Macromolecule Structures and Functions - Biochemistry
Card 1 of 788
Which type of transport does not require a protein?
Which type of transport does not require a protein?
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There are two types of transport: passive transport and active transport. Active transport requires an expenditure of energy and a protein pump. Passive transport includes simple diffusion and facilitated diffusion. Diffusion is the movement of a substance from an area of high concentration to one of low concentration. Simple diffusion is the name for the diffusion process which does not require a protein; facilitated diffusion is the name for the diffusion process which requires a carrier protein for transport. Osmosis is the simple diffusion of water and thus does not require protein.
There are two types of transport: passive transport and active transport. Active transport requires an expenditure of energy and a protein pump. Passive transport includes simple diffusion and facilitated diffusion. Diffusion is the movement of a substance from an area of high concentration to one of low concentration. Simple diffusion is the name for the diffusion process which does not require a protein; facilitated diffusion is the name for the diffusion process which requires a carrier protein for transport. Osmosis is the simple diffusion of water and thus does not require protein.
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Which of the following amino acids coordinates the heme ring in hemoglobin?
Which of the following amino acids coordinates the heme ring in hemoglobin?
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In hemoglobin, the nitrogen group on the amino acid Histidine coordinates the heme ring in hemoglobin by binding to an iron atom located in the middle of the heme ring.
In hemoglobin, the nitrogen group on the amino acid Histidine coordinates the heme ring in hemoglobin by binding to an iron atom located in the middle of the heme ring.
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A nonspecific hexagonal structure that functions to allow movement of molecules between adjacent cells is termed a(n) .
A nonspecific hexagonal structure that functions to allow movement of molecules between adjacent cells is termed a(n) .
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A gap junction is a hexagonal protein that openly connects two adjacent cells. It is nonspecific, meaning it allows various different molecules and ions to travel through it. This type of transport is important for rapid communication between adjacent cells. For instance, gap junctions serve an important function in the heart - allowing the many cells present there to act as a functional syncytium. Integrins and tight junctions do not allow the passage of molecules between adjacent cells.
A gap junction is a hexagonal protein that openly connects two adjacent cells. It is nonspecific, meaning it allows various different molecules and ions to travel through it. This type of transport is important for rapid communication between adjacent cells. For instance, gap junctions serve an important function in the heart - allowing the many cells present there to act as a functional syncytium. Integrins and tight junctions do not allow the passage of molecules between adjacent cells.
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GLUT (glucose transporters) proteins transport glucose from the blood to cells. Which of the following statements about them are true?
I. GLUT proteins are integral membrane proteins.
II . GLUT proteins have their amino and carboxyl termini on the extracellular side of the plasma membrane.
III. Binding of glucose to the transporter protein leads to a conformation change and the transport of glucose to the inner side of the membrane.
IV. GLUT-1, GLUT-3, and GLUT-4 proteins are ubiquitous; GLUT-2 is found in the liver, pancreas and kidney.
GLUT (glucose transporters) proteins transport glucose from the blood to cells. Which of the following statements about them are true?
I. GLUT proteins are integral membrane proteins.
II . GLUT proteins have their amino and carboxyl termini on the extracellular side of the plasma membrane.
III. Binding of glucose to the transporter protein leads to a conformation change and the transport of glucose to the inner side of the membrane.
IV. GLUT-1, GLUT-3, and GLUT-4 proteins are ubiquitous; GLUT-2 is found in the liver, pancreas and kidney.
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GLUT are integral membrane proteins.The proteins cross the membrane having the amino and carboxyl termini on the cytoplasmic side of the plasma membrane. Binding of glucose to the transporter leads to a conformational change, transport of glucose to the other side of the membrane. GLUT-1, GLUT -3 and GLUT-4 are present in most tissues; GLUT-2 is found in the liver, pancreas and kidney.
GLUT are integral membrane proteins.The proteins cross the membrane having the amino and carboxyl termini on the cytoplasmic side of the plasma membrane. Binding of glucose to the transporter leads to a conformational change, transport of glucose to the other side of the membrane. GLUT-1, GLUT -3 and GLUT-4 are present in most tissues; GLUT-2 is found in the liver, pancreas and kidney.
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A protein's primary structure is determined by which of the following?
A protein's primary structure is determined by which of the following?
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A protein's primary structure is defined solely by its amino acid sequence, and is constructred by peptide bonds between adjacent amino acid residues.
