Ch 4 Tour of the Cell

Cells Smallest unit that shows properties of life – Metabolizes – Reproduces Cell Theory – All organisms consist of one or more cells – The cell is the smallest unit of life – New cells arise from old cells – Cells pass hereditary material to offspring

Microscopic Worlds Microscopes led to the discovery of the cell – Discovered “animalcules” and wee “beasties” Antoni van Leeuwenhoek Robert Hooke

Microscopic Worlds

Cell Size House DNA, protein molecules and internal structures Obtain nutrients and diffuse nutrients and O 2 Smaller cells have a greater surface area to volume ratio than do larger cells – Surface area is significant for diffusion and osmosis

Surface area : Volume Volume= 30 um *30 um* 30 um=27000um SA (large)= 6*(30um*30um)=5,400 um SA (small)=(6*(10um*10um))*27=16,200 um 30  m 10  m 30  m 10  m Surface area of one large cube  5,400  m 2 Total surface area of 27 small cubes  16,200  m 2

Domains of Life The 3 domains of life – Bacteria (prokaryotic cells) – Archaea (prokaryotic cells) – Eukarya (all other life forms)

Cells Prokaryotic – Bacteria & Archaea Eukaryotic – Protists, fungi, plants, animals Prokaryotic cells are simpler & usually smaller than Eukaryotic cells Prokaryotic cell Nucleoid region Nucleus Eukar yotic cell Organelles Colorized TEM 15,000 

In Common Bounded by plasma membrane Ribosomes Cytoplasm DNA as genetic material

Prokaryote Do not have membrane bound nucleus Have a cell wall outside their plasma membrane Circular DNA strands No membrane bound organelles Prokar yotic flagella Ribosomes Capsule Cell wall Plasma membrane Nucleoid region (DNA) Pili

Eukaryote Membrane bound nucleus Linear DNA Membrane bound organelles Nucleus Smooth endoplasmic reticulum Rough endoplasmic reticulum Ribosomes Golgi apparatus Plasma membrane Mitochondrion Flagellum Not in most plant cells Lysosome Centriole Microtubule Cytoskeleton Intermediate filament Microfilament Peroxisome

Eukaryotic Cells A typical animal cell: Contains a variety of membranous organelles (underlined) Nucleus Smooth endoplasmic reticulum Rough endoplasmic reticulum Ribosomes Golgi apparatus Plasma membrane Mitochondrion Flagellum Not in most plant cells Lysosome Centriole Microtubule Cytoskeleton Intermediate filament Microfilament Peroxisome Figure 4.4A

Eukaryotic Cells A typical plant cell Smooth endoplasmic reticulum Rough endoplasmic reticulum CYTOSKELETON: NUCLEUS Ribosomes Golgi apparatus Plasma membrane Mitochondrion Peroxisome Cell wall Central vacuole Microtubule Intermediate filament Microfilament Cell wall of adjacent cell Chloroplast Plasmodesmata

Categories of Organelles Structural support, movement, communication – Cytoskeleton, plasma membrane, cell wall (plants) Manufacturing – Nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus Energy processing – Mitochondria (animal), chloroplasts (plants) Hydrolysis – Lysosomes (animals), vacuoles (plants), peroxisomes

Plasma Membrane Forms boundary around cell Controls and regulates material transport -Semi permeable Phospholipid bilayer

Plants and Cell Walls Cell wall – Cellulose Connect by plasmodesmata – Channels between adj. cells Plasma membrane Cytoplasm Plasmodesmata Vacuole Layers of one plant cell wall Walls of two adjacent plant cells

Cytoskeleton Cell’s internal skeleton – Helps organize structure and activities – Consists of network of protein fibers Actin subunit Microfilament 7 nm Fibrous subunits 10 nm Intermediate filamentMicrotubule 25 nm Tubulin subunit

