4.1 Cells are the Fundamental Units of Life. Cell Structure. Cells. Fundamental units of life Cell theory. Except possibly viruses.

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1 Cells 4.1 Cells are the Fundamental Units of Life Fundamental units of life Cell theory All living things are composed of one or more cells. The cell is the most basic unit of life. All cells come from pre-existing cells. Except possibly viruses 10 m Cell Structure Minimal Cell Plasma membrane Phospholipid bilayer Cytoplasm Space inside cell excluding nucleus Genetic information DNA Ribosomes 1 m 100 mm (10 cm) 10 mm (1 cm) 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm Human height Length of some nerve and muscle cells Chicken egg Frog egg Most plant and animal cells Nucleus Most bacteria Mitochondrion Mycoplasmas (smallest bacteria) Viruses Ribosome Proteins Lipids Small molecules Unaided eye Light microscope Electron microscope 0.1 nm Atoms

2 Two Cell Types 4.2 Prokaryotic and Eukaryotic Cells Prokaryotic Bacteria Archaea Eukaryotic Everything else Prokaryotic Cells Average 2 µm to 8 µm long No nucleus Nucleoid (nuclear region) Bacterial cell wall Peptidoglycan Limited organelles Ribosomes Prokaryotic Cells Variety of structures Capsule Some have sticky outer coat Pili or flagella Used for movement

3 Prokaryotic vs. Eukaryotic Prokaryotic cells Eukaryotic cells DNA Size in nucleoid region within membrane-bound nucleus 4.3 The Eukaryotic Cell much smaller much larger Organization always single-celled often multicellular Organelles only one type of organelle many types of organelles Figure 4.2 The Eukaryotic Cell Much larger 10x length 1000x volume Nucleus present Variety of membranous cellular organelles tiny specialized organs Vary in cellular metabolism Dependent on internal cellular membranes Increase areas of specialization nuclear pores nucleus DNA nuclear envelope nucleolus cytoskeleton rough endoplasmic reticulum plasma membrane The Eukaryotic Cell transport vesicle mitochondria smooth endoplasmic reticulum free ribosomes cytosol Golgi complex lysosomes Figure 4.4

4 The Eukaryotic Cell Cytosol aqueous jelly-like fluid excluding nucleus bathes organelles should not be confused with the cytoplasm Cytosol fills cytoplasm Cytoskeleton The Eukaryotic Cell network of protein filaments. functions in cell structure cell movement transport of materials The Eukaryotic Cell The Eukaryotic Cell Plasma membrane outer lining of the cell phospholipid bilayer imbedded with proteins contains cholesterol controls entry and exit of many compounds Components of eukaryotic cells nucleus other organelles cytosol cytoskeleton plasma membrane Figure 4.3

5 Unicellular Eukaryotes Protista The kingdom being reorganized Fungi Yeast Multicellular Eukaryotes Plant No centrioles Cell wall (cellulose) Chloroplast Central vacuole Golgi apparatus NUCLEUS: Nuclear envelope Chromosome Nucleolus Central vacuole Chloroplast Cell wall Plasmodesmata Mitochondrion Peroxisome Plasma membrane Cell wall of adjacent cell Rough endoplasmic reticulum Ribosomes Smooth endoplasmic reticulum CYTOSKELETON: Microtubule Intermediate filament Microfilament Multicellular Eukaryotes Animal Paired centrioles No cell wall Flagella in some (movement) Contractile vacuole No chloroplasts

6 Rough endoplasmic reticulum Lysosome Centriole Peroxisome CYTOSKELETON: Microtubule Intermediate filament Microfilament Smooth endoplasmic reticulum NUCLEUS: Nuclear envelope Chromosomes Nucleolus Ribosomes Golgi apparatus Plasma membrane Mitochondrion Organelles and Functions Four Categories 1. Manufacturing 2. Breakdown 3. Energy Processing 4. Support, Movement and Communication Manufacturing Nucleus control center of the cell Nuclear Envelope Double membrane Perforated (pores) Material movement DNA Chromatin strands Strands make up chromosomes Nucleolus Contains chromatin, RNA and protein Manufactures ribosome Two membranes of nuclear envelope Nucleolus Chromatin Pore Endoplasmic reticulum Nucleus Ribosomes

