Cellular Processes Unit 3

Cell Theory O Developed in the 1800s O All living things are made of one or more cells O Cells are the basic unit of structure and function in organisms O All cells arise from existing cells

Cell Characteristics O Cells are incredibly small O Allows substances to move quickly through the body O Allows needs of cells to be met quickly O More than 100 trillion cells in a human body

Common Cell Features O All 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 interior O Cytoskeleton assist with cell movement O Ribosomes are where proteins are made

Cell Organelles O Organelles are structures that carry out specific functions in a cell O Not all cells have all organelles O Organelles O Nucleus O Contains all DNA O Codes for all proteins O Controls function of cells

Cell Organelles O Other organelles O Ribosomes make protein O Endoplasmic reticulum (ER) move proteins and other substances O Golgi apparatus modify proteins brought by the ER and distributes them throughout the cell or to the cell membrane O Lysosomes break down organic molecules O Mitochondria produce ATP (energy) for the cell

Cell Membrane O Have a fluid structure (like a bubble) O Made up of lipids O Barrier made by lipids separates inside of the cell and the outside O Is selectively permeable (determines what can and cannot enter the cell) O Way phospholipids interact with water cause the selective permeability

Cell Membrane O Phospholipids are arranged in a lipid bilayer O Arranged with polar ends on the outside and inside of the membrane O 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 bilayer O Receptor proteins recognize and bind to substances outside of cell O Transport proteins help substances move across the cell membrane O Marker proteins identify the cell type O Enzymes assist with chemical reactions

Cholesterol in the Cell Membrane O Cholesterol is found in every cell membrane O Is useful in maintaining cell membrane shape O Helps in identifying different substances within and outside of the cell

Cell Membrane Diagram

Homeostasis O Homeostasis means maintaining a balance O Cells must keep proper concentration of nutrients and water O Cells must remove waste products O Plasma membrane is selectively permeable helping to maintain homeostasis

Cell Transport O Cells need to move materials across the cell membrane O Can be done by active or passive transport O Passive transport does not require energy O Active transport does require energy

Passive Transport O Particles move with random motion O 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

Osmosis O 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 Example O 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 diffusion O Carrier proteins move substances across a cell O Still does not require energy O Is used for sugars, ions and salts

Active transport O 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. Multicellular O Specialized cells O Within an organism O Plant vs. Animal O Levels of organization O Cells – tissues – organs – organ systems

Prokaryotic Cells O Prokaryotes are the smallest and simplest cells O Bacteria are prokaryotes O Prokaryotes do have: O Cell walls for structure O Flagella for movement O Prokaryotes do not have: O Nucleus O Many other organelles

Eukaryotic Cells O 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 membrane O Fluid material separating in and out of the cell O Is selectively permeable O Made of phospholipids in a bilayer O Proteins are in the bilayer and allow movement in and out of the cell