.

Interestingly, after Miller’s death, further analysis of his samples revealed that over 20 different amino acids had formed—more than what is typically used in nature.

This experiment is significant because it provided the first experimental evidence supporting the idea that the basic building blocks of life could be synthesized from simple molecules present in Earth’s early environment.

Question 8

What is the polymer of the monomer saccharide (sugar)

Answer 8

Polysaccharide

Question 9

What is the bond of saccharide (sugar)

Answer 9

Glycosidic

Question 10

What is the polymer of nucleotide?

Answer 10

Polynucleotide (nucleic acids)

Question 11

What is the bond of nucleotide?

Answer 11

Phosphodiester

Question 12

What is the polymer of amino acid?

Answer 12

Polypeptide (protein)

Question 13

What is the bond of amino acid

Answer 13

Peptide

Question 14

Van der Waals forces

Answer 14

Weak intermolecular forces arising from temporary fluctuations in the electron distribution within molecules or atoms.

Question 15

Why do molecules like benzene stack up?

Answer 15

Planar molecules like benzene have a strong tendency to stack because fluctuations in the electron clouds of the stacked rings give rise to mutually attractive induced dipoles

Question 16

Where does the stacking distance between base pairs in a DNA molecule come from?

Answer 16

The 0.34 nm stacking distance is due to the Van der Waals forces and hydrophobic interactions that stabilize the stacked nucleotide bases. These forces help maintain the specific spacing and the helical structure of DNA. The distance corresponds to the periodicity of the helical structure, where every base pair contributes to a fixed distance along the axis of the DNA helix.

Question 17

Stacked rings of DNA base pairs

Answer 17

DNA bases (adenine, thymine, guanine, cytosine) are arranged in such a way that they stack like “rings” on top of each other. This stacking provides stability to the double helix structure, largely driven by Van der Waals forces and hydrophobic interactions between the planar surfaces of the nitrogenous bases.

Question 18

Why is a gecko so sticky?

Answer 18

Extensive use of van der Waals interactions: The spatulae make intimate contact with surfaces, allowing van der Waals forces (weak electrostatic forces) to form between the gecko’s foot and the surface. These forces are effective because they occur over very short distances, and the sheer number of contact points allows the gecko to adhere strongly to surfaces without any sticky substances.

Question 19

What molecule would prove life in Mars?

Answer 19

DNA

Question 20

Progression from molecules to fully formed bodies

Answer 20

Molecules: At the smallest level, life begins with molecules, which are made up of atoms. These include proteins, lipids, nucleic acids, and other essential biomolecules that perform various functions within the cell.

Cells: Molecules come together to form cells, the basic building blocks of all living organisms. Each cell contains many molecules working together to maintain life processes.

Tissues: Groups of similar cells organize into tissues, which perform specific functions within organisms (e.g., muscle tissue, connective tissue, etc.).

Bodies: Multiple tissues combine to form organs, which are part of larger body systems, ultimately resulting in a fully formed organism (a “body”).

Question 21

Intermolecular interactions

Answer 21

Intermolecular interactions occur between separate molecules and are generally non-covalent, meaning they do not involve the sharing of electrons between atoms (unlike covalent bonds within a molecule). These interactions are weaker than covalent bonds but play critical roles in biological processes.

Question 22

Intramolecular interactions

Answer 22

Intramolecular interactions occur within a molecule and are generally non-covalent, meaning they do not involve sharing of electrons. These interactions are crucial for maintaining the molecule’s three-dimensional structure.

A key example is how macromolecules, such as proteins, are folded into specific shapes. This folding is stabilized by weak interactions, such as:

Hydrogen bonds
Van der Waals forces
Ionic interactions

Question 23

Bond Distance

Answer 23

Bonds can also be defined by distance between atoms:
Covalent bonds: Atoms are closer together.
Weaker bonds: Atoms are further apart.

Question 24

Energy vs. Distance

Answer 24

As atoms approach each other, they experience attractive forces.
There is an optimal distance where the attractive force is strongest, forming a bond at this energy minimum.
If atoms move too close, they repulse because two objects can’t occupy the same space due to physical laws.

