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 have…Mom’s or Dad’s?)

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 RBC’s

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, doesn’t 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