Energy Organelles & Energy Organelles & the Cytoskeletonthe Cytoskeleton

Section 6.5, 6.6, and 6.7

Mitochondria & ChloroplastsMitochondria & Chloroplasts

Convert energy to forms the cell can use for work

Mitochondria – site of cellular respiration ◦Found in plants & animals◦Process that makes ATP from food◦Oxygen is needed

Chloroplasts – site of photosynthesis◦Found in plants & algae only◦Convert solar energy to chemical energy

Both enclosed by membranes

Mitochondria & ChloroplastMitochondria & Chloroplast

Membranes are made on free ribosomesContain their own ribosomesContain a small amount of DNA

MitochondriaMitochondria

Found in all Eukaryotic cellsA cell can have hundreds to thousands of

mitochondria depending on its functionMove around, change shape & divideSurrounded by a double membraneOuter membrane smoothInner membrane folding (Cristae)

◦Increases surface areaIntermembrane spaceMatrix

Mitochondria SturctureMitochondria Sturcture

ChloroplastsChloroplasts

Member of the plant organelle group plastids◦Amyloplasts – colorless that store starch in

roots and tubers◦Chromoplasts – pigments that give fruits and

flowers orange & yellow colors◦Chloroplasts – contain the green pigment

chlorophyll

ChloroplastsChloroplasts

Double membrane separated by intermembrane space.

Thylakoids are flattened stacks of sacs like pancakes or poker chips

Each stack is called a granum (grana)Fluid outside the thylakoids is the stroma

(space)Chloroplasts grow, move, & divide

PeroxisomesPeroxisomes

Single membraneContain enzymes that transfer hydrogen

from various substances to oxygen Hydrogen peroxide is produced (H2O2)Functions

◦Break fatty acids down◦Detoxify alcohol

H2O2 is converted to water because it is toxic to the cell

Peroxisome structure (TEM)Peroxisome structure (TEM)

CytoskeletonCytoskeleton

A network of fibers extending throughout the cytoplasm

Plays a role in organizing the structures & activities of the cell, supporting the cell, and maintaining its shape

Composed of three types of structures◦Microtubules◦Microfilaments◦Intermediate filaments

Differ in size

CytoskeletonCytoskeleton

Cytoskeleton - SupportCytoskeleton - Support

Gives support Helps the cell maintain shapeProvides anchorage for organellesCan be dismantled and reassembled in a

new location changing the shape of the cell

Cytoskeleton - MotilityCytoskeleton - Motility

Changes in cell locationMovements of parts of the cellInteraction of cytoskeleton with motor

proteinsExamples:

◦Movements of cilia & flagella◦Muscle cell contraction◦Movement of vesicles on “monorail”◦Cytoplasmic streaming

Motor ProteinsMotor Proteins

Cytoskeleton - RegulationCytoskeleton - Regulation

Cytoskeleton can transmit mechanical forces exerted by extracellular molecules via surface proteins of the cell to the interior and even the nucleus

3 Types of Fibers3 Types of Fibers

Microtubules – thickest of the threeMicrofilaments – thinnest of the threeIntermediate filaments – middle range

size filaments

MicrotubulesMicrotubules

Hollow rodsMade from protein tubulin (alpha & beta)Shape and support the cellServe as tracks for motor proteinsExamples:

◦Guide secretory vesicles from the golgi to the plasma membrane

◦Responsible for the separation of chromosomes during cell division

Centrosomes & CentriolesCentrosomes & Centrioles

Microtubules grow out from centrosomes“Microtubule-organizing center”Animal cells contain a pair of centrioles

found at right angles to each otherEach composed of 9 sets of triplet

microtubules arranged in a ringBefore the cell divides the centrioles

replicateHelp in organizing microtubules but not

essential Plants lack centrioles

Cilia & FlagellaCilia & Flagella

Specialized arrangement of microtubules is responsible for beating of cilia & flagella

Flagella ◦1-2 per cell, undulating motion

Cilia◦Large numbers on cell surface, work like oars

Both are made from 9+2 arrangementDynein arms responsible for bending

movements of cilia & flagella◦Similar to a cat walking up a tree

Motion of Flagella & CiliaMotion of Flagella & Cilia

9+2 arrangement of cilia & 9+2 arrangement of cilia & flagellaflagella

Dynein “walking”Dynein “walking”

Microfilaments (Actin filaments)Microfilaments (Actin filaments)

Solid rodsAlso called actin filaments because they

are built from actin proteinTwisted double chain of actin subunitsFunction is to bear pulling forcesPart of the contractile apparatus of muscle

cellsActin & myosin (thicker than actin)

interact to produce muscle contraction

Role of Microfilaments & motilityRole of Microfilaments & motility

Intermediate FilamentsIntermediate Filaments

Mid size filamentSpecialized for bearing tensionVery diverse (keratins)More permanent fixtures of cells Important in reinforcing the shape of a cell

and fixing the position of certain organelles

Extracellular componentsExtracellular components

Things beyond the plasma membranePlants – cell wallAnimals – Extracellular matrix (ECM)

Plant Cell WallPlant Cell Wall

ProtectsMaintains shape Prevents excess uptake of waterThicker than plasma membraneStrong fibers in a matrix formation like

fiberglass make it extremely strongLayers of cell wall are made that include

pectin (thickening agent in jams & jellies), cellulose, & hardening substances.

Extracellular Matrix of AnimalsExtracellular Matrix of Animals

Glycoproteins – proteins with carbohydrate chains

Collagen – accounts for ½ total protein found in the body

Proteoglycans – Collagen is embedded in Fibronectin – attaches the ECM to integrinsIntegrins – span the membraneImportant communication from the cell to

its surroundings

Extracellular MatrixExtracellular Matrix

Intercellular JunctionsIntercellular Junctions

Plants – PlasmodesmataChannels between cell walls that allow

neighboring cells to communicate with one another

Water & small solutes can pass freely from cell to cell

Plant PlasmodesmataPlant Plasmodesmata

Intercellular JunctionsIntercellular Junctions

Animals ◦Tight junctions – form continuous seals around

the cells – prevent leakage◦Desmosomes – fasten cells together into strong

sheets - anchoring◦Gap junctions – communicating junctions –

provide cytoplasmic channels from one cell to an adjacent cell

Animal cell junctionsAnimal cell junctions

Macrophage eating bacteriaMacrophage eating bacteria