Problem #1 of the day: What macromolecule groups do these molecules belong to?

Problem #2 of the day: Why do proteins fold from the first structure to the last structure?

Chapter 6: A Tour of the Cell You must know: n 3 differences between prokaryotic and eukaryotic cells n The structure and function of organelles common to plant and animal cells n The structure and function of organelles found only in plant cells or animal cells Be able to predict and justify how a change in an organelle would affect the function of the cell or organism.

Cells n The structural and functional units of life n All organisms are composed of at least one cell Essential Knowledge 2.A.3 Organisms must exchange matter with the environment to grow, reproduce, and maintain organization

Prokaryotic vs. Eukaryotic CharacteristicsProkaryotic CellsEukaryotic Cells Plasma membraneYes Cytosol with organelles* Yesyes RibosomesYes NucleusNoYes Size1-10 microns microns` Internal membranesNoyes DomainsBacteria and Archaea Eukarya Prokaryotic ribosomes are slightly smaller and differ in their protein and RNA content-allows for antibiotics to harm them and not eukaryotes like us

eukaryoticprokaryotic viruses Size Comparisons of Cells

Plant vs. Animal PlantsAnimals Cell wallYesNo Cell membraneYes MitochondriaYes PlantsAnimals ChloroplastsLysosomes Cell wallCentrioles Central vacuole and tonoplast Flagella (some plants); cilia plasmodesmataECM Desmosomes, tight and gap junctions

Cell Theory n All living organisms are composed of cells n Cells are the fundamental units of all organisms and the chemical reactions of life take place within cells n All cells come from preexisting cells

Underlying Content for Surface Area to Volume Ratio n SA/V affects exchange of nutrients and elimination of wastes n ↑V → ↓SA/V ratio: demand for exchange of materials increases. This restricts cell size n Smaller cells have a more favorable SA/V ratio

Surface Area to Volume Ratio

Compartmentalization n Subset of functions related to energy and matter n Organelles are specialized n Internal membranes facilitate cellular processes by minimizing competing reactions, increase surface area n Archaea and Bacteria lack internal membranes (prokaryotic cells)

The Plasma Membrane n The plasma membrane and organelle membranes are phospholipid bilayers with various proteins attached or embedded in it. The membrane functions to allow for transport of materials into and out of the cell.

Nucleus Contains genetic material... n DNA codes for protein synthesis (mRNA) n chromatin (unwound DNA) n chromosomes (coiled DNA) n Double membrane envelope with pores n nucleolus: rRNA; ribosome synthesis

Ribosomes n Small, universal, comprised of ribosomal RNA and protein n Sites of protein synthesis via translation of genes n Free ribosomes-found floating in cytosol; make proteins used within the cell n Bound ribosomes-attached to endoplasmic reticulum; make proteins to be exported from the cell

Endomembrane system, I Endoplasmic reticulum (ER) n Continuous with nuclear envelope n Internal area is called cisternal space n Smooth ER – Synthesizes lipids – Metabolism of carbohydrates – Detoxification of drugs/poisons n Rough ER – with ribosomes – compartmentalizes cell – Serves as mechanical support – Site specific protein synthesis – Intracellular transport – Proteins are packaged within vesicles which bud off the ER and move toward the Golgi apparatus

Endomembrane system, II n Golgi apparatus – Series of flattened membrane sacs called cisternae – Proteins from vesicles are modified, stored, and shipped – Golgi stacks have “polarity.” Cis-receives and Trans-ships – Production of lysosomes

The endomembrane system can adapt to the needs of the cell. n Thickness, molecular composition, and types of chemical reactions carried out by proteins in a given membrane are not fixed, but maybe be modified several times during the membrane's life.

Vesicle Movement

Mitochondria-found in all eukaryotic cells quantity in cell correlated with metabolic activity; cellular respiration (ATP synthesis) double membrane-allows compartmentalization and is important to function (outer smooth, inner highly folded) cristae/matrix; cristae contain enzymes important to ATP production and increase surface area for ATP production intermembrane space; contain own DNA

Peroxisomes n Single membrane n hydrogen peroxide is produced in cells; peroxisomes break it down. n Metabolism of fatty acids; detoxification of alcohol (liver) n Hydrogen peroxide then converted to water n Another example of the importance of compartmentalization

The Cytoskeleton Network of protein fibers that runs throughout the cytoplasm that is responsible for support, motility, and regulating some biochemical activities. 3 types of fibers: n Microtubules-made of tubulin; largest; shape, support and tracks for organelles; separation of chromosomes in mitosis; cilia and flagella n Microfilaments-made of actin; smaller; support and muscle movement n Intermediate filaments-more permanent fix shape of cell and position organelles *Not essential knowledge; maybe illustrative example.

*Centrosomes/centrioles n Centrosome: region near nucleus from which microtubules grow (MTOC); contain centrioles only in animal cells n Centrioles: 9 sets of triplet microtubules in a ring; used in cell replication; only in animal cells

Lysosomes n Lysosomes: – sac of hydrolytic (digestive) enzymes; – Intracellular digestion of macromolecules – Phagocytosis – Autophagy: recycle cell’s own organic material (apoptosis) – Good example of the importance of compartmentalization

Vacuoles n Vacuoles – membrane-bound sacs (larger than vesicles) – Also plays a role in intracellular digestion and release of waste products – Contractile (pump excess water) – Plants have a large central vacuole; allows for growth and large sa/v ratio (see tonoplast)

*Cilia/flagella n Locomotive appendages n Ultrastructure: “9+2” 9 doublets of microtubules in a ring 2 single microtubules in center connected by radial spokes anchored by basal body dynein protein

*Extracellular matrix (ECM) n Glycoproteins: proteins covalently bonded to carbohydrate n Collagen (50% of protein in human body) embedded in proteoglycan (another glycoprotein-95% carbohydrate) n Fibronectins bind to receptor proteins in plasma membrane called integrins (cell communication?) n Strengthens tissues and its important for cell communication

*Intracellular junctions n PLANTS: n Plasmodesmata: cell wall perforations; water and solute passage in plants n ANIMALS: n Tight junctions~ fusion of neighboring cells; prevents leakage between cells n Desmosomes~ riveted, anchoring junction; strong sheets of cells n Gap junctions~ cytoplasmic channels; allows passage of materials or current between cells

Chloroplasts- n Found in algae and plants; capture energy through photosynthesis n Structure/function relationship allows cells to capture energy from sunlight and convert it to chemical energy n Chloroplasts contain chlorophyll (pred. type A); green color of plants n Double outer membrane; compartmentalized n Thylakids-where energy capture occurs (ATP and NADPH2 produced) n Stroma: energy is used to fuel Calvin cycle where glucose is made (carbon fixation)

n Cell wall: not in animal cells n protection, shape, regulation n Plant cell: primary cell wall produced first n middle lamella of pectin (polysaccharide); holds cells together n some plants, a secondary cell wall; strong durable matrix; wood (between plasma membrane and primary wall) *Cell Wall

Endosymbiont Theory n Explains how eukaryotes appeared n Proposes that mitochondria and plastids were formerly small prokaryotes that began living within larger cells Evidence includes: Both organelles have a double membrane structure Both organelles have their own ribosomes and DNA Both reproduce (binary fission) independently within the cell

Endosymbiont Theory

*Cell Motility

Bioflix Tours n Animal Cell Animal Cell n Plant Cell Plant Cell