Develop and use a model to explain how the structure of cell organelles relates to their functions within the cell (Louisiana Student Standards for Science, High School Biology, HS-LS1-2).

What this topic is asking

Louisiana's LS1 standards (HS-LS1-2) ask you to model the cell as a system of interacting parts and to explain how each organelle's structure suits its function. For LEAP 2025 Biology you should know what the main organelles do and, more importantly, be able to predict which organelle a cell needs based on its job. The test often presents a specialized cell and asks which organelle it would have in large numbers, which is the structure-and-function crosscutting concept in action.

The control center and the genetic library

Because the nucleus holds the DNA, it is effectively the cell's information center: every protein the cell builds is coded by a gene read from the DNA inside the nucleus. This links the nucleus to protein synthesis, covered in the genetics module.

Releasing energy: the mitochondria

When a LEAP item describes a cell that does a lot of work, moves a lot, or actively transports many substances, the expected answer for "which organelle would be abundant" is usually mitochondria, because all of that work needs ATP.

Making and shipping proteins

Several organelles work as a team to produce and export proteins:

• Ribosomes build proteins by joining amino acids in the order coded by the mRNA. They can float free in the cytoplasm or sit on the rough ER.
• The rough endoplasmic reticulum (rough ER) is a membrane network covered in ribosomes; it folds the new proteins and transports them onward. Cells that export a lot of protein have a lot of rough ER.
• The smooth endoplasmic reticulum has no ribosomes and makes lipids.
• The Golgi apparatus receives proteins from the ER, then modifies, packages, and ships them to where they are needed inside or outside the cell.

This assembly line (ribosome to rough ER to Golgi) is a favorite for "explain why this cell has a lot of organelle X" questions.

Plant-cell organelles and storage

Chloroplasts are found only in plant cells (and some protists). They contain the green pigment chlorophyll and are the site of photosynthesis, where light energy is captured to make glucose. Vacuoles store water, food, and waste; a plant cell has one large central vacuole that helps keep the cell firm (turgid), while animal cells have only small vacuoles. The cell wall (plant cells) and the cell membrane (all cells) handle support and transport, and they have their own topic.

Try this

Q1. State the function of the nucleus and the function of the mitochondria. [2]

• Cue. Nucleus stores DNA and controls the cell; mitochondria release energy by cellular respiration.

Q2. Explain why a root-tip cell that actively absorbs minerals from the soil would contain many mitochondria. [2]

• Cue. Active absorption (active transport) requires energy as ATP, which mitochondria supply by cellular respiration, so a cell doing a lot of active transport needs many mitochondria.