CU BOULDER BIEN 2810

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What is a hypothesis?

A testable, falsifiable proposed explanation or answer to a scientific question.

What is the independent variable?

The variable the experimenter deliberately changes or manipulates.

What is the dependent variable?

The variable that is measured or observed in response to the independent variable.

How do you identify the independent and dependent variables?

Independent = what is changed. Dependent = what is measured.

What are experimental and control conditions?

Experimental: the condition where the variable is manipulated. Control: the comparison condition without the experimental manipulation.

What is an atom?

The basic unit of an element.

What is an element?

A substance defined by its atoms having the same number of protons.

What is a molecule?

Two or more atoms chemically bonded together.

What is a compound?

A substance made of two or more different elements chemically bonded together.

What is the atomic number?

The number of protons.

How do you determine protons, neutrons, and electrons?

Protons = atomic number. Neutral electrons = atomic number. Neutrons ≈ mass number − atomic number.

What is required for a molecule to be organic?

In the biological context, organic molecules contain carbon and are generally associated with carbon bonded to hydrogen.

What is a covalent bond?

A bond in which atoms share electrons.

What is an ionic bond?

An attraction between oppositely charged ions resulting from electron transfer.

What is a hydrogen bond?

A relatively weak attraction involving a partially positive hydrogen and an electronegative atom.

What is electronegativity?

An atom's tendency to attract shared electrons toward itself.

How does electronegativity produce a polar covalent bond?

Unequal electron sharing creates partial positive and negative charges.

How do polarity and charge affect hydrophilicity?

Polar and charged substances generally interact favorably with water and are hydrophilic.

What does hydrophobic mean?

Water-avoiding; generally nonpolar.

Why can water form hydrogen bonds?

Oxygen is more electronegative than hydrogen, creating partial charges that allow neighboring water molecules to hydrogen-bond.

What is cohesion?

Attraction between molecules of the same substance.

What is adhesion?

Attraction between molecules of different substances.

What is specific heat?

The amount of heat required to raise a substance's temperature by a given amount.

Why is water's high specific heat important?

It helps living systems resist rapid temperature changes.

What is an acid?

A substance that increases H⁺ concentration in solution.

What is a base?

A substance that decreases H⁺ concentration, often by accepting H⁺ or increasing OH⁻.

How does pH relate to [H⁺]?

As [H⁺] increases, pH decreases. As [H⁺] decreases, pH increases.

What happens when HCl is added to water?

HCl dissociates, increasing H⁺ and Cl⁻; the increased H⁺ lowers pH.

What are the most common elements in biology listed in the guide?

Carbon, oxygen, nitrogen, sulfur, and phosphorus.

What are hydrocarbons?

Molecules composed only of carbon and hydrogen; they are generally hydrophobic.

How does carbon support biological diversity?

Carbon can form four covalent bonds, allowing diverse molecular structures.

How do functional groups affect molecules?

They alter properties such as polarity, charge, reactivity, and hydrophobicity.

What are structural isomers?

Molecules with the same molecular formula but different atom connectivity.

What are stereoisomers?

Molecules with the same formula and connectivity but different 3-D arrangements.

What reaction forms polymers by removing water?

Dehydration synthesis/condensation.

What reaction breaks polymers by adding water?

Hydrolysis.

What is the basic chemical formula for carbohydrates?

Approximately (CH₂O)n.

What is a monosaccharide?

One sugar unit.

What is a disaccharide?

Two monosaccharides joined together.

What is a polysaccharide?

A polymer made of many monosaccharides.

What bond connects monosaccharides?

A glycosidic bond.

What is the difference between branched and linear polysaccharides?

Linear polysaccharides form continuous chains; branched polysaccharides have branches. Branching can provide more accessible ends for enzymes.

What is the monomer of nucleic acids?

A nucleotide.

What are the three parts of a nucleotide?

Sugar, phosphate group, and nitrogenous base.

What sugar is in DNA?

Deoxyribose.

What sugar is in RNA?

Ribose.

What bases are in DNA?

Adenine, thymine, cytosine, guanine.

What bases are in RNA?

Adenine, uracil, cytosine, guanine.

What is the DNA base-pairing rule?

A pairs with T; C pairs with G.

What is the RNA base-pairing rule?

A pairs with U; C pairs with G.

What does 5′→3′ describe?

The polarity/direction of a nucleic acid strand.

What is the complementary strand to 5′-ATCG-3′?

