Cell and Molecular Biology Introduction

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Questions and Answers

Which of the following correctly describes the relationship between the equilibrium constant (Keq) and the direction of an enzymatic reaction?

A low Keq indicates that the reaction favors the formation of products.

A high Keq indicates that the reaction favors the formation of reactants.

A high Keq indicates that the reaction favors the formation of products. (correct)

Keq does not influence the direction of the reaction.

What is the difference between competitive and noncompetitive inhibitors?

Competitive inhibitors are irreversible, while noncompetitive inhibitors are reversible.

Competitive inhibitors increase the enzyme's activity, while noncompetitive inhibitors decrease the enzyme's activity.

Competitive inhibitors bind to the active site, preventing substrate binding, while noncompetitive inhibitors bind to a different site, altering the enzyme's shape and reducing its activity. (correct)

Competitive inhibitors bind to a different site, altering the enzyme's shape and reducing its activity, while noncompetitive inhibitors bind to the active site, preventing substrate binding.

Which of the following correctly describes the relationship between KM and the affinity of an enzyme for its substrate?

A low KM indicates a low affinity, meaning the enzyme binds its substrate loosely.

KM does not reflect the affinity of an enzyme for its substrate.

A high KM indicates a low affinity, meaning the enzyme binds its substrate loosely. (correct)

A high KM indicates a high affinity, meaning the enzyme binds its substrate tightly.

Which of the following is an example of an Hsp70 chaperone?

DnaK (B) Signup and view all the answers

Which of the following correctly describes the difference between PrPc and PrPsc?

PrPc is a normal cellular protein, while PrPsc is a misfolded form that aggregates and causes disease. (C) Signup and view all the answers

Which level of protein structure is primarily determined by hydrogen bonding between the backbone atoms of the polypeptide chain?

Secondary (D) Signup and view all the answers

Which of the following describes the process of a thermodynamically unfavorable reaction occurring in a cell?

The reaction is coupled to a thermodynamically favorable reaction, providing energy to drive the unfavorable reaction. (A) Signup and view all the answers

Which of the following correctly describes the structure of a carboxyl group below its pK?

It exists as a carboxylate ion (COO-) with a negative charge. (D) Signup and view all the answers

What is the main source of trans fats in the diet?

Partially hydrogenated vegetable oils (D) Signup and view all the answers

Which of the following statements about the structure of α-helices and β-pleated sheets is TRUE?

Both α-helices and β-pleated sheets are formed by hydrogen bonding between backbone atoms. (A) Signup and view all the answers

What is the primary function of the Golgi apparatus in a eukaryotic cell?

Modification and packaging of proteins (A) Signup and view all the answers

Which of the following covalent bonds is considered polar due to the difference in electronegativity between the atoms involved?

O-H (B) Signup and view all the answers

Which of the following functional groups is NOT capable of forming hydrogen bonds?

Methyl (-CH3) (C) Signup and view all the answers

What is the key structural difference that distinguishes starch from cellulose, both being polymers of glucose?

Starch contains only alpha-glucose, while cellulose contains only beta-glucose. (D) Signup and view all the answers

Which of the following statements accurately describes the properties of life that are also shared by cells?

Cells exhibit growth, reproduction, and response to stimuli. (B) Signup and view all the answers

The endosymbiotic theory states that:

Mitochondria and chloroplasts originated from free-living bacteria. (A) Signup and view all the answers

In the context of cell theory, what is the primary function of the nucleus?

Storage and protection of genetic material (DNA). (D) Signup and view all the answers

Which of the following is NOT considered a basic property of cells?

Consciousness (A) Signup and view all the answers

Which of the following is NOT common to both eukaryotes and prokaryotes?

B and C (C) Signup and view all the answers

Different laboratory methods allow scientists to isolate specific cellular organelles, so that they can study some cellular processes in more detail. Which organelle would you try to isolate if you wanted to study the enzymes involved in lipid synthesis?

Endoplasmic reticulum (A) Signup and view all the answers

According to the theory of endosymbiosis promoted by , our earliest prokaryotic ancestor was an , who ingested an , the precursor of modern day mitochondria. Ingestion of a second endosymbiont, a , later evolved into chloroplasts.

Lynn Margulis; anaerobic heterotroph; aerobic prokaryote; cyanobacteria Signup and view all the answers

Which of the following is NOT a property of covalent and non-covalent bonds?

Non-covalent bonds require a large amount of energy to break (A) Signup and view all the answers

Based on the following table of electronegativity, which of the following represents the order of polarity, most to least?

O – H = C=O C=O = C-H O=O = O—H C-S = O-H Signup and view all the answers

In a covalent bond formed between Nitrogen and a less electronegative atom, the N atom would have a while the less electronegative atom would have a charge.

partial negative; partial positive Signup and view all the answers

Particular groupings of atoms that often behave as a unit and give organic molecules their physical properties, chemical reactivity and solubility in aqueous solutions are known as:

Functional groups (D) Signup and view all the answers

Which of the following characteristics below (from 1 to 7) are typical of the polysaccharide cellulose?

