Term
| Describe, in detail, the structure of a typical eukaryotic ribosome. |
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Definition
80 S – made of large subunit (60 S) and small subunit (40 S); 4 RNA molecules (rRNA) and 70 proteins RNA acts as scaffolding for the
proteins. 60 S – has 28, 5.8, and 5 S RNA molecules 40 S – has 18 S RNA molecules |
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Term
| Chromosomes in the nucleus of cells were observed to have constrictions called ____ ____ regions. These regions made up the _____ region of a structure called the nucleolus. The nucleolus also has a ______ region. |
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Definition
| Chromosomes in the nucleus of cells were observed to have constrictions called nucleolar organizing regions. These regions made up the fibrillar region of a structure called the nucleolus. The nucleolus also has a granula rregion. |
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Term
| Describe what Barbara McClintock observed when she looked at the activity in the fibrillar region of the nucleolus. Which types of RNA were being transcribed? |
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Definition
| She saw the “Christmas tree” arrangement – beads on a string. Many RNA polymerase molecules transcribing genes, with spacer regions in between. Large rRNA was being transcribed (28, 18, 5.8 S). |
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Term
| Define differential gene expression and give an example. |
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Definition
| Due to varying environmental conditions, different genes are transcribed to varying degrees in different cell types. Example given in class – transcription of the 5 S rRNA gene is dependent on the concentration of TF3A present --> prefers S type to O type --> producing differing percentages of gene transcript in oocyte versus somatic cell |
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Term
| How does the cell promote the transcription of a 5S rRNA gene? |
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Definition
| Small rRNA – promoter region is in the middle of gene (internal control region) from nt 50 – nt 83; region is bound by TF3A on coding strand to attract RNA polymerase III |
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Term
| Draw and label the structure of a typical molecule of tRNA. There are at least __ different tRNA molecules and __ families of tRNA. |
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Definition
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Term
| What are the 3 phases of protein synthesis? |
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Definition
| Initiation, Elongation, Termination |
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Term
| What is the first codon on an mRNA transcript? |
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Definition
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Term
| What are the dual functions of TFIIIA? |
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Definition
| Protein transcription factor will bind to this promotor and allow RNA pol III to come in and bind. escort 5srRNA to granular region to be processed |
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Term
| True or False. The 40S and 60S subunits will be assembled for form 80S inside the nucleus and transported out to the cytoplasm. |
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Definition
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Term
| An ___ ___ ___ is an enzyme that attaches the appropriate amino acid onto its tRNA. There are about ______ different enzymes. |
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Definition
| aminoacyl tRNA synthetase; 20 |
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Term
How many nucleotides are different between O and S type promotors?
Which one does TFIIIA have a higher affinity for? |
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Definition
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Term
| Divide the process of protein synthesis into three phases. List the three phases and describe each one in detail. |
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Definition
Initiation, elongation, and termination; Initiation – IF3 brings the mRNA to bind with the 40 S ribosomal subunit and snaps the first codon (AUG) into its proper place. IF1 and IF2 help escort the first tRNA molecule and amino acid (methionine) and bind its anticodon (UAC) to the first codon. 60 S ribosomal subunit comes in and binds to the mRNA, displacing all initiation factors.
Elongation – Tu and Ts bring in the next tRNA molecule into the lumen of the ribosome and use a GTP to do so. Peptidyl transferase cuts the bond between the adenine on the first tRNA molecule and the carboxyl carbon of the amino acid and uses the energy created to bond the first and second amino acids together. G-translocase will then shift the code, 3 nucleotides at a time, using a molecule of GTP for each shift. What was in the P site will be transferred out of the ribosome and what was in the A site will be transferred to the P site. This cycle is repeated. As the protein elongates, the first amino acid sticks out furthest from the ribosome.
