October 8

Dispatch1) What is the function of the

mitochondria?2) What is the function of the chloroplast?3) Make a Venn Diagram comparing

prokaryotes, plant and animal cells• Osmosis/Diffusion Pre-lab due Tuesday. Background on cell membranes,

diffusion, osmosis• Ecology FAQs due Wed• Pick up cell model questions and attach them to your notebook

Endosymbiotic theory

• http://www.sumanasinc.com/webcontent/animations/content/organelles.html

Endosymbiotic Theory

• Mitochondria and chloroplasts were once free living prokaryotes that were engulfed by ameoba-like eukayotic cells.

Evidence: • 1) same size as bacteria • 2) double membrane• 3) presence of ribosomes• 4) presence of DNA• 5) reproduce on their own

Vacuoles

Vacuoles•membrane-bound sacs

(larger than vesicles)• Store substances• Storage in of water,

sugars, salts, pigments in plants

Peroxisomes

• Single membrane• Produce hydrogen

peroxide (H2O2) in cells

• Metabolism of fatty acids; detoxification of alcohol (liver)

• Hydrogen peroxide then converted to water

The cytoskeleton• The cytoskeleton is a network of

filaments and tubules that extend from the nucleus to plasma membrane.

• Fibrous network in cytoplasm• Support, cell motility, biochemical

regulation

Microtubules: •thickest; •tubulin protein; •shape, support, transport, chromosome separation

Microfilaments :• •thinnest;• •actin protein filaments; • •motility, cell division, shape

Intermediate filaments:middle diameter; •keratin; •shape, nucleus anchorage

Actin filaments or Microfilaments

• Microfilaments are fine, thread-like protein fibers, 3-6 nm in diameter. They are composed predominantly of a contractile protein called actin.

• Microfilaments' association with the protein myosin is responsible for muscle contraction.

• Microfilaments can also carry out cellular movements including gliding, contraction, binding proteins, and cytokinesis.

• They interact with motor molecules, which are proteins that can attach, detach, and reattach along an actin filament.

Intermediate filaments

• Intermediate Filaments Intermediate filaments are about 10 nm diameter and provide tensile strength for the cell.

• They are ropelike assembly of fibrous protein.• Some support nuclear envelop, plasma membrane, in skin

cells

Microtubules

• Microtubules are cylindrical tubes, 20-25 nm in diameter. They are composed of subunits of the protein tubulin--these subunits are termed alpha and beta.

• Microtubules act as a scaffold to determine cell shape, and provide a set of "tracks" for cell organelles and vesicles to move on.

• Microtubules also form the spindle fibers for separating chromosomes during mitosis. When arranged in geometric patterns inside flagella and cilia, they are used for locomotion.

Centrioles • The centrosome, also called the "microtubule organizing center", is an

area in the cell where microtubles are produced. • Within an animal cell centrosome there is a pair of small organelles, the

centrioles, each made up of a ring of nine groups of microtubules. There are three fused microtubules in each group. The two centrioles are arranged such that one is perpendicular to the other.

• During animal cell division, the centrosome divides and the centrioles replicate (make new copies). The result is two centrosomes, each with its own pair of centrioles. The two centrosomes move to opposite ends of the nucleus, and from each centrosome, microtubules grow into a "spindle" which is responsible for separating replicated chromosomes into the two daughter cells.

Cilia and flagella, external movement• Cellular movement is accomplished by cilia and flagella. • Cilia are hair-like structures that can beat in synchrony causing

the movement of unicellular paramaecium. Cilia are also found in specialize linings in eukaryotes. For example, cilia sweep fluids past stationary cells in the lining of trachea and tubes of female oviduct.

• Flagella are whip-like appendages that undulate to move cells. They are longer than cilia, but have similar internal structures made of microtubules. Prokaryotic and eukaryotic flagella differ greatly.

• Both flagella and cilia have a 9 + 2 arrangement of microtubules. This arrangement refers to the 9 fused pairs of microtubules on the outside of a cylinder, and the 2 unfused microtubules in the center. Dynein "arms" attached to the microtubules serve as the molecular motors. Defective dynein arms cause male infertility and also lead to respiratory tract and sinus problems.

Cytoskeleton questions

Which component of the cytoskeleton is most important in:

1)holding the nucleus in place within the cell

2) Guiding transport vesicles from the Golgi to the plasma membrane

3) contracting muscle cells

RibosomesRibosomes: • Are found in prokaryotes and eukaryotes• Are where protein manufacturing occurs• Are composed of 2 subunits (large + small)• Receive RNA from the nucleusTypes of ribosomes:• 1) Free •cytosol; •protein function in cell• 2) Bound •endoplasmic reticulum; •membranes, organelles, and export

Endomembrane system: includes nuclear envelope, ER, Golgi, and vesiclesStarts in ER

Endoplasmic reticulum (ER) is made of flattened vessicles.

Rough ER •with ribosomes• is connected to the nuclear

envelop •metabolism of carbohydratessynthesis of secretory proteins

(glycoproteins), membrane productionSmooth ER is connected to rough ER •no ribosomes •synthesis of lipids, • •detoxification of drugs and poisons

Endomembrane system, from ER to Golgi

Golgi apparatus• Looks like a stack of pancakes• In animal cells, 1 side of the pancake is directed towards the ER and the

other to the plasma membrane. WHY??• In the Gogi, ER products are modified, stored, and then shipped• Trans face (shipping) & Cis face (receiving)• Cisternae: flattened membranous sacs• The Golgi packages its products in transport vesicles that depart at the outer

face.

The Story of Protein Production

DNA RNA

Golgi

ApparatusNucleus

RibosomesERO

utside the Cell

The DNA holds all the genetic information.

But there’s a problem. The DNA can’t leave the nucleus.

This information gives us our traits, such as eye color, hair type and skin tone.

To get the genetic information out tothe cell, DNA makes a copy of itself.

DNA RNA

ER

Golgi

ApparatusNucleus

RibosomesO

utside the Cell

Unlike DNA, this copy (called RNA)CAN leave the nucleus.

The RNA leaves the nucleus andtravels to one of the many ribosomes.

At the ribosome, the RNA is translatedinto protein.

In this case it is the protein that gives usour skin tone.

DNA

Golgi

ApparatusNucleus

RibosomesERO

utside the Cell

This newly made protein is not quitedone yet. It must be modified.

The ER modifies the protein by makinga few additions to it.

The protein is almost done. It is packaged into a bubblecalled a transport vesicle.

Then it shipped to the Golgi apparatus. At the Golgi, some last modificationsare made.Then it is shipped to the cell membrane

where it will be secreted from the cell.This skin protein will travel to a skin cell to give the skin cell color.

Protein Presentations

1) With your partner, practice moving the cards and saying the script

2) You will be called randomly to present