Secondary structure results from hydrogen bonding along the polypeptide backbone, resulting in alpha-helices and beta-pleated sheets. Tertiary structure results from hydrogen bonding between R groups, hydrophobic interactions, and disfulide bridges; these interactions create the three-dimensional structure of the molecule. Finally, quaternary structure arises from the joining of multiple subunits to create a functional protein complex.
A protein's primary structure is defined solely by its amino acid sequence, and is constructred by peptide bonds between adjacent amino acid residues.
Secondary structure results from hydrogen bonding along the polypeptide backbone, resulting in alpha-helices and beta-pleated sheets. Tertiary structure results from hydrogen bonding between R groups, hydrophobic interactions, and disfulide bridges; these interactions create the three-dimensional structure of the molecule. Finally, quaternary structure arises from the joining of multiple subunits to create a functional protein complex.
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Sickle cell anemia results from a missense mutation that replaces a glutamic acid residue with which of the following?
Sickle cell anemia results from a missense mutation that replaces a glutamic acid residue with which of the following?
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A single amino acid substitution from glutamic acid to lysine is responsible for sickle cell anemia. The mutation occurs in the gene that codes for hemoglobin and causes misfolding that results in a lower oxygen affinity.
A single amino acid substitution from glutamic acid to lysine is responsible for sickle cell anemia. The mutation occurs in the gene that codes for hemoglobin and causes misfolding that results in a lower oxygen affinity.
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The structure of a protein corresponds to the linear order of amino acids in a given polypeptide chain.
The structure of a protein corresponds to the linear order of amino acids in a given polypeptide chain.
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With regard to protein structure, primary structure refers to the order of the amino acids, which are held together by peptide bonds. Secondary structure refers to the presence of beta pleated sheets and alpha helices within a protein. Tertiary structure refers to a protein's geometric shape as a result of the interactions between the sidechains of the amino acids in the peptide chain. Quaternary structure concerns side chain interactions within a multiple polypeptide chains.
With regard to protein structure, primary structure refers to the order of the amino acids, which are held together by peptide bonds. Secondary structure refers to the presence of beta pleated sheets and alpha helices within a protein. Tertiary structure refers to a protein's geometric shape as a result of the interactions between the sidechains of the amino acids in the peptide chain. Quaternary structure concerns side chain interactions within a multiple polypeptide chains.
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What type of bonds are found in the primary structure of a protein?
What type of bonds are found in the primary structure of a protein?
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Primary structure consists of amino acids joined by peptide bonds. Peptide bonds are between the alpha-carboxyl of one amino acid, and the alpha-amine of the next amino acid. A peptide bond is an example of an amide bond. Hydrogen bonds are found in secondary structure, tertiary structure exhibits Van Der Waals interactions.
Primary structure consists of amino acids joined by peptide bonds. Peptide bonds are between the alpha-carboxyl of one amino acid, and the alpha-amine of the next amino acid. A peptide bond is an example of an amide bond. Hydrogen bonds are found in secondary structure, tertiary structure exhibits Van Der Waals interactions.
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What is an aldotriose?
What is an aldotriose?
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Aldotrioses are monosaccharides that contain both an aldehyde (an aldose) and three carbons (a triose). Knowing the definition of the word, and the breakdown of parts of the word, can help you recognize the molecule. The simplest aldotriose is glyceraldehyde.
A related concept involves ketotrioses, which are monosaccharides that contain both a ketone (a ketose) and three carbonds (a triose). Dihydroxyacetone is an example of a ketotriose.
Aldotrioses are monosaccharides that contain both an aldehyde (an aldose) and three carbons (a triose). Knowing the definition of the word, and the breakdown of parts of the word, can help you recognize the molecule. The simplest aldotriose is glyceraldehyde.
A related concept involves ketotrioses, which are monosaccharides that contain both a ketone (a ketose) and three carbonds (a triose). Dihydroxyacetone is an example of a ketotriose.
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Mirror-image stereoisomers are called .
Mirror-image stereoisomers are called .
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Enantiomers are chiral molecules that are non-superimposable mirror images of each other. Diastereomers result when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent stereocenters and are not mirror images of each other. An epimer is one of two stereoisomers that differ in configuration at only one stereocenter. An anomer is a type of epimer; it is one of two stereoisomers of a cyclic sugar that differs only in its configuration at the hemiacetal or acetal carbon (the anomeric carbon).