7 Ribosomes Two subunits Made of ribosomal (r)rna and proteins Assemble amino acids into polypeptides Using transfer (t)rna Every cell has ribosomes! Ribosomes ER Cytoplasm Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit Endoplasmic Reticulum (ER) Rough ER (due to ribosomes) Makes membrane bound proteins Makes secretory proteins Smooth ER Synthesis of lipids In the liver, helps regulate blood sugar Drug breakdown Storage of calcium Amount of Smooth ER or Rough ER in the cells depends on the function of the cell Smooth ER Rough ER Ribosomes Nuclear envelope

8 Golgi Apparatus Ribosome 1 Transport vesicle buds off 3 4 Secretory protein inside transport vesicle Sugar chain Receives and modifies substances manufactured in the ER Finishes, sorts and ships products # of GA depend on how active the cell is in secreting proteins Receiving and Shipping sides (cis and trans) Contents may either leave the cell or become part of the cell s organelles or membrane Polypeptide 2 Glycoprotein Rough ER The Golgi Complex Lysosomes 1. Transport vesicle from RER fuses with Golgi 2. Protein undergoes more processing in Golgi Golgi complex cisternae cisternal space Digestive enzymes (hydrolytic) in a membranous sac Only work in a very acidic environment Stuff that needs to be broken down is brought into the membranous sac (recycling) Engulfing bacteria Fusing with food vacuoles Embryonic development (programmed cell death) Side chains are edited (sugars may be trimmed, phosphate groups added). 3. Proteins are sorted and shipped for export out of cell to plasma membrane to cytosol vesicle Figure 4.8

9 Lysosomes and Cellular lysosome worn-out Recycling organelle digestive enzymes 1. Lysosome fuses with worn-out organelle. 2. Organelle broken down. 5. Usable molecules recycled to make new organelles. 3. Small molecules returned to cytosol. Peroxisomes Contains enzymes in a membranous sac that produce H 2 O 2 Help survive environmental toxins including alcohol Help the cell use oxygen to break down fatty acids 4. Waste molecules expelled from cell. Figure 4.9 Vacuoles Plants, can be a large lysosome store water, chemicals, pigments, poisons or waste product Animals contractile vacuole to maintain water balance Central vacuole Chloroplast Nucleus

10 Mitochondria Nucleus Mitochondria Energy converting organelle Cellular Respiration Converting chemical energy in food to chemical energy of ATP for cellular work Contractile vacuoles Mitochondria (continued) Double membrane two compartments (outer and inner membranes) 1. Intermembrane space - between the membranes where H+ build up occurs 2. Cristae - increase surface area for ATP production - ATP Synthase is embedded here 3. Mitochondrial matrix - The Citric Acid Cycle is located here Mitochondrion food oxygen Mitochondria and Energy water carbon dioxide ATP outer membrane inner membrane Figure 4.10

11 The Cytoskeleton (a) Microfilaments Cytoskeleton (b) Intermediate filaments (c) Microtubules Internal Scaffolding web of protein strands Microfilaments Intermediate filaments Microtubules Provides structure Facilitates the movement of materials inside the cell Facilitates cell movement. 7 nm 10 nm 25 nm Main function: changes in cell shape Main function: maintenance of cell shape Main functions: maintenance of cell shape, movement of organelles, cell mobility (cilia and flagella) Figure 4.11 Microfilaments Microfilaments Made of protein actin They help the cell move and capture prey by forming rapidly in the direction of movement and decomposing rapidly at their other end. Figure 4.12

