Bio exam 1

What are the advantages and disadvantages of light microscopes? What are the advantages and disadvantages of electron microscopes?

Advantage: In light microscopes, the light beam does not kill the cell. Electron microscopes are helpful in viewing intricate details of a specimen and have high resolution. Disadvantage: Light microscopes have low resolving power. Electron microscopes are costly and require killing the specimen.

Most organisms carry their hereditary genetic information as DNA. However, some viruses use RNA instead. The HIV virus has RNA, but its genetic information is found in host DNA. How does this happen?

An enzyme reverses the usual process, producing DNA from the viral RNA.

How can an unsaturated fat be made to function like a saturated one?

An unsaturated fat can be made into a trans fat by hydrogenation, attaching extra hydrogen atoms. This makes it function as if saturated, but keeping its unsaturated name. This can cause confusion as to just what it is and how it functions.

Discuss how buffers help prevent drastic swings in pH.

Buffers absorb excess hydrogen and hydroxide ions to prevent increases or decrease in pH. An example is the bicarbonate system in human body.

What property of carbon makes it essential for organic life?

Carbon is found in all living things because it can form up to four covalent bonds. These strong covalent bonds allow the formation of long chains that combine to form proteins and DNA

How many neutrons do carbon-12 and carbon-13 have, respectively?

Carbon-12 contains 6 neutrons while carbon-13 contains 7 neutrons.

What property of carboxyl makes carboxyl containing molecules hydrophilic? Which macromolecules contain carboxyl?

Carboxyl groups release H+, making its parent molecule hydrophilic. It is found amino acids and fatty acids.

What is structurally different between starch and cellulose that gives them different physical properties?

Cellulose is formed by β-1,4 glycosidic linkages and crosslinks, making it rigid. Starch has α-1.4 and α-1.6 glycosidic linkages without the tight crosslinks of cellulose.

What are the similarities and differences between the structures of centrioles and flagella?

Centrioles and flagella are made of microtubules but show different arrangements.

What type of compound functions in hormone production, contributes to membrane flexibility, and is the starting molecule for bile salts?

Cholesterol, which is a lipid and also a steroid, functions here.

A change in DNA on a chromosome affects all proteins made from that gene for the life of the cell. A change in the RNA involved in protein production is short lived. What is the difference between the effects of the changes in the two types of nucleic acids?

DNA is the genetic material that is passed from parent cells to daughter cells and to future generations.

Which of the following organisms is a prokaryote? A. Amoeba B. Influenza A virus C. Charophyte algae D. E. coli

E. coli

What makes ionic bonds different from covalent bonds?

Ionic bond involves the transfer of electrons whereas covalent bond involves the sharing of electrons.

Both of the regular intravenous solutions administered in medicine, normal saline and lactated Ringer's solution, are isotonic. Why is this important?

Isotonic solutions maintain equilibrium and avoid the exchange of materials to or from the blood.

Vegans are people who do not consume any animal products in their diet. Why do vegans need to pay special attention to the protein they eat?

It is more difficult to obtain all essential amino acids from single plant sources.

Cells lining the intestine absorb a lot of nutrients. How did those cells adapt to their function?

Membrane folds called microvilli increase the surface area.

Why do phospholipids tend to spontaneously orient themselves into something resembling a membrane?

Phospholipids are amphipathic molecules. The polar head faces towards water and the nonpolar fatty acid tails face towards other fatty acid tails.

What are two similarities and two differences between plant and animal cells that can be seen under a microscope?

Plant cells have cell walls which provide structure to the plant and also chloroplasts which allow for photosynthesis. Animal cells do not have either of these structures. Both cells have nuclei, the command center of the cell, and cytoplasm, the gel-like solution that fills the cell.

Which of these is a possible explanation for the presence of a rigid cell wall in plants?

Plants are subjected to osmotic pressure and a cell wall helps them against bursting or shrinking.

What categories of amino acids would you expect to find on the surface of a soluble protein and which would you expect to find in the interior? Which of these are some examples for each part of the answer?

Polar and charged amino acids will be found on the surface whereas non-polar in the interior.

You already know that ribosomes are abundant in red blood cells. In what other cells of the body would you find them in great abundance?

Ribosomes are abundant in muscle cells as they contain large amounts of protein-based filaments necessary for contractions.

What is a difference between saturated and unsaturated fats?

Saturated fats are solid at room temperature and unsaturated fats are liquid at room temperature

Animals cannot digest cellulose due to the type of bonding between the glucose monomers. The glucose monomers are there for an energy source but are unattainable. Yet ruminants such as cows and sheep, and termites eat cellulose in the form of grasses and wood. How do they do it?

Specialized bacteria and protists are found in the digestive tracts of these animals making cellulase that result in cellulose breakdown.

