A Tour of the Cell Chapter 6

Overview: The Importance of Cells  Cell Theory: All organisms are made of cells  The cell is the simplest collection of matter that can live Cells

 All cells have several basic features in common  They are bounded by a plasma membrane  They contain a semifluid substance called the cytosol (cytoplasm is the physical area between membrane and nucleus which contains the cytosol)  They contain chromosomes made of DNA  They have ribosomes The Cell

 Prokaryotic cells  Do not contain a nucleus or other membrane bound organelles  Have their DNA located in a region called the nucleoid Two Types of Cells

Pili Nucleoid Ribosomes Plasma membrane Cell wall Capsule Flagella (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM) 0.5 µm Prokaryotic Cell

 Eukaryotic cells  Contain a true nucleus, bounded by a membranous nuclear envelope  Contain many other specialized membrane bound organelles  Are generally quite a bit bigger than prokaryotic cells Two Types of Cells

In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm) ECM Desmosomes, tight junctions, gap junctions Eukaryotic Cells: Animal

In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata Eukaryotic Cells: Plant

 Endomembrane system is a related series of membrane bound structures responsible for protein and lipid synthesis. Includes :  Plasma/cell membrane  Nuclear membrane  Endoplasmic reticulum  Golgi apparatus  Lysosomes  Vacuoles and vesicles Endomembrane System

Outside of cell Hydrophilic region Hydrophobic region Hydrophilic region Phospholipid Proteins 0.1 µm Inside of cell Plasma membrane: Selective Barrier Carbohydrate

Pore complexes Nuclear lamina Nucleus Nucleolus Nuclear envelope : Nuclear pore Pore complex 1 µm 0.25 µm Nucleus and its Envelope: Contains DNA

Ribosomes ER Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit TEM showing ER and ribosomes Diagram of a ribosome rRNA and proteins 0.5 µm Ribosomes: Protein Factories

Smooth ER Rough ER ER lumen Cisternae Ribosomes Transport vesicle Transitional ER 200 µm Endoplasmic reticulum (ER): Series of Membranes

 Rough ER:  Contains bound ribosomes so manufactures proteins  These proteins often destined to be exported from cell  Smooth ER:  No ribosomes so no protein synthesis  Lipid synthesis such as making fatty acids, steroids  Metabolizes carbohydrates  Detoxification of drugs by adding hydroxyl groups (makes water soluble) Roles of Rough and Smooth ER

Golgi apparatus cis face receiving” Cisternae trans face “shipping” side TEM of Golgi apparatus µm 5 3 Golgi apparatus: “Post Office” of the Cell

Lysosome 1 µm Vesicle containing damaged mitochondrion Digestion Food vacuole Plasma membrane Lysosome Digestive enzymes Phagocytosis : lysosome digesting food Autophagy : lysosome breaking down damaged organelle Lysosome Digestion Lysosome Lysosomes: Digestive Enzyme Packets

Central vacuole T onoplast Central vacuole 5 µm Plant Cell Vacuole

Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Mitochondrial DNA Inner membrane Cristae Matrix 100 µm Mitochondrion: Site of Cellular Respiration (ATP Synthesis) Endosymbiosis? “living within”

Granum Chloroplast DNA Ribosomes Stroma Inner and outer membranes Thylakoid 1 µm Chloroplast: Site of Photosynthesis Also endosymbiosis?

 Network of fibers in cytoplasm that organize and anchors organelles and gives structural support  3 types of cytoskeleton  Microtubules  Microfilaments  Intermediate filaments Cytoskeleton

 Structure  Thickest of 3 types, hollow  Made of tubulin  Dynamic structure Microtubules

 Function  Provides organelle tracks  Moves chromosomes during cell division  Forms structure of locomotive appendages cilia and flagella

 Structure  Thinnest of 3 types, solid  Made of actin  Twisted, double chain  Dynamic stucture Microfilaments

 Function  Interacts with myosin for muscle contraction  Creates cleavage furrow during cell division  Responsible for gel-sol state  Pseudopodia  Cytoplasmic streaming Microfilaments

Structure Intermediate in size Made of keratin Permanent structure Intermediate Filaments

Function Organelle anchor Comprises nuclear lamina Desmosomes Intermediate Filaments

Plasma membrane 1 µm Central vacuole Plant cell walls Plasmodesmata Plant Cell Walls: Made of cellulose

Tight junctions prevent fluid from moving across a layer of cells Tight junction 0.5 µm 1 µm Space between cells Plasma membranes of adjacent cells Gap junctio n Tight junctions 0.1 µm Intermediate filaments Desmosome Gap junctions. “Communicating” TIGHT JUNCTIONS DESMOSOMES GAP JUNCTIONS Intercellular Junctions in Animal Tissues “Rivets” “Seals”