Cell Structure and Function Chapter 3

The Cell--Considerations Basic unit of life Protection and support Movement Communication Metabolism and energy release Inheritance

Cell Theory All living things are made up of cell(s) Cells are smallest living unit of structure and function for all organisms All cells arise from preexisting cells (No spontaneous generation)

Why Are Cell So Small?

Sizes of living things

Prokaryotes vs Eukaryotes Prokaryotes –“Before nucleus” –DNA in nucleoid region –Ribosomes –Cell membrane –No membrane–bound organelles Eukaryotes –“True nucleus” –DNA in double membrane bound nucleus –Ribosomes –Cell membrane –Membrane –bound organelles

Typical Bacterium---A Prokaryote

Typical Animal Cell-A Eukaryote

Plasma Membrane

Animal cell anatomy

Plant cell anatomy

Nucleus--The Brains of the Cell

Nucleus DNA dispersed throughout Consists of : –Nuclear envelope: Separates nucleus from cytoplasm and regulates movement of materials in and out –Chromatin: Condenses to form chromosomes during cell division –Nucleolus: Assembly site of large and small ribosomal units

Ribosomes Sites of protein synthesis Composed of a large and small subunit Types –Free –Attached to endoplasmic reticulum

Composition of eukaryotic and prokaryotic ribosomes

Cryoelectron microscopy–based image of the E. coli ribosome at ~25 Å resolution. Mol. Biol. Gene, Fig

The Endomembrane System Nuclear envelope Endoplasmic reticulum Golgi apparatus Vesicles

Endoplasmic Reticulum Types –Rough Attached ribosomes Proteins produced and modified –Smooth No attached ribosomes Manufacture lipids Cisternae or Lumen: Interior spaces isolated from rest of cytoplasm

Golgi Apparatus—Traffic Cop Modification, packaging, distribution of proteins and lipids for secretion or internal use Flattened membrane sacs stacked on each other

Function of Golgi Apparatus

Action of Lysosomes

Peroxisomes and Proteasomes Peroxisomes –Smaller than lysosomes –Contain enzymes to break down fatty and amino acids –Hydrogen peroxide is a by-product of breakdown Proteasomes –Consist of large protein complexes –Include several enzymes that break down and recycle proteins in cell

Energy Management Organelles Mitochondria –Aerobic Respiration Chloroplasts –Photosynthesis

Circle of Life Carbon compounds, O 2 CO 2, H 2 O Respiration Photosynthesis Energy Mitochondria Chloroplasts Complex>>Simple

Mitochondria—Powerhouse of the Cell In all eukaryotes Major site of ATP synthesis Membranes –Outer –Cristae: Infoldings of inner membrane Matrix: Substance located in space formed by inner membrane

Chloroplast

Animal cell anatomy

Plant cell anatomy

The Cytoskeleton Function: –Maintenance of cells shape –Movement within cytoplasm –Cell movement –Intracellular communication? Three components –Actin filaments –Microtubules –Intermediate filaments

FUNCTION: CYTOSKELETON= complex network of filamentous proteins extending throughout the cytoplasm Three types of filaments: Microtubules Microfilaments Intermediate Filaments Cell shape Motility: crawling, chemokinesis chemotaxis endo- and exo-cytosis) Anchoring of organelles and cellular structures Organelle movement Cell polarity Tensile strength Chromosome movement

helical structure, diameter ~ 7 nm EX. intestinal microvilli ACTIN FILAMENTS

MICROFILAMENTS ACTIN STRUCTURES IN CELLS: MICROVILLI STRESS FIBRES FOCAL ADHESIONS LAMELLIPODIA FILOPODIA (or MICROSPIKES CONTRACTILE RING (cell division)

hollow cyllinders, diameter ~ 25 nm, emanating from the MTOC

Microtubule structure Made of  and β Tubulin

rope-like fibres, diameter ~ 10 nm, nuclear, cytoplasmic, connecting cell-cell junctions

Structure of intermediate filaments

micro- tubules micro- filaments intermediate filaments Cytoskeleton Elements

Centrioles

In specialized zone near nucleus: Centrosome Each unit consists of microtubules Before cell division, centrioles divide, move to ends of cell and become spindle fibers

Cilia and flagella Cilia (small and numerous) and flagella (large and single) –9 + 2 pattern of microtubules – Iinvolved in cell movement. –Each has a basal body at its base. Plant cells lack centrioles

Structure of a flagellum or cilium

Prokaryotes vs Eukaryotes Prokaryotes –“Before nucleus” –DNA in nucleoid region –Ribosomes –Cell membrane –No membrane–bound organelles Eukaryotes –“True nucleus” –DNA in double membrane bound nucleus –Ribosomes –Cell membrane –Membrane –bound organelles

Evolution of the eukaryotic cell- Endosymbiotic Hypothesis

SUMMARY Cell Theory Physics of Cell Size Eukaryotes –Nucleus –Membrane Bound Organelles ER Golgi Vesicles, ex. Lysosomes –Energy Management Organelles –Cytoskeleton –Prokaryotes –Endosymbiosis