Cell Structure and Function II

Chapter 3

http://www.cnas.missouristate.edu/labimages/Biology/Bio122/week8.htm

Outline

2. Cytoplasma. General constituents

b. Major organelles and their functions

c. Cytoskeletal elements

3. Nucleusa. Main constituents

b. Chromatin condensation

Cytoplasm

Fig. 3.3

Cytosol

• Cytosol– Viscous fluid– Water– Dissolved material such as

ions, ATP and nucleotides

General constituents

Fig. 3.5

cytosol

Organelles

– Organelles• “little organs”

General constituents

Fig. 3.5

Various organelles

Inclusions

• Non-functional formed elements

• Storage – Lipid, glycogen

General constituents

Fig. 3.5

Representative Animal Cell

Mitochondria

Organelles

The Mitochondrion

Bounded by adouble membrane

Inner membrane and matrixare packed with metabolic

enzymes – where fuel is convertedto energy in the form of ATP

Main site of ATP Production

Organelles

Cristae (pl)

Mitochondria

• What type of cells have a lot of mitochondria?

Muscle

Organelles

Representative Animal Cell

Endoplasmic Reticulum (ER)

Endoplamsic Reticulum (er)• “inside cytoplasm

network”• Branching network in

the cell• Flattened tube

compartmentalized by lipid bilayer

• Hollow– Space inside is

cisternae• reservoir

Organelles

Fig. 3.26

Endoplasmic Reticulum• Rough and smooth forms• Rough has ribosomes on

the outer surface while smooth doesn’t

• Rough is for protein synthesis

• Smooth is for lipid (steroid) synthesis and detox

• Where do you think smooth would be found?

Fig. 3.26

Organelles

Representative Animal Cell

Free ribosomes

Organelles

Ribosomes

• Protein and rRNA• Very small• Not membrane bound• Important in protein

synthesis

Complete ribosome

large subunit

small subunit

Fig. 3.26

Organelles

Representative Animal Cell

Golgi Complex

Organelles

Golgi Complex• Camillo Golgi• Single bilayer• Like an flattened,

extended sac• Golgi vesicles associated

with them• “cellular post office” while

vesicles are the delivery vehicles

• Finishes the protein– Cuts, splices, adds carbs

to glycoproteins• Gets stuff from the er

Organelles

Fig. 3.27

The Golgi Complex

plasma membrane lysosomes

Vesicles directed to

Organelles

from er

Representative Animal Cell

Lysosomes

Organelles

Lysosomes• “splitting body”• Single membrane• Produced by Golgi• Contain acid hydrolases

– pH inside is 3-4• Break apart many things

– All classes of biomolecules, phagocytized bacteria, worn out organelles and cells

• e.g. DNases, RNases, proteases, lipases

• Apoptosis– Programmed cell death

Organelles

Fig. 3.5

Cytoskeleton

• Protein filaments and cylinders that help give the cell shape and support– Insoluble in water

• Also involved in intracellular movement and movement of the whole cell

• Not membrane bound

cytoskeleton

Fig. 3.31

Fig. 3.31

Cytoskeleton

• Three types (in increasing size)

– Microfilaments– Intermediate filaments– microtubules

cytoskeleton

Microfilaments

• Diameter of 7 nm (10-9 m)• Composed of actin

– Links together to form a chain– 2 chains form a helix

• Supports plasma membrane• Scaffolding

– Core of microvillus

• Important in muscle contraction

• Important in cytokinesis

http://perso.wanadoo.fr/i-magesdemarc/introfigure4.htm

cytoskeleton

http://liquidbio.pbworks.com/Matthew-Damstrom-Organelles-Project

Terminal web

Intermediate filaments

• Diameter 10 nm• Not a single type of

protein but dependent upon the type of cell

• e.g. keratin of epithelial cells

• Support -“guy wires”• Reinforce desmosomes• Toughest type of

cytoskeletal element

http://www.cytochemistry.net/Cell-biology/intermediate_filaments.htm

cytoskeleton

Microtubules

• Diameter 25 nm• Not stable – break down

and assemble quickly• Hollow tube

– Made up of protein called tubulin

• Critical in mitosis• Highway to move material• e.g. flagella, cilia,

centrioles Fig. 3.32

cytoskeleton

Representative Animal Cell

Centrioles

cytoskeleton

Centrioles

• Every cell has at least one pair– During mitosis it must

replicate so it will have 2 pairs

• Composed of 9 triplets of microtubules

• Lies in an area of the cell called the centrosome– Microtublule organizing

center

cytoskeleton

Fig. 3.30b

• Fig. 3.31

centrosome

nucleus

Main constituents

Nuclear envelope (membrane) isa double membrane

Nucleolus (nucleoli, pl.)site of ribosome formation

Chromatin

The Nucleus

• Largest organelle• Where the DNA is

located• Most cells have one

(uninucleate)• RBC’s have no

nucleus (anucleate)• Skeletal muscle has

more than one (multinucleate)

Nucleus

Fig. 3.25a

The Nucleus

• Nuclear envelope– Double membrane– Forms pores for the

passage of materials

Fig. 3.25b

Nucleus

The Nucleus

• Nucleolus (nucleoli)– Site of ribosome

synthesis– Can be more than one in

a nucleus

Fig. 3.25a

Nucleus

The Nucleus

• Chromatin– Complex of DNA and

protein– Compacted/condensed

during mitosis– 3 meters in a typical cell– Proteins responsible for

the condensing– Looks like beads on a

stringFig. 3.25b

Nucleus

Chromatin

Fundamental structural unit of chromatin

“beads on a string”

DNA compaction

Nucleus