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Active transport: Movement of molecules across the membrane requiring energy (ATP) to move substances against their concentration gradient (low to high concentration).

Amphipathic: Has both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions.

Anaphase: The stage of mitosis where sister chromatids are pulled apart to opposite sides of the cell, ensuring each daughter cell gets a full set of chromosomes.

Apoptosis: Programmed cell death, a controlled process that allows the body to eliminate damaged or unnecessary cells, often during development or in response to DNA damage.

Benign: Refers to a tumor or growth that is non-cancerous, non-invasive, and does not spread to other parts of the body. Benign tumors typically have a favorable prognosis.

Carrier proteins: Proteins that change their shape to move substances across the cell membrane.

Cell cycle: The series of stages through which a cell goes to prepare for division, involving growth, DNA replication, and cell division. It includes interphase, mitosis, and cytokinesis.

Cell membrane: Also called the plasma membrane, is a selectively permeable structure that surrounds the cell, providing protection and regulating the movement of substances in and out.

Cell recognition proteins: Proteins that mark a cell’s identity so that it can be recognized by other cells.

Centromere: The region where two sister chromatids are joined together.

Centrosomes: Regions near the nucleus that contain centrioles, involved in the organization of the microtubules and spindle formation during cell division.

Channel proteins: Proteins that selectively allow materials, such as certain ions, to pass into or out of the cell.

Checkpoint: Control points in the cell cycle where the cell ensures that it is ready to proceed with DNA replication or cell division. If errors are detected, the cell cycle may be halted.

Chromatid: One of the two identical halves of a chromosome after DNA replication.

Chromatin: A complex of DNA and proteins (histones) found in the nucleus, which condenses into chromosomes during cell division.

Cleavage furrow: A groove that forms in the cell membrane during cytokinesis in animal cells, helping to divide the cell into two daughter cells.

Cilia: Short, hair-like projections from the cell surface that are involved in movement of the cell or the movement of substances along the cell surface.

Concentration gradient: A difference in the concentration of a substance across a space or membrane, driving diffusion and osmosis.

Cytokinesis: The final step of cell division, where the cytoplasm divides and two distinct daughter cells are formed.

Cytoplasm: The gel-like substance inside the cell membrane, excluding the nucleus, that contains organelles and the cytosol, where most cellular processes occur.

Cytoskeleton: A network of protein fibers that provides structural support, facilitates cell movement, and plays a role in intracellular transport and cell division.

Cytosol: The gel-like fluid inside a cell where organelles, proteins, and molecules are suspended.

Diffusion: The passive movement of molecules from an area of higher concentration to lower concentration until equilibrium is reached.

Diploid: A cell that contains two full sets of chromosomes (2n), one set from each parent.

Dual receptor proteins: A membrane receptor that can bind to two different ligands or perform two distinct functions within a signaling pathway.

Endocytosis: A process where the cell engulfs substances by forming a vesicle, allowing the intake of large molecules.

Endoplasmic reticulum (ER): An extensive network of membranes involved in protein and lipid synthesis. It comes in two forms: smooth and rough.

Eukaryotic cells: Cells that contain a nucleus and other membrane-bound organelles, such as mitochondria and the endoplasmic reticulum.

Exocytosis: A process where vesicles fuse with the plasma membrane to release substances outside the cell, used for removing waste or secreting proteins.

Extracellular fluid: Watery environments outside of the cell.

Extracellularly: Outside the cell.

Facilitated diffusion: A type of passive transport where molecules (e.g., glucose, ions) move across the membrane with the help of carrier or channel proteins.

Flagella: Long, whip-like structures that enable the cell to move.

Germ (or sex) cells: Reproductive cells (e.g., sperm and eggs) that carry half the genetic information (haploid, n) and combine during fertilization to form a zygote.

Glucose: A simple sugar that serves as the primary energy source for cells, used in cellular respiration to produce ATP.

Glucose transporter: A membrane protein that facilitates the movement of glucose into the cell through facilitated diffusion or active transport.

Golgi apparatus: A stack of membranous sacs involved in the modification, sorting, and packaging of proteins and lipids for secretion or delivery to other organelles.

Growth 1 phase (G1 phase): The first phase of interphase, where the cell grows, synthesizes proteins, and prepares for DNA replication.

Growth 2 phase (G2 phase): The final phase of interphase, where the cell continues to grow and prepares for mitosis by synthesizing proteins necessary for cell division.

Homologous: Refers to chromosomes that are similar in structure, size, and genetic content, one inherited from each parent.

Hypertonic: A solution with a higher solute concentration outside the cell, causing water to move out of the cell, leading to cell shrinkage (crenation in animal cells).

Hypotonic: A solution with a lower solute concentration outside the cell, causing water to move into the cell, which may lead to cell swelling or bursting (lysis in animal cells).