Question 25

Bond Energy/Strength

Answer 25

Bonds range from covalent bonds (strong) to progressively weaker interactions (van der Waals, the weakest).
Covalent bonds are held together by attractive forces between positive and negative charges, similar to weaker interactions but much stronger.

Question 26

Interaction diagram

Answer 26

Question 27

pH in the Body

Answer 27

Saliva: pH ranges between 6.0 to 7.4, slightly acidic to neutral.
Blood Cells in the Lungs: pH is approximately 7.4, slightly alkaline, which is necessary for oxygen and carbon dioxide exchange in the lungs.
Blood Cells in Active Tissues: pH drops to around 7.2, slightly more acidic due to increased metabolic activity and production of CO₂ in active tissues.
Urine: pH ranges from 4.5 to 8.0, depending on the body’s needs for excretion and maintaining acid-base balance.

Question 28

pH Scale

Answer 28

The pH scale ranges from 0 to 14, with:
Acids: pH < 7 (e.g., gastric acid ~1-2).
Neutral: pH = 7 (pure water).
Alkaline (bases): pH > 7 (e.g., bleach, ammonia).
pH Formula: pH is calculated as -log[H⁺], which measures the concentration of hydrogen ions in a solution.

Question 29

Blood pH, Buffering, and Imbalance

Answer 29

Normal Blood pH Range: Maintained between 7.35 and 7.45, which is slightly alkaline.

Why pH Balance is Important:
Blood pH must stay within this narrow range for proper physiological function. Small deviations can have serious consequences.

Question 30

pH Imbalance and Its Effects

Answer 30

Acidosis: Occurs when blood pH drops below 7.35. It can lead to symptoms like fatigue, confusion, and respiratory issues.

Severe acidosis (pH near 7.0) can be life-threatening.
Alkalosis: Occurs when blood pH rises above 7.45. It can cause muscle twitching, nausea, and irritability.

Severe alkalosis (pH above 7.8) is also life-threatening.
Extreme pH Imbalances:

pH values lower than 6.8 or higher than 7.8 are usually incompatible with life and can lead to death.

Question 31

Which mechanisms maintain pH

Answer 31

Renal System (Kidneys):

The kidneys regulate pH by excreting hydrogen ions (H⁺) and reabsorbing bicarbonate (HCO₃⁻) into the bloodstream.
This helps control the acid-base balance over hours to days.
Respiratory System (Lungs):

The lungs control blood pH by regulating the levels of carbon dioxide (CO₂).
Increased CO₂ (from respiration) forms carbonic acid (H₂CO₃), lowering pH, while exhaling CO₂ raises pH.
Buffer Systems:

Chemical buffers in the blood (such as the bicarbonate buffer system) help resist sudden changes in pH by balancing the concentration of acids and bases.
Acid (HA) ⇌ H⁺ (Proton) + A⁻ (Conjugate Base): This equation represents how an acid releases a proton, and the conjugate base helps neutralize excess H⁺.

Question 32

Acid-base equilibrium involving a carboxylic acid functional group - shows how many biomolecules contain functional groups that are ionizable when dissolved in water

Answer 32

A carboxylic acid (depicted as having a -COOH group) donates a proton (H⁺) and becomes a carboxylate ion (-COO⁻), which is the conjugate base.
The reaction is in equilibrium, meaning the carboxylic acid can release a proton to form its conjugate base, and the conjugate base can accept a proton to reform the acid.

Question 33

pKa

Answer 33

It provides insight into the strength of an acid; lower pKa values indicate stronger acids that dissociate more readily to give up a proton (H⁺), whereas higher pKa values indicate weaker acids.

Question 34

Carboxylic Acid Example

Answer 34

The image shows a carboxylic acid (-COOH), which loses a proton to become carboxylate (-COO⁻).
The pKa of a typical carboxylic acid is around 4, indicating it’s a relatively weak acid that dissociates partially in water.

Question 35

Amine Example

Answer 35

The image shows an amine group (-NH₃⁺) losing a proton to become its neutral form (-NH₂).
Amines have a pKa around 10, meaning they are weaker acids compared to carboxylic acids.

