HSS2305 L2,3

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Questions and Answers

What is one of the primary roles of free radicals in relation to health?

They help in energy production.

They are a significant cause of disease. (correct)

They enhance antioxidant activity.

They support cellular repair mechanisms.

Which of the following statements about hydrogen bonds is true?

Hydrogen bonds only occur between identical atoms.

Hydrogen bonds contribute to the structure of biological molecules. (correct)

Hydrogen bonds are stronger than covalent bonds.

Hydrogen binds covalently with oxygen and forms strong bonds.

Which characteristics are associated with hydrophilic molecules?

They form aggregates in aqueous solutions.

They are water-fearing.

They are typically nonpolar.

They participate in hydrogen bonding. (correct)

What is the main reason hydrophobic molecules aggregate in water?

To minimize exposure to polar surroundings. Signup and view all the answers

What type of interactions are classified as Van der Waals interactions?

Weak bonds based on transient charge separations. Signup and view all the answers

What defines a molecule as a compound?

It contains more than one type of atom. Signup and view all the answers

Which of the following is an example of a polar molecule?

H2O Signup and view all the answers

What type of bond involves the sharing of electron pairs between atoms?

Covalent Bonds Signup and view all the answers

What charge do cations carry after losing electrons?

Positive charge Signup and view all the answers

What are free radicals characterized by?

Unpaired electrons Signup and view all the answers

Which of the following elements is commonly found in polar molecules?

Oxygen Signup and view all the answers

What is a characteristic of nonpolar molecules?

They lack polarized bonds. Signup and view all the answers

Which of the following best describes the relationship between structure and function in cells?

Structure directly influences cellular function. Signup and view all the answers

What is the primary building block of proteins?

Amino acids Signup and view all the answers

Which of the following components can be added to proteins after synthesis?

Flavoproteins Signup and view all the answers

At which pH are amino acids almost always fully charged?

pH 7 Signup and view all the answers

What type of bond can be formed between charged R groups and negatively charged molecules like DNA?

Ionic bonds Signup and view all the answers

Which category of amino acid R groups includes those that are weakly acidic or basic?

Polar uncharged R groups Signup and view all the answers

What is the primary function of buffers in living systems?

To prevent changes in pH Signup and view all the answers

Which of the following best describes the Bohr Effect?

It enhances the unloading of oxygen from hemoglobin. Signup and view all the answers

How many atoms can carbon bond with at most?

Four Signup and view all the answers

Which property of water significantly contributes to its role as a solvent?

Its asymmetrical structure Signup and view all the answers

What do amphoteric molecules do?

Can act as both acids and bases Signup and view all the answers

Which type of organic molecule is primarily composed of carbon and hydrogen?

Lipids Signup and view all the answers

Which of the following statements about van der Waals forces is correct?

They are crucial for binding complementary surfaces. Signup and view all the answers

What effect does a decrease in blood pH have on hemoglobin's oxygen affinity?

Decreases its affinity for oxygen. Signup and view all the answers

Which type of fat is characterized by having no double bonds in its fatty acid chain?

Saturated Signup and view all the answers

What is the primary function of phospholipids in biological systems?

Cell membrane structure Signup and view all the answers

What type of bond connects nucleotides in DNA and RNA?

Phosphodiester bonds Signup and view all the answers

Which of the following molecules is classified as a lipid?

Cholesterol Signup and view all the answers

What is the role of adenosine triphosphate (ATP) in biological systems?

Energy currency Signup and view all the answers

Which of the following is a characteristic feature of steroids?

Four-ring hydrocarbon skeleton Signup and view all the answers

Which of the following nitrogenous bases is found in RNA but not in DNA?

Uracil Signup and view all the answers

What defines a molecule as amphipathic?

It contains both hydrophilic and hydrophobic parts. Signup and view all the answers

What type of macromolecules perform nearly all cellular activities?

Proteins Signup and view all the answers

Which kind of fatty acids have hydrogen atoms on opposite sides of the double bond?

Trans fatty acids Signup and view all the answers

Study Notes

Superoxide and Hydroxyl Radical

Superoxide (O2-) and hydroxyl radical (OH·) are highly reactive molecules that can readily donate or accept electrons.
They are considered free radicals, which are unstable molecules with unpaired electrons.

Free Radicals and Disease

Free radicals can damage macromolecules like DNA, lipids, proteins, and carbohydrates.
They are a significant contributor to aging and various diseases.
While free radicals are naturally produced during metabolism, aberrant or unmanaged free radicals are detrimental to health.

Hydrogen Bonds

Hydrogen bonds form between covalently bound hydrogen atoms and the electrons of a second atom.
They occur in biological molecules, such as the strands of DNA.
They determine the structure and properties of water.

Hydrophilic and Hydrophobic Interactions

Hydrophilic: Water-loving, participate in hydrogen bonding, enhance solubility in water, occur between polar molecules (e.g., amino acids, sugars).
Hydrophobic: Water-fearing, nonpolar molecules, insoluble in water, form aggregates to minimize exposure to polar surroundings (e.g., fats, steroids).
Van der Waals interactions: Weak bonds between hydrophobic molecules, based on electrostatic interactions.