3′-TAGC-5′.

How does base pairing affect nucleotide prevalence in double-stranded DNA?

A = T and C = G.

What is the monomer of proteins?

An amino acid.

What are the components of a generic amino acid?

A central carbon attached to an amino group, carboxyl group, hydrogen, and R group.

What makes amino acids different?

Their R groups.

What bond connects amino acids?

A peptide bond.

What is primary protein structure?

The amino acid sequence.

What is secondary protein structure?

Local structures such as α-helices and β-sheets, stabilized mainly by backbone hydrogen bonds.

What is tertiary protein structure?

The overall 3-D shape of one polypeptide caused by interactions among its parts, especially R groups.

What is quaternary protein structure?

The arrangement/interactions of multiple polypeptide subunits.

What interactions contribute to tertiary structure?

Hydrophobic interactions, hydrogen bonds, ionic interactions, and disulfide bonds.

How do hydrophobic and hydrophilic R groups affect folding?

Hydrophobic R groups tend to avoid water; hydrophilic R groups can interact with water.

What is denaturation?

Disruption of a protein's normal structure that can cause loss of function.

What levels can ordinary denaturation affect?

Secondary, tertiary, and/or quaternary structure; primary structure generally remains intact.

What common feature defines lipids?

They are generally hydrophobic or largely nonpolar and are not defined by one repeating monomer.

What is a saturated fatty acid?

A fatty acid with no carbon-carbon double bonds.

What is an unsaturated fatty acid?

A fatty acid with one or more carbon-carbon double bonds.

How does saturation affect lipid properties?

Unsaturated double bonds create bends/kinks and affect packing; saturated chains are straighter and pack more tightly.

What are the components of a triglyceride?

Glycerol + three fatty acids.

What are the components of a phospholipid?

Glycerol + two fatty acid tails + phosphate-containing polar head.

What is the basic structure of a steroid?

Four fused carbon rings.

What are the three elements of cell theory?

All living organisms consist of one or more cells; the cell is the basic unit of life; all cells come from pre-existing cells.

What features are shared by all cells?

Plasma membrane, cytoplasm/cytosol, genetic material, and ribosomes.

What is a prokaryotic cell?

A cell without a membrane-bound nucleus or other membrane-bound organelles.

What is a eukaryotic cell?

A cell with a membrane-bound nucleus and membrane-bound organelles.

What is a capsule?

A specialized prokaryotic outer layer that can help with protection and attachment.

What are flagella?

Structures used for movement.

What are pili?

Hair-like prokaryotic structures involved in attachment and, for some pili, DNA transfer.

What is the nucleus?

A membrane-bound organelle containing most eukaryotic DNA and serving as a major site of genetic regulation.

What is the nuclear envelope?

The double membrane surrounding the nucleus.

What are nuclear pores?

Openings that regulate movement between nucleus and cytoplasm.

What is the nuclear lamina?

A protein network lining the inner nuclear envelope that provides structural support.

What is the nucleolus?

A nuclear region where rRNA is produced and ribosomal subunits are assembled.

What do ribosomes do?

They synthesize proteins.

What is rough ER?

ER covered with ribosomes; involved in synthesis/initial processing of many proteins.

What is smooth ER?

ER lacking ribosomes; involved in lipid synthesis and other functions.

What does the Golgi apparatus do?

Modifies, sorts, and packages proteins and lipids received from the ER.

How are the ER and Golgi connected?

Transport vesicles carry materials from the ER to the Golgi for modification and sorting.

What do lysosomes do?

Digest/break down cellular materials using digestive enzymes.

What do mitochondria do?

Carry out most stages of aerobic cellular respiration and produce ATP.

What do chloroplasts do?

Carry out photosynthesis in plants and other photosynthetic eukaryotes.

What features of mitochondria and chloroplasts support endosymbiosis?

They contain their own DNA and ribosomes and have other prokaryote-like features.

What is the endosymbiosis theory?

Mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral cells.

What are microfilaments?

Thin cytoskeletal filaments primarily composed of actin; involved in cell shape and movement.

What are intermediate filaments?

Cytoskeletal fibers providing mechanical strength and structural stability.

What are microtubules?

Hollow tubulin-based tubes involved in organization, chromosome movement, and intracellular transport.

How does the cytoskeleton help intracellular transport?

Microtubules and actin provide tracks for motor proteins carrying cargo.

What is the role of the centrosome?

A major microtubule-organizing center, especially important during cell division.