Question 36

Buffer Components

Answer 36

The buffer system consists of an acid (HA) and its conjugate base (A⁻).
In equilibrium, the acid can donate protons (H⁺), while the conjugate base can accept protons, thereby preventing drastic changes in pH.

Question 37

Perturbation by Adding Strong Acid

Answer 37

When a strong acid is added (e.g., H⁺ ions), the buffer system compensates by having the conjugate base (A⁻) accept the excess protons, forming more of the weak acid (HA).
This reaction helps to “soak up” the added protons and prevents the pH from dropping significantly.

Question 38

Perturbation by Adding Strong Base

Answer 38

When a strong base is added (e.g., OH⁻ ions), the added base reacts with the available protons (H⁺), forming water (H₂O).
The equilibrium shifts to release more protons from the weak acid (HA), replenishing the lost H⁺ ions, and thus, buffering the pH change.

Question 39

Equilibrium in Buffering

Answer 39

The buffer operates around the equilibrium:
HA ⇌ H+ + A −
The ability of the buffer to maintain pH depends on the concentrations of both the weak acid (HA) and the conjugate base (A⁻).

Question 40

pH and pKa

Answer 40

pH vs. pKa:
pKa represents the pH at which a molecule’s functional group is 50% protonated and 50% deprotonated.
When the pH of the solution equals the pKa, the concentrations of the protonated and deprotonated forms of the functional group are equal.

Carboxylic Acid Example (pKa ~ 4):
At pH = 4 (the pKa of the carboxylic acid), the solution contains 50% protonated carboxylic acid (-COOH) and 50% deprotonated carboxylate (-COO⁻).
As the pH increases:
At pH = 5, about 90% of the carboxylic acid is deprotonated (carboxylate form), and only 10% remains protonated.

Amine Example (pKa ~ 10):
At pH = 10 (the pKa of the amine group), 50% of the amine group is protonated (-NH₃⁺), and 50% is deprotonated (-NH₂).
As the pH decreases:
At pH = 9, approximately 90% of the amine group remains protonated, and 10% is deprotonated.

How pH Influences Ionization:
When the pH is lower than the pKa, the molecule will mostly be in its protonated form (HA for acids, NH₃⁺ for amines).
When the pH is higher than the pKa, the molecule will mostly be in its deprotonated form (A⁻ for acids, NH₂ for amines).

Question 41

Drug Elimination and Toxicity

Answer 41

Charged drugs are more easily eliminated in urine, while uncharged drugs can pass through membranes back into the bloodstream, potentially causing toxicity.

Question 42

Water’s Unique Property

Answer 42

Water is the only known liquid that becomes less dense when frozen due to hydrogen bonding. This is why ice floats, and it’s significant in many biological contexts.

Question 43

Protein Folding

Answer 43

Proteins are chains of amino acids that fold into unique three-dimensional structures.
The specific structure of a protein determines its function.
Examples of protein function based on structure:
ATP synthase: produces ATP.
Hemoglobin: carries oxygen in the blood.
Antibodies: fight infections.
Serum albumin: transports non-polar (hydrophobic) molecules in the blood.

Question 44

Misfolding and Unfolding

Answer 44

Misfolding: when proteins fold incorrectly, affecting function.
Unfolding: when proteins lose their proper structure.
Both can cause serious issues in cells and are linked to diseases.

Question 45

Neurodegenerative Diseases

Answer 45

Alzheimer’s disease:
Caused by misfolded amyloid-beta protein.
Leads to amyloid plaques and tangled neurons.
Parkinson’s disease:
Caused by misfolded alpha-synuclein protein.
Huntington’s disease: also involves misfolded proteins.
Prion diseases (e.g., Mad Cow Disease, Kuru):
Caused by misfolded prion proteins.

Question 46

Prions

Answer 46

Infectious proteins that cause brain degeneration.
Prions are virtually indestructible, making them highly dangerous.
Prions cannot be destroyed by:
Boiling, Alcohol, Acid, Standard autoclaving methods
Radiation
Even brains preserved in formaldehyde for decades can still transmit prion diseases.
Cooking infected meat (e.g., a burger) to “well done” does not destroy prions.

