Cell Structure and Function Chapter 7 Life is Cellular Section 7-1 The Cell Theory 1. All living things are composed of cells. 2. Cells are the basic units of structure and function. 3. All cells come from preexisting cells. Who helped to develop theory? a. Robert Hooke b. Leeuwenhoek c. Robert Brown d. Schleiden and Schwann e. Rudolf Virchow Basic Cell Structures Most cells contain the following structures: 1. Cell membrane 2. Genetic material (DNA) 3. Cytoplasm Two main types of cells: 1. Prokaryotes - no nucleus 2. Eukaryotes - nucleus present Prokaryotes All Bacteria! No nucleus but has DNA No organelles Has ribosomes Always unicellular Can move with flagella or cilia Eukaryotes Nucleus present with DNA Unicellular or Multicellular Plants, animals, fungi and protists Has all major organelles Can move at unicellular level Prokaryote vs. Eukaryote Cell Structures Section 7-2 Cell Wall Found in Plant, fungi, and prokaryotes. Outermost layer, exterior to cell membrane Function: provide support and protection Main component: CELLULOSE Indigestible fiber, used in making paper Nucleus and other parts Function: controls cell processes and contains DNA. Chromatin chromosomes clumped together. Chromosomes groups of condensed DNA Nucleolus small region inside nucleus, makes ribosomes, and RNA. Nuclear envelope membrane surrounding nucleus Centrioles Found only in animal cells Function: Involved in cell reproduction Cytoskeleton Network of protein filaments that helps the cell to maintain its shape. Two Types: Microtubules centrioles, cilia, flagella Microfilaments muscle fibers Ribosomes Function: making proteins Can be found free- floating in the cytoplasm or bound to endoplasmic reticulum. Endoplasmic Reticulum Inter-connected tube system Two types: rough and smooth Function: Assembly lines to make cell membrane parts and organic molecules Rough assembles and transports proteins Smooth assembles and transports lipids and carbohydrates Golgi Apparatus & Lysosomes Packages proteins for transport out of the cell Filled with digestive enzymes breaks down food, foreign bodies and worn out organelles Vacuoles Function: To store materials which could be water, food molecules or waste. Plants have a large central vacuole filled with mostly water. Animals have smaller vacuoles usually called vesicles. Chloroplasts Only found in plant cells. Contains own DNA Function: Photosynthesis light energy is turned into chemical-food energy. Chlorophyll: green pigment ; absorbs and reflects light. Plastids other pigment containing organelles (cannot photosynthesize) Mitochondria Function: Release energy from food molecules ( a.k.a cell respiration ) Powerhouse of the cell Contains own DNA (whose mito-DNA do you haveMoms or Dads?) Nuclear envelope Ribosome (attached) Ribosome (free) Smooth endoplasmic reticulum Nucleus Rough endoplasmic reticulum Nucleolus Golgi apparatus Mitochondrion Cell wall Cell Membrane Chloroplast Vacuole Section 7-2 Figure 7-5 Plant and Animal Cells Plant Cell Centrioles Nucleolus Nucleus Nuclear envelope Rough endoplasmic reticulum Golgi apparatus Smooth endoplasmic reticulum Mitochondrion Cell Membrane Ribosome (free) Ribosome (attached) Section 7-2 Figure 7-5 Plant and Animal Cells Animal Cell Movement Through the Membrane Section 7-3 Cell Membrane Function: To regulate what enters and exits the cell; protection and support. SELECTIVELY PERMEABLE Structures: a.Phospholipid bilayer hydrophobic b.Proteins gatekeeper for substances c.Carbohydrates cell recognition Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Section 7-3 Figure 7-12 The Structure of the Cell Membrane Cell Membrane Cell Transport Types: Passive Movement: No energy required Active Movement: Energy required by cell Diffusion Passive Movement of a substance from high to low concentration Ex: Movement of O 2 and CO 2 through membranes This is also the same as: going down the concentration gradient! Osmosis Movement of water from high to low concentration across a selectively permeable membrane. (Only permeable to water) What determines the direction of water movement? The solute! (what is dissolved in the solvent) Solution types: 1. Hypertonic solute is in high concentration so water is low. 2. Hypotonic solute is in low concentration so water is high. 3. Isotonic solute concentration is equal on both sides. For each beaker, which way will water move? IN or OUT of the blob cell Beaker A = isotonic solutions NO MOVEMENT Beaker B = water will move INTO the cell Beaker C = water will move OUT of the cell How do cells cope with osmotic pressure? 1.Tough cell walls protect from bursting 2. Contractile vacuoles pump out excess water in unicellular animals Many cells cannot cope with osmotic pressure: *dangerous to drink sea water it will speed up dehydration (and death) by drinking sea water. *water injected into you will burst RBCs Facilitated Diffusion Movement of substance from high to low concentration across a membrane through a protein channel. Ex: large molecules or ions. Glucose, neurotransmitters, sodium, potassium Active Transport Require energy for the cell to complete. Movement of molecules from LOW to HIGH. (against the concentration gradient) Examples: Sodium/Potassium pump for nerve impulse condution. Other Energy Requiring Transport Methods: Bulk Movement Endocytosis larger molecules inside cell, doesnt need concentration gradient. 1. Phagocytosis - cell eating, macrophages 2. Pinocytosis cell drinking Exocytosis removal of large molecules Endocytosis and Exocytosis Endocytosis Exocytosis Cell Diversity Section 7-4 Diversity of Cellular Life Unicellular Organisms Multicellular Organisms 1. Cell Specialization cells perform certain functions based on DNA segment that is turned activated. 2. Levels of Organization Muscle cellSmooth muscle tissueStomachDigestive system Section 7-4 Levels of Organization