Biology: Water, pH, and Organic Molecules (Carbohydrates & Lipids)

Flashcards cover water properties (hydrogen bonding, solvent, surface tension, density changes), pH and buffers, monomers and polymers, carbohydrates (mono-, di-, poly-, cellulose, starch, glycogen, chitin), and basic lipid/organic chemistry concepts from the lecture.

What property of water arises from the polarity of the molecule and leads to attractions between water molecules rather than forming true chemical bonds?

Hydrogen bonding between water molecules.

Is a hydrogen bond a true chemical bond like covalent or ionic bonds?

No. It is an attraction between molecules, not a covalent or ionic chemical bond.

Why is water considered an excellent solvent?

Because of its polarity and ability to form hydrogen bonds with many substances, especially hydrophilic ones.

What does the term hydrophilic mean?

Water-loving; substances that dissolve easily in water.

What does the term hydrophobic mean?

Water-fearing; substances that do not interact with water (e.g., oils).

In a solution, what are solute and solvent?

Solute is the substance dissolved in the solvent; solvent is the liquid doing the dissolving (water is the universal solvent).

How does water dissolve table salt (NaCl)?

Water’s partially negative oxygen attracts Na+, and partially positive hydrogens attract Cl−, pulling the ions apart and surrounding them.

What causes surface tension in water?

Cohesion from hydrogen bonding among water molecules at the surface, creating a 'skin' that can support small objects.

Why does ice float on liquid water?

Ice is less dense than liquid water due to the open lattice structure formed by hydrogen bonds in ice.

What is pH a measure of?

The concentration of hydrogen ions; 7 is neutral, below 7 is acidic, above 7 is basic.

What do acids and bases do in terms of hydrogen ions?

Acids donate hydrogen ions; bases accept hydrogen ions (or release hydroxide ions in solution).

What is a buffer and why is it important?

A system that resists changes in pH, such as the carbonic acid/bicarbonate system in blood, helping maintain homeostasis.

What is the typical pH range you aim for to maintain body homeostasis?

Approximately 7.3 to 7.5.

Describe the carbonic acid–bicarbonate buffer system.

CO2 + H2O forms H2CO3, which can dissociate to H+ + HCO3−; buffers respond to added acid or base to keep pH around neutrality.

What is a monomer and what is a polymer?

A monomer is a small molecule that can join other monomers to form a polymer, a large molecule made of many repeating units.

What are the four major classes of polymers in biology?

Carbohydrates, lipids, proteins, and nucleic acids.

What is a monosaccharide?

A simple sugar, usually 5–6 carbons, with a carbonyl group and hydroxyl groups.

What are disaccharides?

Two monosaccharides joined together (e.g., lactose, sucrose).

Name the three glucose-based polysaccharides and a key feature of each.

Cellulose (long, straight chains, hydrogen-bonded, plant structural; not digestible by humans); starch (spiral chain, energy storage in plants); glycogen (branched chains, energy storage in animals, mainly in liver and muscles).

What is chitin and where is it found?

A polysaccharide of nitrogen-containing sugar monomers; found in fungal cell walls and exoskeletons of insects, spiders, and crustaceans.

Why are carbohydrates important in metabolism?

They provide fast energy through readily breakable bonds and also serve as structural materials and energy storage in organisms.

What is the simplest hydrocarbon and what does a hydrocarbon mean?

Methane; a hydrocarbon is an organic compound consisting only of carbon and hydrogen.

What is the role of enzymes in metabolism?

Enzymes speed up metabolic reactions, enabling growth, reproduction, and maintaining homeostasis.