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 phoshoplipid 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 JunctionsPLANTS: 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