Prion-related diseases include:
Bovine spongiform encephalopathy (Mad Cow Disease)
Creutzfeldt-Jakob disease in humans
Other spongiform encephalopathies

Question 47

Other Examples of Misfolding

Answer 47

Cataracts:
Caused by misfolded alpha-crystallin in the eye lens, leading to cloudiness.
Type 1 Diabetes:
Insulin injections can cause misfolded insulin at the injection site, forming protein aggregates.

Question 48

When does Protein folding occur

Answer 48

happens spontaneously when proteins are synthesized

Question 49

Proteins can exist in two forms

Answer 49

Unfolded (random structure)
Folded (specific three-dimensional structure)

Question 50

Folding Equilibrium

Answer 50

When first synthesized, proteins shift between unfolded and folded states.
The rates of folding (𝑘f) and unfolding (𝑘u) determine the equilibrium.
Inside the cell, proteins reach an equilibrium between the unfolded and folded forms.
At equilibrium, the balance between folded and unfolded proteins ensures proper function.

Question 51

Perturbing Protein Folding Equilibrium

Answer 51

The relative concentrations of unfolded and folded proteins can be altered by perturbing the equilibrium.
This implies that changes in the environment or conditions can shift the balance between the folded and unfolded states of proteins.

Question 52

Different ways to think about Energy and Spontaneous Protein Folding: Energy landscape

Answer 52

Energy Landscape:
For a protein to fold spontaneously, the folded state must be at a lower energy than the unfolded state.
The energy landscape represents this as a downhill process where proteins “roll” into their lowest energy configuration.

Question 53

Different ways to think about Energy and Spontaneous Protein Folding: Gibbs Energy (ΔG = ΔH - TΔS)

Answer 53

Gibbs free energy change (ΔG) must be negative for folding to be spontaneous.
ΔH: Change in enthalpy (heat energy), usually favorable for folding.
TΔS: Change in entropy (disorder), typically unfavorable because folding reduces disorder.
Favorable factors: Hydrophobic interactions contribute to reducing ΔG.
A negative ΔG indicates that folding is thermodynamically favorable.

Question 54

Protein Conformational States - unfavourable for folding

Answer 54

Unfolded state: (favoured)
Proteins in the unfolded state have many conformations (varied structures).
This state is high in entropy due to the many possible ways the protein can be arranged.

Folded state:
In the folded state, the protein assumes essentially one conformation.
This state has lower entropy as the number of possible conformations is reduced.

Entropy and Folding:
Entropy is not just disorder or chaos; it represents the number of different ways an object can be arranged.
Folding is unfavorable for entropy because it reduces the number of conformations, thus lowering the system’s entropy.

Question 55

Energy Requirement for Protein Folding

Answer 55

To change a protein from the unfolded to the folded state, energy must be put into the system.
This energy input is required because folding often reduces entropy, and the system needs energy to overcome this loss of disorder.

Question 56

Folding Requires Energy Input

Answer 56

The process of protein folding is like organizing scattered LEGO bricks: it requires energy to assemble them into a specific structure.
Just as effort is needed to turn a pile of bricks into a structured object, energy is needed to transform an unfolded protein into its folded, functional state.

Question 57

Where does the energy required come from?

Answer 57

Formation of Weak Interactions: These include hydrogen bonds, van der Waals forces, and ionic interactions. Each new bond formed during folding releases a small amount of energy, lowering the overall energy of the protein structure. These weak interactions favor the folding process and help to lower the system’s overall energy.

Hydrophobic Effect: Nonpolar (hydrophobic) side chains of the protein tend to avoid contact with water. When the protein folds, these hydrophobic regions are buried inside the protein structure, allowing the surrounding water molecules to increase their entropy. This contributes to the driving force for protein folding. (A key driver of protein folding is the hydrophobic effect, where hydrophobic side chains in the protein avoid water. In an unfolded protein, water molecules form cage-like structures around these side chains, creating a low-entropy and unfavorable environment. When the protein folds and buries these hydrophobic regions inside, water is released, leading to a higher-entropy, more favorable state.)