A scientist compares the plasma membrane composition of an animal from the Mediterranean coast with one from the Mojave Desert. Which hypothesis is most likely to be correct?

The cells from the Mojave Desert animal will have a higher cholesterol concentration in the plasma membranes.

Paramecia are unicellular protists that have contractile vacuoles to remove excess intracellular water. In an experimental investigation, Paramecia were placed in salt solutions of increasing osmolarity. The rate at which a Paramecium's contractile vacuole contracted to pump out excess water was determined and plotted against osmolarity of the solutions, as shown in the graph. Which of the following is the correct explanation for the data?

The contraction rate increases as the osmolarity decreases because the amount of water entering the Paramecium by osmosis increases.

Dehydration is a word usually used to mean the removal of water. How does this apply to macromolecules?

The hydroxyl groups of two monomers are used to form a bond by removing a hydrogen from one monomer and a hydroxyl group from the second forming a molecule of water.

What happens to the proteins that are synthesized on free ribosomes in the cytoplasm? Do they go through the Golgi apparatus?

The proteins do not go through the Golgi apparatus and remain free in the cytosol.

Why does the structure of the cytoplasmic membrane point to a common ancestor?

The similar arrangement of phospholipids and proteins points to common ancestry. The similar arrangement of macromolecules, phospholipids and proteins in the form of a lipid bilayer makes it a primitive trait.

Bacteria do not have organelles; yet, the same reactions that take place on the mitochondria inner membrane, the phosphorylation of ADP to ATP, and chloroplasts, photosynthesis, take place in bacteria. Where do these reactions take place?

These reactions occur on the plasma membrane of bacteria.

Why have trans fats been banned from some restaurants? How are they created?

Trans fat is produced by the hydrogenation of oil that makes it more saturated and isomerized. It increases LDL amounts.

ATC/GTT/GTA/CTG/TAG/GAT/AAA what mRNA would be made from this DNA fragment?

UAG/CAA/CAU/GAC/AUC/CUA/UUU

When the temperature of liquid water is reduced, water freezes and becomes less dense. This is a property not seen in most other liquids. Ice floats on liquid water because it is less dense. What molecular property of water allows for this phenomenon?

When water cools, hydrogen bonds between hydrogen atoms push water molecules further apart.

Name the three functional groups in the compound pictured.

carbonyl, methyl and carboxyl

With which cellular structure does the extracellular matrix interact?

cytoskeleton

Which structure or structures allow bacteria to move about?

flagella and fimbriae

What are the four types and functions of RNA?

mRNA is a single stranded transcript of DNA. rRNA is found in ribosomes. tRNA transfers specific amino acids to a developing protein strand. miRNA regulates the expression of mRNA strands.

Which organelle is responsible for the production of energy in all eukaryotic cells?

mitochondrion. Mitochondria are responsible for producing the energy currency of the cell that is ATP.

In which human tissues would you find desmosomes? Think of tissues that undergo strong mechanical stress and must be held together with some flexibility.

muscle cells and skin cells

You are making a poster of a generic bacterium for your class. Which of the following structures will you leave out of your poster?

nucleolus

You are looking at a sample under a light microscope and observe a new type of cell. You come to the conclusion that it is a bacterium and not a eukaryotic cell. What would you observe to come to this conclusion?

the cell does not have a nucleus

The following is a short segment of DNA using the slash symbol ( / ) to separate the codons for easy viewing: ATC/GTT/GAA/CTG/TAG/GAT/AAA A change has occurred in the segment resulting in the following: ATC/GTT/GTA/CTG/TAG/GAT/AAA What kind of change has occurred?

A substitution of T for A, changing the coding for the third codon

How does a chaperone work with proteins?

Chaperones (or chaperonins) associate with the target protein during the folding process. They act by preventing aggregation of polypeptides that make up the complete protein structure, and they disassociate from the protein once the target protein is folded.

The protein sequence of cytochrome c from chimpanzees and humans is identical. The protein sequence of cytochrome c from rhesus monkeys differs from the human sequence by one amino acid. What do these comparisons suggest?

Chimpanzees are more closely related to humans than rhesus monkeys.

Which of the following bodily process would most likely be hindered by a lack of water in the body?

Digestion involves chemically breaking down larger polymers within food into smaller molecules. Hydrolysis is a process that breaks down molecules. An inability to perform hydrolysis would negatively affect digestion.

Fiber is not really a nutrient, because it passes through our body undigested. Why can't fiber be digested and why is it important to our diet?

The enzymes required to digest cellulose are not produced in human body; undigested fiber adds bulk to the food easing bowel movements.

How does the extracellular matrix function?

The extracellular matrix helps in the attachment of the cell to other cells and to various substrata. The extracellular matrix helps in support and attachment for animal tissues. It also functions in the healing and growth of the tissue.

