Chapter 3Cytoplasmic Organelles and the Nucleus

What general features can be identified in this “typical”

generalized cell?

A Tour Inside a Cell (video)

Cells

• Structural unit of all living things• 50 – 100 trillion cells in human body• 200 different cell types that vary in size,

shape, function• A cells SHAPE reflects its function

Fibroblasts

Erythrocytes

Epithelial cells

Macrophage

Nerve cell

Fat cell

Sperm

Skeletalmusclecell

Smoothmuscle cells

(a) Cells that connect body parts, form linings, or transport gases

(c) Cell that stores nutrients

(b) Cells that move organs and body parts

(d) Cell that fights disease

(e) Cell that gathers information and controls body functions

(f) Cell of reproduction

Diversity of Cell Structure and Function

Nucleus • Porous phospholipid

membrane• Inner membrane lined

with intermediate filaments (nuclear lamina) that maintains shape

• ER often is an extension of the nuclear membrane

• Contain DNA of eukaryotic cells – “brain” of cell

A single strand of DNA can be 3 meters long. How does all that DNA fit?

Condensation of Eukaryotic Chromosomes

Nucleosome = DNA coils around histone proteins

Chromatin = supercoiled nucleosomes

Looped Domains = supercoiled chromatin

Chromosome = supercoiled looped domains

Ribosomes

•Assembles amino acids into polypeptide chain, which eventually folds into functional protein

•Made of rRNA and protein

•2 subunits: large and small

Nucleolus

•Located inside nucleus

•makes ribosomal subunits by combining rRNA and proteins imported from cytoplasm

•subunits leave nuclear pore and assembles into a ribosome in the cytoplasm

What is the endomembrane system?

• System of membrane-bound organelles in cells that work cooperatively together to create secretory proteins, membrane-bound proteins, or plasma membrane proteins– Nucleus– ER– Golgi– Transport Vesicles– Lysosomes– Peroxisomes– Vacuoles– Plasma Membrane

Rough Endoplasmic ReticulumRER w/ bound ribosomes

Space w/in ER = cisternae space

Fcn: to fold and modify secretory proteins (glycoproteins) within cisternae space

-attaches carbohydrates called oligosaccharides to growing and folding polypeptide chain -- vesicles bud off from RER and delivers glycoprotein to Golgi

Rough ER

Smooth ER

Ribosomes

Interior of rough ER

Protein being made inside ER

mRNA outside ER

Ribosome outside ER

Vesicle

Rough ER

Golgi Apparatus

Accepts vesicles from RER (cis side)

Adds and removes monomers of sugar (small subunits) from glycoproteins

Adds “ID” tags (like phosphate groups) and uses these to “sort” proteins into different vesicles

Dispatches vesicles w/glyco-proteins for shipping (trans side)

Protein inside Golgi apparatus

VesicleGolgi apparatus

Golgi apparatus

Vesicle

Cytoskeleton

3 destinations for proteins within Golgi vesicles1) Secreted from cell2) Remains within vesicles vacuole,

lysosome, peroxisome3) Protein becomes part of plasma

membrane

Vesicle Plasma membrane

Proteins

Protein Synthesis and Export of Proteins

Secretion by exocytosisExtracellular fluid

Plasma membrane

Vesicle incorporatedinto plasma membrane

Coatomercoat

Lysosomes containing acidhydrolase enzymes

PhagosomeProteins in cisterna

Membrane

Vesicle

Pathway 3

Pathway 2Secretory vesicles

Proteins

Pathway 1

Golgi apparatus

Cisterna Rough ER

Vacuoles

- Stores water, organic compounds, ions, waste

- Supplemental role in endo and exocytosis as a “vesicle”

Lysosomes• Membrane-bound sac

of digestive enzymes • Acidic env’t

maintained by pumping H+ ions from cytoplasm

• Digests food, worn out cell parts, programmed cell death (webbing b/t fingers, tadpole tails)

Lysosome

Damaged mitochondrion

Peroxisome

• Breaks down toxic substances in liver• Breaks down fatty acids into

carbohydrates for use in CR• In breakdown process, oxygen and

hydrogen combine to create H2O2

• Peroxide = metabolic waste

• ER w/o ribosomes• Makes lipids, oils, steroids• Helps break down CHO• Detoxifies drugs by adding –OH groups

water soluble toxins flushed from body

Smooth ER

MitochondriaMitochondria- Cellular Respiration site- requires oxygen (O2) to

make ATP from glucose (C6H12O6)

- ATP is the energy form used for cellular work

- CO2 and H2O is produced as waste and bi-product of cellular respiration

Oxygen is delivered to our mitochondria from the air and carbon dioxide is released back as waste. Which system is responsible for this function?

MitochondrionInner membrane

Outer membrane

ATP

Cytoskeleton

Network of fibers in the cytoplasm that a) maintains cell shape/mechanical supportb) anchors and/or moves organelles c) helps w/ cell motility

3 components1) microtubules2) microfilaments3) intermediate filaments

Intermediate filament

MicrofilamentCytoskeleton

Microtubule

Microtubules

Structure:Hollow tube made up of α

and β tubulin polypeptide 25 nm diameterCompression Resistent

supports cell shapeForms spindle fibers for

separation of chromosomes, makes up centrioles, and cilia/flagella

Microtubule9 sets of 3 arrangement

(ring formation)Ex. Centrioles, spindle

fibers, basal body of cilia and flagella

9 + 2 arrangement (9 doublets surrounding a pair in the center)

Ex. Cilia and Flagella

Radial Spokes and Dynein Arms of Microtubule

• Dynein arms “walk” along the microtubules to bend and move flagella, using ATP energy

Microfilaments

AKA: actin fibersStructure: twisted double chain of

actin protein that forms a solid rod7 nm diameterTension resistent (protects against

“pulling” forces) Makes up microvilli core,

contracts muscles, causes cytoplasmic streaming and pseudopod extensions in cells

Intermediate Filaments

• In btwn microtubules and microfilaments in size (10 nm)

• Fixes positions of organelles• Organelles w/motor proteins

can move by “walking” along intermediate filaments (as if along a track)

• Helps to maintain cell shape

Plasma MembraneA cell boundary that selectively controls the movement of substances into and out of the cell = Selective Permeability

Made up of a “mosaic” or collection

Phospholipids

Cholesterol

Peripheral/Surface Proteins

GlycoproteinsTransmembrane/Integral protein

Glycolipid

Glycolipid and glycoproteins = Glycocalyx

Why do cells need to increase permeability rate of the plasma

membrane?

Outside of cells bathed in interstitial fluid• Nutrient rich “soup”

– Amino acids, sugars, fats, vitamins, hormones, proteins, salt, waste, neurotransmitters

• Cells need to absorb what they need from this fluid AND remove waste in an efficient manner as needed

One method: microvilli

MicrovilliFingerlike-extensions of plasma membrane

Supported by actin (microfilament) core

Increases cell’s surface area relative to its volume, to increase absorptive and expelling properties

Microvilli and the glycocalyx help cells “stick” together (imagine your fingers interlocked and covered in sugar)

Race to the Board – Cell Drawing

• Class divided into two teams to draw a cell, with all of its organelles. All organelles covered in lecture must be represented in the illustration.

• No use of notes allowed. Must be done from memory.

• All organelles must be accurately drawn, labeled with correct spelling.

• Proper scientific illustration protocol must be followed.