Essential Knowledge 4.A.2

The structure and function of subcellular components, and their interactions, provide essential cellular processes.

Ribosomes are small, universal structures comprised of two interacting parts: ribosomal RNA and protein. In a sequential manner, these cellular components interact to become the site of protein synthesis where the translation of the genetic instructions yields specific polypeptides.

Endoplasmic reticulum (ER) occurs in two forms: smooth and rough. Rough endoplasmic reticulum functions to compartmentalize the cell,

serves as mechanical support, provides site-specific protein synthesis with membrane-bound ribosomes and plays a role in intracellular transport. In most cases, smooth ER synthesizes lipids.

The Golgi complex is a membrane-bound structure that consists of a series of flattened membrane sacs (cisternae). Functions of the Golgi include synthesis and packaging of materials (small molecules) for transport (in vesicles), and production of lysosomes.

Mitochondria specialize in energy capture and transformation. Mitochondria have a double membrane that allows compartmentalization

within the mitochondria and is important to its function.The outer membrane is smooth, but the inner membrane is highly convoluted, forming folds called cristae. Cristae contain enzymes important to ATP production; cristae also increase

the surface area for ATP production.

Lysosomes are membrane-enclosed sacs that contain hydrolytic enzymes, which are important in intracellular digestion, the recycling of a cell’s organic materials and programmed cell death (apoptosis). Lysosomes carry out intracellular digestion in a variety of ways.

A vacuole is a membrane-bound sac that plays roles in intracellular digestion and the release of cellular waste products. In plants, a large vacuole serves many functions, from storage of pigments or poisonous substances to a role in cell growth. In addition, a large central vacuole allows for a large surface area to volume ratio.

Chloroplasts are specialized organelles found in algae and higher plants that capture energy through photosynthesis. The structure and function relationship in the chloroplast allows cells to capture the energy available in sunlight and convert it to chemical bond energy via photosynthesis. Chloroplasts contain chlorophylls, which are responsible for the green color of a plant and are the key light-trapping molecules in photosynthesis. There are several types of chlorophyll, but the predominant form in plants is chlorophyll a. Chloroplasts have a double outer membrane that creates a compartmentalized structure, which supports its function. Within the chloroplasts are membrane-bound structures called thylakoids. Energy-capturing reactions housed in the thylakoids are organized in stacks, called “grana,” to produce ATP and NADPH₂, which fuel carbon-fixing reactions in the Calvin-Benson cycle. Carbon fixation occurs in the stroma, where molecules of CO₂ are converted to carbohydrates.

Students should be able to:

LO 4.4 make a prediction about the interactions of subcellular organelles.

LO 4.5 construct explanations based on scientific evidence as to how interactions of subcellular structures provide essential functions.

LO 4.6 use representations and models to analyze situations qualitatively to describe how interactions of subcellular structures, which possess specialized functions, provide essential functions.