AP Bio - Unit 2: Cells

The cell

The simplest collection of matter that can be alive

Cells

Basic structural and functional units of every organism

Prokaryotic cells

Domains Bacteria and Archaea; no nucleus or membrane-bound organelles

Eukaryotic cells

Protists, fungi, plants, and animals; contain nucleus and membrane-bound organelles

Cell membrane

Boundary that encloses all cells

Cytosol

Jellylike substance inside the cell where organelles are suspended

Chromosomes

Structures that contain DNA

Ribosomes

Structures that synthesize proteins

Nucleus

Control center of the cell; contains DNA and mRNA

Nuclear envelope

Double membrane surrounding the nucleus

Nuclear pores

Regulate what enters and leaves the nucleus

Chromatin

DNA + protein complex that makes up chromosomes

Nucleolus

Region where ribosomal subunits are formed

Ribosomes are

Protein synthesis structures made of rRNA and proteins

Free ribosomes

Produce proteins used within the cell

Bound ribosomes

Attached to ER; make proteins for export or membranes

Endomembrane system

Includes nuclear envelope, ER, Golgi, lysosomes, vesicles, vacuoles, and plasma membrane

Vesicles

Membrane sacs used for transport

Endoplasmic reticulum (ER)

Network of membranes involved in protein and lipid synthesis and transport

Rough ER

Has ribosomes; protein synthesis and compartmentalization

Smooth ER

Synthesizes lipids and detoxifies the cell

Golgi apparatus

Modifies, packages, and ships materials in vesicles

Cisternae

Flattened membrane sacs of the Golgi

Cis face

Golgi side that receives vesicles

Trans face

Golgi side that ships vesicles

Lysosomes

Membrane sacs with hydrolytic enzymes for digestion

Lysosome function

Intracellular digestion, recycling materials, apoptosis

Vacuoles

Membrane-bound sacs for storage

Central vacuole

Large plant vacuole that stores water and maintains turgor pressure

Mitochondria

Site of cellular respiration and ATP production

Cristae

Folds of inner mitochondrial membrane that increase surface area

Matrix

Inner fluid-filled compartment of mitochondria

ATP

Short-term energy storage molecule

Chloroplasts

Site of photosynthesis in plants

Thylakoids

Membrane disks where light reactions occur

Grana

Stacks of thylakoids

Stroma

Fluid surrounding thylakoids

Chlorophyll

Pigment that captures light energy

Peroxisomes

Break down fatty acids and detoxify alcohol using H2O2

Cytoskeleton

Network of protein fibers for support, motility, and regulation

Microtubules

Involved in chromosome movement and cell division

Microfilaments

Cell shape, movement, and division

Intermediate filaments

Anchor nucleus and organelles

Centrosome

Microtubule-organizing center

Centrioles

Cylinders involved in cell division

Flagella

Long, few structures that propel cells

Cilia

Short, numerous structures for movement or fluid flow

Cell wall

Rigid layer that protects plant cells and maintains shape

Cellulose

Main component of plant cell walls

Plasmodesmata

Channels connecting plant cells

Extracellular matrix (ECM)

Network outside animal cells made of glycoproteins

ECM function

Strengthens tissues and transmits signals

Tight junctions

Watertight seals between animal cells

Desmosomes

Rivet-like junctions that hold cells together

Gap junctions

Channels allowing ions and small molecules to pass

Prokaryote

No nucleus, DNA in nucleoid, small and simple

Eukaryote

Has nucleus, organelles, larger and more complex

Animal cells

No cell wall, no chloroplasts, store energy as glycogen

Plant cells

Have cell wall, chloroplasts, central vacuole, store starch

Endosymbiont theory

Mitochondria and chloroplasts evolved from engulfed prokaryotes

Endosymbiont evidence

Double membranes, own DNA and ribosomes, independent reproduction

Cell size

Cells must be small to maintain high surface area to volume ratio

Surface area to volume ratio

Affects rate of exchange with environment

Plasma membrane

Selectively permeable barrier

Fluid mosaic model

Membrane is fluid with embedded proteins

Phospholipid bilayer

Double layer of amphipathic phospholipids

Amphipathic

Hydrophilic head and hydrophobic tail

Hydrophobic barrier

Prevents passage of ions and polar molecules

Membrane fluidity

Affected by temperature, unsaturated fats, and cholesterol

Cholesterol

Maintains membrane stability across temperatures

Integral proteins

Embedded in membrane; often transmembrane

Peripheral proteins

Attached to membrane surface

Membrane protein functions

Transport, enzymes, signaling, recognition, adhesion

Carbohydrates on membrane

Cell-cell recognition and communication

Glycoproteins

Proteins with carbohydrate chains

Glycolipids

Lipids with carbohydrate chains

Selective permeability

Membrane allows some substances to cross more easily

Small nonpolar molecules

Cross membrane easily (O2, CO2, N2)

Ions and large polar molecules

Require transport proteins

Passive transport

No ATP required; movement down gradient

Diffusion

Movement from high to low concentration

Osmosis

Diffusion of water

Hypotonic solution

Less solute than cell; water enters cell

Hypertonic solution

More solute than cell; water leaves cell

Isotonic solution

Same solute concentration; no net water movement

Facilitated diffusion

Transport proteins help molecules cross membrane

Channel proteins

Provide hydrophilic passageway

Carrier proteins

Bind and carry molecules across membrane

Aquaporins

Water channel proteins

Active transport

Requires ATP; moves against gradient

Electrogenic pumps

Generate voltage across membrane

Sodium-potassium pump

Pumps Na+ out and K+ into cell

Proton pump

Moves H+ across membrane

Cotransport

Downhill movement of one solute drives uphill transport of another

Bulk transport

Movement of large molecules via vesicles

Endocytosis

Cell takes material in via vesicles

Exocytosis

Vesicles fuse with membrane to release contents

Water potential

Measurement of the amount of free energy in a mole of water; indicates how likely water is to move

Free energy

Energy available to do work or cause movement

What water potential measures

How likely water molecules are to move from one place to another