exam 2 Prin Bio Lec

Cytology

The study of cells.

Magnification

The process of enlarging the appearance of an object.

Resolution

The ability to distinguish two close objects as separate; determines image clarity.

Contrast

The difference in brightness between parts of a specimen that makes structures visible.

Micrometer (µm)

One millionth of a meter (10⁻⁶ m).

Nanometer (nm)

One billionth of a meter (10⁻⁹ m).

Cell fractionation

Process of separating cell components using centrifugation to isolate organelles.

Cytosol

The jelly-like fluid inside the cell where organelles are suspended.

Nucleoid

The DNA-containing region of a prokaryotic cell that is not membrane-bound.

Microvilli

Finger-like projections that increase surface area for absorption.

Phospholipids

Molecules with a hydrophilic phosphate head and hydrophobic fatty acid tails that form the plasma membrane.

Chromatin

Uncoiled DNA and proteins found in the nucleus.

Chromosome

Condensed chromatin visible during cell division.

Nucleolus

Region of the nucleus where rRNA is made and ribosomes are assembled.

Endomembrane system

The network of membranes including the nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane.

Cristae

Folds of the inner mitochondrial membrane that increase surface area for ATP production.

Mitochondrial matrix

The fluid-filled interior of the mitochondrion where the Krebs cycle occurs.

Thylakoids

Flattened membrane sacs in chloroplasts where the light-dependent reactions of photosynthesis occur.

Stroma

The fluid surrounding thylakoids where the Calvin cycle occurs.

Cilia

Short, numerous projections used for movement or moving fluids across a cell's surface.

Flagella

Long whip-like projections used for cell movement.

Pseudopodia

Temporary extensions of the cytoplasm used for movement and feeding.

Cell wall

Rigid outer layer that provides support and protection in plants, fungi, and bacteria.

Plasmodesmata

Channels through plant cell walls that connect adjacent cells.

Extracellular matrix (ECM)

Network outside animal cells that provides support, attachment, and communication.

Tight junctions

Cell junctions that prevent leakage between adjacent animal cells.

Desmosomes

Cell junctions that anchor neighboring cells together.

Gap junctions

Cell junctions that allow ions and small molecules to pass directly between animal cells.

Light microscope

Uses visible light; can observe living cells; lower magnification and resolution than electron microscopes.

Electron microscope

Uses beams of electrons; provides much higher magnification and resolution; specimens must be dead.

Prokaryotic cells

Cells without a nucleus or membrane-bound organelles; found in bacteria and archaea.

Eukaryotic cells

Cells with a nucleus and membrane-bound organelles; found in plants, animals, fungi, and protists.

Features of every cell

Plasma membrane, cytoplasm, DNA, and ribosomes.

Plasma membrane

Selectively permeable barrier that regulates what enters and leaves the cell.

Nucleus

Stores DNA and controls cell activities.

Ribosomes

Site of protein synthesis.

Rough endoplasmic reticulum (Rough ER)

Contains ribosomes; synthesizes proteins for secretion and membranes.

Smooth endoplasmic reticulum (Smooth ER)

Synthesizes lipids, detoxifies drugs, and stores calcium ions.

Golgi apparatus

Modifies, sorts, packages, and ships proteins and lipids.

Lysosome

Contains digestive enzymes that break down food, pathogens, and worn-out organelles.

Transport vesicle

Membrane-bound sac that transports materials throughout the cell.

Vacuole

Stores water, nutrients, and wastes; central vacuole helps maintain plant cell pressure.

Peroxisome

Breaks down fatty acids and detoxifies harmful substances such as hydrogen peroxide.

Mitochondria

Produce ATP through cellular respiration.

Chloroplast

Carry out photosynthesis in plant cells.

Cytoskeleton

Provides shape, support, movement, and organelle transport.

Microtubules

Hollow tubes involved in cell shape, chromosome movement, organelle transport, cilia, and flagella.

Microfilaments

Thin actin fibers involved in muscle contraction, cell movement, and cell division.

Intermediate filaments

Rope-like fibers that strengthen cells and anchor organelles.

Selective permeability

The property of a membrane that allows some substances to pass while preventing others from crossing.

Amphipathic

Having both a hydrophilic (water-loving) region and a hydrophobic (water-fearing) region.

