Glossary
ATP Production
The process by which cells generate adenosine triphosphate, the main energy currency of the cell, primarily through cellular respiration.
Example:
Efficient ATP production is vital for all cellular activities, from muscle contraction to active transport.
Acidic Interior (Lysosomes)
The low pH environment within lysosomes, maintained by proton pumps, which is optimal for the activity of their hydrolytic enzymes.
Example:
The acidic interior of a lysosome ensures that its digestive enzymes function efficiently, much like how stomach acid aids digestion.
Animal Cells
Eukaryotic cells that lack a cell wall and chloroplasts, typically have centrioles, and obtain nutrients by consuming other organisms.
Example:
Animal cells are diverse, ranging from muscle cells that contract to nerve cells that transmit signals.
Apoptosis
Programmed cell death, a controlled process of cellular self-destruction that is essential for normal development and tissue homeostasis.
Example:
During embryonic development, the webbing between fingers and toes is removed through apoptosis.
Bound Ribosomes
Ribosomes attached to the endoplasmic reticulum that synthesize proteins destined for secretion, insertion into membranes, or delivery to certain organelles.
Example:
Bound ribosomes are responsible for making proteins like insulin, which will be secreted out of the cell to regulate blood sugar.
Cell Wall
A rigid outer layer found in plant cells, fungi, bacteria, and some protists, providing structural support and protection to the cell.
Example:
The sturdy cell wall of a plant prevents it from bursting when it absorbs too much water.
Central Vacuole
A large, membrane-bound sac found in mature plant cells that stores water, nutrients, and waste products, and helps maintain turgor pressure.
Example:
The large central vacuole in a plant cell can swell with water, pushing against the cell wall and keeping the plant upright.
Centrioles
Cylindrical structures found in animal cells, typically in pairs, that organize microtubules and are involved in cell division.
Example:
During cell division, centrioles help form the spindle fibers that pull chromosomes apart.
Chlorophyll
A green pigment found in chloroplasts that absorbs light energy for photosynthesis.
Example:
Without chlorophyll, plants wouldn't be able to capture sunlight and produce their own food.
Chloroplast
Double-membraned organelles found in plant cells and other eukaryotic autotrophs that are the sites of photosynthesis.
Example:
The green color of leaves comes from the numerous chloroplasts within their cells, busy converting sunlight into sugar.
Cis Face
The 'receiving' side of the Golgi apparatus, typically located near the ER, where transport vesicles fuse and deliver their contents.
Example:
Proteins arriving from the ER enter the cis face of the Golgi, ready for further processing.
Contractile Vacuoles
Specialized vacuoles found in some freshwater protists that pump excess water out of the cell to maintain osmotic balance.
Example:
A paramecium uses its contractile vacuole to prevent bursting by expelling water that constantly diffuses in.
Cristae
The numerous folds of the inner mitochondrial membrane that increase its surface area, providing more space for the electron transport chain components.
Example:
The extensive cristae in mitochondria are like terraced fields, maximizing the area available for energy production.
Double Membrane (Mitochondria)
The characteristic two-membrane structure of mitochondria, consisting of a smooth outer membrane and a highly folded inner membrane.
Example:
The double membrane of the mitochondria creates distinct compartments, essential for the different stages of cellular respiration.
Endoplasmic Reticulum (ER)
An extensive network of membranes in eukaryotic cells, continuous with the outer nuclear membrane, involved in protein and lipid synthesis.
Example:
The endoplasmic reticulum (ER) is like a cellular highway system, transporting molecules throughout the cell and serving as a manufacturing site.
Flagella
Long, whip-like appendages that extend from the cell surface, used for locomotion in some prokaryotic and eukaryotic cells.
Example:
Many bacteria use a rotating flagella to propel themselves through liquid environments.
Fluid Mosaic Model
A model describing the plasma membrane as a dynamic structure where proteins are embedded in or associated with a fluid phospholipid bilayer.
Example:
The fluid mosaic model explains why membrane proteins can move laterally, much like icebergs floating in a lipid sea.
Free Ribosomes
Ribosomes suspended in the cytosol that synthesize proteins primarily for use within the cell itself.
Example:
Free ribosomes produce proteins like enzymes for glycolysis, which remain in the cytoplasm to perform their functions.
Genetic Information (DNA)
The hereditary material, deoxyribonucleic acid, found primarily in the nucleus, which carries instructions for building and maintaining an organism.
Example:
The genetic information (DNA) in every human cell contains the blueprint for an entire individual, from eye color to enzyme production.
Golgi Apparatus
An organelle in eukaryotic cells consisting of flattened membranous sacs (cisternae) that modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.
Example:
The Golgi apparatus functions like a cellular post office, receiving, modifying, and then shipping out proteins to their correct destinations.
Hydrolytic Enzymes
Enzymes that catalyze hydrolysis reactions, breaking down large molecules into smaller ones by adding water.
Example:
The hydrolytic enzymes within lysosomes are crucial for digesting worn-out organelles and cellular waste.
Hydrophilic Heads
The water-attracting phosphate groups of phospholipids that face the aqueous environments inside and outside the cell.
Example:
The hydrophilic heads of the cell membrane are like tiny magnets, drawn to the watery cytoplasm and extracellular fluid.
Hydrophobic Tails
The water-fearing fatty acid chains of phospholipids that are tucked away in the interior of the membrane, forming a nonpolar core.