Cytoskeleton Microfilaments (actin filiments) – Enable cells to change shape and move Intermediate filaments – Reinforce the cell and anchor certain organelles Microtubules – give the cell rigidity, provide anchors for organelles, act as tracks for organelle movement Actin subunit Microfilament 7 nm Fibrous subunits 10 nm Intermediate filamentMicrotubule 25 nm Tubulin subunit

Nucleus Contains most of the cells DNA Eukaryotic chromosomes made of chromatin Enclosed by nuclear enveloper Nucleolus – rRNA synthesized Nucleus Chromatin Nucleolus Pore Ribosomes Rough endoplasmic reticulum Two membranes of nuclear envelope

Ribosomes Free and bound ribosomes Composed of 2 subunits – Involved in protein synthesis

Endomembrane System Interconnected structurally and functionally – Physically connected OR – Connected via vesicles Nucleus Smooth ER Nuclear envelope Golgi apparatus Lysosome Vacuole Plasma membrane Rough ER Transport vesicle from ER to Golgi Transport vesicle from Golgi to plasma membrane

Rough Endoplasmic Reticulum Membrane continuous with nuclear envelope – Makes more membrane – Transferred via vesicles Bound ribosomes – Produces proteins – Transported or secreted Smooth ER Rough ER Nuclear envelope Rough ER Ribosomes Smooth ER TEM 45,000  Figure 4.7

Fig. 4-9b Transport vesicle buds off Secretory protein inside trans- port vesicle Glycoprotein Polypeptide Ribosome Sugar chain Rough ER

Smooth ER Lacks bound ribosomes Involved in metabolic processes – Synthesis of lipids, hormones, enzymes Stores calcium

Golgi Apparatus Vesicles from ER go to Golgi Receives and modifies products Golgi apparatus TEM 130,000  Transport vesicle from the Golgi “Shipping” side of Golgi apparatus Golgi apparatus “Receiving” side of Golgi apparatus Transport vesicle from ER New vesicle forming

Lysosomes Digestive enzymes enclosed by membrane sac Destroy ingested bacteria, recycle damaged organelles Break down food Digestive enzymes Lysosome Plasma membrane Food vacuole Digestion Lysosome Vesicle containing damaged mitochondrion Digestion

Lysosomes Figure 4.10A Golgi apparatus Plasma membrane “Food” Food vacuole Lysosomes Lysosome engulfing damaged organelle Digestion Engulfment of particle Transport vesicle (containing inactive hydrolytic enzymes) Rough ER

Vacuoles Membranous sac Central Vacuole – hydrolytic function Contractile Food Chloroplast Central vacuole Nucleus Colorized TEM 8,700 

Peroxisomes Metabolize fatty acids & inactivate toxins Enzymes that digest peroxides Come only from ER

Mitochondria Cellular respiration – Converts chemical energy to ATP – Phospholipid bilayer membrane – Has own DNA and ribosomes Mitochondrion Outer membrane Intermembrane space Matrix Inner membrane Cristae TEM 44,880 

Chloroplasts Convert solar energy to chemical energy (photosynthesis) Stroma – Contains DNA, ribosomes and enzymes Thylakoids – Interconnected sacs that form stacks called granum

Endosymbosis Hypothesis of endosymbosis – Mitochondria and chloroplasts were once small prokaryotes living independently – At some point, began living within larger cells

Movement Cilia – Short appendage, numerous – Move via coordinated beating – Stirs fluid around stationary cells Flagella – Long appendage, whip-like – Move via bending Pseudopods – Irregular long lobes – Bulge outward and drag cell

Movement Cilia lining lungs

Extracellular matrix Holds cells to tissues Protect and support PM – Integrins Regulate behavior, transmit information, coordinate cells

Cell Junctions Tight junctions can bind cells together into leakproof sheets Anchoring junctions link animal cells into strong tissues Gap junctions allow substances to flow from cell to cell Anchoring junction Tight junctions Gap junctions Extracellular matrix Space between cells Plasma membranes of adjacent cells Figure 4.18B

Fig. 4-23

Videos Overview Basic cell structure Cytoskeleton Cell membrane and wall