Biology Ch. 3

• Unit of life
• All organisms consist of cells
• The smallest unit of life that can function independently

First person to see the outlines of cells

Improved lenses to see cells and drew observations

• All organisms are made of one or more cells
• A cell is the fundamental unit of life
• All cells come from preexisting cells (AKA biogenesis)
• Disproved spontaneous generation

• Glass lenses focus visible light
• Need both the lenses and light

Greater magnification and better resolution but the specimen must be dead

• Uses beam of electrons focused by magnetic field
• Specimen must be dead

scans beam of electrons over metal coated specimen

• Genetic info- DNA
• Proteins-carry out cell's work
• RNA-participates in producing proteins
• Ribosomes-manufacture proteins
• Cytoplasm
• Cell membrane
• Complex cells also have organelles- compartments for specialized function

• All cells are small
• Require large surface area
• Surface area limitation on size of cell
• May be avoided through:
• Flattened shape
• Fingerlike extensions
• specialized organelles to improve efficienct

MAde of lipids and proteins

• Glycerol, 2 fatty acids and a phosphate gorup
• Head is hydrophilic, tail is hydrophobic
• Spontaneously forms a phospholipid bilayer

• When the hydrophilic surfaces form the "bread" layers of the sandwich, exposed to the watery medium outside and inside the cell
• Hydrophobic tails face each other on the inside of the sandwich, away from water

What the cell membrane is often called b/c both proteins and phospholipids are free to move laterally withing the bilayer

• embedded in the phospholipid bilayer
• Creates passageways through which water-soluble molecules and ions pass into or out of the cell

A protein that facilitates chemical reactions that would otherwise not proceed quickly enough to sustain life

Carbohydrates that attach to cell surface proteins and serve as name tags so the body recognizes its own cells

Membrane proteins that enable cells to stick to one another

Exposed on the outer face of the membrane that bind molecules outside the cell and trigger a reaction inside the cell

• When a cell receives an external message and converts it into an internal signal
• Process:
• Receptor proteins bind to stimulus molecule, first messenger
• Triggers chemical reaction whose product is second messenger
• Second messenger provokes cell's response-->activates particular genes or enzymes

• Simplest and most ancient forms of life whos cells lack organelles
• AKA bacteria

Cells that contain organelles

• Bacteria (Prokaryote)
• Archaea (Prokaryote)
• Eukarya (Eukaryote)

• Lack membrane bound nuclei
• 1 circular DNA molecule found in the nucleoid
• Rigid cell wall in most- for protection and shape
• Some have capsule (can protect from white blood cells) and flagella (movement)
• Have one chromosome

• Resemble bacteria superficially
• Phospholipids, cell walls, and flagella unique
• Some are extremofiles-live in harsh environments
• Has pseudopeptoglycons (proteins and sugar)

• Huge diversity in groups
• Larger than prokaryotes

• Ancient organism engulfed another organism and stayed as partners
• Supported by mitochondria and chloroplasts

• Contains- DNA (infor. specifying code for every protein a cell can make
• Nuclear pores through the nuclear envelope-->RNA and ribosomes come out of it
• Nucleolous (assembles ribosomes

• Watery soup of dissolved substances, organelles and cytoskeleton
• Keeps the cell's movement and support

Originates at the nuclear membrane and winds throughout the cell

• Rough ER or RER
• Studded with ribosomes making proteins destined for secretion (like milk)
• Proteins are folded and modified

• Smooth ER or SER
• Synthesizes lipids, detoxifies drugs and poisons
• Lipids and proteins are made by ER exit in vesicles

• The processing center for vesicle contents
• Proteins complete intricate folding and become functional
• Some proteins will become membrane surface proteins
• Others packaged for secretion from the cell

• Contain enzymes that lyse substrates
• Specific pH inside lysosome prevents enzymes from damaging the cell
• In animals

• Found in plants
• Enzymes degrade and recycle materials
• Important in growth and maintaining rigidity

• Dispose of toxic substances
• Some reactions produce hydrogen peroxide (H2O2)
• enzyme produces harmless water molecules
• In animal cells

• The site of photosynthesis
• Uses energy from sunlight to produce glucose
• Occurs specifically in thylakoids
• Endosymbiosis theory support- has own DNA

• Cellular respiration extracts energy from food
• Cristae constains enzymes for cellular respiration
• Also contains its own DNA
• The POWERHOUSE of the cell

• 3 major types: distinguished by protein type, diameter, and aggregation
• 1. Microtubules- largest
• 2. Microfilamets- smallest
• 3. Intermediate filaments- middle size

• Compsed of tubulin (forms hollow tubes)
• Size- 23 nm in diameter
• Assembled, disassemble byadding or removing tubulin molecules--> how they can change length of tube
• Provides for many cellular movements
• Acts as a "train track" within the cell
• Cilia-short, many, for moving and taking in food
• Flagella- long and few

• Composed of Actin
• Size- long thin rods 7 nm in diameter
• Machinery to move

• Size- 10 nm in diameter
• Made of different proteins in different specialized cell types
• Form internal scaffold for the cell

• Location- surround cell membrane of nearly all bacteria, archaea, fungi, algae, and plants
• Not just a barrier
• built of different components
• All plants have a primary cell wall (made of single layer cellulose) very elastic
• secondary wall- layed down inside primary wall- less flexible , more rigid
• Middle lamella holds the two walls together

• Connects adjacent cells
• The openings between cell walls

• Animal cells lack cell walls
• Secrete complex- extracellular matrix
• Intercellular junctions
• 1. tight junctions for impermeable barriars
• 2. Anchoring or adhering junctions connect cells by linking intermediate filaments
• 3. Gap junctions link cytoplasm to adjacent cells