82 terms

BMB 280 Exam 1

bmb 280 at the university of Maine Orono
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Hydrogen bonding by water
Orients the phospholipids in a membrane.
Helps determine the way a protein will fold.
Answer: B & C.
A bacterium was isolated from a glacier where it was thriving in the cold. Based on your knowledge of plasma membranes phospholipids you would expect a predominance of:
Relatively short, unsaturated fatty acids.
Cystic fibrosis is a recessive genetic disorder resulting from a malfunction in transporting:
Cl-
Which of the following conditions below is likely to increase the likelihood of skeletal muscle contraction?
absence of tropomyosin in the cell. Myosin binding site on actin will be open
The primary (1) sequence of a protein:
is ultimately determined by the base sequence of DNA.
determines secondary (2), tertiary (3), and quaternary (4) protein structure.
All of the following are characteristic of passive facilitated transport via a membrane transporter protein EXCEPT:
The transport requires energy input from the hydrolysis of ATP.
What are the characteristics of passive facilitated transport?
a) The molecule to be transported is transiently bound to the transporter protein.
b) The transport is specific for the molecule being transported.
c) The transport is driven by the concentration gradient of the molecule being transported.
e) Transport of the molecule is accompanied by a conformational change in the transporter protein.
With respect to the inner and outer faces of the lipid bilayer making up the plasma membrane, phospholipids are:
Asymmetrical. Remember some phospholipids are found predominantly in the inner bilayer, others in the outer & they are moving around in the plane of the bilayer.
Water molecules can move through the plasma membrane:
by passive diffusion.
through porins.
Breakdown of triglycerides release this water soluble component(s):
glycerol
Which of the following forces stabilize protein tertiary structure?
a) Hydrogen bonding between polar amino acid side chains.
b) Electrostatic interactions between positively and negatively charged amino acid side chains.
c) Disulfide bonds between cysteine residues.
d) Van der waals forces.
The Fluid Mosaic Model describes:
the current model of membrane structure.
Activities associated with the smooth endoplasmic reticulum (ER) include:
a) Synthesis of membrane lipids and steroids
b) Drug detoxification
Functions of the Golgi apparatus include:
Glycosylation of proteins (adding sugar groups)
By definition, prokaryotic cells do not possess __________.
a nucleus
Yeast, in addition to their role in baking and brewing, are used by scientists who study molecular and cellular biology because they are easy to grow on plates of agar or in culture vessels. They are an example of :
eukaryotic cell
Covalent bonds:
is a chemical bond that involves the sharing of electron pairs between atoms
For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration
A cytosine plus a ribose is _________
a nucleoside
The linkage between two sugars is a __________
glycosidic bond
Each nucleotide in DNA and RNA has an aromatic base. Water does not interact with the bases because of
hydrophobic interactions
too little space inside the helix
The aromatic rings that form the bases of DNA and RNA are called bases because
they have nitrogen in the ring structure that acts as a hydrogen ion acceptor
Ion channels
allow transport of specific ions down their electrochemical gradient
Which of the following statements is correct
b) Bacterial DNA is found in the cytosol
c) In human cells, DNA can be found in both the nucleus and the mitochondria
d) Nuclei and mitochondria are surrounded by a double membrane
Which of the following is true: a) alpha helices are the underlying structures of beta-sheets
b) beta-sheets are stabilized by hydrogen bonds between the peptide bonds.
c) coiled coils are random loops of protein
d) random loops are created by phosphodiester linkages
beta-sheets are stabilized by hydrogen bonds between the peptide bonds.
Molecular oxygen (O2) crosses the plasma membrane of a red blood cell
By passive (simple) diffusion
Why is the decrease in the surface area/volume ratio as cells increase in size a problem for cells?
a) The ability of a cell to obtain a sufficient amount of nutrients from the environment is hampered.
b) The ability of a cell to get rid of wastes at a high enough rate is compromised by the lower ratio.
