Unit 2 AP Biology Exam: Cellular Structure and Function

Cell

The basic structural and functional unit of all living organisms, acting as the smallest unit of life that can perform essential life processes

Prokaryote

A microscopic, single-celled organism that lacks a true nucleus and other membrane-bound organelles

Eukaryote

An organism composed of cells that contain a membrane-bound nucleus and other membrane-bound organelles like mitochondria and chloroplasts

Cytoplasm/Cytosol

The cytoplasm is the entire content within the cell membrane, excluding the nucleus, and is composed of the jelly-like cytosol and various cellular components like organelles and molecular assemblies

Cell Wall

A rigid outer layer surrounding the plasma membrane of cells in plants, fungi, bacteria, algae, and some archaea, providing structural support, protection, and maintaining the cell's shape

Ribosome

A cellular machine made of RNA and protein that translates genetic information from messenger RNA (mRNA) into amino acid chains to synthesize proteins

Nuclear Envelope

The double-layered membrane that surrounds the nucleus in eukaryotic cells, separating the genetic material within the nucleus from the cytoplasm

Nuclear Pores

A large, protein-lined channel through the nuclear envelope that regulates the transport of molecules between the nucleus and the cytoplasm of eukaryotic cells

Nucleoid

The irregular region in a prokaryotic cell (like a bacterium) where its genetic material—the DNA chromosome—is located, but it is not enclosed by a membrane, unlike the nucleus of a eukaryotic cell

Flagella

Long, whip-like appendages that enable cells to move through liquid environments

RER

A network of membranes in eukaryotic cells studded with ribosomes that are essential for synthesizing, processing, and transporting proteins destined for secretion, incorporation into membranes, or delivery to other organelles

SER

Crucial for synthesizing lipids and steroid hormones, metabolizing carbohydrates, detoxifying harmful substances like drugs and poisons, and storing calcium ions, which is especially important for muscle contraction

Golgi Apparatus

A membrane-bound organelle in eukaryotic cells that receives proteins and lipids from the endoplasmic reticulum, modifies them, and then sorts and packages them into vesicles for delivery to other organelles or for secretion outside the cell

Lysosomes

A membrane-bound organelle found in eukaryotic cells, containing powerful digestive enzymes called acid hydrolases that break down waste materials, cellular debris, and foreign invaders

Peroxisome

A small, membrane-bound organelle in eukaryotic cells that performs crucial metabolic functions, including the breakdown of fatty acids and the detoxification of harmful substances like hydrogen peroxide

Vacuole

A membrane-bound organelle found in the cells of plants, fungi, and some protists that serves various functions, including storage of water, nutrients, and waste products, maintaining turgor pressure in plant cells, and facilitating digestion and waste removal

Central Vacuole

A large, membrane-bound organelle in plant cells that stores water, nutrients, ions, and waste products, and plays a crucial role in maintaining turgor pressure and cellular rigidity

Cytoskeleton

A dynamic network of protein filaments and tubules found in the cytoplasm of eukaryotic cells that provides structural support, maintains cell shape, enables cell movement, and facilitates the intracellular transport of organelles and vesicles

Nucleus

A double-membraned organelle found in eukaryotic cells that contains the cell's genetic material in the form of DNA organized into chromosomes

Chromatin

The complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells

Chromosome

A thread-like structure located in the cell's nucleus that consists of long strands of DNA wound around proteins

Nucleolus

A dense, non-membrane-bound structure within the nucleus of a eukaryotic cell that is primarily responsible for producing and assembling ribosomes

Chloroplast

An organelle in plant and algae cells that performs photosynthesis, using chlorophyll to capture light energy from the sun and convert it into chemical energy in the form of glucose and other organic molecules

Thylakoid

A membrane-bound compartment within a chloroplast that contains chlorophyll and other photosynthetic pigments, forming the sites where the light-dependent reactions of photosynthesis take place

Stroma

The structural, non-functional tissue that supports an organ or gland, or the fluid-filled space within a chloroplast where the Calvin cycle of photosynthesis occurs

Granum

A stack of flattened, membrane-bound sacs called thylakoids within the chloroplast of a plant or algal cell

Mitochondria

Double-membraned organelles found in eukaryotic cells that generate most of the cell's energy supply in the form of adenosine triphosphate (ATP) through oxidative phosphorylation

Cristae

The folds of the inner mitochondrial membrane that significantly increase its surface area

Matrix

The non-cellular material surrounding cells in tissues or the internal substance of organelles, providing structural support and a medium for biochemical reactions

Centrosome/Centrioles

The primary microtubule-organizing center (MTOC) in most eukaryotic cells, crucial for cell division and maintaining cell structure

Cilia

Short, hair-like projections from a cell's surface that can be either motile or non-motile

Vesicle (Transport, Secretory)

A small, membrane-bound sac that functions to transport and store substances within a cell

Cell Theory

The fundamental biological principle that (1) all living organisms are made of one or more cells, (2) the cell is the basic unit of structure and function in all organisms, and (3) all cells arise from pre-existing cells through cell division

Endomembrane System

A collection of membranes and organelles within eukaryotic cells, such as the endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane, that collectively work to modify, package, and transport proteins and lipids throughout the cell and for export

Endosymbiotic Theory

Explains the origin of eukaryotic cells by proposing that key organelles, like mitochondria and chloroplasts, were once free-living prokaryotic organisms engulfed by larger host cells

