Amino Acids and Macromolecule Monomers

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Questions and Answers

Which component of the cell membrane is responsible for creating a hydrophilic environment?

Cholesterol

Cytosol

Phosphate head (correct)

Fatty acid tails

What name corresponds to structure A in the cell membrane?

Phospholipid

Cytosol

Membrane protein (integral) (correct)

Cholesterol

Which statement correctly describes the characteristics of starch in relation to its movement across the plasma membrane?

Starch can easily fit through the phospholipid bilayer.

Starch is too large and polar, preventing its diffusion. (correct)

Starch is too polar to diffuse through the membrane.

Starch is small enough to pass through the bilayer easily.

Which structure provides stability to the cell membrane by preventing it from becoming too fluid?

Cholesterol Signup and view all the answers

What type of transport would a large polar molecule, such as starch, most likely require to enter a cell?

Endocytosis Signup and view all the answers

What type of interaction is most likely between aspartic acid and lysine?

Ionic interaction Signup and view all the answers

Which amino acids exhibit dipole-dipole interactions?

Serine and lysine Signup and view all the answers

What is the primary bond type present in the quaternary structure of a protein?

All of the above Signup and view all the answers

What reaction type is specifically involved in the breakdown of carbohydrates?

Hydrolysis Signup and view all the answers

What features characterize the monomer of carbohydrates?

Multiple hydroxyl groups and an ether in a carbon ring Signup and view all the answers

In terms of polarity, how would you classify fatty acids?

Non-polar due to CH bonds Signup and view all the answers

Why is the three-dimensional shape of a protein important?

It influences the protein's function and interaction with molecules Signup and view all the answers

Which structural level of proteins is characterized by amino acid sequences joined by peptide bonds?

Primary Signup and view all the answers

What is the primary bond that links amino acids together in a protein?

Peptide bond Signup and view all the answers

How do intermolecular forces contribute to the structure of proteins?

They facilitate the folding and stability of the protein. Signup and view all the answers

What role does the specific shape of a protein play?

It allows for specific substrates or receptors to bind. Signup and view all the answers

Which of the following best describes the 'beads on a string' model in relation to protein structure?

It represents the secondary structure stabilized by hydrogen bonds. Signup and view all the answers

Which types of intermolecular forces are significant in holding polypeptides together?

Dipole-dipole interactions, hydrogen bonds, and ionic interactions. Signup and view all the answers

How does an increase in substrate concentration generally affect enzyme activity?

It increases enzyme activity to a point, then levels off. Signup and view all the answers

What effect does temperature have on enzyme activity beyond 50°C?

Enzyme activity dramatically decreases. Signup and view all the answers

What is the role of feedback regulation in enzyme activity?

It can positively or negatively affect enzyme activity. Signup and view all the answers

Which of the following best describes competitive inhibition?

It involves the inhibitor competing with the substrate for the active site. Signup and view all the answers

Which term refers to non-amino acid components of a functional protein?

Co-factors Signup and view all the answers

What distinguishes a co-enzyme from a co-factor?

Co-enzymes are organic cofactors. Signup and view all the answers

Explain why an enzyme that breaks glycosidic bonds cannot break peptide bonds.

They involve entirely different bond types and require different active sites. Signup and view all the answers

How can one determine that enzymes are involved in a chemical reaction?

By noting the change in reaction rates with varying substrate concentrations. Signup and view all the answers

What happens to a cell placed in a hypotonic environment?

The cell swells as water moves in. Signup and view all the answers

Which type of transport is used to move Na+ ions from the cytoplasm into the extracellular fluid (ECF)?

Primary active transport. Signup and view all the answers

What is the primary reason that transporting ions can generate more potential energy than transporting neutral molecules?

Ions experience both chemical and electrical gradients. Signup and view all the answers

Under which condition is endocytosis and exocytosis most likely to occur?

With both small and large molecules. Signup and view all the answers

What does an electrochemical gradient refer to?

The simultaneous presence of a chemical and electrical gradient. Signup and view all the answers

Which statement best describes the movement of water in a hypotonic solution?

Water moves into the cell due to higher solute concentrations inside. Signup and view all the answers

Why is primary active transport necessary for cell function?

It helps maintain concentration gradients for ions. Signup and view all the answers

Which force drives particles to move from an area of higher concentration to an area of lower concentration?

Chemical gradient. Signup and view all the answers

Study Notes

Amino Acid Interactions

Aspartic acid and lysine can interact via ionic bonds, as aspartic acid has a negatively charged carboxyl group, and lysine has a positively charged amino group.
Phenylalanine and alanine primarily interact via London dispersion forces, as they are both nonpolar amino acids.
Serine and lysine can interact via dipole-dipole interactions due to the polar hydroxyl group in serine and the polar amino group in lysine.

