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Cytoskeleton is made up of
a number of different proteins that form thread- or tube- like structures.
Cytoskeletal Proteins smallest to largest
Microfilaments- actin (smallest)
Intermediat filament- keratin, vimentin, neurofilament protein, lamins
Microtubule- tubulin +, microtubule-associated proteins (MAPs) (largest)
What are the two structures that are found as surface extensions of the cell that are supported by the cytoskeleton?
cell extensions that carry out functions of changing shape.
When a cell wants to move along a surface, sampling its environment as it goes, it uses a
Digestive enzymes and cell "flags" form a sugar-protein coat called the
What are microvilli
little shaggy hairs that a cell can increase its surface area with.
The intestinal microvilli provide a tremendous increase in surface area, which serves
to increase absorption of nutrients.
Inside each microvillus
there is a core of actin microfilaments
True or False:Actin filaments are involved in the extension of lamellipodia
How are Microfilaments assembled
made of globular actin protein assembled into two strands
How are Microtubules assembled?
25 nm diameter
hollow tube made of two different forms of tubulin protein
How are Intermediate Filament assembled
10 nm diameter
many different proteins can make these.
The cytoskeleton is needed, not only to keep the structure of individual cells, but as
a framework for the cell to pull against if it has to move itself or be moved by other cells.
Microfilimants and intermediat filaments are
What are used like "railroad tracks" in the cell to move larger particles from one place to another?
Centrosome build the
microtubules that are used to pull chromosomes apart when cells divide.
Centrosomes are an example of
Microtubule-organizing centers (MTOCs)
Microtubule-organizing centers are
cell locations where microtubules are built, so they represent the origin of microtubules.
Centrosomes are comprised of
What is a spindle apparatus?
a rigid structure which lines up, and then divides, chromosomes.
the packed genetic material that must be evenly split between the two daughter cells.
Ribosomes are the site of
What is the job of ribosomes?
to make proteins
Ribosomes are made of two subunits. What are they and what are they called?
What does "s" refer to?
Large subunit- called 60S
Small subunit- called 40S
"s" refers to how fast they fall down to the bottom of a centrifuge tube
Free ribosomes synthesize proteins in
Ribosomes are also found as part of the organelle known as
Rough Endoplasmic Reticulum (RER).
The RER is a collection of membrane bags with ribosomes arranged all along the outside.
Ribosomes use another type of RNA called
messenger RNA (mRNA)- as the instruction sheet
transfer RNA (tRNA)- as a carrier for the raw materials of proteins (amino acids).
At the ribosomes, amino acids are joined together by
peptide bonds to form a protein chain.
What are the 2 types of endoplasmic reticulum?
Rough Endoplasmic Reticulum (RER)
Smooth Endoplasmic Reticulum (SER)
The ribosomes of the RER are part of a system of protein synthesis: the proteins are made by
ribosomes of the RER, and then are released into the RER sacs and the Golgi complex for further processing.
Ribosomes lie on the
surface of the rough endoplasmic reticulum
Genetic code material is copied in the nucleus, then
taken out to the RER to be read.
The SER is actually several different organelles with
similar appearance, so that they cannot be distinguished in electron micrographs of the cell.
Functions of the SER include:
Synthesis- synthesis of lipids and steroids.
Storage- storage of Ca++ in muscle.
- Digestion-Destruction of toxins
- Recycling of cell membrane
- Metabolism of carbohydrates
- Metabolism of steroids
How does the Golgi complex process materials destined for export?
receives unprocessed proteins from the rough endoplasmic reticulum and modifies them into their final form. Then, the Golgi packages the proteins and "tags" them for export to their final destination.
The Golgi is curved, and its functions are not distributed
What does the Entry face (cis face) receive?
receives transported material from the rough endoplasmic reticulum.
What does the Exit face (trans face) give rise too?
Gives rise to secretory vesicles.
What are the first 3 steps in processing protein?
1. Proteins are synthesized in the rough endoplasmic reticulum.
2. Transport vesicles carry "raw", unprocessed proteins to the Golgi.
3. Transport vesicles fuse with the entry (cis) face of the Golgi.
What are the last 3 steps in processing protein?
4. As proteins are processed, they are moved from one Golgi stack to the next by transfer vesicles. In the Golgi stacks, the unused part of proteins are removed by one set of enzymes and, if a glycoprotein is being produced, the branched sugar groups are added here.
5. The last transfer vesicle fuses with the exit (trans) face of the Golgi.
6. The processed, completed protein is packaged into a vesicle and the vesicle is shed from the exit face of the Golgi.
After the protein is packaged into a vesicle, it may end up in one of three places.
1. If a secretory protein, it is packaged into a vesicle and released from the cell by exocytosis.
2. If a membrane protein, it is packaged into a membrane vesicle which fuses with the cell membrane. The proteins or glycoproteins then become part of the cell surface.
3. If the protein is defective or not needed, then it is packaged into a vesicle which is directed to the lysosome for beakdown and recycling.