Cell Structure, Function, & Organization

What is the correct sequence of the biological hierarchy from simplest to most complex?

Cells → Tissues → Organs → Organ Systems → Organisms

• Cells: Fundamental, elementary unit of life

• Tissues: Groups of similar cells working together for a unified function (e.g., cardiac muscle tissue)

• Organs: Combinations of tissues working together (e.g., heart, kidneys)

• Organ Systems: Interconnected organs collaborating to perform complex bodily functions (e.g., digestive system)

• Organism: Complete individual composed of integrated organ systems working together for survival

What are the three core principles of Modern Cell Theory?

1. Cells represent the most fundamental, elementary unit of life across all organisms

2. All living entities are composed of cells (either unicellular like bacteria, or multicellular like humans)

3. Cells arise from pre-existing cells through cell division

What structures do both Prokaryotes and Eukaryotes share?

1. Genetic material (DNA)

2. Cytoplasm (jelly-like fluid housing structures)

3. Ribosomes (site of protein synthesis; non-membrane-bound)

4. Cell membrane/Plasma membrane (selectively permeable barrier maintaining homeostasis)

What is the major distinction between Prokaryotes and Eukaryotes?

• Prokaryotes (“PRO means NO”): Lack a nucleus and lack membrane-bound organelles (include Bacteria and Archaea)

• Eukaryotes (“EU means DO”): Possess a true membrane-bound nucleus and complex membrane-bound organelles (includes Animals, Plants, Fungi, and Protists)

What is the function of the Nucleus and the Nucleolus?

• Nucleus: Control center of the eukaryotic cell; houses and protects genomic DNA

• Nucleolus: Dense region inside the nucleus responsible for assembling and producing ribosomes

What is the function of Ribosomes, and where are they located?

• Function: Primary site of protein synthesis; they read mRNA instructions and assemble amino acids into polypeptide chains

• Location: Can float freely in the cytoplasm or be anchored to the Rough Endoplasmic Reticulum (RER)

How do the Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER) differ in structure and function?

• Rough ER: Studded with ribosomes; specializes in the synthesis, folding, and transport of proteins via budding transport vesicles

• Smooth ER: Lacks ribosomes; specializes in lipid synthesis and detoxification of harmful substances (highly abundant in liver cells)

What is the role of the Golgi Apparatus?

Acts as the cell’s packaging and distribution center. It receives vesicles from the ER, uses enzymes to modify, sort, and organize molecules, and packages them into vesicles for delivery inside the cell or to the cell membrane for secretion/expulsion.

What is the role of the Mitochondria, and how does it generate cellular energy?

Known as the “Powerhouse of the cell”; produces ATP (adenosine triphosphate) through aerobic cellular respiration, consuming glucose and oxygen.

What are Lysosomes, and what is their role in cell maintenance?

The cell’s waste disposal and recycling system. Membrane-bound sacs filled with digestive hydrolytic enzymes that break down biomolecules (proteins, lipids, carbs), cellular debris, and invasive pathogens like bacteria.

How do Chloroplast and large Vacuoles function in plant cells?

• Chloroplasts: Site of photosynthesis; convert light energy into chemical energy (glucose); contains light-absorbing chlorophyll pigments that reflect green light.

• Vacuoles: Large fluid-filled sacs that store nutrients and waste, sequester toxic substances, and maintain internal hydrostatic pressure (turgor pressure) to support plant cell growth.