Chapter Three: Cell Structure and Function

Section One: Cell Theory Cells were first discovered by Robert Hooke Anton van Leeuwenhoek was the first to describe cells Cell Theory All organisms are made of cells All existing cells are produced by other living cells The cell is the most basic unit of life

Section One: Cell Theory Cell Parts and Cell Types Part of Every Cell Cytoplasm: a jellylike substance that contains dissolved molecular building blocks (proteins, lipids, carbohydrates) Types of Cells Prokaryotic: no nucleus or membrane bound organelles DNA is suspended in the cytoplasm All are single celled Eukaryotic: have a nucleus and other membrane bound organelles DNA is housed in the nucleus Can be single or multicellular

Section One: Cell Theory

Section Two: Cell Organelles Cell’s Internal Structure Cytoskeleton: a network of proteins that is constantly changing to meet the needs of the cell Made of microtubules, intermediate filaments, and microfilaments Microtubules: give the cell shape and separate DNA during cell division Intermediate filaments: give the cell strength Microfilaments: enable the cells to move and divide

Section Two: Cell Organelles

Section Two: Cell Organelles Eukaryotic Cell Organelles Nucleus The storehouse for most of the genetic information, or DNA in your cells Protects the DNA and makes it available for use when proteins need to be made DNA is found inside the nuclear envelope of the nucleus Contains nucleolus: area where ribosomes are made

Section Two: Cell Organelles Eukaryotic Cell Organelles Endoplasmic Reticulum Called the ER Smooth and Rough ER And interconnected network of thin folded membranes (cisternae) Interior of folds are called lumen Protein and lipids are made here

Section Two: Cell Organelles Eukaryotic Cell Organelles Ribosome Tiny organelles that link amino acids together to form proteins Some are attached to the ER and is why some parts are called rough ER Site of protein synthesis Some ribosomes are suspended in the cytoplasm

Section Two: Cell Organelles Eukaryotic Cell Organelles Golgi Apparatus Closely layered stacks of membrane-enclosed spaces that process, sort, and deliver proteins Has enzymes that make additional changes to proteins Packages and stores some proteins

Section Two: Cell Organelles

Section Two: Cell Organelles Eukaryotic Cell Organelles Vesicles Small membrane bound sacs that divide some materials from the rest the cytoplasm and transport these materials from place to place within the cell Usually short lived and are recycled as needed Transport proteins from the ER to the Golgi Apparatus Transport proteins after they leave Golgi

Section Two: Cell Organelles Eukaryotic Cell Organelles Mitochondria Supply energy to the cell Bean shaped and have 2 membranes Converts molecules from the food you eat into energy through chemical reactions Have their own ribosomes and DNA Suggests that they were once free living prokaryotes that were “eaten” by larger cells

Section Two: Cell Organelles Eukaryotic Cell Organelles Vacuoles Fluid-filled sacs used for storage of materials needed by the cell Can store water, food, enzymes, etc. Plants have a central vacuole for water storage

Section Two: Cell Organelles Eukaryotic Cell Organelles Lysosomes Membrane-bound organelles that contain enzymes Defend the cell from invading bacterial and viruses Break down damaged or worn down cell parts

Section Two: Cell Organelles Eukaryotic Cell Organelles Centrosome Small region of the cytoplasm that produces microtubules Contain centrioles in animals Centriole Cylinder-shaped organelles made of short microtubules arranged in a circle 2 centrioles are perpendicular to each other Doubles with the centrosome before cell division Can organize microtubles to form cilia or flagella

Section Two: Cell Organelles Cell Walls Found in plants, algae, fungi, and most bacteria A rigid layer surrounding the cell membrane that gives protection, support, and shape to the cell NOT IN ANIMAL CELLS!

