Here it is…the structure!...the function! Chapter 6: the Cell

Differential centrifugation Cell Fractionation Homogenization Homogenate Differential centrifugation

(1,000 times the force of gravity) Cell Fractionation 1,000 g (1,000 times the force of gravity) 10 min Supernatant poured into next tube 20,000 g 20 min 80,000 g 60 min Pellet rich in nuclei and cellular debris 150,000 g 3 hr Pellet rich in mitochondria (and chloro-plasts if cells are from a plant) Pellet rich in “microsomes” (pieces of plasma membranes and cells’ internal membranes) Pellet rich in ribosomes

Surface Area The logistics of carrying out cellular metabolism sets limits on the size of cells The surface area to volume ratio of a cell is critical As the surface area increases by a factor of n2, the volume increases by a factor of n3 Small cells have a greater surface area relative to volume

Surface Area Total Surface Area 6 150 750 Total Volume 125 125 1 S / V Ratio

The Generic Cell ALL cells have A plasma membrane, DNA, cytosol, and ribosomes Differences between Prokaryotic and Eukaryotic? Eu means true, Karyon means kernel (nucleus) Pro means before

The Prokaryotic Cell Fimbriae Nucleoid Ribosomes Plasma membrane Fig. 6-6 The Prokaryotic Cell Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial chromosome Cell wall Capsule 0.5 µm Flagella (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM)

The EUKaryotic Animal Cell Nuclear envelope ENDOPLASMIC RETICULUM (ER) Nucleolus NUCLEUS Rough ER Smooth ER Flagellum Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome

The Plant Rough endoplasmic reticulum Nuclear envelope Nucleolus Fig. 6-9b Nuclear envelope Rough endoplasmic reticulum The Plant NUCLEUS Nucleolus Chromatin Smooth endoplasmic reticulum Ribosomes Central vacuole Golgi apparatus Microfilaments Intermediate filaments CYTO- SKELETON Microtubules Mitochondrion Peroxisome Chloroplast Plasma membrane Cell wall Plasmodesmata Wall of adjacent cell

Nucleus Nuclear envelope: double membrane- EACH a lipid bilayer Pore complex lines each pore Nuclear lamina lines envelope Nuclear matrix Chromosomes Chromatin Nucleolus

Close-up of nuclear envelope Fig. 6-10 Nucleus 1 µm Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Rough ER Surface of nuclear envelope Ribosome 1 µm 0.25 µm Close-up of nuclear envelope Pore complexes (TEM) Nuclear lamina (TEM)

Ribosomes Free Bound Both

EndoMembrane System Components of the endomembrane system: Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane These components are either continuous or connected via transfer by vesicles

ER Lumen-space inside Saclike structure called cisternae Smooth: lipid synthesis, detoxification by attaching OH- making toxins more soluble and easy to flush from cells and body, Ca+ storage Rough: secrete proteins (especially glycoproteins), helps fold proteins as they pass through pores Transitional ER buds off transport vesicles

Smooth ER Nuclear envelope Rough ER ER lumen Cisternae Transitional ER Fig. 6-12 Smooth ER Nuclear envelope Rough ER ER lumen Cisternae Transitional ER Ribosomes Transport vesicle 200 nm Smooth ER Rough ER

Golgi Apparatus Cisternae Cis face (ER side) Trans face (shipping side) Proteins modified as they go from cistrans Molecular ID tags added to products to direct shipment

Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi Fig. 6-16-3 Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi

Mitochondria 2 inner membranes Cristae Matrix Imtermembrane space Some enzymes necessary for respiration are bound to membranes

Chloroplast Double membrane with stacks of membranous sacs inside those Thylakoids Grana Stroma

Peroxisome Single membrane bound Transfers H to O to form H2O2 Break down fatty acids, detoxification Enzymes to break down H2O2 too Glyoxysomes in plant seeds turn fatty acids to ______________________________. Often have a granular or crystalline core

peroxisome .

The Cytoskeleton A network of fibers extending throughout the cytoplasm Maintains shape of cell, gives support Allows cellular motility through interactions of the cytoskeleton with motor proteins Cytoplasmic streaming, vesicular migration, cilia, flagella, etc.

cytoskeleton Microtubules Microfilaments Intermediate filaments Centrosomes and centrioles Cilia and flagella

http://www.youtube.com/watch?v=nGagdu--xPc

Centrosomes and Centrioles Centrosome: near nucleus, “microtubule organizing center” Centrioles: nine sets of triplet microtubules arranged in a ring

Cilia and Flagella Difference in numbers and movement Can propel a cell, or propel fluid along a cell. Examples? Some cilia act as receptors and usually there is only one per cell! 9+2: 9 doublets of microtubules around outside with 2 single microtubules in the center. (non-motile cilia have a 9+0) Dynein proteins allow for movement

9+2 Cilia and flagella .

Extracellular Components: Cell Walls of Plants Cell Walls of Plants: primary cell wall-first temporary wall constructed by new plant Middle lamella glues adjacent cells together with sticky polysaccharides (pectins) Secondary cell wall grows between the membrane and primary cell wall: stronger

Exxtracellular components: Animals ECM: Extracellular matrix composed of glycoproteins (like collagen) embedded in proteoglycans (woven network of protein and carbos) Fibronectin: ECM glycoprotein attached to integrins: surface receptor proteins that can transmit signals between the ECM and the cytsoskeleton

ECM .

Intercellular JUnctions In plants: Plasmodesmata: channels between plant cells through which cytoplasm can flow In animals: Tight junctions, desmosomes, and gap junctions.

Animal Intercellular Junctions .