A Tour of the Cell reference: Chapter 6 Reference: Chapter 2 Monkey Fibroblast Cells stained with fluorescent dyes to show the nucleus (blue) and cytoskeleton (yellow and red fibers), image courtesy of 1 Nikon Instruments & Florida State University
Overview & Objectives v Outline Basic Features of Cells Animal Cell Structures v Objectives List the major structures that make up animal cells and describe their functions Be able to recognize and label organelles and other cell structures in a picture of a cell v Important concepts: Cells are the building blocks of all life Cells are the smallest living things Cells arise only from other cells
Cells v Living organisms are either Prokaryotes Single-celled organisms that lack specialized internal structures, such as a nucleus e.g. bacteria Eukaryotes Organisms whose cells contains a nucleus and other complex internal structures May be single-celled (e.g. protozoa such as amoebae Multi-celled, such as plants and animals (and you!)
THE MICROSCOPIC WORLD OF CELLS v Scale: mm = millimeter = one thousandth of a meter (small; barely see it) µm = micrometer = one millionth of a meter (really small; can t see it) nm = nanometer = one billionth of a meter (really, really really small)
Cell Structures v All cells consist of two basic components: Plasma Membrane (aka Cell Membrane) This encloses the contents of the cell and regulates the passage of materials into and out of the cell Cytoplasm Internal contents of the cell v Many cells also possess an Extracellular Matrix Material that forms a coating around the cell Holds cells together in tissues; can also be the starting material for bone and other structures
Cell Structures: The Plasma Membrane v Separates the living cell (cytoplasm) from its nonliving surroundings v The membranes of cells are composed of macromolecules Lipids Proteins Carbohydrate
Cell Structures: The Plasma Membrane v The lipids belong to a special category called phospholipids Glycerol backbone Two hydrophobic fatty acid tails Hydrophilic phosphate head Organic group (R) sometimes attached to phosphate proteins carbohydrates
Cell Structures: The Plasma Membrane v Phospholipids form a two-layered membrane, the phospholipid bilayer v This thin, flexible bilayer surrounds the cell contents and prevents most materials from entering or leaving the cell Outside cell (a) Phospholipid bilayer of membrane Cytoplasm (inside cell)
Cell Structures: The Plasma Membrane v Carbohydrate chains attach to the proteins and lipids in the plasma membrane Important in cell-cell recognition
Cell Structures: The Cytoplasm v A semi-fluid matrix that fills the interior of the cell v Most cellular activities occur in the cytoplasm Highly organized Consists of 3 components 1. Cytosol Gooey liquid; makes up about 80% of the cell Composed of water, salts, organic molecules 2. Organelles Little organs ; specialized structures in the cytoplasm 3. Vesicles Membrane-bound sacks that transport materials and carry out chemical reactions within the cell
Cell Organelles: The Nucleus v The nucleus is the manager of the cell Contains chromatin (DNA) that carries the genes which code for proteins Bordered by a double membrane called the nuclear envelope Also contains the nucleolus, a region of the nucleus where ribosomes are assembled
Cell Organelles: Ribosomes v Ribosomes are small organelles Mixture of protein and RNA (ribonucleic acid) synthesize the cell s proteins
Cell Organelles: The Endomembrane System v Many of the membranous organelles in the cell belong to the endomembrane system They manufacture and distribute cell products v Four components: 1. Rough Endoplasmic Reticulum (RER) 2. Smooth Endoplasmic Reticulum (SER) 3. Golgi Apparatus 4. Lysosomes
The Endoplasmic Reticulum v The endoplasmic reticulum (ER) Produces an enormous variety of molecules Nuclear envelope Is composed of smooth and rough ER Ribosomes Rough ER Smooth ER
1. Rough Endoplasmic Reticulum, RER v Roughness of the rough ER is due to ribosomes that stud the outside of the ER membrane v The functions of the RER include: Producing proteins Producing new membrane RER
1. Rough Endoplasmic Reticulum, RER v After the rough ER synthesizes a molecule it packages the molecule into transport vesicles Transport vesicle buds off 4 Ribosome 3 Secretory protein inside transport vesicle 1 2 Protein Rough ER Polypeptide
2. Smooth Endoplasmic Reticulum, SER v SER lacks the surface ribosomes of RER Produces a different variety of compounds, such as lipids, including steroids SER
3. The Golgi Apparatus v Golgi works in partnership with the ER Refines, stores, and distributes the products of cells The UPS Store of the cell Consists of flattened membranous sacks Vesicles fuse and pinch off from the sacks Transport vesicle from ER Receiving side of Golgi apparatus Golgi apparatus New vesicle forming Transport vesicle from the Golgi Shipping side of Golgi apparatus Plasma membrane
4. Lysosomes v A lysosome is a membrane-enclosed sack contains digestive enzymes Lysosomes have 2 functions: 1. fuse with food vacuoles to digest food
4. Lysosomes 2. break down damaged organelles
Visual Summary: The Endomembrane System
Cell Organelles: Mitochondria v Cells require a constant energy supply to carry out the work of life v Cells use a chemical form of energy known as ATP (adenosine triphosphate) v Mitochondria are Powerplants that supply the cell s energy needs by producing ATP v Production of ATP is known as Cellular Respiration mitochondria
Cell Structures: The Cytoskeleton v The cytoskeleton is the infrastructure of the cell v Consists of a network of protein fibers v Controls cell shape and movement
Flagella and Cilia v Cilia and flagella are external appendages v Flagella propel the cell in a whiplike motion Useful when you need to get somewhere in a hurry, like the sperm cell shown below
Flagella and Cilia v Cilia are smaller than flagella Usually occur rows along the surface of the cell Beat in a coordinated fashion for locomotion or to move particles toward or away from the cell v The ciliates are a group of single-celled protists that have cilia covering the entire body v Small animals like rotifers use cilia to gather food
Flagella and Cilia v More structurally complex animals often have ciliated cells within their bodies v The human windpipe is lined with cilia, as is the lining of the female reproductive tract v In the windpipe, the cilia beat in unison to propel dust and mucus out of the lungs
A Panoramic View of Eukaryotic Cells
Summary: Prokaryotic Cells Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial chromosome (a) A typical rod-shaped bacterium Cell wall Capsule Flagella 0.5 µm (b) A thin section through the bacterium Bacillus coagulans (TEM)
Summary: Prokaryotic Cells v Prokaryotic cells are characterized by having No nucleus DNA in an unbound region called the nucleoid No membrane-bound organelles Cytoplasm bound by the plasma membrane
Summary: Eukaryotic Cells v Eukaryotic cells are characterized by having DNA in a nucleus that is bounded by a membranous nuclear envelope Membrane-bound organelles Cytoplasm in the region between the plasma membrane and nucleus v Eukaryotic cells are generally much larger than prokaryotic cells
Summary: Eukaryotic Cells (Animal) ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER Nuclear envelope Nucleolus NUCLEUS Flagellum Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome
NUCLEUS Nuclear envelope Nucleolus Chromatin Rough ER Plant cells are also Eukaryotic, but have a few unique features Smooth ER Ribosomes Golgi apparatus Central vacuole Microfilaments Microtubules CYTOSKELETON Mitochondrion Peroxisome Plasma membrane Cell wall Wall of adjacent cell Plasmodesmata Chloroplast