12 Intermediate Filaments Several different kinds of proteins can be IMF s (in red below) Provide support and structure to the cell. Microtubules Structural Facilitate the movement of materials inside the cell transport rails. Cilia and flagella are extensions of cells composed of microtubules. Functions of Microtubules (a) Transport monorails (b) Cilia (c) Flagellum transport vesicle motor proteins microtubule Support and Movement Cilia Microtubule extending from cell Short and many present Line trachea to sweep mucous containing debris out of lungs Line oviducts to move the egg toward the uterus Figure 4.13

13 Support and Movement Flagella Fewer in number than cilia but longer Sperm Cilia Support and Movement Flagellum Both Dynein arms for movement (9 + 2) arrangement Anchor in basal body Are tubular extensions of the plasma membrane Function is to move either the whole cell or move material across cell or into cell

14 Cross sections: Flagellum Outer microtubule doublet Central microtubules Radial spoke Dynein arms Plasma membrane Support and Movement Animal Cell Surfaces Animal and other eukaryotes are organized into single functional organisms These are held together with cell surfaces Triplet Basal body Basal body Support and Movement Extracellular Matrix Helps hold cells together, affects cell behavior by contacting proteins in plasma membrane and cytoskeleton within the cell Glycoprotein complex with long polysaccharide Collagen fiber Connecting glycoprotein Integrin EXTRACELLULAR FLUID Plasma membrane Microfilaments CYTOPLASM

15 Tour of an Animal Cell Suggested Media Enhancement: Tour of an Animal Cell To access this animation go to folder C_Animations_and_Video_Files and open the BioFlix folder. 4.7 The Plant Cell Copyright 2009 Pearson Education, Inc., publishing as Benjamin Cummings. Plant Cells Like animal cells, have: Ribosomes Nucleus RER Golgi Plasma membrane mitochondria Do NOT possess lysosomes Plant Cells 3 structures not found in animal cells: a cell wall cellulose a large central vacuole provides turgor pressure chloroplasts carry out photosynthesis

16 Plant cells have a cell wall, chloroplasts, and a central vacuole, while animal cells do not. cytoskeleton cell wall chloroplast central vacuole Plant Cells nuclear envelope nuclear pores nucleus DNA nucleolus rough endoplasmic reticulum smooth endoplasmic reticulum free ribosomes Golgi complex cytosol plasma membrane mitochondrion Central Vacuole Stores water and nutrients degrades waste products like lysosome in animal cells Figure 4.16 Cell Wall Gives the plant structural strength helps regulate the intake and retention of water. Chloroplasts Sites of photosynthesis Double membrane like mitochondria Internal space like mitochondria Contain stacks of thylakoids (not like mito)

17 Chloroplasts water carbon dioxide minerals outer membrane inner membrane sugar (food) oxygen Figure 4.18 Cell-to-Cell Communication 4.8 Cell-to-Cell Communication Cells are able to communicate with each other through special structures. Plasmodesmata Gap junctions Copyright 2009 Pearson Education, Inc., publishing as Benjamin Cummings.

18 Communication Among Plant Cells Communication Among Animal Cells Plasmodesmata Channels always open connects the cytoplasm of one plant cell with that of another Gap junctions Channels composed of protein assemblages that open only as necessary. allow the movement of small molecules and electrical signals between cells. Plant tissues Cell Communication Binding Cells Together Animal tissues plasmodesmata gap junction plasma membrane cell walls cytoplasm plasma membranes cytoplasm (a) Plasmodesmata In plants, a series of tiny pores between plant cells, the plasmodesmata, allow for the movement of materials among cells. Thanks to the plasmodesmata channels, the cytoplasm of one cell is continuous with the cytoplasm of the next; the plant as a whole can be thought of as having a single complement of continuous cytoplasm. (b) Gap junctions In animals, protein assemblies come into alignment with one another, forming communication channels between cells. A cluster of many such assemblies perhaps several hundred is called a gap junction. Tight Junctions leak proof sheet digestive or nervous system Anchoring Junctions rivets with cytoskeleton Gap junctions also connect cells Figure 4.19

19 Structures in Plant and Animal Cells Tight junctions Anchoring junction Gap junctions Plasma membranes of adjacent cells Extracellular matrix Table 4.1