Unit 2 - Cell Structure and Function

These flashcards cover key vocabulary related to cell structure and function, highlighting important organelles, concepts, and their definitions.

Cell

The basic structural and functional unit of every organism.

Prokaryotes

Single-celled organisms that lack a nucleus; includes domains Bacteria and Archaea.

Eukaryotes

Organisms whose cells contain a nucleus and membrane-bound organelles, including protists, fungi, animals, and plants.

Organelles

Membrane-bound structures within eukaryotic cells that perform specific functions.

Endomembrane System

A system of membranes that includes the nuclear envelope, endoplasmic reticulum, Golgi complex, lysosomes, vesicles, and plasma membrane.

Compartmentalization

The organization of cellular functions into specific locations within organelles to increase efficiency and reduce interference.

Nucleus

The membrane-bound organelle that contains chromosomes and is the control center of the cell.

Ribosomes

Molecular machines composed of rRNA and proteins that synthesize proteins by translating mRNA.

Endoplasmic Reticulum (ER)

A network of membranous sacs and tubes involved in synthesizing membranes and proteins; has rough (with ribosomes) and smooth (without ribosomes) types.

Golgi Complex

An organelle that modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

Lysosomes

Membrane-bound organelles containing hydrolytic enzymes for digesting macromolecules and recycling cellular components.

Vacuoles

Large vesicles that transport and store substances in cells, with specific functions such as maintaining turgor pressure in plants.

Mitochondria

Organelles known as the powerhouses of the cell, where cellular respiration occurs to produce ATP.

Chloroplasts

Organelles found in photosynthetic organisms that contain chlorophyll and are the site of photosynthesis.

Cytoskeleton

A network of fibers providing structural support, anchoring organelles, and facilitating movement in the cell.

Microtubules

Hollow rod-like structures made of tubulin that provide support and aid in the movement of organelles.

Microfilaments

Thin solid rods made of actin that maintain cell shape and assist in muscle contraction.

Intermediate Filaments

Fibrous proteins that provide tensile strength and structural stability to cells.

Endosymbiont Theory

The theory that explains the origins of mitochondria and chloroplasts as once independent prokaryotic cells engulfed by eukaryotic cells.

Cellular Metabolism

Depends on Cell Size as at a certain size, it begins to be too difficult for a cell to regulate what comes in and what goes out of the plasma membrane

Cell Function

The size of a cell will dictate it; Cells need a high surface area-to-volume ratio to optimize the exchange of material through the plasma membrane

Surface Area and Volume Ratio

Cells tend to be small: Small cells have a high SA:V ratio; Optimizes exchange of materials at the plasma membrane

Larger cells have a lower SA:V ratio: Lose efficiency exchanging materials; The cellular demand for resources increases; Rate of heat exchange decreases

Plasma Membrane

Separates internal cell environment from external environment; Comprised primarily of phospholipids forming a bilayer

Selective permeability

The ability of membranes to regulate the substances that enter and exit

Fluid Mosaic Model

A model to describe the structure of cell membranes and it is fluid because the membrane is held together by weak hydrophobic interactions and can therefore move and shift and mosaic because it is composited of many macromolecules; Temperature affects fluidity; Unsaturated hydrocarbon tails help maintain fluidity at low temps as kinked tails prevent tight packing of phospholipids

Integral proteins

Proteins that are embedded into the lipid bilayer aka transmembrane proteins; Amphipathic

Peripheral proteins

Proteins that are not embedded into the lipid bilayer; Loosely bonded to the surface

Glycolipids

Carbohydrates bonded to lipids

Glycoproteins

Carbohydrates bonded to proteins; Most abundant

Cell Wall

Found in plant cells that covers their plasma membranes; Provides: Shape/structure, Protection, Regulation of water intake; composed of cellulose; Thicker than plasma membranes; Contain plasmodesmata (Hole-like structures in the cell wall filled with cytosol that connect adjacent cells)

Osmosis

diffusion of water down its concentration gradient across a selectively permeable membrane

Tonicity

the ability of an extracellular solution to cause a cell to gain or lose water; Depends on the concentration of solutes that cannot pass through the cell membrane

Osmoregulation

cells must be able to regulate their solute concentrations and maintain water balance; Animal cells will react differently than cells with cell walls, like plants, fungi, and some protists

isotonic solution

no net movement of water; The concentration of nonpenetrating solutes inside the cell is equal to that outside the cell; Water diffuses into the cell at the same rate water moves out of the cell

hypertonic solution

loses water to their extracellular surroundings; The concentration of nonpenetrating solutes is higher outside of the cell; Water will move to the extracellular fluid; Cells shrivel and die

hypotonic solution

gains water; The concentration of nonpenetrating solutes is lower outside of the cell; The cell will gain water ; Animal cells swell and lyse; Plant cells work optimally

Water potential

a physical property that predicts the direction water will flow; Includes the effects of solute concentration and physical pressure; Water will flow from areas of: High water potential to areas of low water potential, Low solute to areas of high solute concentration, and High pressure to areas of low pressure

Selective Permeability

Some substances can cross the membrane more easily than others; Easy passage across the membrane: Small nonpolar, hydrophobic molecules; Difficult passage or protein assisted passage:

Hydrophilic, polar molecules, large molecules, ions

Passive Transport

transport of a molecule that does not require energy from the cell because a solute is moving with its concentration or electrochemical gradient; Involved in the import of materials and export of waste

Diffusion

spontaneous process resulting from the constant motion of molecules; Substances move from a high to low concentration; Move DOWN the concentration gradient

Facilitated diffusion

diffusion of molecules through the membrane via transport proteins; Increases rate of diffusion for: Small ions, water, carbohydrates; Two categories of transport proteins: channel and carrier: Each transport protein is specific for substances it can facilitate movement for

Channel proteins

rovide a channel for molecules and ions to pass; Channel is hydrophilic; Many are gated channels; Only allow passage when there is a stimulus

Aquaporins

specific channel protein for water

Carrier proteins

undergo conformational changes for substances to pass

Active Transport

transport of a molecule that requires energy because it moves a solute against its concentration gradient

Adenosine Triphosphate (ATP)

Energy source used by cells

Pumps

maintain membrane potential/unequal concentrations of ions across the membrane results in an electrical charge (electrochemical gradient)

Electrogenic pumps

proteins that generate voltage across membranes, which can be used later as an energy source for cellular processes

Proton pump

integral membrane protein that builds up a proton gradient across the membrane; Used by plants, fungi, and bacteria; Pumps H+ out of the cell

Cotransport

the coupling of a favorable movement of one substance with an unfavorable movement of another substance

Exocytosis

the secretion of molecules via vesicles that fuse to the plasma membrane; Vesicles can fuse to the membrane by forming a bilayer

Endocytosis

he uptake of molecules from vesicles fused from the plasma membrane (think: opposite of exocytosis)

Phagocytosis

when a cell engulfs particles to be later digested by lysosomes

Pinocytosis

nonspecific uptake of extracellular fluid containing dissolved molecules