Compartmentalization

The process of dividing a cell or a tissue into distinct, separate compartments, each with specific functions, environments, and specialized structures, often using membranes

Endosymbiont

A type of symbiont (an organism in a symbiotic relationship) that lives inside the body or cells of another organism, known as the host

Surface-area-to-volume ratio

A fundamental concept that compares an object's outer surface area to its internal volume, with a higher ratio indicating more surface area relative to its size

Metabolic Rate

The speed at which an organism uses energy, or calories, to fuel its bodily functions, measured over a specific time period

Microvilli

Tiny, finger-like projections that extend from the surface of some animal cells, particularly epithelial cells, to significantly increase their surface area

Fluid Mosaic model

describes the cell membrane as a flexible, dynamic structure where proteins, cholesterol, and carbohydrates are embedded or attached to a fluid lipid bilayer, allowing for movement and interaction that facilitates cellular functions like transport and signaling

Phospholipid

An amphipathic molecule that is a primary component of all cell membranes. It consists of a hydrophilic (water-attracting) phosphate-containing "head" and two hydrophobic (water-repelling) fatty acid "tails"

Amphipathic

A molecule that has both a hydrophilic (water-attracting) part and a hydrophobic (water-repelling) part

Hydrophilic

Molecules or substances that have a strong affinity for water, meaning they tend to dissolve in water, interact with it, and are attracted to it

Hydrophobic

The property of a substance or molecule that repels water, doesn't dissolve well in water, and tends to cluster together in aqueous environments to minimize its contact with water

Polar

Molecules with an uneven distribution of electrical charge, creating partial positive and negative ends

Nonpolar

Molecules with an equal distribution of electrons, meaning they lack distinct positive and negative ends

Unsaturated fatty acid

A fatty acid containing one or more carbon-carbon double bonds in its hydrocarbon chain, which creates kinks that prevent dense packing, leading to higher membrane fluidity and lower melting points

Saturated Fatty acid

A type of fat with no double bonds between carbon atoms in their chains, making them "saturated" with hydrogen

Cell (plasma) membrane

The outer boundary of all cells, consisting mainly of a phospholipid bilayer that regulates the transport of substances in and out of the cell

Selecvively permable

A membrane allows certain molecules or ions to pass through while restricting others

Passive Transport

The movement of substances across a cell membrane from an area of high concentration to low concentration, a process that does not require energy

Simple Diffusion

The passive movement of molecules from an area of high concentration to low concentration across a membrane, without the need for energy or transport proteins

Facilitated diffusion

The passive transport of molecules across a cell membrane down a concentration gradient with the help of membrane proteins, such as channel or carrier proteins

Active Transport

Moving molecules or ions across a cell membrane against their concentration gradient, meaning from a region of lower concentration to a region of higher concentration

Concentration gradient

The difference in the concentration of a substance between two areas, causing the substance to move from an area of higher concentration to an area of lower concentration

Equilibrium

A state of balance and stability where opposing forces are equal, resulting in no net change in a biological system

Exocytosis

the biological process where a cell expels molecules, by fusing a vesicle with its plasma membrane, which then releases the contents outside the cell

Endocytosis (pino-, phago-, and receptor-mediated endocytosis)

The biological process by which a cell engulfs material from its surroundings, bringing it into the cell within a membrane-bound vesicle

Pino - cell drinking

Phag - Solid particles

Receptor-mediated - uses receptors proteins

Na⁺/K⁺ Pump (ATPase)

A membrane protein that uses energy from ATP to actively transport three sodium (Na+) ions out of a cell for every two potassium (𝐾+) ions it pumps into the cell

Membrane potential

the electrical voltage difference across a cell's plasma membrane, created by the uneven distribution of ions like sodium (Na+), potassium (𝐾+), and chloride (𝐶𝑙−)

Electrochemical gradient

The combined difference in concentration and electric charge across a biological membrane that drives the movement of ions

Aquaporin

Specialized proteins embedded in cell membranes that act as channels for water, allowing it to pass through much faster than it could on its own

Channel Protein

An integral membrane protein that forms a pore or channel through the cell membrane, allowing specific ions or molecules to pass through the membrane via passive transport, such as facilitated diffusion

Carrier Protein

Membrane proteins that help transport specific molecules across the cell membrane by binding to them and changing shape to move them to the other side

Protein Pump

A transmembrane protein that actively transports molecules or ions across a cell membrane against their concentration or electrochemical gradient, requiring energy input

Osmosis

The passive movement of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration

Solute

A substance that is dissolved in a liquid, known as the solvent, to form a solution

Hypotonic

Asolution with a lower solute concentration and a higher water concentration compared to another solution

Hypertonic

A solution with a higher concentration of solutes compared to another solution, such as the inside of a cell

Isotonic

A solution with the same solute concentration as another solution, particularly the fluid inside a cell

Water potential

The measure of the potential energy in water, which determines its tendency to move from one area to another

Solute potential (osmotic potential)

A measure of how much the presence of solutes lowers the water potential of a solution

Pressure potential

The component of water potential that represents the physical pressure exerted by water within a system, such as a plant cell

Osmoregulation

The biological process of maintaining a stable internal balance of water and solutes (like salts) in an organism's body

Contractile vacuole

 A specialized organelles in many single-celled organisms, particularly protists, that regulate internal water balance by collecting and expelling excess water

Osmolarity

A measure of the total concentration of all dissolved solute particles in a solution, expressed as osmoles per liter