Passive transport

The movement of substances across a membrane without using cellular energy (ATP).

Diffusion

The net movement of molecules from an area of higher concentration to an area of lower concentration.

Dynamic equilibrium

A state in which molecules continue to move, but there is no net change in concentration.

Osmosis

The diffusion of water across a selectively permeable membrane.

Aquaporins

Special channel proteins that allow water molecules to move quickly across cell membranes.

Tonicity

The ability of a solution to cause a cell to gain or lose water.

Isotonic

A solution with the same solute concentration as the cell; there is no net movement of water.

Hypertonic

A solution with a higher solute concentration than the cell; water leaves the cell.

Hypotonic

A solution with a lower solute concentration than the cell; water enters the cell.

Osmoregulation

The regulation of water balance within cells and organisms.

Facilitated diffusion

Passive transport using transport proteins to move substances across a membrane.

Channel proteins

Transport proteins that form pores or channels allowing specific molecules or ions to cross the membrane.

Carrier proteins

Transport proteins that bind to molecules and change shape to move them across the membrane.

Active transport

The movement of substances against their concentration gradient using ATP.

Membrane potential

The electrical potential difference across a cell membrane caused by unequal ion distribution.

Electrogenic pump

A membrane protein that pumps ions across the membrane, creating a voltage difference.

Cotransport

A type of active transport in which the movement of one substance down its concentration gradient powers the movement of another substance against its gradient.

Exocytosis

The process by which vesicles fuse with the plasma membrane to release substances outside the cell.

Endocytosis

The process by which the plasma membrane surrounds and brings substances into the cell by forming vesicles.

Plasma membrane

A selectively permeable barrier composed mainly of phospholipids and proteins that surrounds the cell.

Fluid mosaic model

The model describing the plasma membrane as a flexible phospholipid bilayer with embedded proteins that move freely.

Phospholipid bilayer

Two layers of phospholipids that form the basic structure of the plasma membrane.

Hydrophilic head

The phosphate-containing region of a phospholipid that is attracted to water.

Hydrophobic tails

The fatty acid chains of a phospholipid that repel water.

Integral protein

A protein embedded within the phospholipid bilayer, often involved in transport or signaling.

Peripheral protein

A protein attached to the surface of the membrane, often involved in support or communication.

Glycoprotein

A membrane protein with attached carbohydrate chains used in cell recognition.

Glycolipid

A membrane lipid with attached carbohydrate chains used for cell recognition.

Cholesterol

A lipid that stabilizes animal cell membranes by regulating membrane fluidity.

Concentration gradient

The difference in the concentration of a substance across a space or membrane.

Solute

A substance dissolved in a solvent.

Solvent

The substance in which a solute dissolves; water is the most common solvent in cells.

Solution

A mixture of solute dissolved in solvent.

Transport protein

A membrane protein that helps move substances across the membrane.

Bulk transport

The movement of large molecules or particles using vesicles through endocytosis or exocytosis.

Receptor protein

A membrane protein that receives chemical signals from outside the cell.

Recognition protein

A membrane protein that identifies cells using carbohydrate chains.

Enzymatic protein

A membrane protein that catalyzes chemical reactions.

Adhesion protein

A membrane protein that joins neighboring cells together.

Cell signaling

The process by which cells communicate using chemical messengers.

Receptor-mediated endocytosis

Endocytosis in which receptor proteins bind specific molecules before bringing them into the cell.

Phagocytosis

A type of endocytosis in which a cell engulfs large particles or microorganisms ("cell eating").

Pinocytosis

A type of endocytosis in which a cell takes in extracellular fluid ("cell drinking").

Structure of the plasma membrane

A phospholipid bilayer containing proteins, cholesterol, and carbohydrates.

Main function of the plasma membrane

Controls what enters and leaves the cell while protecting the cell.

Fluid mosaic model explanation

The membrane is fluid because phospholipids move sideways and mosaic because many different proteins are embedded throughout it.

Effect of high temperature on membrane fluidity

Increases membrane fluidity by causing phospholipids to move faster.

Effect of low temperature on membrane fluidity

Decreases membrane fluidity by slowing phospholipid movement.

Role of cholesterol in membranes

Prevents membranes from becoming too rigid in cold temperatures and too fluid in warm temperatures.