Cellular Processes

Unit 3

Cell Theory

ODeveloped in the 1800sOAll living things are made of

one or more cellsOCells are the basic unit of

structure and function in organisms

OAll cells arise from existing cells

Cell Characteristics

OCells are incredibly smallOAllows substances to move

quickly through the bodyOAllows needs of cells to be

met quicklyOMore than 100 trillion cells in a

human body

Common Cell FeaturesOAll cells have certain characteristics

O Cell membrane is an outer boundary and separates inside and outside of the cell – controls what enters and exits the cell

O Cytoplasm is the cell interiorO Cytoskeleton assist with cell

movementO Ribosomes are where proteins are

made

Cell OrganellesO Organelles are structures that carry

out specific functions in a cellO Not all cells have all organellesO Organelles

O Nucleus O Contains all DNAO Codes for all proteinsO Controls function of cells

Cell OrganellesO Other organelles

O Ribosomes make proteinO Endoplasmic reticulum (ER) move proteins

and other substancesO Golgi apparatus modify proteins brought

by the ER and distributes them throughout the cell or to the cell membrane

O Lysosomes break down organic moleculesO Mitochondria produce ATP (energy) for the

cell

Cell MembraneO Have a fluid structure (like a bubble)O Made up of lipidsO Barrier made by lipids separates

inside of the cell and the outsideO Is selectively permeable (determines

what can and cannot enter the cell)O Way phospholipids interact with water

cause the selective permeability

Cell MembraneO Phospholipids are arranged in a lipid

bilayerO Arranged with polar ends on the

outside and inside of the membraneO Nonpolar ends are found in the

middle of the membrane (page 59) – Water repels the nonpolar ends

Proteins and Cell Membranes

O Proteins are embedded in the lipid bilayer (cell membrane)

O There are many different types of proteins in the lipid bilayerO Receptor proteins recognize and bind

to substances outside of cellO Transport proteins help substances

move across the cell membraneO Marker proteins identify the cell typeO Enzymes assist with chemical

reactions

Cholesterol in the Cell Membrane

O Cholesterol is found in every cell membraneO Is useful in maintaining cell

membrane shapeO Helps in identifying different

substances within and outside of the cell

Cell Membrane Diagram

HomeostasisO Homeostasis means maintaining a

balance O Cells must keep proper

concentration of nutrients and water O Cells must remove waste productsO Plasma membrane is selectively

permeable helping to maintain homeostasis

Cell TransportO Cells need to move materials across

the cell membraneO Can be done by active or passive

transportO Passive transport does not require

energyO Active transport does require energy

Passive TransportO Particles move with random motionO Diffusion is when particles move from

an area of high concentration to an area of low concentrationuntil equilibrium is reached (Move across a concentration gradient)

O Diffusion continues after equilibrium is reached

O There is the same amount of material on each side of the cell

O Diffusion of water is osmosis

OsmosisO Water moves into cells through a

selectively permeable membrane when a hypotonic solution is in the cell (Not as much water in the cell as outside)

O Water moves out of cells through a selectively permeable membranewhen a hypertonic solution is in the cell (More water in the cell than outside)

O When solutions are equal, water moves in and out of the cell at the same rate

Osmosis ExampleO If there is more salt inside of a cell

than outside, what will happen?O Water moves across the membrane to

even the concentration of salt water in both areas

O The cell swells with the water moving in

O Solution can be moved out of the cell

Facilitated diffusionO Carrier proteins move substances

across a cellO Still does not require energyO Is used for sugars, ions and salts

Active transportO Active transport occurs when substances must

be moved against a concentration gradient (moving from low concentration to high concentration)

O Proteins that must be pumped across the membrane (sodium/potassium pumps)

O Endocytosis forms a pocket around the material and pulls it into the membrane and in to the cell

O Exocytosis forms a vacuole around the material and joins with the membrane and out of the cell

O Energy is needed in all of these processes (ACTIVE TRANSPORT)

Diversity of Cellular Life

O Unicellular vs. MulticellularO Specialized cells

O Within an organismO Plant vs. Animal

O Levels of organizationO Cells – tissues – organs – organ

systems

Prokaryotic CellsO Prokaryotes are the smallest and

simplest cellsO Bacteria are prokaryotesO Prokaryotes do have:

O Cell walls for structureO Flagella for movement

O Prokaryotes do not have:O NucleusO Many other organelles

Eukaryotic CellsO Eukaryotic cells have a nucleus

O Nucleus contains all genetic information (DNA)

O Many other organelles – structures with different functions

O Structure/Function of cell membraneO Fluid material separating in and out of the

cellO Is selectively permeableO Made of phospholipids in a bilayerO Proteins are in the bilayer and allow

movement in and out of the cell