1.4-1.5 Carbohydrates & Lipids

What are the monomers and polymers of carbohydrates?

Monosaccharides are the monomers (simple sugars), and polysaccharides are the polymers (complex carbohydrates).

What is the typical elemental ratio of C, H, and O in simple monosaccharides like glucose?

A 1:2:1 ratio (e.g., C6H12O6).

What structural form do monosaccharides primarily take in aqueous biological environments?

A cyclic or ring form (strongly favored over the linear form in cells).

How do ribose and deoxyribose differ as five-carbon sugars (pentoses)?

Ribose is the sugar in RNA, while deoxyribose (lacking one oxygen atom) is the sugar in DNA.

What type of covalent bond connects monosaccharides together to form complex carbohydrates?

A glycosidic bond (formed via dehydration synthesis).

What is a disaccharide, and what are three common examples?

A double sugar made of 2 monosaccharides; examples include maltose, lactose, and sucrose.

What structural patterns can complex polysaccharides exhibit?

They can be linear or branched chains depending on the arrangement of their monosaccharide monomers.

Which polysaccharides function as energy storage in plants vs. animals?

Starch stores energy in plants; glycogen stores energy in animals.

Which polysaccharides provide structural support in plant cell walls and arthropod exoskeletons?

Cellulose forms plant cell walls; chitin forms arthropod exoskeletons and fungal cell walls.

What defines lipids, and why are they distinct from other biological macromolecules?

Lipids are nonpolar, hydrophobic molecules that are NOT true polymers.

What are the components that construct a fat (triglyceride)?

One glycerol molecule (a 3-carbon alcohol) attached to three fatty acid chains via ester linkages.

How do saturated fatty acids differ structurally and physically from unsaturated fatty acids?

Saturated fatty acids have only single C-C bonds, are linear, and are solid at room temp (e.g., animal fats). Unsaturated fatty acids have one or more double bonds (causing a kink), and are liquid at room temp (e.g., plant oils).

Why are unsaturated fatty acids liquid at room temperature?

Double bonds create kinks/bents in the hydrocarbon chains, preventing molecules from packing tightly together.

What is the structural composition of a steroid?

A carbon skeleton consisting of four fused rings.

What are the primary functions of steroids in living organisms?

They act as hormones supporting physiological functions (e.g., growth, development, metabolism) and cholesterol provides structural stability in animal cell membranes.

What is the structural makeup of a phospholipid?

Glycerol attached to two fatty acid tails (hydrophobic) and one negatively charged phosphate group head (hydrophilic).

Why is the amphipathic nature of phospholipids crucial for cell membranes?

The hydrophilic phosphate heads face the water inside/outside the cell, while the hydrophobic fatty acid tails face inward, forming a phospholipid bilayer that acts as a selective barrier.