1.1 Molecules, Transport and Health – Key Concepts (Water, Saccharides, Core Practical, Condensation & Hydrolysis, Triglycerides)

A comprehensive set of QUESTION_AND_ANSWER flashcards covering water properties, saccharides, core practical tests, glycosidic bonds, and triglycerides from the provided lecture notes.

What makes a water molecule polar?

Unequal sharing of electrons in the O–H covalent bonds creates δ− on oxygen and δ+ on hydrogen, producing a dipole.

What type of bond holds the H and O atoms together in a water molecule?

Covalent bonds.

Why is water considered a good solvent in biological systems?

Because it is a polar solvent that can dissolve ions and other polar molecules, forming hydration shells around solutes.

What are hydrogen bonds in water and why are they important?

Weak bonds between the δ+ hydrogen of one water molecule and the δ− oxygen of a neighbouring molecule; they give water its cohesion and many properties important to life.

What is a dipole?

A molecule with a positive and a negative pole due to uneven electron distribution.

What defines a polar molecule?

A molecule with areas of partial positive and partial negative charge (dipoles) due to unequal electron distribution.

Define cohesion.

The attraction between water molecules themselves.

Define adhesion.

The attraction of water molecules to surfaces or other substances.

How does water’s polarity support transport in organisms?

Its polarity makes it a powerful solvent and enables dissolution and movement of ions and polar molecules.

What is the role of dissolved solutes in metabolic reactions?

Dissolved solutes become chemically available for reactions and transport within cells and around the body.

What are the three main types of carbohydrates?

Monosaccharides, disaccharides, and polysaccharides.

What are monosaccharides?

Simple sugars; the basic monomer units of carbohydrates.

What is polymerisation in carbohydrates?

Joining many monosaccharides to form disaccharides or polysaccharides (carbohydrate polymers).

Name the carbon-count groups used for monosaccharides.

Triose (3C), pentose (5C), and hexose (6C).

Give an example of a hexose monosaccharide.

Glucose.

Describe glucose’s ring structure as it appears in textbooks.

Glucose commonly forms a ring with carbons 1–5 forming the ring and carbon 6 sticking out above the ring.

What are the two anomeric forms of glucose and how do they differ?

Alpha glucose has the H above C1 and OH below; beta glucose has the H below C1 and OH above.

What is the main function of monosaccharides like glucose?

To store and release energy and to act as building blocks for more complex carbohydrates; they are soluble for transport.

What is a disaccharide?

A sugar formed from two monosaccharides linked by a glycosidic bond.

Explain maltose’s composition and glycosidic bond.

Glucose + glucose linked by a 1,4-glycosidic bond.

Explain sucrose’s composition and glycosidic bond.

Glucose + fructose linked by a 1,2-glycosidic bond.

Explain lactose’s composition and glycosidic bond.

Glucose + galactose linked by a 1,4-glycosidic bond.

What is the function of disaccharides?

Provide a quick-release source of energy; easily broken down to monosaccharides; they are soluble and sweet.

Define a polysaccharide.

A carbohydrate polymer formed by many monosaccharides joined by glycosidic bonds.

Name storage polysaccharides in plants and in animals/fungi.

Plants store starch; animals and fungi store glycogen.

What are the two components of starch?

Amylose (unbranched, 1,4) and amylopectin (branched, 1,4 and 1,6).

Why is starch insoluble in water?

Its insolubility prevents changes to the water potential of cells, aiding storage.

Describe glycogen’s structure and storage.

Highly branched, compact polymer of glucose stored in liver and muscles; insoluble.

How does glycogen differ from amylopectin in branching?

Glycogen is more highly branched, giving many terminal glucose units for rapid release or storage.

What is the general difference between starch and glycogen in terms of storage?

Starch is the plant storage polymer; glycogen is the animal/fungi storage polymer; both store glucose but differ in branching.

What is a glycosidic bond?

A covalent bond formed between monosaccharides during a condensation reaction, releasing a water molecule.

What determines whether a glycosidic bond is 1,4 or 1,6?

The OH group locations on the linked monosaccharides (C1–C4 for 1,4; C1–C6 for 1,6).

What is condensation in carbohydrate formation?

Two hydroxyl groups react to form a glycosidic bond and release a water molecule.

What is hydrolysis in carbohydrate breakdown?

Water is added to break glycosidic bonds, yielding monosaccharides.

What is Benedict’s test used to detect?

Reducing sugars.

What is Benedict’s reagent composed of?

A blue solution containing copper(II) sulfate ions (CuSO4).

What indicates a positive Benedict’s test for reducing sugars?

Color change from blue toward green, yellow, orange, or brown/red depending on sugar concentration.

How are non-reducing sugars tested with Benedict’s reagent?

Hydrolyse with acid (e.g., dilute HCl), neutralise, then perform Benedict’s test.

Why is acid hydrolysis used in testing for non-reducing sugars?

It breaks glycosidic bonds to yield monosaccharides that can act as reducing agents in Benedict’s test.

What is the purpose of a colorimeter in these tests?

To quantify color intensity and estimate sugar concentration via a calibration curve.

What is a calibration curve?

A plot of absorbance versus known concentrations used to determine the concentration of an unknown sample.

What is a serial dilution used for in this context?

To create a set of standards with known concentrations for calibration and comparison.

How is starch detected qualitatively?

Using an iodine solution; starch yields a distinctive blue-black complex.

What does a semi-quantitative iodine test show about starch concentration?

Darker blue-black color indicates higher starch concentration.

What are the core objectives of Core Practical 1: Estimating sugar and starch concentrations?

Use Benedict’s test to detect reducing sugars and iodine test to detect starch, with quantitative support via colorimetry and calibration curves.

What are triglycerides and what are their components?

Lipids formed from glycerol and three fatty acids.

What is the shorthand formula for a fatty acid?

RCOOH.

How are triglycerides formed?

Three fatty acids esterify with glycerol in esterification (a condensation reaction), forming three ester bonds and releasing three water molecules.

What is an ester bond in triglycerides?

Bond between the glycerol hydroxyl group and fatty acid carboxyl group in an ester linkage.

What is the role of glycerol in triglycerides?

Backbone molecule (glycerol) with three hydroxyl groups that bind to fatty acids.

What determines whether a fatty acid is saturated or unsaturated?

Saturated: no C=C bonds; unsaturated: one or more C=C bonds (mono- or poly-).

What is the difference between cis- and trans-fatty acids?

Cis: hydrogen on the same side of the double bond; trans: hydrogens on opposite sides; trans fats are less easily metabolised and linked to CHD.

Give examples of fatty acids often cited for saturated and unsaturated types.

Stearic acid (saturated) and oleic acid (monounsaturated).

Why are lipids like triglycerides important biologically?

They provide energy storage, insulation, buoyancy, and protection; they are non-polar and hydrophobic.

How many carbon atoms can fatty acids have in their chains?

Typically 4 to 24 carbons.

What is the role of water in condensation and hydrolysis reactions?

Condensation forms bonds with release of water; hydrolysis uses water to break bonds.

What is the health concern associated with certain unsaturated fats?

Trans fats; they are not easily metabolised and are linked to coronary heart disease.