Molecules of Life Practice Flashcards

Comprehensive flashcards covering the structure and properties of water, carbohydrates, lipids, proteins, and nucleic acids based on Chapter 1 and 2 lecture notes.

What is the bond angle and shape of a single water molecule?

The water molecule has a V shape with an angle of $104.5^o$.

Why is water described as a polar molecule?

Opposite ends of the molecule have opposite charges due to unequal distribution of shared electrons; the oxygen atom is more electronegative ($\delta-$) compared to the hydrogen atoms ($\delta+$).

What defines a hydrogen bond in water?

A chemical bond formed when the partially positive ($\delta+$) hydrogen of one molecule is attracted to the partially negative ($\delta-$) oxygen in another water molecule.

To how many other water molecules can a single water molecule form hydrogen bonds?

A maximum of four water molecules.

How does water act as a universal solvent for ionic compounds like $NaCl$?

The partially negative oxygen atoms are attracted to positively charged sodium ions ($Na^+$), while the partially positive hydrogen atoms are attracted to negatively charged chloride ions ($Cl^-$), forming a hydration shell around them.

What is the specific heat capacity of water in Joules?

$4.2\,J/g^oC$ (or $1\,cal/g^oC$).

What is the biological importance of water's high latent heat of vaporization?

It provides evaporative cooling effects (e.g., sweating in humans, transpiration in plants, and panting in dogs) to maintain optimum body temperature.

At what temperature does water reach its maximum density?

$4^oC$.

Define 'cohesion' in the context of water molecules.

The force of attraction (hydrogen bonds) between water molecules, which causes high surface tension.

Which sugar is the most common monosaccharide and more stable in ring form?

Glucose.

What is the difference between $\alpha$-glucose and $\beta$-glucose?

The position of the $-OH$ group differs on carbon number 1.

What components make up a Maltose molecule and what bond connects them?

$\alpha$-glucose + $\alpha$-glucose joined by an $\alpha$-1,4 glycosidic linkage.

Which disaccharide is classified as a non-reducing sugar?

Sucrose.

Compare the structures of Amylose and Amylopectin.

Amylose is a long, coil/helical unbranched chain with $\alpha$-1,4 glycosidic linkages, while Amylopectin is a branched chain with $\alpha$-1,4 (linear) and $\alpha$-1,6 (branch point) glycosidic linkages.

Where is glycogen primarily stored in animals?

Mostly found in liver cells and muscle cells.

What is the monomer and bond type for Cellulose?

The monomer is $\beta$-glucose joined by $\beta$-1,4 glycosidic linkages.

Why is lipid not considered a polymer?

Lipid is not built up by repeating monomers.

What are the components of a triglyceride molecule?

One glycerol and three fatty acids joined by ester linkages.

Distinguish between saturated and unsaturated fatty acids.

Saturated fatty acids contain only single bonds and have the maximum number of hydrogen atoms; unsaturated fatty acids have at least one double bond and fewer hydrogen atoms.

What characterizes the structure of a steroid?

It consists of four fused hydrocarbon rings with different functional side chains.

Explain the amphipathic nature of a phospholipid.

It has a hydrophilic head (glycerol, phosphate group, and R group) and two hydrophobic tails (hydrocarbon chains of fatty acids).

Describe the basic components of an amino acid.

An amino group ($-NH_2$), a carboxyl group ($-COOH$), a hydrogen atom, and a variable R group attached to an alpha ($\alpha$) carbon.

Define a 'zwitterion' in the context of amino acids.

At cellular pH (approx. $7.4$), amino acids exist as bipolar ionic molecules with positive and negative charges on the same molecule.

What interactions stabilize the tertiary (3°) structure of a protein?

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

What causes the denaturation of a protein?

Changes in pH or high temperature ($>40^oC$) break chemical bonds and interactions, causing the protein to lose its original shape and become biologically inactive.

What is a 'conjugated protein'?

A protein consisting of amino acids and non-protein materials called prosthetic groups (e.g., Haemoglobin which has a heme group).

Name the three components of a nucleotide.

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

According to the Watson and Crick Model, how are the two DNA strands arranged?

They are arranged in opposite directions (antiparallel), one ending with a $3'$ hydroxyl group and the other with a $5'$ phosphate group.

How many hydrogen bonds link Cytosine and Guanine in DNA?

3 hydrogen bonds.

Name the three types of RNA and their primary functions.

mRNA (carries genetic info from DNA), rRNA (forms ribosomal subunits), and tRNA (transfers specific amino acids to the ribosome).