Understanding Homeostasis at the Cellular Level CELL THEORY AND STRUCTURE

What are the 3 parts of the Cell Theory? All living things are made of cells Cells are the basic unit of structure and function in an organism (basic unit of life) Cells come from the reproduction of existing cells (cell division)

History of Cells & the Cell Theory In 1665,Hooke is responsible for naming cells In 1673, Leeuwenhoek was first to view living organisms in pond water In 1838, Schleiden concluded that all plants were made of cells In 1839, Schwann concluded that all animals were made of cells In 1855, Virchow observed, under the microscope, cells dividing and reasoned that all cells come from other pre-existing cells by cell division

Remember Endosymbiotic Theory In 1970,Lynn Margulis, provided evidence that some organelles within cells were at one time free living cells themselves – this is called Endosymbiotic Theory Chloroplasts and mitochondria were the organelles she pointed to as evidence of this theory Chloroplast and Mitochondria have their own DNA which is different from the DNA of the cell

Number of Cells Unicellular – composed of one cell Ex: bacteria, yeast Multicellular - composed of many cells that may organize Ex: butterfly, flower

Prokaryotes Have a nucleoid region contains the DNA (no nucleus) Have a cell membrane & cell wall Contain ribosomes to make proteins in their cytoplasm

Eukaryotic Cell Contain 3 basic cell structures: Nucleus (containing DNA) Cell Membrane Cytoplasm with organelles Organelles have specific functions

Two Main Types of Eukaryotic Cells Plant Cell Animal Cell

Lysosome Contain digestive enzymes Use Active Transport to trap and break down food an worn out cell parts

Nucleolus Inside nucleus Produces the ribosomes that make proteins

Smooth & Rough Endoplasmic Reticulum Smooth ER - lacks ribosomes & detoxifies poisons and synthesizes lipids Rough ER - has ribosomes on its surface & makes proteins to EXPORT

Mitochondria Site of Cellular respiration – the capturing of energy from food Breaks down glucose to produce energy ATP

Plant Cell Organelles Chloroplast Process called photosynthesis occurs here

Plant Cell Cell wall Made of cellulose Found in plant cells

Plant Cell Organelles Vacuole Have a large central vacuole

Animal Cell Organelles Glycogen is stored in the cytoplasm of animal cells for food energy glycogen granule

Animal Cell Organelles Near the nucleus in an animal cell Help cell divide

Differences between plant cells and animal cells Relatively small in size Relatively large in size Irregular shape Regular shape No cell wall Cell wall present

Differences between Plant Cells and Animal Cells Vacuole small or absent Large central vacuole Glycogen as food storage Starch as food storage Nucleus at the center Nucleus near cell wall

The Cell Membrane

Cell or Plasma Membrane Composed of double layer of phospholipids and proteins Controls what enters or leaves the cell Surrounds outside of ALL cells Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

Semipermeable Membrane The cell membranes of all cells are selectively permeable This means that some materials can pass easily through the membrane Examples: H20, CO2 and O2 This also means that some materials cannot pass easily through the membrane Examples: glucose and salts

Cell Membrane Proteins Proteins help move large molecules or aid in cell recognition Peripheral proteins are attached on the surface (inner or outer) Integral proteins are embedded completely through the membrane

Other Functions of Plasma Membrane Provide a binding site for enzymes Interlocking surfaces bind cells together (junctions) Contains the cytoplasm (fluid in cell)

Phospholipids Phospholipid bilayer makes up the cell membrane Contains a polar head (attracts H2O) and 2 non-polar fatty acid tails (repels H2O) How is a phospholipid different from a triglyceride?

Fluid-Mosaic Model of the Cell Fluid: individual phospholipids and proteins can move side-to-side within the layer, like a liquid. Mosaic: the pattern produced by the scattered proteins on the surface of the cell when the membrane is viewed from above.

