Chemical Level of Organization and Biomolecules

Flashcards covering atoms, bonds, water, pH, organic compounds, lipids, proteins, nucleic acids, enzymes, ATP, and DNA/RNA as described in the lecture notes.

What is matter?

Anything that takes up space and has mass.

On Earth, mass is the same as weight. True or false?

True—the notes state that mass is the same as weight on Earth.

What is an atom?

The smallest stable unit of matter.

What are the three main subatomic particles and their charges?

Electrons (e−) are negative; Protons (p+) are positive; Neutrons (n or n0) are neutral.

How does the mass of an electron compare to that of a proton or neutron?

An electron is about 1/1800th the mass of a proton or neutron.

What is the atomic number?

The number of protons in an atom.

What is the mass number?

The sum of protons and neutrons in the nucleus.

What is an isotope?

Atoms of the same element with different numbers of neutrons.

What is an electron cloud?

The region around the nucleus where electrons move; electrons are attracted to protons by electrical forces.

What is an element?

A pure substance composed of atoms that all have the same atomic number.

What is atomic weight (amu)?

The actual mass of an atom, expressed in daltons (atomic mass units); it is a weighted average reflecting isotope proportions.

What is a mole (mol)?

A quantity of substance in grams equal to its atomic weight; one mole contains the same number of atoms as any other element's mole.

What is molecular weight?

The sum of the atomic weights of all atoms in a molecule.

Name some principal elements in the human body.

Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N), Calcium (Ca), Phosphorus (P), Potassium (K), Sodium (Na), Chlorine (Cl), Magnesium (Mg), Sulfur (S), Iodine (I); plus trace elements.

Which element accounts for about 65% of total body weight?

Oxygen (O).

Which element is the main component of organic molecules and essential for respiration?

Carbon (C).

Which element is found in bones and teeth and important for membrane function, nerve impulses, muscle contraction, and blood clotting?

Calcium (Ca).

Which element is found in bones, teeth, nucleic acids, and high-energy compounds?

Phosphorus (P).

Which element is important for proper membrane function, nerve impulses, and muscle contraction?

Potassium (K).

Which element is important for blood volume, membrane function, nerve impulses, and muscle contraction?

Sodium (Na).

Which element is important for blood volume and water absorption?

Chlorine (Cl).

What is Magnesium’s role in the body?

A cofactor for many enzymes.

What is Sulfur’s significance?

Found in many proteins.

What is Iron’s role in the body?

Essential for oxygen transport and energy capture.

What is Iodine’s role in the body?

A component of thyroid hormones.

What are reactive elements?

Elements with unfilled outer energy levels that readily react with other elements.

What are inert elements?

Elements with filled outer energy levels; they do not readily react.

What is an ion?

An atom that has gained or lost electrons, giving it a net charge.

What is a cation?

An atom that has lost electrons, becoming positively charged.

What is an anion?

An atom that has gained electrons, becoming negatively charged.

What is an ionic bond?

An electrical attraction between cations and anions; involves transfer of electrons to achieve stability (e.g., NaCl).

What is a covalent bond?

Sharing of electrons between atoms; can be single or double bonds.

What is a nonpolar molecule?

A molecule in which electrons are shared equally between atoms, resulting in no net charge.

What is a polar molecule?

A molecule with unequal sharing of electrons, producing partial charges (e.g., H2O).

What is a hydrogen bond?

A weak attraction between a slightly positive hydrogen on one molecule and a slightly negative atom on another molecule, important in water and many biomolecules.

What is a chemical reaction?

Process where reactants are transformed into products; involves bond breaking and forming; core of metabolism.

What is activation energy?

The energy required to start a chemical reaction; enzymes lower this energy barrier.

What is an enzyme?

A protein that acts as a catalyst to lower activation energy and speed up reactions.

What is a substrate?

The reactant that binds to an enzyme at the active site.

What is an enzyme-substrate complex?

The temporary molecular complex formed when a substrate binds to an enzyme’s active site.

What is a metabolic pathway?

A series of enzymatic reactions that support life.

What is an exergonic reaction?

A reaction that releases energy.

What is an endergonic reaction?

A reaction that absorbs energy.

What is a catalyst?

A substance that accelerates a chemical reaction without being consumed; enzymes are biological catalysts.

What are nucleic acids?