Cellular Function and Structure

Understanding cellular function requires knowledge of the structure of molecules and atoms.
Structure and function in cells are closely related to the structure of molecules and atoms.

Atomic Bonds

Atoms: The basic unit of matter consisting of a dense central nucleus surrounded by electrons.
Covalent Bonds: Bonds between atoms formed by sharing electron pairs.
Molecules: Stable combinations of atoms held together by covalent bonds.
Compounds: Molecules with more than one type of atom.

Polarity

Polar Molecules: Have asymmetric distributions of electrical charge, leading to greater reactivity.
Nonpolar Molecules: Lack polarized bonds, generally inert (e.g., fats, waxes, CO2).
Many biological molecules have both polar and nonpolar regions.

Ionization

Ions: Atoms with a strong electronegativity that gain or lose electrons during chemical reactions.
- Cations: Lose electrons (e.g., Na+).
- Anions: Gain electrons (e.g., Cl-).
Free Radicals: Unstable atoms or molecules with unpaired electrons, highly reactive and formed during normal metabolism.

Water

Water's life-supporting qualities arise from its molecular structure:
- It is asymmetric.
- It has highly polarized O-H bonds.
- It readily forms hydrogen bonds.
- It has a high heat of vaporization.
- It is an excellent solvent for many substances.

Acids, Bases, and Buffers

Acids release protons (H+).
Bases accept protons (H+).
Amphoteric molecules can act as both acids and bases (e.g., water).
Biological processes are sensitive to pH.
Buffers resist changes in pH (e.g., bicarbonate ions and carbonic acid buffer blood).

Carbon: The Foundation of Organic Compounds

Carbon's size and electronic structure allow for the formation of diverse organic molecules.
It can bind to up to four other atoms.
It forms stable linear, branched, and cyclic carbon backbones.

Hydrocarbons

Hydrocarbons comprise only carbon and hydrogen.
They represent the simplest group of organic molecules, but are not common in living cells.

Common Functional Groups

Functional groups are groups of atoms that replace hydrogens on a carbon skeleton, giving organic molecules unique characteristics and properties.

Macromolecule Classification

Macromolecules: Large complex molecules essential for life.
- Carbohydrates
- Lipids
- Nucleic acids
- Proteins
Building Blocks of Macromolecules: Simpler subunits that make up macromolecules.
- Sugars
- Fatty acids
- Nucleotides
- Amino acids

Lipids

Diverse group of molecules (fats, steroids, phospholipids).
Fats: Glycerol linked to three fatty acids by ester bonds, forming a nonpolar molecule.
- Long-term energy storage.
- Fatty Acids: Long unbranched hydrocarbon chains with a carboxyl group.
  - Saturated: No double bonds.
  - Unsaturated: Contains double bonds (monounsaturated or polyunsaturated).
  - Cis- and trans-: Describe the hydrogen atom positions on the same or opposite sides of the double bond.
Steroids: Built around a four-ringed hydrocarbon skeleton, nonpolar (e.g., cholesterol).
Phospholipids: Similar to fats but with only two fatty acid chains, a phosphate group bound to glycerol, and a small polar group. Primary function in cell membranes.

Nucleic Acids

Polymers of nucleotides that store and transmit genetic information.
Deoxyribonucleic Acid (DNA): Stores genetic information.
Ribonucleic Acid (RNA): Transmits genetic information into proteins.
Nucleotide: A (deoxy)ribose sugar + a phosphate group + a nitrogenous base.
Nitrogenous Bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C), and Uracil (U).
Nucleotides are connected by 3'-5' phosphodiester bonds between the phosphate of one nucleotide and the 3' carbon of the next ribose sugar.

Proteins

Macromolecules that perform virtually all cellular activities.
Functions: Enzymes, transporters, hormones, growth factors, regulators of cell function, structural and/or movement machinery, antibodies, toxins.
Each protein has a unique structure to enable its function and selective interactions with molecules.
Building blocks of proteins: Amino Acids.
Amino Acid Structure: All amino acids have a central α carbon, an amino group, a carboxyl group, and a variable R group.
Peptide Bonds: Amino acids are joined within a polypeptide chain by peptide bonds.
Protein Components: Many proteins contain additional components beyond the polypeptide chain, like carbohydrates (glycoproteins), metal-containing groups (metalloproteins), or organic groups (flavoproteins).

Amino Acid Diversity

20 different amino acids exist.
R Groups: Variable side chains that give amino acids diverse structures and functions.
- Polar charged
- Polar uncharged
- Nonpolar
- Unique properties

Charged R Groups:

These R groups act as strong organic acids or bases.
They are almost always fully charged at pH 7.
They can form ionic bonds.
- Example: Histones with arginine (+ charge) binding to negatively charged phosphate groups of DNA.

Polar Uncharged R Groups:

These R groups are weakly acidic or basic.
They are not fully charged at pH 7.
They can form hydrogen bonds with other molecules.
Example:

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Description

Explore the roles of superoxide and hydroxyl radicals in biological systems and their impact on health. This quiz covers free radicals' effects on macromolecules, the significance of hydrogen bonds, and the interactions of hydrophilic and hydrophobic molecules. Test your understanding of these foundational concepts in biochemistry.