Macromolecule Monomers

Carbohydrates: Monosaccharides (simple sugars), like glucose and fructose. These molecules contain multiple polar hydroxyl groups and ether bonds, making them polar. Monosaccharides form disaccharides through glycosidic bonds (formed through dehydration synthesis), a type of condensation reaction.
Lipids: Glycerol (a polar molecule with three hydroxyl groups) and fatty acids (long chains of hydrocarbons with a carboxyl group at one end). Fatty acids are nonpolar due to their hydrocarbon chains. These monomers form triglycerides (or fats) through ester bonds.
Proteins: Amino acids, which contain both a polar amino group and a polar carboxyl group, as well as a variable R-group that can be polar or nonpolar. Amino acids join to form polypeptides through peptide bonds, a type of amide bond.

Importance of Water for Breakdown

Carbohydrate and protein breakdown requires water because these molecules are broken down through hydrolysis reactions. Hydrolysis involves adding a water molecule to break a bond between monomers, resulting in two smaller units.

Protein Structure and Function

The 3D shape and conformation of a protein is crucial for its function.
Primary structure: This is the linear sequence of amino acids in the polypeptide chain, determined by peptide bonds.
Secondary structure: The folding of the polypeptide chain into alpha-helices or beta-sheets, due to hydrogen bonding between the backbone carbonyl oxygen and the backbone amino hydrogen.
Tertiary structure: The overall 3D shape of a single polypeptide chain, formed by interactions between the R-groups of the amino acids, including hydrogen bonding, ionic interactions, hydrophobic interactions, and disulfide bridges.
Quaternary structure: The arrangement of multiple polypeptide chains, each folded into its tertiary structure, also stabilized by interactions between the R-groups, including hydrogen bonding, ionic interactions, hydrophobic interactions, and disulfide bridges.

Enzyme Activity

Substrate concentration: Increased substrate concentration generally leads to an increased rate of reaction until the enzyme becomes saturated.
Temperature: Enzymes have an optimal temperature for activity. The rate of reaction increases with temperature until the optimal temperature is reached. Then, the rate of reaction drops significantly due to denaturation of the enzyme.
pH: Enzymes have an optimal pH for activity. The rate of reaction decreases dramatically at acidic or basic pH due to changes in enzyme structure.
Feedback regulation: The product of a reaction can act as an allosteric regulator, either promoting or inhibiting further activity of the enzyme.
Competitive inhibition: An inhibitor molecule competes with the substrate for the active site of the enzyme, decreasing the intended enzyme activity.

Enzyme Regulation

Allosteric activation: An activator molecule binds to a site other than the active site, causing a conformational change in the enzyme that increases its activity.
Allosteric inhibition/non-competitive inhibition: An inhibitor molecule binds to a site other than the active site, causing a conformational change in the enzyme that decreases its activity.
Competitive inhibition: An inhibitor molecule competes with the substrate for the active site of the enzyme, decreasing the intended enzyme activity.

Cofactors, Coenzymes & Prosthetic Groups

Cofactors: Non-protein components that are required for the activity of some enzymes.
Coenzymes: Organic cofactors that are loosely bound to enzymes.
Prosthetic groups: Cofactors that are permanently associated with enzymes.

Enzyme Specificity

An enzyme that catalyzes the breakdown of a glycosidic bond (in carbohydrates) is unlikely to catalyze the breakdown of a peptide bond (in proteins) because these bonds are structurally different. Enzymes are highly specific for their substrates, requiring specific active binding sites for recognition and catalysis.

Cell Membrane

The plasma membrane is a selectively permeable barrier that controls the movement of substances into and out of the cell.
It's composed of a phospholipid bilayer.
A: Integral membrane protein.
B: Peripheral membrane protein.
C: Phosphate head (hydrophilic).
D: Fatty acid tails (hydrophobic).
E: Phospholipid.
F: Cytosol.
G: Cholesterol.

Starch and Cell Membrane

Starch cannot pass through the plasma membrane via simple diffusion for two reasons:
- Size: Starch molecules are too large to fit through the phospholipid bilayer.
- Polarity: The multiple hydroxyl groups on starch molecules make them polar, making it difficult to pass through the nonpolar interior of the phospholipid bilayer.

Cell Transport

Hypotonic Environment: A cell placed in a hypotonic environment will swell up. Water will move into the cell (higher solute concentration inside the cell will draw water in) to try to reach equilibrium.
Primary Active Transport: Energy is directly used (usually from ATP hydrolysis) to move molecules against their concentration gradient.
Secondary Active Transport: Energy is indirectly utilized by coupling the movement of one molecule against its concentration gradient with the simultaneous movement of another molecule down its concentration gradient.
Electrochemical gradient: The combination of both a chemical gradient (concentration difference) and an electrical gradient (difference in charge) drives the movement of charged molecules (ions).

Endocytosis and Exocytosis

Endocytosis and exocytosis are processes that involve the movement of large molecules or particles into or out of the cell via membrane-bound vesicles.

Transporting Ions Against Gradient

Transporting ions against a gradient requires more energy than transporting neutral molecules against a gradient because of both the chemical gradient (concentration difference) and the electrical gradient (charge difference) that must be overcome.

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Description

Test your knowledge on amino acid interactions and the monomers of macromolecules. This quiz covers ionic bonds between aspartic acid and lysine, as well as the structures and functions of carbohydrates and lipids. Perfect for students studying biochemistry or molecular biology.