BIO201 Test 1 Material

What are the four major classes of organic biomolecules?

Carbohydrates, lipids, proteins, and nucleic acids

What is a monomer?

A molecular building block that can be linked to other monomers

What is a polymer?

A molecule made of many linked monomers

What reaction joins monomers into polymers?

Dehydration reaction

What reaction breaks polymers into monomers?

Hydrolysis

What are the two main functions of carbohydrates?

Energy and structure

What is the most basic type of sugar?

Glucose

What is a monosaccharide?

A single sugar monomer

What is a polysaccharide?

A polymer made of many monosaccharides

Why is glucose hydrophilic?

It contains polar covalent bonds such as O-H bonds

What reaction forms polysaccharides?

Dehydration

What reaction breaks apart polysaccharides?

Hydrolysis

What is the key structural difference between starch and cellulose?

Starch has α 1-4 glucose linkages, while cellulose has β 1-4 glucose linkages

Is starch digestible?

Yes, starch is easily digested

Is cellulose digestible?

No, cellulose is indigestible roughage

Why can starch and cellulose have different functions despite being made from glucose?

They have different linkages that produce different molecular shapes

What determines the function of a molecule?

Its shape

What is a triglyceride?

Three fatty acids bound to a glycerol scaffold

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have the maximum number of hydrogens, while unsaturated fatty acids contain carbon-carbon double bonds

Why do saturated fats tend to be solid at room temperature?

Their fatty acids stack together easily

Why do unsaturated fats tend to be liquid at room temperature?

Their fatty acids do not stack together as easily

What type of fatty acids predominate in bacon fat?

Saturated fatty acids

What type of fatty acids predominate in olive oil?

Unsaturated fatty acids

What are the two regions of a phospholipid?

A hydrophilic region and a hydrophobic region

How does fatty acid saturation affect membrane fluidity?

More unsaturated fatty acids make membranes more fluid, while more saturated fatty acids make them more solid

What are the monomers of nucleic acids?

Nucleotides

What are the three components of a nucleotide?

A sugar, a nitrogenous base, and one to three phosphate groups

What are the two sugars found in nucleic acids?

Ribose and deoxyribose

Which sugar is found in DNA?

Deoxyribose

Which sugar is found in RNA?

Ribose

What are the two categories of nitrogenous bases?

Purines and pyrimidines

What are the purines?

Adenine and guanine

What are the pyrimidines?

Cytosine, thymine, and uracil

Which nitrogenous base is found in DNA but not RNA?

Thymine

Which nitrogenous base replaces thymine in RNA?

Uracil

How are nucleotides joined together?

By covalent phosphodiester linkages

What does a phosphodiester linkage connect?

The phosphate of one nucleotide to the 3′ carbon of the sugar of the next

What forms the backbone of a nucleic acid strand?

Sugar and phosphate groups

Why are the 3′ and 5′ carbons important?

They determine the directionality of a nucleic acid strand

What structure does DNA form?

A double helix

Whose X-ray crystallography data helped Watson and Crick determine DNA's structure?

Rosalind Franklin's

What is the complementary base-pairing rule in DNA?

A pairs with T, and C pairs with G

What base pairs with adenine in RNA?

Uracil

How many hydrogen bonds form between A and T?

Two

How many hydrogen bonds form between C and G?

Three

Why does a DNA sequence with more C-G pairs require more heat to separate?

C-G pairs have three hydrogen bonds compared with two in A-T pairs

What does it mean that DNA strands are antiparallel?

The two strands run in opposite directions

If double-stranded DNA contains 166 adenine bases, how many thymine bases are present?

166

If a DNA molecule has 298 base pairs and 166 adenine bases, how many guanine bases are present?

132

When is DNA especially highly condensed?

During cell division

What are the monomers of proteins?

Amino acids

How many different amino acids are used by life?

20

What part of an amino acid gives it its unique chemical properties?

The R group

What determines whether an amino acid is hydrophobic or hydrophilic?

The chemical properties of its R group

What are polypeptides?