All of the following proteins are made on rough endoplasmic reticulum-bound ribosomes EXCEPT for:
proteins of the inner mitochondrial membrane
Which proteins are made on the rough endoplasmic reticulum-bound ribosomes
a) integral membrane proteins of the plasma membrane
b) membrane glycoproteins
c) secretory proteins
d) soluble proteins found inside lysosomes
The major structural elements of the cytoskeleton are
Microfilaments, intermediate filaments and microtubules.
Which of the following statements about the unfolded protein response (UPR) is true
Activation of the UPR results in the production of more ER membrane.
The UPR is activated in response to the accumulation of unfolded proteins in the lumen of the
rough ER.
Which of the following reflects the appropriate pathway for a protein destined to be excreted from the cell?
rough endoplasmic reticulum → Golgi → vesicle → fusion with the plasma membrane & release
These contractile units shorten during skeletal muscle contraction:
sarcomeres
Glucose is phosphorylated immediately after entering the cell which:
(to glucose -6-phosphate)
a) Keeps it from being transported back out of the cell.
b) Allows the cell to maintain a relatively higher level of glucose outside the cell.
Also the first step in glycolysis (to break it down & release energy) or formation of glycogen
The following cytoskeletal elements acts "railroad" tracks to move organelles through the cell
microtubules
Which of the following molecular motors is/are associated with microtubules
a) kinesin
b) dynein
Gunter Blobel received the Noble Prize in Medicine in 1999 for his work that identified
the "signals" present in the protein primary sequence that direct them to their final location
What feature of the lipid rafts may explain their more gelated state (less fluid) as compared to the surrounding membrane regions
b) The fatty acid tails are more saturated.
c) The fatty acid tails are longer.
In the Na+/glucose co-transporter, _____ moving down its/their gradient drive the transport of _____ against its/their gradient.
Na+ ions, glucose
How do Na+ ions enter a neuron when an action potential is initiated
through a voltage-gated Na+ channel
How is a nerve impulse transmitted across a synapse from a nerve cell to a skeletal muscle cell
via a neurotransmitter
Transmembrane protein
s a type membrane protein—specifically, an integral membrane protein—that spans the entirety of a biological membrane. That is, transmembrane proteins span from one side of a membrane through to the other side of the membrane. Many TPs function as gateways or "loading docks" to deny or permit the transport of specific substances across the biological membrane,
Which of the following characteristics is (are) a basic property of cells
a) Cells are highly complex and organized.
b) Cells possess a genetic program and the means to use it.
c) Cells are capable of producing more of themselves.
d) Cells acquire and utilize energy.
What kind of bond results from an unequal sharing of electrons
polar covalent bond
What bond is responsible for the branch points in glycogen and amylopectin
(1—>6) glycosidic linkages
Which of the following is a nucleotide
adenine + ribose + phosphate
Enthalpy is ________.
the total energy content of a system
Given the equation G = H - TS, which set of conditions would result in a reaction that is unambiguously nonspontaneous
entropy decreases and the reaction is endothermic
What property of membranes allows interactions to take place within the membrane, including the assembly of membrane protein clusters at particular sites and the formation of specialized structures
membrane fluidity
You modify the gene for an integral membrane protein so that the cytoplasmic portions of the protein are deleted. When the gene is inserted in cells, what happens to the mobility of this protein in the membrane
They move much greater distances than the intact protein
Hydrophobic interactions
Occur between water and hydrophobes, which are nonpolar molecules and usually have a long chain of carbons that do not interact with water molecules.
Hydrophillic interactions
Occur between water and substances that can typically hydrogen bond
Hydrophobic interactions are most likely to occur:
buried in the core of a cytosolic protein
Water molecules can transiently dissociate to form
H+ and OH- ions
Triglycerides differ from one another by:
The chain length of their constituent fatty acids
and whether they contain saturated or unsaturated constituent fatty acids.
