Movement of molecules across a cell membrane from a region of low concentration to high concentration, requiring energy in the form of ATP. This is against the concentration gradient and is essential for maintaining cellular ion balances and nutrient uptake.

A carrier protein that actively transports 3 Na⁺ out of the cell and 2 K⁺ in using 1 ATP. Critical for nerve impulse transmission, muscle contraction, and maintaining resting membrane potential.

Process by which cells engulf large particles or fluids by wrapping the plasma membrane around them to form a vesicle. Requires energy (ATP).

“Cell eating” – a type of endocytosis where large solid particles (e.g., bacteria, dead cells) are engulfed and taken into the cell. Common in immune cells like macrophages and white blood cells.

Process by which cells release large molecules (e.g., hormones, neurotransmitters, waste) by fusing secretory vesicles with the plasma membrane. Requires ATP.

Organelle in freshwater protists (e.g., Paramecium, Amoeba, Euglena) that collects excess water and expels it via exocytosis to maintain osmotic balance in hypotonic environments.

The ability of a cell to maintain a stable internal environment despite changes in external conditions. Involves regulation of temperature, pH, ion concentrations, and water balance.

All chemical reactions within a cell that sustain life, including catabolism (breaking down molecules for energy) and anabolism (building complex molecules).

Mnemonic for essential life processes:
Regulation, Reproduction, Respiration,
Growth, Excretion, Nutrition, Transport, Synthesis

Control and coordination of all life functions via hormones, nerves, and feedback systems.

Production of new individuals of a species (asexual or sexual). At the cellular level: mitosis (growth/repair) or meiosis (gamete formation).

Breaking down glucose to transfer energy to ATP molecules. Includes glycolysis, Krebs cycle, and electron transport chain (aerobic) or fermentation (anaerobic).

Increase in cell size (hypertrophy) and/or cell number (hyperplasia).

Elimination of cellular waste: nitrogenous wastes (urea, ammonia), CO₂, excess water, salts.

1) Ingestion – taking in food
2) Digestion – breaking down food into absorbable units
3) Egestion – removal of undigested waste

Absorption, circulation, and distribution of materials to cells (via bloodstream) or within cells (cytoplasm). Includes diffusion, active transport, vesicular transport.

Chemical reactions that combine small compounds to form larger, complex molecules (e.g., protein synthesis, lipid synthesis).

Simple cells lacking a nucleus and membrane-bound organelles. DNA is in a nucleoid region. Includes bacteria and archaea. Usually unicellular.

Complex cells with a true nucleus and membrane-bound organelles. DNA in linear chromosomes within nucleus. Includes protists, fungi, plants, animals.

Single-celled (unicellular): Entire organism is one cell (e.g., bacteria, amoeba).
Multi-celled (multicellular): Organism made of many specialized cells working together (e.g., humans, trees).

Cell → Tissue → Organ → Organ System → Organism
Smallest to largest unit of structural/functional organization.

Process by which unspecialized stem cells develop into specialized cells with specific structures and functions (e.g., muscle, nerve, blood cells).

Control center of the cell. Contains DNA (chromatin/chromosomes) and nucleolus. Surrounded by nuclear envelope with pores.

Thread-like DNA-protein complex. Condenses into chromosomes during cell division. Contains genes.

Dense region inside nucleus where rRNA is synthesized and ribosomes are assembled.

Paired cylindrical structures made of microtubules. Organize spindle fibers during animal cell division (mitosis).

Double membrane with nuclear pores that regulates transport of mRNA, ribosomes, and proteins between nucleus and cytoplasm.

Tubular network without ribosomes. Functions: lipid synthesis, detoxification, calcium storage.

Studded with ribosomes. Site of protein synthesis and modification for secretion or membrane insertion.

Small structures (70S in prokaryotes, 80S in eukaryotes) made of rRNA and protein. Site of protein synthesis (translation). Found free in cytoplasm or attached to RER.

Stack of flattened sacs. Modifies, sorts, and packages proteins and lipids from the ER into vesicles for secretion or use within the cell.

Fluid-filled sac for storage (water, ions, nutrients, waste). Small and numerous in animal cells; large central vacuole in plant cells.

Membrane-bound vesicles containing hydrolytic enzymes. Break down macromolecules, old organelles, and engulfed pathogens. “Cellular recycling center.”

Double-membrane organelle with cristae (inner folds). Site of cellular respiration – produces ATP via oxidative phosphorylation. Has its own circular DNA.

Jelly-like fluid (cytosol + organelles) inside the cell but outside the nucleus. Site of glycolysis, protein synthesis, and many metabolic pathways.

Phospholipid bilayer with embedded proteins. Regulates what enters/exits the cell. Maintains cell shape and enables communication.

Large, fluid-filled organelle occupying up to 90% of plant cell volume. Stores water, ions, pigments, toxins. Maintains turgor pressure for structural support.

Rigid layer outside plasma membrane made of cellulose (plants), chitin (fungi), or peptidoglycan (bacteria). Provides shape, support, and protection.

Double-membrane organelles containing chlorophyll. Site of photosynthesis – convert light energy into chemical energy (glucose). Contain thylakoids and stroma. Have own DNA.

Network of protein fibers providing structural support, shape, and enabling movement (cell crawling, organelle transport, cytokinesis).

Hollow tubes made of tubulin. Involved in:

• Maintaining cell shape
• Chromosome separation in mitosis
• Forming cilia, flagella, centrioles
• Intracellular transport (with motor proteins kinesin/dynein)

Thin fibers made of actin. Involved in:

• Muscle contraction (with myosin)
• Cell movement (amoeboid motion)
• Cytokinesis (contractile ring)
• Cell shape and anchorage

Step-by-step journey of a secreted protein:
1. RER – Protein synthesized by ribosomes
2. Transport vesicle – Buds from RER, carries protein to Golgi
3. Golgi apparatus – Modifies, sorts, packages protein
4. Secretory vesicle – Carries protein to plasma membrane
5. Exocytosis – Vesicle fuses with membrane, releases protein outside cell