A1.1 B1.1 Water, Carbs and Lipids

Where did the first cells originate, and why does liquid water remain essential today?

First cells originated in water; water acts as a liquid solvent for chemical reactions.

What are the primary reasons why water is considered a substance on which all life depends?

Water acts as a vital metabolite and functions as a temperature buffer.

How is the structure of an atom related to the formation of ions?

Ions form when atoms gain or lose electrons, creating a net electrical charge.

What is the difference between an ionic bond and a covalent bond?

Ionic bonds attract opposite charges; covalent bonds involve shared electron pairs.

How does unequal electron sharing lead to polar covalent bonds in water?

Oxygen attracts electrons more strongly than hydrogen, creating partial negative and positive charges.

What causes hydrogen bonds between water molecules, and what is their collective consequence?

Attraction between opposite partial charges of different molecules; collective strength provides high stability.

How is cohesion defined in the context of water molecules?

Water molecules sticking to each other via intermolecular hydrogen bonds.

How does water move through the xylem of a vascular plant under tension?

Evaporation creates negative pressure, pulling a continuous column of cohesive water upward.

What physical cause leads to surface tension, and how does this benefit organisms?

Inward force at the surface creates an elastic membrane used as a habitat.

What is the definition of adhesion, and how does it differ from cohesion?

Adhesion is attraction to other polar/charged surfaces; cohesion is attraction to itself.

Why is water electrostatically attracted to molecules that are polar or charged?

Water is a dipole; its partial charges attract opposite charges on solute molecules.

What is the cause of capillary action, and how does it function in plants and soil?

Caused by adhesion and cohesion; moves water through soil pores and plant cell walls.

In a solution, how do you distinguish between the solvent and the solute?

The solvent is the liquid; the solute is the substance that dissolves in it.

What is solvation, and why can water dissolve many different molecules?

Formation of hydration shells; water's polarity allows interaction with charged or polar solutes.

How does the function of certain molecules depend on them being hydrophobic?

Hydrophobic lipids spontaneously form stable, non-dissolving cell membrane boundaries in aqueous environments.

How does water serve as a medium for metabolism and transport?

Dissolves reactants for metabolic collisions and carries solutes through vascular systems.

Define buoyancy, viscosity, thermal conductivity, and specific heat capacity.

Buoyancy: upward force. Viscosity: flow resistance. Conductivity: heat movement. Specific heat: temperature change resistance.

Why does water have a much higher specific heat capacity than air?

Numerous hydrogen bonds require high energy to break before temperature can rise.

How do water's physical properties affect the Ringed seal and Black-throated loon?

Seals use insulating blubber against heat loss; loons have solid bones to overcome buoyancy.

What unique chemical properties of carbon allow it to form diverse compounds?

Carbon forms four stable covalent bonds, creating complex shapes like rings or chains.

What is the difference between anabolism and catabolism?

Anabolism builds molecules using energy; catabolism breaks down molecules, releasing energy.

How are a monomer and a polymer defined?

Monomer: a single sub-unit. Polymer: many linked monomers.

What occurs during a condensation reaction?

Two monomers covalently join, releasing water as a by-product and requiring energy.

How does a hydrolysis reaction use water to digest polymers?

A water molecule is split to break the covalent bond between monomers.

What is a monosaccharide, and how do pentose and hexose sugars differ?

A single sugar unit; pentose has five carbons, while hexose has six.

What properties of glucose make it central to respiration?

High solubility for transport, chemical stability for storage, and high energy yield.

What are the structural differences between alpha (α) and beta (β) glucose?

Alpha-glucose has Carbon 1 -OH pointing down; beta-glucose has it pointing up.

Compare the structure and function of amylose, amylopectin, and glycogen.

Amylose: unbranched helix. Amylopectin: branched plant storage. Glycogen: highly branched animal storage.

Why are storage polysaccharides typically insoluble and compact?

Insolubility avoids osmotic effects; compactness allows efficient energy storage in small spaces.

How does the alternating orientation of beta-glucose lead to straight cellulose chains?

Every second monomer must be inverted, preventing coiling and producing straight chains.

How do hydrogen bonds contribute to the strength of cellulose microfibrils?

Hydrogen bonds cross-link parallel cellulose chains, bundling them into strong microfibrils.

What are the components of a triglyceride, and what bond connects them?

One glycerol and three fatty acids, connected by ester bonds.

How does a phospholipid differ from a triglyceride?

A phosphate group replaces one fatty acid, making the molecule amphipathic.

What is the difference between saturated, monounsaturated, and polyunsaturated fatty acids?

Saturated: zero double bonds. Monounsaturated: one double bond. Polyunsaturated: multiple double bonds.

How do you distinguish between cis- and trans-unsaturated fatty acids?

Cis: hydrogens on same side (kinked). Trans: hydrogens on opposite sides (straight).

What properties of triglycerides make them suitable for storage in adipose tissue?

High energy density, insolubility preventing osmotic effects, and thermal insulation.

What is the structural feature of a steroid, and why is cholesterol important?

Four fused carbon rings; cholesterol regulates membrane fluidity and acts as hormone precursor.