Chains of amino acids linked together

What reaction joins amino acids into a polypeptide?

Dehydration

What are the two ends of a polypeptide called?

The N-terminus and C-terminus

Why does a polypeptide fold into a unique structure?

Different amino acids have different local properties that cause the chain to fold

What is hydrophobic clustering?

The tendency of hydrophobic regions to cluster together during protein folding

What is the goal of protein folding in terms of energy?

To reach a stable, low-energy state

What is quaternary protein structure?

The organization of multiple polypeptides into one functional unit

What happens when a protein is denatured?

Its normal folded structure is disrupted

Why does denaturation often cause a protein to lose function?

Protein function depends on its specific three-dimensional shape

What happens to proteins when an egg is cooked?

Heat causes the proteins to unfold or denature

What is the relationship between protein shape and function?

A protein's shape determines its function

What is the activation energy barrier?

The energy required to start a chemical reaction

What do enzymes do to the activation energy barrier?

They lower it

What is the active site of an enzyme?

The region that binds a specific substrate and helps the reaction occur

What is a substrate?

The molecule that binds to an enzyme's active site

Why is the shape of an enzyme's active site important?

It holds the substrate in the proper orientation for the reaction

What is a competitive inhibitor?

An inhibitor that competes with the substrate for the active site

What is a non-competitive inhibitor?

An inhibitor that inhibits enzyme activity without directly competing for the active site

What are kinases?

Enzymes that transfer phosphate groups from ATP to other molecules

What is phosphorylation?

The addition of a phosphate group to a molecule

How can phosphorylation affect a protein?

The added negative charge can change its shape and therefore activate or deactivate its function

What is biological feedback?

The modification or control of a process or system by its results or effects.

How does feedback apply to cells?

Cells use products of processes to influence the processes that produced them.

What are the two basic types of feedback?

Positive feedback and negative feedback.

What is positive feedback?

A feedback system in which the product promotes the process.

How is positive feedback represented in biology?

With an arrow.

What is negative feedback?

A feedback system in which the product hinders the process.

How is negative feedback represented in biology?

With a blunted arrow.

What is a feedback loop?

A system in which the beginning and end of a process influence or support each other.

What are the two major cellular mechanisms of feedback regulation discussed in the lecture?

Gene regulation and enzyme regulation.

How does gene regulation control a cellular process?

It changes how much protein is present by making more protein or stopping protein production.

How does enzyme regulation differ from gene regulation?

Enzyme regulation controls the activity of proteins that already exist rather than changing their amount.

What is allosteric regulation?

Regulation by a molecule other than the substrate at a site other than the active site.

What does the word allosteric mean based on its Greek roots?

Allos means "other" and stereos means "object."

What structural feature do allosterically regulated enzymes typically have?

They typically have multiple subunits.

What conformational states can allosteric enzymes occupy?

Active and inactive conformations.

Why can an allosteric enzyme switch between active and inactive states?

Both conformations are stable, allowing the enzyme to shift back and forth between them.

What is cooperativity?

When one subunit changes shape, causing the other subunits to tend to follow suit.

How do allosteric inhibitors and activators affect enzyme activity?

They stabilize one enzyme conformation over the other.

Why can allosteric regulation affect multiple subunits at once?

Cooperativity causes the conformational change in one subunit to influence the others.

When does allosteric regulation become feedback regulation?

When the regulatory molecule is a product of the pathway.

What is feedback inhibition?

A regulatory mechanism in which a product inhibits an enzyme involved in producing that product.

Why is feedback inhibition useful to cells?

Once enough of a product has been produced, the cell can shut down the reactions used to make more of it.

In the isoleucine example, what happens when enough isoleucine has been produced?

Isoleucine binds as an inhibitor to an enzyme involved in its production.

What is the purpose of feedback inhibition in amino acid production?

To prevent the cell from continuing to produce an amino acid once enough is available.

How does the toilet-tank analogy illustrate feedback inhibition?

A float senses the water level and turns the water on when the level is too low, preventing unnecessary continued filling.