Enantiomers are chiral molecules that are non-superimposable mirror images of each other. Diastereomers result when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent stereocenters and are not mirror images of each other. An epimer is one of two stereoisomers that differ in configuration at only one stereocenter. An anomer is a type of epimer; it is one of two stereoisomers of a cyclic sugar that differs only in its configuration at the hemiacetal or acetal carbon (the anomeric carbon).
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Why is it that reducing sugars can be metabolized in humans, but non-reducing sugars cannot?
Why is it that reducing sugars can be metabolized in humans, but non-reducing sugars cannot?
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When it comes to metabolizing sugars, only reducing sugars are able to undergo breakdown. This is because reducing sugars are able to be converted from their closed chain form into their open chain form. It is only in the open chain form that sugars such as glucose can be metabolized.
Only reducing sugars can be converted into their open chain form. The reason for this is that the anomeric carbon for these sugars is not occupied. In their ring form, such sugars exist as hemiacetals that can readily and reversibly undergo chain opening. Additionally, some hemiketals can be converted into their open chain form, but they need to be able to tautomerize into their aldose form first.
Non-reducing sugars have their anomeric carbon tied up in a bond, and thus are locked in an acetal or ketal form. Consequently, they cannot convert into their open chain form, meaning that they cannot be metabolized.
When it comes to metabolizing sugars, only reducing sugars are able to undergo breakdown. This is because reducing sugars are able to be converted from their closed chain form into their open chain form. It is only in the open chain form that sugars such as glucose can be metabolized.
Only reducing sugars can be converted into their open chain form. The reason for this is that the anomeric carbon for these sugars is not occupied. In their ring form, such sugars exist as hemiacetals that can readily and reversibly undergo chain opening. Additionally, some hemiketals can be converted into their open chain form, but they need to be able to tautomerize into their aldose form first.
Non-reducing sugars have their anomeric carbon tied up in a bond, and thus are locked in an acetal or ketal form. Consequently, they cannot convert into their open chain form, meaning that they cannot be metabolized.
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Glucose polysaccharides are linked together at branch points in glycogen by what type of bond?
Glucose polysaccharides are linked together at branch points in glycogen by what type of bond?
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In glycogen, glucose molecules are attached one after the other by alpha-1,4 linkages. However, in order to make glycogen more compact for storage, branch points are created to created links between many shorter glucose polysaccharides. These branch points connect glucose molecules by alpha-1,6 linkages.
In glycogen, glucose molecules are attached one after the other by alpha-1,4 linkages. However, in order to make glycogen more compact for storage, branch points are created to created links between many shorter glucose polysaccharides. These branch points connect glucose molecules by alpha-1,6 linkages.
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Why does glycogen have more branches than starch?
Why does glycogen have more branches than starch?
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Lots of alpha-1,4 linkages allow for longer chain lengths in carbohydrates like starch and glycogen. However, it is the amount of alpha-1,6 linkages that determine the number of branches - since glycogen has many more alpha-1,6 linkages than starch does, it has more branches. This allows for easy breakdown of glycogen into glucose in the liver should there not be enough glucose in the body to supply the body's demand for energy production. Recall that glycogen phosphorylase can only break terminal alpha-1,4 glycosidic bonds; hence, with more branches there are more terminal glucose molecules that are substrates for this catabolic enzyme.
Lots of alpha-1,4 linkages allow for longer chain lengths in carbohydrates like starch and glycogen. However, it is the amount of alpha-1,6 linkages that determine the number of branches - since glycogen has many more alpha-1,6 linkages than starch does, it has more branches. This allows for easy breakdown of glycogen into glucose in the liver should there not be enough glucose in the body to supply the body's demand for energy production. Recall that glycogen phosphorylase can only break terminal alpha-1,4 glycosidic bonds; hence, with more branches there are more terminal glucose molecules that are substrates for this catabolic enzyme.
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Glycogen is not a single chain of glucose units, but many chains branching off of one another. Why is the branching of glycogen important?
Glycogen is not a single chain of glucose units, but many chains branching off of one another. Why is the branching of glycogen important?
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Because glycogen is so heavily branched, it is able to pack more glucose units together in a small space, thus it is more compact and has a greater solubility. Moreover, the branching allows for glycogen enzymes to act more efficiently on the chains of glucose, and so both degradation and synthesis have increased rates.
