Announcements ● Tutoring Center SCI I, 407 M 12-3, 5:30-6:30; W 8-9, 5:30-6:30, Th 8-12, 6-7; F 8-9 ● MasteringBiology Assignment due Tuesday 4/19 ● Exam I Tuesday 4/19 ● Scantron ABF-10-ID-200A

Review ● Importance of Carbon ● Biologically Important Molecules Macromolecules: Carbohydrates Proteins Nucleic Acids Lipids

● Organisms are either: Single-celled, such as most prokaryotes and protists or Multicelled, such as plants, animals, and most fungi The Microscopic World of Cells

How do we study cells? Light microscopes can be used to explore the structures and functions of cells.

The Microscopic World of Cells ● Electron Microscope 10 m 1 m 10 cm 1 cm 1 mm 100 mm 10 mm Human height Chicken egg Frog eggs Length of some nerve and muscle cells Unaided eye Light microscope Plant and animal cells Most bacteria Nucleus Mitochondrion 1 mm 100 nm 10 nm 1 nm 0.1 nm Smallest bacteria Viruses Ribosomes Proteins Lipids Small molecules Atoms Electron microscope Figure 4.3

The Microscopic World of Cells Light Micrograph (LM) (for viewing living cells) Light micrograph of a protist, Paramecium LM Colorized SEM Scanning Electron Micrograph (SEM) (for viewing surface features) Scanning electron micrograph of Paramecium TYPES OF MICROGRAPHS Transmission Electron Micrograph (TEM) (for viewing internal structures) Transmission electron micrograph of Paramecium Colorized TEM

The Two Major Categories of Cells ● The countless cells on earth fall into two categories: Prokaryotic cells — Bacteria and Archaea Eukaryotic cells — Eukarya protists, plants, fungi, and animals ● All cells have several basic features. 1. They are all bound by a thin plasma membrane. 2. All cells have DNA. 3. All cells have ribosomes. Cytoplasm-the entire contents of a cell

Prokaryotic Cells Plasma membrane (encloses cytoplasm) Cell wall (provides Rigidity) Capsule (sticky coating) Prokaryotic flagellum (for propulsion) Ribosomes (synthesize proteins) Nucleoid (contains DNA) Pili (attachment structures) Colorized TEM ● Prokaryotes Are smaller than eukaryotic cells Lack internal structures surrounded by membranes Lack a nucleus Have a rigid cell wall

Eukaryotic Cells ● Eukaryotic cells are fundamentally similar. *Generalized animal cell *Generalized plant cell

Membrane Structure ● The plasma membrane separates the living cell from its nonliving surroundings. (a) Phospholipid bilayer of membrane (b) Fluid mosaic model of membrane Outside of cell Hydrophilic head Hydrophobic tail Hydrophilic region of protein Hydrophilic head Hydrophobic tail Hydrophobic regions of protein Phospholipid bilayer Phospholipid Proteins Cytoplasm (inside of cell)

Membrane Structure ● Phospholipid structure Phospholipids are amphipathic molecules

Membrane Structure ● The plasma membrane separates the living cell from its nonliving surroundings. (a) Phospholipid bilayer of membrane (b) Fluid mosaic model of membrane Outside of cell Hydrophilic head Hydrophobic tail Hydrophilic region of protein Hydrophilic head Hydrophobic tail Hydrophobic regions of protein Phospholipid bilayer Phospholipid Proteins Cytoplasm (inside of cell)

Membrane Structure Fibers of extracellular matrix Cytoskeleton Cytoplasm Attachment to cytoskeleton and extracellular matrix a b Cell signaling c d Enzymatic activity Transport e Intercellular joining f Cell-cell recognition Cytoplasm ● Some functions of membrane proteins ● Cell surface – Extracellular Matrix

Chromatin Nucleolus Pore Nuclear envelope Surface of nuclear envelope Nuclear pores TEM ● The nucleus is an organelle that houses the genetic material of the cell. Nucleus Chromatin Nuclear envelope Nucleolus Nuclear Pore

Chromatin DNA molecule Chromosome Proteins Chromatin fiber Figure 4.9

Ribosomes Composed of proteins and Ribosomal RNA Free: proteins for cytosol Membrane-bound: proteins for cell membranes and export ● Ribosomes build all the cell’s proteins (protein synthesis)

How DNA Directs Protein Synthesis Synthesis of mRNA in the nucleus 1 2 Movement of mRNA into cytoplasm via nuclear pore 3 Synthesis of protein in the cytoplasm DNA mRNA Nucleus Cytoplasm mRNA Ribosome Protein ● DNA controls the cell by transferring its coded information into RNA –The information in the RNA is used to make proteins

● Many of the membranous organelles in the cell belong to the endomembrane system The Endomembrane System

The Endoplasmic Reticulum –Produces an enormous variety of molecules –Is composed of smooth and rough ER Nuclear envelope Ribosomes Rough ER Smooth ER

After the rough ER synthesizes a molecule it packages the molecule into transport vesicles Transport vesicle buds off Ribosome Secretory protein inside transport vesicle Protein Rough ER Polypeptide The Endoplasmic Reticulum

The Golgi Apparatus –Works in partnership with the ER –Refines, stores, and distributes the products of cells Transport vesicle from ER “Receiving” side of Golgi apparatus New vesicle forming Transport vesicle from the Golgi “Shipping” side of Golgi apparatus Plasma membrane

A lysosome is a membrane-enclosed sac Lysosomes – It contains digestive enzymes –The enzymes break down macromolecules –They break down damaged organelles (b) Lysosome breaking down damaged organelle Lysosome Damaged organelle Digestion

Rough ER Transport vesicle from ER Golgi apparatus Secretory vesicle from Golgi Secretory protein Vacuole Lysosome Plasma membrane The Endomembrane System

Mitochondria are the sites of cellular respiration, which involves the production of ATP from food molecules Figure 4.18 Outer membrane Inner membrane Cristae Matrix Space between membranes Cellular energy conversion

Cytoskeleton ● Provides mechanical support to the cell and maintain its shape

The cytoskeleton can change the shape of a cell –This allows cells like amoebae to move Cytoskeleton

Cilia and flagella are motile appendages Cilia and Flagella Flagella propel the cell in a whiplike motion Cilia move in a coordinated back-and-forth motion

Vacuoles are membranous sacs Vacuoles –Two types are the contractile vacuoles of protists and the central vacuoles of plants Contractile vacuoles Central vacuole (a) Contractile vacuoles in a protist(b) Central vacuole in a plant cell

Cytoskeleton Mitochondrion Nucleus Rough endoplamsic reticulum (ER) Ribosomes Smooth endoplasmic reticulum (ER) Golgi apparatus Plasmodesmata Plasma membrane Chloroplast Cell wall Central vacuole Not in animal cells Plant Cells

Plant cells are encased by cell walls Walls of two adjacent plant cells Vacuole Plasmodesmata (channels between cells) Plant Cells

Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy Chloroplasts Inner and outer membranes of envelope Space between membranes Stroma (fluid in chloroplast) Granum