The Fluid-Mosaic Model describes:
proteins afloat in a sea of phospholipids
Despite the diversity, cells resemble each other to an astonishing degree in their chemistry. For example, the same 20 ________ are used to make proteins.
Amino Acids
The flow of genetic information is controlled by a series of biochemical reactions that result in the production of proteins, each with its own specific order of amino acids. Choose the correct series of biochemical reactions from the options present here:
replication, transcription, translation
Cytosine is a ____
Pyrimidine
DNA related Pyrimidines are:
Cytosine, thymine, and uracil
DNA related Purines are:
Adenine, and guanine
Nucleotide
Sugar (ribose or deoxyribose), nitrogenous base, and a phosphate group
Nucleoside
Sugar (ribose or deoxyribose) and a nitrogenous base
A sugar unit linked to a purine is a
Nucleoside
The linkage between two nucleotides is a
Phosphodiester bond
Knowing the properties of water is important to understand:
Why polymers adopt the secondary and tertiary structures they do. How phospholipids orient in biological membranes as they do.
In the bacterium, E. coli, the enzyme desaturase is responsible for creating unsaturated bonds from saturated ones in fatty acids of the plasma membrane phospholipids. This would tend to:
make the plasma membrane more fluid.
Active transport across a membrane
is able to concentrate molecules within a compartment
Cystic fibrosis is a recessive genetic disorder
Whose molecular basis is a defect in a ligand-gated Cl^- channel. and involving mutations in the CFTR gene, a member of the ABC transporter family
Enzymes:
Lower the activation energy (EA) of a reaction causing bond strain, destabilizing existing bonds
siamese cats... lol but really
Warmer areas of the cat, the temperature is just high enough to denature the enzyme. Since it is denatured, it will not function and dark pigment will not be produced in those areas
In the cell, many proteins are "helped" to fold into their optimal 3-D structure by other proteins called
chaperones
The relative proportion of protein to lipid in a membrane:
is maintained close to 1:1 in all cell membranes by phospholipid translocases. Is unusually high in the inner membrane of the mitochondria.
Phospholipids are:
Amphipathic molecules that may form liposomes and bilayers
Which of the following forces stabilize protein tertiary structure
hydrogen bonding between polar R-groups on the surface of secondary structures. Electrostatic interactions between positively and negatively charged R-groups. Disulfide bonds between cysteine residues.
Allosteric modulators
distort the tertiary conformation of an enzyme
The Na+/K+ pump transports ions in a cyclic manner. The plant toxin ouabain inhibits the pump by preventing binding of K+ ions. As a consequence of ouabain binding:
The energy store build up in the Na+ electrochemical gradient is sufficient to sustain Na+ linked transport processes for many minutes before the cell dies.
Cells come in a wide variety of sizes and types: prokaryotic, eukaryotic, animal, plant, muscle, brain, etc. Which structure defines a cell as a cell?
A cytoplasmic membrane
Each nucleotide in DNA and RNA has an aromatic base. What is the principal force that keeps the bases in a polymer from interacting with water?
Hydrogen bonds
The aromatic rings that form the bases of DNA and RNA are called bases because:
They have nitrogen in the ring structure
Alpha helices can interact together to form
Coiled coil
Which of the following statements are correct?
a) The hereditary info of a cell is passed by its proteins.
b) Bacterial DNA is found in the cytosol
c) all cells, except eggs and sperm cells, have the same number of chromosomes
d) nuclei and mitochondria are surrounded by a double membrane
e), b, c, and d
b) Bacterial DNA is found in the cytosol
c) all cells, except eggs and sperm cells, have the same number of chromosomes
d) nuclei and mitochondria are surrounded by a double membrane
e), b, c, and d
Why is the decrease in surface area/volume ratio as cells increase in size a problem for cells?
The ability of a cell to obtain a sufficient amount of nutrients from the environment is hampered.