If the nucleolus were not able to carry out its function, what other cellular organelles would be affected?

The free ribosomes and the rough endoplasmic reticulum, which contains ribosomes, would not form. The ribosome producing genes are found inside the nucleolus. Thus, the free ribosomes and the rough endoplasmic reticulum would be affected.

Is the nuclear membrane part of the endomembrane system? Why or why not?

The nuclear membrane is part of the endomembrane system as it is continuous with the rough endoplasmic reticulum. The nuclear envelope is considered a part of the endomembrane system as it is continuous with the rough endoplasmic reticulum, which itself is a part of endomembrane system.

What organelle would be the largest in rapidly dividing cells?

The nucleus must be the largest as the cell starts the next round of division and it does not have time to expand.

Describe the pH scale and how it relates to living systems. Give an example of how drastic pH changes are prevented in living systems.

The pH scale ranges from 0 to 14, where anything below 7 is acidic and above 7 is alkaline. The bicarbonate system in the human body buffers the blood.

How do phospholipids contribute flexibility to cell membrane structure?

The phospholipids containing unsaturated fatty acids cannot be tightly packed which provides membrane flexibility.

Which of these describe some of the similarities and differences between glycogen and starch?

Which of these describe some of the similarities and differences between glycogen and starch?

What are three examples of how the characteristics of water are important in maintaining life?

First, the lower density of water as a solid versus a liquid allows ice to float, forming an insulating surface layer for aquatic life. Second, the high specific heat capacity of water insulates aquatic life or bodily fluids from temperature changes. Third, the high heat of vaporization of water allows animals to cool themselves by sweating.

Why is it advantageous for the plasma membrane to be fluid in nature?

Fluidity allows greater flexibility to the cell and motion of membrane components required for transport. Fluidity helps provide flexibility to the cell and allows some membrane components to move, which is essential for transport processes.

Vesicles pinch off the rough endoplasmic reticulum. Where do they go from there?

Golgi apparatus

Looking at the above figure, can you infer which two groups together will form a strong ionic bond?

Group 1 and Group 17

Which molecule carries information in a form that is inherited from one generation to another?

Hereditary information is stored in DNA.

Thiomargarita namibiensis is a large single cell organism, which can reach lengths of 700μm700μm. The cell is classified as a bacterium. What is the main argument to justify the classification?

Like the other prokaryotes, Thiomargarita namibiensis does not possess a nucleus or any other organelles, and is thus classified as a bacterium.

What are three functions that lipids serve in plants and/or animals?

Lipids serve in the storage of energy, as a structural component of hormones, and also as signaling molecules.

Macrophages ingest and digest many pathogens. Which organelle plays a major role in the activity of macrophages?

Lysosomes contain the hydrolytic enzymes that digest the ingested pathogen.

Which organelles would be present in high numbers in the leg muscles of a marathon runner?

Mitochondria produce the required energy in the form of ATP to run a marathon.

How do phospholipids contribute to cell membrane structure?

Phospholipids orient their heads towards the polar molecules and tails in the interior of the membrane, thus forming a bilayer.

Which categories of amino acid would you expect to find on the surface of a soluble protein, and which would you expect to find in the interior?

Polar and charged amino acids will be found on the surface. Non-polar amino acids will be found in the interior.

The word hydrolysis is defined as the lysis of water. How does this apply to polymers?

Polymers break by separating water into hydrogen and hydroxyl group that are added to the monomers.

Which of the following is not an extracellular matrix role of carbohydrates?

Provide energy for muscle movement

Compare and contrast saturated and unsaturated triglycerides.

Saturated triglycerides contain single bonds and are solids at room temperature, while unsaturated triglycerides contain double bonds and are liquids at room temperature.

What are the structural and functional similarities and differences between mitochondria and chloroplasts?

Similarities: double membrane, inter-membrane space, ATP production, contain DNA. Differences: mitochondria have inner folds called cristae, chloroplast contains accessory pigments in thylakoids, which form grana and a stroma.

Why are electron microscopes crucial for the study of cell biology?

Some electron microscopes allow visualization of three dimensional external shapes at very high magnification in a way that is not possible with standard light microscopes.

What are the four classes of lipids and what is an example of each?

1. lipids like margarine 2. wax-like the coating on feathers 3. phospholipids like cell membrane constituents 4. steroid-like cholesterol

The following chemical reactants produce the ester ethyl ethanoate (C4H8O2): C2H6O + CH3COOH What type of reaction occurs to make ethyl ethanoate?

Condensation

The shape of hair proteins is maintained by a combination of hydrogen bonds and covalent, disulfide bonds. Heat is sufficient to break the hydrogen bonds, but harsh chemicals are required to break the disulfide bonds. Why is it harder to break the disulfide bonds than the hydrogen bonds?

