Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test 2026 - Free MCAS Biology Practice Questions and Study Guide

A carbohydrate is defined as an organic compound that is primarily composed of carbon, hydrogen, and oxygen, usually arranged in a ratio of roughly 1:2:1. This means that for every carbon atom, there are typically two hydrogen atoms and one oxygen atom. Carbohydrates serve several critical functions in living organisms, including providing energy, serving as structural components, and playing roles in cell signaling.

The structure of carbohydrates can vary greatly, ranging from simple sugars like glucose to complex polysaccharides like starch and cellulose, but they all share this foundational composition. This understanding is vital in biology, as carbohydrates are a key macromolecule that organisms utilize for energy and as building material for various structures, such as cell walls in plants.

The other options refer to distinct classes of biomolecules. Proteins, for example, are made up of amino acids and serve a wide range of functions, including enzymatic activity and structural roles in cells. Lipids are a different type of organic molecule, generally hydrophobic, involved in long-term energy storage and signaling. Nucleic acids, like DNA and RNA, carry genetic information and play critical roles in heredity and protein synthesis. Each of these has its own unique functions and structures, clearly differentiating