Cell Structure & Function Flashcards 9th Grade Biology RVC '26

Vocabulary practice flashcards covering cell structure, organelles, microscopy, and basic cell biology principles based on Ch. 7 Honors Biology notes.

van Leeuwenhoek

The 17th-century scientist credited with inventing the microscope.

Robert Hooke

The scientist who named "cells" in 1665 after observing cork under a microscope.

Schleiden

A scientist who contributed to cell theory by studying plant cells.

Schwann

A scientist who contributed to cell theory by studying animal cells.

Virchow

A scientist who determined that new cells arise only from the division of existing cells.

Cell Theory

The fundamental biological principle stating that all living things are made of one or more cells, cells are the smallest unit of life, new cells come only from the division of existing cells, and each cell passes genetic material to offspring.

Light Microscope

A microscope that enables viewing of the overall shape and structure of a cell by shining visible light through a specimen.

Scanning Electron Microscope (SEM)

An electron microscope developed in the 1950s that uses a beam of electrons to create detailed 3D images of a cell's surface.

Transmission Electron Microscope (TEM)

An electron microscope that sends a beam of electrons through a cell to view its internal structures.

Surface Area to Volume Ratio

A mathematical ratio that limits cell size, where smaller cells have a larger surface area relative to volume compared to larger cells, facilitating efficient nutrient intake and waste disposal.

Prokaryotes

Organisms (such as bacteria) with smaller, simpler cells that lack a membrane-bound nucleus (having DNA in a nucleoid region) or organelles, contain single circular DNA, and divide by binary fission.

Eukaryotes

Organisms (including animals, plants, fungi, and protists) with larger, more complex cells containing a membrane-bound nucleus, linear chromosomes, membrane-bound organelles, a cytoskeleton, and dividing via mitosis.

Fluid Mosaic Model

A model describing the plasma membrane as a flexible mosaic composed of a phospholipid bilayer, embedded transport proteins, and cholesterol molecules.

Phospholipid Bilayer

A two-layered membrane structure in which hydrophilic heads face the outer and inner aqueous environments and hydrophobic tails point inward away from water.

Cholesterol (in membrane)

Molecules embedded within the plasma membrane that help keep the membrane fluid at lower temperatures.

Nucleus

The cell's genetic control center containing chromatin and a nucleolus, enclosed by a double membrane known as the nuclear envelope.

Nucleolus

A structure inside the nucleus that makes ribosomes, which leave through nuclear pores to enter the cytoplasm or attach to the rough ER.

Endomembrane System

A collective network of cellular organelles—including the rough ER, smooth ER, Golgi body, vesicles, and vacuoles—that makes, modifies, and transports proteins and lipids.

Ribosomes

Small circular cellular structures, either free-floating in the cytoplasm or attached to the rough ER, that manufacture proteins.

Rough Endoplasmic Reticulum (Rough ER)

A network of interconnected membranous sacs studded with ribosomes that functions in protein synthesis and folding.

Smooth Endoplasmic Reticulum (Smooth ER)

A region of the endoplasmic reticulum that synthesizes lipids, regulates carbohydrate metabolism, and breaks down toxins and drugs.

Golgi Apparatus

Stacks of membranous sacs that receive and modify products from the ER, then send them to other organelles or the cell membrane.

Lysosomes

Membrane-enclosed sacs budded off the Golgi apparatus containing hydrolytic digestive enzymes that break down food, waste, bacteria, and damaged organelles.

Peroxisomes

Specialized vesicles containing the enzyme catalase to break down fatty acids and convert the toxic waste product hydrogen peroxide ($\text{H}_2\text{O}_2$) into water ($\text{H}_2\text{O}$) and oxygen ($\text{O}_2$).

Central Vacuole

A large organelle found in plant cells that performs lysosomal and water storage functions, helping maintain cell shape and size.

Contractile Vacuole

A specialized vacuole found in protists that pumps out excess water from the cell and aids in movement.

Chloroplasts

Energy-converting organelles found in plants and some protists that convert solar energy into chemical energy in sugars.

Mitochondria

Energy-converting organelles found in all eukaryotic cells that convert chemical energy from food into $\text{ATP}$ to power cellular work.

Endosymbiotic Theory

The scientific theory stating that mitochondria and chloroplasts evolved from free-living prokaryotes that were engulfed by ancestral eukaryotic cells.

Microfilaments

Cytoskeletal fibers composed of actin subunits with a diameter of $7\,\text{nm}$ that enable cells to change shape and move.

Intermediate Filaments

Cytoskeletal fibers composed of fibrous subunits with a diameter of $10\,\text{nm}$ that reinforce cell structure and anchor organelles.

Microtubules

Cytoskeletal tubes composed of tubulin subunits with a diameter of $25\,\text{nm}$ that provide cell rigidity, anchor organelles, and act as tracks for organelle movement.

Cell Wall

A rigid outer layer surrounding the plasma membrane in plant cells, fungi, and prokaryotes that provides structural support and protection.

Cytoplasm

The gelatinous liquid composed of water, salts, and organic molecules that fills the interior of all cells.

Centrioles

Paired organelles composed of microtubule triplets involved in the development of spindle fibers during mitosis in animal cells.

Cilia

Slender protuberances projecting from the cell body that aid in movement or function as a filtration system.

Flagella

Lash-like appendages protruding from the cell body that function primarily in cellular locomotion.

Plasmodesmata

Channels between adjacent plant cells that allow transport and communication across cell walls.