Hydrophilic: Molecules or substances that are attracted to water and can dissolve or interact with it easily.

Hydrophobic: Molecules or substances that repel water and do not dissolve in it.

Integral proteins: Proteins that are embedded in the membrane.

Interphase: The phase of the cell cycle where the cell grows, replicates DNA, and prepares for mitosis.

Ion channel proteins: Membrane proteins that form pores in the cell membrane, allowing specific ions (e.g., Na⁺, K⁺, Ca²⁺, Cl⁻) to pass through.

Isotonic: A solution in which the concentration of solutes is equal inside and outside the cell, resulting in no net movement of water across the membrane.

Ligand: A molecule that binds to a receptor protein to initiate a biological response.

Lipid bilayer: The fundamental structure of the cell membrane, composed of two layers of phospholipids with hydrophobic tails facing inward and hydrophilic heads facing outward.

Lysosome: An organelle containing digestive enzymes that break down waste, cellular debris, and foreign substances.

Meiosis: A type of cell division that reduces the chromosome number by half, producing four genetically unique haploid gametes (sperm or eggs).

Metaphase: The stage of mitosis where chromosomes align in the middle of the cell along the metaphase plate.

Microfilaments: Thin protein fibers that help support the cell shape and assist with movement.

Microtubules: Hollow protein structures that form part of the cytoskeleton and are involved in intracellular transport and cell division.

Mitochondria: Organelles known as the powerhouse of the cell, responsible for ATP production through cellular respiration.

Mitosis: A process of cell division in which a single cell divides to produce two identical daughter cells, maintaining the same chromosome number as the original cell.

Nuclear envelope: A double membrane surrounding the nucleus, containing nuclear pores that regulate the passage of materials between the nucleus and cytoplasm.

Nucleolus: A dense structure within the nucleus responsible for ribosome production.

Nucleoplasm: The gel-like substance inside the nucleus, containing chromatin and the nucleolus.

Nucleus: The control center of the cell, containing genetic material (DNA) and regulating cell activities.

Organelles: Specialized structures within a cell that perform specific functions (e.g., mitochondria, Golgi apparatus, lysosomes).

Osmosis: The passive movement of water molecules across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Passive transport: The movement of substances across the cell membrane without requiring energy, including diffusion, facilitated diffusion, and osmosis.

Peripheral proteins: Proteins that are attached to the surface of the cell membrane and participate in cell signaling and structural support.

Phagocytosis: A type of endocytosis where the cell engulfs large particles or microorganisms, forming a vesicle that fuses with a lysosome for digestion.

Phospholipid: A molecule with a hydrophilic head and two hydrophobic tails that makes up the cell membrane.

Pinocytosis: A type of endocytosis where the cell engulfs extracellular fluid and dissolved substances into small vesicles.

Plasma membrane: Another term for the cell membrane, a selectively permeable barrier that controls the movement of substances in and out of the cell.

Polar: A molecule with regions of partial positive and negative charge, allowing it to interact with water.

Prokaryotic cells: Cells that lack a nucleus and membrane-bound organelles, such as bacteria.

Prophase: The first stage of mitosis, where chromatin condenses into chromosomes, the nuclear envelope breaks down, and spindle fibers begin to form.

Protein synthesis: The process of creating proteins from amino acids using information encoded in DNA and carried out by ribosomes.

Receptor proteins: Proteins in the cell membrane that bind to specific molecules (ligands) to trigger a cellular response.

Ribosomes: Small organelles that synthesize proteins by translating messenger RNA (mRNA).

Rough endoplasmic reticulum (RER): A type of endoplasmic reticulum covered with ribosomes, responsible for protein synthesis and modification.

Selective permeability: The ability of the cell membrane to regulate which substances can enter or exit the cell.

Simple diffusion: The movement of small, nonpolar molecules across the membrane from a higher to a lower concentration without the help of membrane proteins.

Sodium-potassium pump: A transport protein that actively moves sodium ions out of the cell and potassium ions into the cell, maintaining cellular ion balance.

Spindle fibers: Microtubules that form during mitosis and help separate chromosomes.

Telophase: The final stage of mitosis, where chromosomes reach opposite ends of the cell, the nuclear envelope reforms, and the chromosomes decondense into chromatin.

Tonicity: The ability of a solution to affect cell volume by influencing water movement across the membrane.

Transport proteins: Proteins that help move substances across the cell membrane, either passively or actively.

Vacuole: A membrane-bound sac used for storage of substances such as water, nutrients, and waste products.

Vesicle: A small, membrane-bound sac that transports substances within or outside the cell.

Wastes: Unwanted byproducts of cellular metabolism that must be removed to maintain homeostasis, such as carbon dioxide (CO₂) and urea.