Solubility of the Membrane Materials that are soluble in lipids can pass through the cell membrane easily Ex: Oxygen, carbon dioxide, and water

Cell Transport Mechanisms Passive Transport Active Transport Does not require cellular energy Types: Simple Diffusion Osmosis Facilitated Diffusion Does require cellular energy Types: Membrane Pumps Endocytosis Exocytosis

Passive Transport

Simple Diffusion Movement of materials from a region of high concentration to a region of low concentration Materials are moving down/with their concentration gradient Example: Oxygen diffusing into a cell and carbon dioxide diffusing out using kinetic energy

Simple Diffusion

Osmosis Osmosis is the passive transport (diffusion) of water across a membrane Moves from a region of HIGH water potential (low solute) to a region of LOW water potential (high solute)

Osmosis The purpose of osmosis is to balance out the concentration of materials between the environment inside of the cell and the environment outside the cell Water moves because the other materials cannot This allows the cell to be in equilibrium - balance

Types of Solutions a Cell May be Found In Solution - a liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent). Examples – salt water or glucose solutions; solutes are salt or glucose, solvent is water Types of solutions: Isotonic Hypotonic Hypertonic

Isotonic Solution ENVIRONMENT CELL 10% NaCL 90% H2O ENVIRONMENT CELL 10% NaCL 90% H2O Q: What is the direction of water movement in an isotonic solution? A: No net movement (water molecules moving equally back and forth)

Hypotonic Solution ENVIRONMENT CELL 10% NaCL 90% H2O CELL 20% NaCL 80% H2O Q: What is the direction of water movement in a hypotonic solution? A: Water moves into the cell

Hypertonic Solution ENVIRONMENT CELL 15% NaCL 85% H2O CELL 5% NaCL 95% H2O Q: What is the direction of water movement in a hypertonic solution? A: Water moves out of the cell.

Hypertonic or Hypotonic? Hypotonic solution will result in cytolysis – cell bursts from build up of water inside cell Hypertonic solution will result in plasmolysis – cell membrane pulls away from the cell wall in plant, fungal or bacterial cells Plant cells prefer a hypotonic environment Animal cells prefer an isotonic environment

Label the pictures: hypotonic, hypertonic, isotonic

Facilitated Diffusion Uses transport proteins to move materials from high to low concentration Examples: Glucose or amino acids moving from blood stream into a cell.

Active Transport

Proteins and Cell Membrane Function Types of Membrane Proteins: Structural Cell recognition Communication Transport: Channel proteins are embedded in the cell membrane & have a pore for materials to cross Carrier proteins can change shape to move material from one side of the membrane to the other

materials to pass across Channel Proteins Channel proteins act as bridges to allow materials to pass across the membrane

Carrier Proteins Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer

Protein Pumps Cells need a steady supply of sodium (Na+), potassium (K+), calcium (Ca2+) and hydrogen (H+) in order to function correctly Protein pumps that span the cell membrane are powered by ATP and supply these materials to the cell on demand This requires a steady supply of ATP Materials are moving from and area of low concentration to an area of high concentration They are moving up/against their concentration gradient

3 Na+ pumped out for every 2 K+ pumped in Sodium Potassium Pump 3 Na+ pumped out for every 2 K+ pumped in

Types of Active Transport using Vesicles Q: What is a vesicle? A: A small bubble within a cell surrounded in its own lipid bilayer. Q: What is the function of a vesicle? A: Vesicles are involved in: Metabolism Transport of materials Enzyme storage Types of active transport using vesicles: Exocytosis Endocytosis

Exocytosis -using a vesicle to move big stuff out of the cell

Exocytosis How it works: Vesicle is formed around some sort of material made by the cell (like proteins or hormones) Vesicle is released and travels toward cell membrane Vesicle fuses with cell membrane Vesicle expels materials to the outside of the cell membrane

Endocytosis Large amount of materials move into the cell by one of two forms of endocytosis: Pinocytosis - Materials dissolve in water to be brought into cell Called “Cell Drinking” Phagocytosis - Used to engulf large particles such as food, bacteria, etc. into vesicles. Called “Cell Eating” White blood cells eat foreign substances in your body this way

Endocytosis Pinocytosis