1, 3, 4, 5, 7 (B) Signup and view all the answers

Compounds rich in [blank] tend to be liquid at room temperature. These compounds can be altered so they are solid at room temperature by [blank].

unsaturated fats = Increasing the amount of double bonds saturated fats = Decreasing the amount of single bonds Signup and view all the answers

The following structures represent , which are maintained at room temperature, due to the __ of double bonds.

saturated fats; solid; absence Signup and view all the answers

A patient with hyperlipidemia has been counseled to reduce the saturated fats in his diet, so he has replaced butter with a butter substitute that he knows is made from a polyunsaturated oil. The manufacturer of this butter substitute has partially hydrogenated this product. Which one of the following is the best description of why this product was partially hydrogenated?

Hydrogenation reduces the double bonds, creating a more saturated product, which is more marketable. (D) Signup and view all the answers

As a scientist you find an unknown sample and run some tests to identify this unknown sample. Molecular analysis found glycerol, fatty acids, phosphate and choline. Given this, which conclusion is most probable?

It is only phospholipid. (D) Signup and view all the answers

You treat a partially purified preparation of protein with mercaptoethanol, a reagent that can break bonds formed between sulfur atoms. Which level of protein structure is likely to be affected?

C and D are correct (E) Signup and view all the answers

Amino acids 1 to 4 are all part of the same solution at a particular pH. If kept at the same pH, hydrogen bonds, could be formed between the R groups of: (See figures in document)

Between 1 and 3 (D) Signup and view all the answers

Amino acids 1 to 4 are all part of the same solution at a particular pH. If kept at the same pH, ionic bonds could be formed between the R groups of: (See figures in document)

None of these pairs is capable of forming ionic bonds unless pH is changed (D) Signup and view all the answers

How many amino acids are in this peptide?: (See figure in document)

Eight (A) Signup and view all the answers

What is the role of misfolded proteins in Creutzfeld-Jakob Disease?

B, C and D are correct. (C) Signup and view all the answers

Free energy is . A reaction will be spontaneous when

the energy available to do work; the free energy of the reactants is lower than that of the products Signup and view all the answers

Conversion of A → B is an endergonic reaction. Which of the following reactions could be coupled with A→B so that both A→B and C D can occur?

Both A and C (D) Signup and view all the answers

The continual flow of oxygen and other materials into and out of cells allows cellular metabolism to exist in a steady state because

The concentrations of reactants and products remain relatively constant. (C) Signup and view all the answers

Enzymes speed up reactions by lowering the . This can be accomplished by forming an enzyme-substrate complex, where the R chains of the amino acids in the enzyme's and the substrate are bound together by __.

activation energy; active site; noncovalent bonds Signup and view all the answers

Dissolving a sugar cube in water and breaking down complex glycogen molecules into smaller molecules are examples of decrease in entropy in a system.

False (B) Signup and view all the answers

The amino acids glutamine and glutamic acid are shown below. They differ only in the structure of their side chains (circled). At pH 7, glutamic acid can participate in molecular interactions that are not possible for glutamine. What types of interactions are these? (See figure in the document)

Ionic bonds (B) Signup and view all the answers

Which of the following amino acids has side chains with the greatest potential to form a) hydrogen-bonds b) ionic-bonds and c) hydrophobic interactions? (assume you don't change the pH) (See figure in the document)

a) 4; b) 2; c) 1 = a) 3; b) 1; c) 5 Signup and view all the answers

You mix reagents (A, B, C, D) so that each is present at an initial concentration of

[0.25][0.25] / [0.15] [0.15] (E) Signup and view all the answers

What type of bond is this and what structure do long chains of this make up? (See figure in the document)

Beta1,4 Cellulose (B) Signup and view all the answers

A fatty acid consists of three hydrocarbon chains linked to a glycerol backbone.

False (B) Signup and view all the answers

Is the following statement correct? “Amino acids used in making a polypeptide have an amino group and a carboxyl group, and these groups can be present on any carbon atoms”

No, amino acids require a very specific structure and must have all groups attached to the alpha carbon. (A) Signup and view all the answers

An enzyme in the liver that removes glucose from blood has a high K™; another that does the same thing in brain tissue has a small K™. Which of the following options would BEST describe how this information would relate to glucose uptake in an organism?

The enzyme in brain tissue can take glucose from the bloodstream even when levels are low, and the enzyme in liver will not take glucose from blood unless levels are high (C) Signup and view all the answers

Flashcards

Cell Theory

Three fundamental principles about cells: all living things are made of cells, cells are the basic unit of life, and all cells arise from pre-existing cells.

Lynn Margulis

A prominent biologist known for her theory on the symbiotic origin of eukaryotic cells.

Electronegativity

A measure of an atom's ability to attract and hold electrons, varying across the periodic table.

Polar Covalent Bonds

Chemical bonds where electrons are shared unequally, resulting in a molecule with a partial positive and negative charge.