Section Two: Cell Organelles Chloroplasts Organelles that carry out photosynthesis ONLY IN PLANT CELLS! Have an outer and inner membrane Stacks of disc shaped sacs filled with chlorophyll Have their own ribosomes and DNA Suggests they were once free-living prokaryotes

Section Three: Cell Membrane Cell Membranes Also called the plasma membrane Forms a boundary between cell and the outside environment and controls the passage of materials into and out of the cell Made of a phospholipid bilayer Phospoholipids are made of three parts: a charged phosphate group, glycerol, and two fatty acid chains Glycerol and phosphate form the head and are hydrophilic. This means water loving. Fatty acids form the tail and are hydrophobic, which means water fearing.

Section Three: Cell Membrane Cell Membranes Phospholipid Bilayer The phospholipids arrange themselves in layers The hydrophobic tail are in the center and the hydrophilic heads are on the outside The heads of the outside interact with the watery fluid on the outside of the cell and cytoplasm on the inside of the cell The tails are protected from the watery environment on the inside and outside of the cell by the heads

Section Three: Cell Membrane Cell Membranes Other molecules are found in the cell membrane Cholesterol molecules strengthen the cell membrane Some proteins go through one or both of the phospholipid layers and move materials in and out Some proteins help make up the cytoskeleton Carbohydrates serve as ID tags which allow cells to identify one another

Section Three: Cell Membrane Fluid Mosaic Model Describes the arrangement of molecules that make up the cell membrane Cell membrane is flexible Phospholipids can move from side to side, but cannot flip vertically Proteins cannot move in the membrane

Section Three: Cell Membrane Selective Permeability Property of the cell membrane It allows some materials to go into and out of the cell but not all Allows cell to maintain homeostasis

Section Three: Cell Membrane Chemical Signals and Receptors Receptor: a protein that detects a signal molecule and performs an action in response Recognizes and binds to only certain molecules called ligands Upon binding of the receptor and ligand, they change shape Two Types of Receptors Intracellular Receptors Membrane Receptors

Section Three: Cell Membrane Receptors Intracellular Receptors Located inside the cell Molecules that bind are usually small and nonpolar Ex: hormones Membrane Receptors Located in the cell membrane Receptor sends message to cell interior

Section Three: Cell Membrane

Section Four: Diffusion and Osmosis Passive Transport The movement of molecules across a cell membrane without energy input from the cell 3 types: Diffusion, Osmosis, and Facilitated Diffusion

Section Four: Diffusion and Osmosis Passive Transport Diffusion: the movement of molecules in a fluid or a gas from a region of higher concentration to a region of lower concentration Works through a concentration gradient: the difference in concentration of a substance from one location to another

Section Four: Diffusion and Osmosis Passive Transport Osmosis: the movement of water across a semipermeable membrane from an area of higher concentration to an area of lower concentration Solutions can be described as isotonic, hypotonic, or hypertonic relative to another solution or cell Isotonic: concentration of the solution on the outside is the same as the concentration of a solution on the inside Hypertonic: solution has a higher concentration of particles than the cell Hypotonic: solution has a lower concentration of particles than the cell

Section Four: Diffusion and Osmosis

Section Four: Diffusion and Osmosis Passive Transport Facilitated Diffusion: the diffusion of molecules across a membrane through transport proteins For molecules that can move easily across a membrane Move down the concentration gradient so no energy is used

Section Five: Active Transport, Endocytosis, and Exocytosis Active Transport: drives molecules across the membrane form a region of lower concentration to a region of higher concentration Goes against the concentration gradient Uses transport proteins powered by chemical energy Most common form of energy used is called ATP

Section Five: Active Transport, Endocytosis, and Exocytosis Endocytosis: the process of taking liquids or fairly large molecules into the cell by engulfing them in a membrane The cell makes a pocket around the substance and pinches off the pocket inside the cell to form a vesicle Lysosomal enzmes break down the vesicle components and release it into the cell

Section Five: Active Transport, Endocytosis, and Exocytosis Phagocytosis: a type of endocytosis in which the cell membrane engulfs large particles White blood cells use this to fight infection

Section Five: Active Transport, Endocystosis, andExocytosis Exocytosis: the release of substances out of the cell by the fusion of a vesicle with the membrane Used in nerve cells to transmit signals