Large organic molecules (DNA and RNA) composed of nucleotides; contain carbon, hydrogen, oxygen, nitrogen, and phosphorus.

What are the three types of RNA?

Messenger RNA (mRNA), Transfer RNA (tRNA), Ribosomal RNA (rRNA).

What are nucleotides composed of?

A nitrogenous base, a pentose sugar, and a phosphate group.

What are the two main bases in DNA and RNA and how do they pair?

DNA: adenine (A) pairs with thymine (T); cytosine (C) pairs with guanine (G). RNA uses uracil (U) instead of thymine and pairs with adenine.

What is the structure of DNA?

A double helix formed by two complementary nucleotide strands held together by hydrogen bonds between base pairs.

What is the role of RNA?

It performs protein synthesis as directed by DNA.

What distinguishes DNA from RNA in terms of sugar and structure?

DNA contains deoxyribose and is typically double-stranded; RNA contains ribose and is single-stranded.

What is a nucleotide’s backbone made of?

Phosphate and sugar linked by dehydration synthesis.

What is the role of hydrogen bonds in DNA structure?

Hydrogen bonds hold complementary base pairs together in the double helix.

What are the four levels of protein structure?

Primary, secondary, tertiary, and quaternary structure.

What is denaturation?

Loss of protein structure and function due to extreme conditions like heat or pH changes.

What are the four main types of protein structure?

Primary, secondary, tertiary, and quaternary structure.

What are amino acids made of?

A central carbon with an amino group, a carboxyl group, and a variable R group.

What is a peptide bond?

A covalent bond formed between the carboxyl group of one amino acid and the amino group of another via dehydration synthesis.

What is a dipeptide?

Two amino acids linked together.

What is a polypeptide?

Three or more amino acids linked; peptides with more than ~100 amino acids are proteins.

What are the four levels of protein structure and their significance?

Primary: amino acid sequence; Secondary: alpha-helix or beta-pleated sheet; Tertiary: 3D folding; Quaternary: interaction of multiple polypeptides.

What is the function of proteins?

Role in structure, enzymes, transport, signaling, and regulation; they are the most abundant organic molecules in the body.

What are carbohydrates and their general formula relationship?

Carbohydrates contain carbon, hydrogen, and oxygen in a roughly 1:2:1 ratio; they are mainly energy sources.

What is a monosaccharide?

A simple sugar with 3–7 carbon atoms (e.g., glucose).

What is a disaccharide?

Two monosaccharides joined together (e.g., sucrose); formed by dehydration synthesis and digested by hydrolysis.

What is a polysaccharide?

Many monosaccharides linked together (e.g., glycogen, starch); used for storage and energy.

What is glycogen and where is it stored?

A polysaccharide (animal starch) stored in muscle and liver; broken down to glucose when needed.

What are lipids and their general properties?

Lipids have a C:H ratio around 1:2, contain less oxygen than carbohydrates, are mostly insoluble in water, and serve as energy sources and membrane components.

What are fatty acids?

Building blocks of lipids with a hydrocarbon tail and a carboxyl group; can be saturated or unsaturated.

What is a triglyceride?

A glyceride with three fatty acids attached to glycerol; formed by dehydration synthesis and breakdown by hydrolysis.

What are phospholipids and glycolipids?

Phospholipids have a phosphate head and two fatty acid tails; glycolipids have a carbohydrate attached; both are major membrane components.

What are eicosanoids?

Lipid-derived signaling molecules (e.g., prostaglandins and leukotrienes) that coordinate local cellular activities.

What are steroids and give examples?

Lipids with four fused carbon rings; cholesterol is a key example and hormone precursors like testosterone and estrogen.

What is the role of cholesterol in cells?

Steroid that helps maintain plasma membranes and is a precursor to hormones.

What is the role of phospholipids in cell membranes?

Form a phospholipid bilayer with polar heads facing the inside and outside of the cell and nonpolar tails forming the interior barrier.

What are secondary and tertiary structures in proteins driven by?

Hydrogen bonds and interactions with water; these determine the protein’s shape and function.

What are the main components of a nucleotide?

Nitrogenous base, pentose sugar, and phosphate group.

What is the difference between DNA and RNA base composition?

DNA contains A, G, C, T; RNA contains A, G, C, U.

What is the function of DNA?

Stores genetic information that controls protein synthesis.

What is the function of RNA?

Performs protein synthesis as directed by DNA.