Enthalpy and Entropy Balance: The enthalpy change due to the formation of new interactions and the entropy gained by water molecules are key factors in the folding process.

Question 58

Small Energy Difference in Folded vs. Unfolded Proteins

Answer 58

The energy difference between folded and unfolded proteins is small, which makes proteins susceptible to denaturation (unfolding) with slight increases in temperature, such as during a fever.
Proteins like ribonuclease are only held together by a few hydrogen bonds, highlighting how sensitive they are to changes in conditions.

Question 59

Amino acid sequence determines the 3D structure of a protein

Answer 59

Hydrophilic Side Chains:
These side chains can form hydrogen bonds and charge-dipole interactions with water molecules.
Examples of hydrophilic groups include hydroxyl (-OH) and carboxylate (-COO) groups, which interact favorably with water due to their polar nature.

Hydrophobic Side Chains:
Hydrophobic side chains cannot form hydrogen bonds and have unfavorable interactions with water.
These side chains tend to be buried inside the protein structure, away from water, during folding.

Question 60

Prion Proteins and Misfolding

Answer 60

Misfolding of proteins, such as prions, can lead to diseases. Misfolded proteins can form aggregates or amyloid fibrils stabilized by hydrogen bonds, making them difficult to revert to their native folded state.

Question 61

Amyloid Fibrils and Disease

Answer 61

The formation of amyloid fibrils, stabilized by millions of hydrogen bonds, is linked to diseases like Alzheimer’s. Once these fibrils form, the protein becomes stuck in a low-energy, highly stable state, which cannot easily refold back to its native structure.

Question 62

Ice vs. Liquid Water

Answer 62

Ice has a single fixed state, forming a hexagonal structure. Since ice has a rigid form, it has low entropy (limited ways to arrange molecules).
In contrast, liquid water molecules are constantly moving, making and breaking hydrogen bonds, resulting in high entropy (many possible molecular arrangements). In biological processes, the liquid form of water is the favorable state due to its high entropy and flexibility.

Question 63

Hydrophobic Effect

Answer 63

When a non-polar molecule (such as grease) is in water, the water molecules form a cage-like structure around the hydrophobic molecules.
This cage-like structure is similar to the structure of ice, restricting the movement of water molecules and lowering entropy.
Hydrophobic groups in water create these cage-like structures, which are energetically unfavorable.

(A): In this case, a water molecule is surrounded by other water molecules, allowing it to rotate freely while still maintaining its hydrogen bonds. This demonstrates the high degree of freedom in liquid water, where water molecules can rotate in many directions without losing their hydrogen-bonding partners. This is an example of high entropy, as the water molecules have many possible configurations.

(B): Here, a water molecule is near a hydrophobic group (represented by the yellow sphere). The water molecule is more restricted in its rotation because it cannot form hydrogen bonds with the hydrophobic group. It can only form hydrogen bonds with other water molecules nearby, limiting its movement. This restriction leads to low entropy, as the number of possible configurations is reduced.

Question 64

Water Interaction with Proteins

Answer 64

Water molecules near folded proteins behave as if the protein is invisible, meaning they don’t interact with it like they would with hydrophobic molecules.

Question 65

How do membrane proteins fold differently from aqueous proteins?

Answer 65

Membrane proteins are embedded in a hydrophobic environment (lipid bilayers), and this affects their folding behavior. Hydrophobic side chains may interact differently.

Aqueous proteins (those that function in water) tend to fold with their hydrophobic side chains buried in the interior and their hydrophilic side chains on the surface, allowing them to interact with water and maintain solubility.
Membrane proteins, on the other hand, are embedded in the lipid bilayer of the membrane, which is hydrophobic in the middle and hydrophilic on the outside (where it contacts the cytoplasm or extracellular environment). As a result, membrane proteins tend to have hydrophobic side chains on the outer surfaces that are in contact with the lipid bilayer, and hydrophilic regions on the parts of the protein that are exposed to the aqueous environment (cytoplasmic and extracellular sides).

