Lecture 3 - Molecules of Life & Digestion

Comprehensive practice questions covering organic chemistry basics, macromolecules (carbohydrates, lipids, proteins, nucleic acids), metabolism, nutrition, and the human digestive system based on lecture notes.

What is the concentration of carbon in a living organism with and without water included?

Organisms are $18\%$ carbon with water and $50\%$ without water.

How many electrons does carbon have in its outer shell, and what is its bonding capacity?

Carbon has four electrons in its outer shell and a high bonding capacity, forming long, stable chains through covalent bonds.

Define Monomers and Polymers.

Monomers are smaller molecules that combine to create polymers; Polymers are large molecules made up of many similar or identical subunits.

Match the monomers (Monosaccharide, Amino acid, Nucleotide) to their corresponding polymers.

Monosaccharides form Polysaccharides; Amino acids form Polypeptides or Proteins; Nucleotides form Nucleic acids.

What is the elemental ratio found in carbohydrates, and what is the chemical formula for glucose?

Carbohydrates have a $1:2:1$ ratio of Carbon:Hydrogen:Oxygen; the formula for glucose is $C_6H_{12}O_6$.

Differentiate between simple and complex carbohydrates.

Simple carbohydrates are monomers (monosaccharides and disaccharides like glucose and fructose); complex carbohydrates are polymers (polysaccharides like starch, glycogen, cellulose, and chitin).

What are the specific roles of starch, glycogen, cellulose, and chitin?

Starch is for plant energy storage; glycogen is for animal energy storage (liver/muscles); cellulose is for plant cell wall structure; chitin is for arthropod external skeletons and fungi cell walls.

Define the structure and properties of Lipids.

Lipids are non-polar molecules insoluble in water, such as fats, oils, waxes, and hormones, used for energy storage, insulation, and membrane structure.

What is the difference between Saturated and Unsaturated fatty acids?

Saturated fatty acids have no double bonds and are saturated with $H$ atoms; unsaturated fatty acids contain one or more double bonds between carbon atoms.

Compare LDL and HDL cholesterol.

Low-density lipoproteins (LDLs) are 'bad cholesterol' that can clog heart arteries; High-density Lipoproteins (HDLs) are 'good cholesterol' that clear cholesterol from the body and move it to the liver.

What are the two essential fatty acids for humans?

Alpha-linolenic acid (omega-3 fatty acid) and linoleic acid (omega-6 fatty acid).

What is the structure of a Phospholipid?

A charged lipid composed of a glycerol, a phosphate group, and two fatty acids, featuring a hydrophilic head and hydrophobic tails.

How many amino acids exist, and how many are essential to humans?

There are $20$ different amino acids, and $9$ are essential (must be obtained through diet).

Describe the four levels of protein structure.

Primary (amino acid sequence); Secondary (twists and folds by hydrogen bonds); Tertiary (complex 3D shape); Quaternary (two or more bonded polypeptide chains).

What is the function of enzymes and the definition of a catalyst?

Enzymes are proteins that accelerate chemical reactions; catalysts are agents that increase reaction rates without being consumed.

What is protein denaturing?

The loss of protein shape and function due to external stress or hazardous compounds.

Identify the primary differences between DNA and RNA.

DNA is a double helix containing Adenine, Thymine, Cytosine, and Guanine; RNA is involved in protein synthesis and uses Uracil instead of Thymine.

Differentiate between Catabolic and Anabolic metabolic pathways.

Catabolic pathways break down larger molecules and release energy/heat; Anabolic pathways build new molecules and require energy.

What are the caloric values per gram for proteins, carbohydrates, and fats?

Proteins provide $4\,Cal/g$, carbohydrates provide $4\,Cal/g$, and fats provide $9\,Cal/g$.

How are essential vitamins categorized?

Fat soluble ($A, D, E, K$) and Water soluble (B vitamins and Vitamin $C$).

Distinguish between Major Minerals and Trace Minerals.

Major Minerals require more than $100\,mg/day$ (e.g., Calcium, Sodium); Trace Minerals require less than $100\,mg/day$ (e.g., Iron, Iodine).

Explain the role of the Mouth in digestion.

It performs mechanical breakdown and releases salivary amylase (sugar breakdown) and lingual lipase (lipid breakdown).

Define peristalsis and the function of the epiglottis.

Peristalsis is the wave of muscle contractions pushing food along the tract; the epiglottis is cartilage that covers the trachea during swallowing.

What is the composition and environment of the Stomach?

It contains Gastric juice (mixture of $HCl$ and pepsin) with a $pH = 2$, producing a food mixture called chyme.

What are the three parts of the Small Intestine and its main function?

Duodenum, Jejunum, and Ileum; its main function is nutrient absorption ($80\%$ of total absorption occurs here).

State the functions of the Liver and Gallbladder in the digestive process.

The Liver produces bile for fat digestion and regulates nutrients; the Gallbladder stores the bile produced by the liver.

Describe the negative feedback loop for high blood glucose levels.

The Pancreas secretes insulin, which facilitates the conversion of glucose to glycogen for storage, decreasing blood glucose levels.

Describe the negative feedback loop for low blood glucose levels.

The Pancreas secretes glucagon, which facilitates the breakdown of glycogen into glucose, increasing blood glucose levels.

Which structures increase the surface area for absorption in the small intestine?

Intestinal folds, villi, and microvilli, creating a surface area of $200-300\,m^2$.

What are the functions of the components of the Large Intestine?

The Colon, Cecum, and Rectum absorb water and form feces; the Appendix has a minor role in immunity.