Cells… part II

Converting Energy Mitochondria convert sugars and fats to NRG (ATP) with the help of oxygen Cellular respiration Chloroplasts convert sunlight (solar NRG) to chemical NRG Photosynthesis Both have: 2 membranes Their own DNA and ribosomes Ability to grow and reproduce independently of the cell

Mitochondria • quantity in cell correlated with metabolic activity •location of cellular respiration •double phospholipid membranes w/ imbedded proteins - infoldings = cristae - space inside folds = matrix (contains enzymes, DNA, etc) - intermembrane space between cristae and smooth outer membrane

Chloroplasts •type of plastid - contain pigments and used for storage in plants - amyloplasts store starch, chromoplasts store orange pigments, etc. •thylakoids (flattened disks) and grana (stacked thylakoids) •stroma (fluid surrounding thylakoids)- contains enzymes, DNA, etc.

Peroxisomes Single membrane Don’t bud from endomembrane system like lysosomes Metabolism of fatty acids; detoxification of alcohol (liver) Creates H2O2 as a byproduct of detoxification Hydrogen peroxide then converted to water and oxygen by enzymes

The Cytoskeleton Fibrous network in cytoplasm Support for organelles Cell motility through interaction w/ motor proteins Biochemical regulation- sending of mechanical signals

Components of the Cytoskeleton Microtubules: •thickest •tubulin protein •shape, support, transport, chromosome separation • centrosomes, centrioles, cilia, and flagella Microfilaments : •thinnest; •actin protein filaments; •motility, cell division, shape •includes actin and myosin Intermediate filaments: •middle diameter •keratin; •shape, nucleus anchorage • nuclear lamina and cell framework

Centrosomes/centrioles Type of microtubule Centrosome: region near nucleus Centrioles: 9 sets of triplet microtubules in a ring; used in cell replication; only in animal cells

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

Dynein “walking” Responsible for movement of cilia and flagella Arms of microtubules “walk” along the adjacent ones, causing a wave-like motion

Microfilament Movement Thin strands of actin and thicker strands of myosin allow: Muscles to contract Amoebas to move w/ pseudopodia Cytoplasm to “stream” in plant cells

Cell Wall Only in plant cells primary cell wall produced first middle lamella of pectin (polysaccharide) forms later holds cells together some plants have a secondary cell wall strong durable matrix wood between plasma membrane and primary wall

Extracellular matrix (ECM) Glycoproteins proteins covalently bonded to carbohydrate Collagen 50% of protein in human body embedded in proteoglycan (another glycoprotein-95% carbohydrate) Fibronectins bind to receptor proteins in plasma membrane called integrins cell communication

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