Termination – Stop codons (UAA, UAG, UGA) are recognized by releasing factors (R1 and R2) and the protein is removed from tRNA and the tRNA is removed from the ribosome. IF3 breaks the mRNA-ribosome complex and process is ready to begin again. |
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Term
| What is the first codon on an mRNA transcript? What are the three possible stop codons? |
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Definition
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Term
| True or False: A protein will fold into its higher order structure during the process of elongation |
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Definition
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Term
| How do most antibiotics work? Give an example of a chemical that will block eukaryotic protein synthesis. |
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Definition
Antibiotics block prokaryotic protein synthesis. Cycloheximide blocks
eukaryotic protein synthesis. |
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Term
| What three compounds make up the plasma membrane and in what quantities? |
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Definition
| Lipids (about 50%), Proteins (about 45%), Carbohydrates (about 5%) |
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Term
| What are three ways to regulate the fluidity of a plasma membrane? |
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Definition
Make the fatty acid tails longer or shorter. Regulate saturation of the fatty acid tails – increase/decrease number of double bonds
Increase/decrease amount of cholesterol in the membrane |
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Term
| What is diffusion and what types of molecules can diffuse? |
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Definition
| Diffusion is the movement of molecules from high concentration to low concentration. Small, nonpolar molecules readily diffuse across the plasma membrane. |
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Term
| What are the three types of carrier proteins? Give an example of each. |
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Definition
| Uniport – moving one type of molecule in one direction; ex. Movement of amino acids Symport - moving two types of molecules in one direction; ex. Glucose-sodium transport in gut cells Antiport – moving two types of molecule in opposite directions; ex. Sodium-potassium ATPase (pump) |
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Term
| List a few functions of the proteins present in the plasma membrane. |
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Definition
| Enzymatic activity Transport Structural components Cell signaling (especially glycoproteins |
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Term
| Give an example of a cell that will use endocytosis. Give an example of a cell that will use exocytosis. |
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Definition
Macrophages; any type of secretory or glandular cell (like pancreatic
cells) |
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Term
| Describe the differences between endocytosis and receptor-mediated endocytosis. What is one molecule that needs to enter the cell through receptor-mediated endocytosis? Why is a clathrin coat needed for some vesicles? |
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Definition
Receptor-mediated endocytosis is very specific for the type of material that it will bring into the cell – requires a receptor on the cell
membrane specific for a particular ligand Clathrin coat needed in receptor-mediated endocytosis to protect the vesicle for destruction vesicle and contents will go to a very specific location once inside the cell LDL (cholesterol) is an example of a molecule that needs to enter the cell through receptor-mediated endocytosis. |
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Term
| What are the components of ground cytoplasm and in what quantities are they present? |
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Definition
| 70% water, 20-25% protein, 5% small organic material and ions |
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Term
| What are the two differences in structure between rough and smooth endoplasmic reticulum? |
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Definition
| Rough ER has 80 S ribosomes bound to it, while smooth ER does not. Rough ER looks like a tube in cross section (flat and planar), while smooth ER resembles a sphere. |
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Term
| The __ S subunit of a ribosome is bound to the membrane of the rough ER, and the __ S subunit is bound to it forming a functional __ S ribosome. This indicates that the primary function of rough ER is what? |
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Definition
| 60; 40; 80; protein synthesis |
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Term
| What is the difference between excretion and secretion? True or False: The Golgi is involved in both of these processes. |
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Definition
| False; Excretion – getting rid of waste products Secretion – physiologically valuable products transported to affect other cells/organisms |
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Term
| Describe the Golgi’s part in membrane recycling. |
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Definition
| Vesicles come back to the Golgi after they move their contents and the membrane is reprocessed/modified to re-use the lipids and proteins |
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Term
| What is the function of a nuclear pore? What regulates the molecules that go through pores? |
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Definition
Nuclear pores are breaks in the nuclear membrane that are distributed uniformly along membrane – any traffic that wants to get into the nucleus must go through this hole, easier to fit through a pore than
through a lipid bilayer Fibrous proteins regulate what will go through the pore – have to have a special tag |
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Term
| What is a leader sequence? |
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Definition
| First 20 codons on mRNA whose corresponding amino acids are generally very hydrophobic signals the rest of translation to occur in another location like the rough ER or the mitochondria |
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Term
| What types of proteins are generally synthesized in the rough ER? |
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Definition
All membrane-bound proteins (transmembrane, peripheral)
Luminal proteins that are eventually moved to other organelles (organellar proteins, with the exception of mitochondrial proteins) or secreted out of the cel |
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Term
| Describe the process of glycosylation in the rough ER. What monosaccharides are used in this process? This process is more correctly named ______ glycosylation. |
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Definition
| Phosphate group added to a dolichol (lipid in the membrane of the rough ER) and sugars continually added to this group until the synthesis of the oligosaccharide is over. Sugar is built on the cytoplasmic side of the rough ER and then flipped to the luminal side. Glycosylases cut the sugar from the dolichol and attach it to a protein that was synthesized in the rough ER. Sugar will only attach to the amino acid asparagine (asn) and only to those that have a serine or threonine one amino acid away. N-acetylgulcosamine, mannose, and glucose are the sugars used in this process. |
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Term
| List and describe the two functions of the smooth endoplasmic reticulum. |
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Definition
Lipid synthesis – phospholipids built from scratch and as a monolayer by enzymes on the cytoplasmic side of the smooth ER; some are flipped to the
luminal side after synthesis (phosphotidyl-choline) Detoxification – reduced chemicals are oxidized by cytochromes (like cytochrome P450) |
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Term
| Why is it so easy for the ER to expand and shrink quickly? |
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Definition
| The ER can expand and shrink quickly and on demand because it makes all the necessary components of a membrane (lipids, proteins) on site whenever it needs/wants to. |
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Term
| How do we transport proteins and lipids out of the ER to their functional location? |
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Definition
Proteins and lipids travel to the transitional ER and are packaged in vesicles made of transitional ER membrane. These vesicles travel to the Golgi
apparatus to be packaged and processed. |
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