Question 66

Folding Rules for Biomolecules

Answer 66

Proteins, DNA, and lipids follow different rules based on their structure and environment:
Proteins fold with hydrophobic side chains buried inside.
DNA has distinct polarity in its components (nucleotide bases, phosphate backbone, sugar) and follows similar folding principles.
Lipids don’t fold, but their assembly into bilayers involves the hydrophobic effect, where hydrophobic tails aggregate away from water.

Question 67

Metamorphic Proteins

Answer 67

Some proteins, like the prion protein, can switch between forms (e.g., from an alpha-helix to a beta-sheet structure), with a low energy barrier between these forms.
These changes can lead to misfolded proteins, like prions, which are implicated in diseases.

Question 68

Amyloid Fibrils and Disease

Answer 68

Proteins like insulin can form amyloid fibrils when misfolded. These fibrils consist of beta-sheet structures that aggregate into long, stable fibers.
Diseases like Alzheimer’s involve the formation of these amyloid fibrils, which are highly stable due to extensive hydrogen bonding.
Once amyloid fibrils form, they are stuck in a low-energy state and can’t revert to their native form, driving the disease process forward.

Question 69

Gibbs Energy

Answer 69

Question 70

How insulin regulates blood sugar levels when they are high

Answer 70

High blood sugar: After eating or during times of increased glucose intake, blood sugar levels rise.
Pancreas response: The pancreas detects high blood sugar and releases insulin.
Insulin action:
Glucose uptake: Insulin promotes the uptake of glucose from the blood into body cells.
Glycogen formation: Insulin stimulates the liver to convert glucose into glycogen (a stored form of glucose) for future energy needs.
Result: These actions lower blood sugar to maintain a healthy balance of glucose in the blood, ensuring it doesn’t remain too high.

Question 71

How glucagon regulates blood sugar levels when they are too low

Answer 71

Low blood sugar: When blood sugar levels drop, typically due to fasting or prolonged physical activity, the body needs to raise glucose levels.
Pancreas response: The pancreas detects low blood sugar and releases glucagon.
Glucagon action:
Glycogen breakdown: Glucagon signals the liver to break down glycogen (stored glucose) into glucose.
Glucose release: The liver then releases this glucose into the bloodstream, increasing blood sugar levels.
Result: These actions raise blood sugar to maintain adequate glucose levels for energy and overall body function.

Question 72

Glucagon to a banana in an analogy to describe its molecular interaction with its receptor

Answer 72

Glucagon is an alpha helix: In its structural form, glucagon is a protein that takes on an alpha-helical shape. This shape is important for how it functions and interacts with other molecules in the body.
Glucagon binds to its receptor: Glucagon, like many hormones, exerts its effects by binding to a specific receptor on the surface of cells (such as liver cells). This binding triggers a series of cellular responses, such as the breakdown of glycogen into glucose to raise blood sugar.
Analogy: The analogy of glucagon being like a banana refers to how its receptor recognizes glucagon’s shape (like a hand grasping a banana). The receptor recognizes glucagon’s size, shape, and chemical properties, which allows for a precise fit, much like recognizing the feel, shape, and texture of a banana.

Question 73

Recognizing Glucagon (Banana Analogy)

Answer 73

First key recognition: Size.
Size of a cylindrical object (like glucagon) can be described by two parameters:
Height/length and radius/diameter.
Glucagon can be roughly described as a cylinder in terms of shape and size.
The glucagon receptor acts like a “hand” that recognizes the shape and size of glucagon.
However, there are many alpha-helical proteins floating around in cells. So how does the receptor specifically recognize glucagon?
Proteins Can’t “See” or “Hear”:

Proteins don’t have senses like humans do, but they have a “sense of touch,” which refers to recognizing molecular characteristics.
This “touch” involves detecting specific chemical functionalities, such as:
Functional groups.
Polarity.
Weak interactions.

Chemistry of Glucagon:
The receptor recognizes glucagon’s unique chemistry through these specific weak interactions. This allows the glucagon receptor to bind to glucagon and not other similar proteins.
These weak interactions include:
Charge interactions.
Hydrogen bonding.
Van der Waals forces.

Question 74

Side chains

Answer 74