Covalent bonds are stronger than hydrogen bonds, therefore harder to break.

Choose the statement that describes processes of receptor-mediated endocytosis, exocytosis, and the changes in the membrane organization.

Endocytosis involves the opsonization of a receptor and its ligand in clathrin-coated vesicles, along with the inward budding of the plasma membrane. In exocytosis, waste material is enveloped in a membrane that fuses with the interior of the plasma membrane via attachment proteins.

An experiment was set up to determine the movement of molecules through a dialysis-tubing bag into water. A dialysis-tubing bag containing 5% lactose and 5% fructose was placed in a beaker of distilled water, as illustrated. After four hours, fructose is detected in the distilled water outside of the dialysis-tubing bag, but lactose is not. What conclusions can be made about the movement of molecules in this experiment?

Fructose, being a monosaccharide, diffused through the dialysis bag into the distilled water. However, lactose, being a disaccharide, could not diffuse through the dialysis bag.

Inhibitors of microtubule assembly, vinblastine for example, are used for cancer chemotherapy. How does an inhibitor of microtubule assembly affect cancerous cells?

The inhibitors restrict the separation of chromosomes, thereby stopping cell division. The inhibitors restrict the process of polymerization and depolymerization of the microtubules, thereby affecting the working of the spindle fibers. This inhibits the separation of chromosomes and stops cell division.

List the mass number and atomic number of carbon-12 and carbon-13, respectively.

The mass number and atomic number of carbon-13 is 13 and 6, while that of carbon-12 is 12 and 6, respectively.

Why does water move through a membrane?

Difference in concentration of solute and solvent

How do the differences in amino acid sequences lead to different protein functions?

Different amino acids produce different proteins based on the bonds formed between them

An atom may give, take, or share electrons with another atom to achieve a full valence shell, the most stable electron configuration. Looking at this figure, how many electrons do elements in group 1 need to lose in order to achieve a stable electron configuration? How many electrons do elements in groups 14 and 17 need to gain to achieve a stable configuration?

Elements of group 1 need to lose one electron, elements of group 14 need to gain 4 electrons, and elements of group 17 need to gain 1 electron

If a doctor injected a patient with what was labeled as an isotonic saline solution, but then the patient died, and an autopsy revealed that several of the patient's red blood cells had burst, would it be true that the injected solution was really isotonic? Why or why not?

False, the solution was hypotonic. The correct solution would have been hypotonic.

The sodium-potassium (Na+/K+) pump functions like an anti-porter transporting Na+ and K+ across membranes using ATP. This protein spans the membrane with intracellular and extracellular domains. It has a binding site for Na+, K+, and ATP. An experiment was conducted to determine the locations of these binding sites. Artificial cells were created and incubated in buffers containing ATP, ouabain (or oubain), Na+, and K+ in varying combinations inside and outside of the cell as indicated in the chart. The transport of Na+ and K+K+ was measured to determine activity of the Na+/K+ pump. Which of the following conclusions is supported by the data?

The ATP binding site of the Na+/K+ pump is located on the intracellular domain of the pump.

For many years, scientist believed that proteins were the source of heritable information. There are many thousands of different proteins in a cell, and they mediate the cell's metabolism, producing the traits and characteristics of a species. Researchers working with DNA viruses proved that it is DNA that stores and passes on genes. They worked with viruses with an outer coat of protein and a DNA strand inside. How did they prove that it was DNA, not protein, which is the primary source of heritable information?

The DNA and protein of the virus were tagged with different isotopes and exposed to host cell where only the DNA was transferred to the host.

Diseased animal cells may produce molecules that activate death cascades to kill the cells in a controlled manner. Why would neighboring healthy cells also die?

The death molecule passes through gap junctions.

What causes the changes in protein structure through the three or four levels of structure?

The primary chain forms secondary α-helix and β-pleated sheets which fold onto each other forming the tertiary structure.

How does the sodium-potassium pump contribute to the net negative charge of the interior of the cell?

The sodium-potassium pump forces out three (positive) Na+ ions for every two (positive) K+ ions it pumps in, thus the cell loses a net positive charge of one at every cycle of the pump.

Which of the following statements is false? A. Molecules with the formulas CH3CH2COOH and C3H6O2could be structural isomers. B. Molecules must have a double bond to be cis-trans isomers. C. To be enantiomers, a molecule must have at least three different atoms or groups connected to a central carbon. D. To be enantiomers, a molecule must have at least four different atoms or groups connected to a central carbon.

To be enantiomers, a molecule must have at least three different atoms or groups connected to a central carbon.

The fatty acids of triglycerides are classified as saturated, unsaturated, or trans fats. What is it about the structure of these compounds that gives them their physical characteristics?

Unsaturated fats and trans fats have some double bonded carbon atoms, while saturated fats do not.