Example:
The hydrophobic tails of the phospholipids huddle together in the membrane's center, avoiding the surrounding water like oil in a salad dressing.
Lysosomes
Membrane-bound organelles containing hydrolytic enzymes that break down waste materials, cellular debris, and foreign invaders.
Example:
When a white blood cell engulfs bacteria, lysosomes fuse with the vesicle to digest the invaders.
Membrane Proteins
Proteins embedded within or associated with the cell membrane, performing various functions such as transport, signaling, and adhesion.
Example:
Specific membrane proteins on a cell's surface act as receptors, allowing it to 'hear' chemical messages from other cells.
Microtubules
Hollow rods made of tubulin protein that are components of the cytoskeleton, involved in cell shape, organelle movement, and chromosome separation.
Example:
Microtubules act as tracks for motor proteins to transport vesicles and organelles throughout the cell.
Mitochondria
Double-membraned organelles in eukaryotic cells that are the primary sites of cellular respiration and ATP production.
Example:
Muscle cells, which require a lot of energy, are packed with mitochondria to generate the necessary ATP for contraction.
Mitochondrial Matrix
The fluid-filled space enclosed by the inner mitochondrial membrane, where the Krebs cycle (citric acid cycle) occurs.
Example:
The mitochondrial matrix is where glucose breakdown continues after glycolysis, releasing carbon dioxide and generating electron carriers.
Nucleolus
A dense structure within the nucleus where ribosomal RNA (rRNA) is synthesized and assembled with proteins to form ribosomes.
Example:
The nucleolus is like a ribosome factory, churning out the components needed for protein synthesis.
Nucleus
A large, membrane-bound organelle in eukaryotic cells that contains the cell's genetic material (DNA) and controls cell activities.
Example:
The nucleus is the cell's command center, directing protein synthesis and cell division.
Phagocytosis
A type of endocytosis where a cell engulfs large particles, such as bacteria or cellular debris, by extending its plasma membrane around them.
Example:
A macrophage performing phagocytosis is like a Pac-Man, consuming foreign particles to protect the body.
Phospholipid Bilayer
The fundamental structure of the plasma membrane, consisting of two layers of phospholipid molecules arranged tail-to-tail.
Example:
The phospholipid bilayer acts like a fence, keeping water-soluble molecules out while allowing small, lipid-soluble ones to pass through easily.
Photosynthesis
The process used by plants, algae, and some bacteria to convert light energy into chemical energy, typically in the form of glucose.
Example:
Through photosynthesis, plants produce the oxygen we breathe and the food that sustains most life on Earth.
Plant Cells
Eukaryotic cells characterized by the presence of a cell wall, chloroplasts, and a large central vacuole, capable of photosynthesis.
Example:
Plant cells are the fundamental units of trees, flowers, and grasses, enabling them to grow and produce food.
Plasma Membrane
A selectively permeable barrier that encloses the cytoplasm of a cell, regulating the passage of substances into and out of the cell.
Example:
The plasma membrane of a nerve cell allows specific ions to flow in and out, enabling the transmission of electrical signals.
Prokaryotic Cells
Simple cells that lack a nucleus and other membrane-bound organelles, with their genetic material located in the cytoplasm.
Example:
Bacteria are prokaryotic cells, much smaller and structurally simpler than the cells that make up your body.
Ribosomes
Non-membrane-bound organelles composed of rRNA and protein, responsible for synthesizing proteins through translation.
Example:
When a cell needs to make a new enzyme, ribosomes are the tiny machines that read the mRNA instructions and assemble the amino acids.
Rough ER
The portion of the endoplasmic reticulum studded with ribosomes, primarily involved in the synthesis, folding, modification, and transport of proteins destined for secretion or insertion into membranes.
Example:
Pancreatic cells, which secrete digestive enzymes, have extensive rough ER to produce and process these proteins.
Site of Translation
The location where the genetic code carried by mRNA is decoded to produce a specific sequence of amino acids, forming a polypeptide chain.
Example:
The site of translation is where the cell's genetic message is finally converted into a functional protein.
Smooth ER
The portion of the endoplasmic reticulum that lacks ribosomes and is involved in lipid synthesis, carbohydrate metabolism, detoxification, and calcium storage.
Example:
Liver cells have abundant smooth ER to help detoxify harmful substances like alcohol and drugs.
Stroma
The fluid-filled space within the inner membrane of a chloroplast, where the Calvin cycle (light-independent reactions) of photosynthesis occurs.
Example:
The enzymes needed for sugar synthesis during photosynthesis are located in the stroma of the chloroplast.
Thylakoids
Flat, interconnected membrane-bound sacs within the chloroplast stroma, where the light-dependent reactions of photosynthesis take place.
Example:
The stacked thylakoids (grana) within a chloroplast are like solar panels, capturing light energy.
Trans Face
The 'shipping' side of the Golgi apparatus, where modified proteins and lipids are packaged into new vesicles for transport to their final destinations.
Example:
Once processed, proteins exit the trans face of the Golgi in vesicles, heading towards the plasma membrane or other organelles.
Vacuoles
Membrane-bound sacs within the cytoplasm of eukaryotic cells that serve various storage and transport functions.
Example:
Some single-celled organisms use vacuoles to store excess water or food particles.
rRNA
Ribosomal RNA, a type of RNA molecule that is a primary component of ribosomes and plays a crucial role in protein synthesis.
Example:
The structural backbone of a ribosome is largely made of rRNA, which also helps catalyze the formation of peptide bonds.