Because glycogen is so heavily branched, it is able to pack more glucose units together in a small space, thus it is more compact and has a greater solubility. Moreover, the branching allows for glycogen enzymes to act more efficiently on the chains of glucose, and so both degradation and synthesis have increased rates.
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During times of glucose deprivation in the human body, the liver is able to supply glucose to the bloodstream by breaking down a large, branched polysaccharide that it holds in reserve until it is needed. Which of the following lists the correct type of glycosidic bonds found in this polysaccharide.
During times of glucose deprivation in the human body, the liver is able to supply glucose to the bloodstream by breaking down a large, branched polysaccharide that it holds in reserve until it is needed. Which of the following lists the correct type of glycosidic bonds found in this polysaccharide.
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For this question, we're told some background information about the liver's role in providing glucose homeostasis. We're told that when blood glucose levels are lowered, the liver is able to help restore glucose levels by keeping a large polysaccharide of glucose in store. In times of need, the liver can break this compound down to provide glucose to the bloodstream.
Even though the question doesn't explicitly tell us what the polysaccharide is, we should be able to infer that the compound in question is glycogen. Therefore, to answer the question, we need to know which kind of glycosidic bonds are found in glycogen.
First, let's recall that an individual glucose molecule is composed of six carbon atoms. In its ring form, glucose can exist as one of two epimers, depending on how its ring closes when transitioning from its straight chain form to its closed ring form. The anomeric carbon of the glucose molecule can be arranged in one of two ways when its ring closes. The anomeric carbon is the one that goes from being achiral to chiral as the ring closes. In the alpha configuration, the hydroxyl group attached to the anomeric carbon faces down, while in the beta configuration it faces up.
In addition to existing as either an alpha or a beta epimer, glucose also participates in glycosidic linkages using its first, fourth, and sixth carbon atom.
In glycogen, each individual glucose molecule is in the alpha configuration. Thus, we can rule out both answer choices that include beta. Moreover, the fourth carbon atom of each glucose molecule is attached to the first carbon atom (the anomeric carbon) in the next glucose molecule in the straight chain. To make branch points at various points along the straight chain, some of the glucose molecules have their sixth carbon atom attached to the anomeric carbon of other glucose molecules.
In conclusion, 
glycosidic bonds are responsible for branch points and 
glycosidic bonds are responsible for the straight chain.
For this question, we're told some background information about the liver's role in providing glucose homeostasis. We're told that when blood glucose levels are lowered, the liver is able to help restore glucose levels by keeping a large polysaccharide of glucose in store. In times of need, the liver can break this compound down to provide glucose to the bloodstream.
Even though the question doesn't explicitly tell us what the polysaccharide is, we should be able to infer that the compound in question is glycogen. Therefore, to answer the question, we need to know which kind of glycosidic bonds are found in glycogen.
First, let's recall that an individual glucose molecule is composed of six carbon atoms. In its ring form, glucose can exist as one of two epimers, depending on how its ring closes when transitioning from its straight chain form to its closed ring form. The anomeric carbon of the glucose molecule can be arranged in one of two ways when its ring closes. The anomeric carbon is the one that goes from being achiral to chiral as the ring closes. In the alpha configuration, the hydroxyl group attached to the anomeric carbon faces down, while in the beta configuration it faces up.
In addition to existing as either an alpha or a beta epimer, glucose also participates in glycosidic linkages using its first, fourth, and sixth carbon atom.
In glycogen, each individual glucose molecule is in the alpha configuration. Thus, we can rule out both answer choices that include beta. Moreover, the fourth carbon atom of each glucose molecule is attached to the first carbon atom (the anomeric carbon) in the next glucose molecule in the straight chain. To make branch points at various points along the straight chain, some of the glucose molecules have their sixth carbon atom attached to the anomeric carbon of other glucose molecules.
In conclusion,
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You discover that your patient is lactose intolerant, having a mutation that does not allow them to produce an enzyme that cleaves the disaccharide lactose. If they had the lactase enzyme, which glycosidic bond would it cleave?
You discover that your patient is lactose intolerant, having a mutation that does not allow them to produce an enzyme that cleaves the disaccharide lactose. If they had the lactase enzyme, which glycosidic bond would it cleave?
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lactose is made up of galactose and glucose and is bound via a beta 1,4 glycosidic bond.
the enzyme lactase cleaves this bond to break down the sugar lactose. Maltose is glucose- alpha 1,4- glucose, and sucrose is glucose- alpha, 1,2- fructose.
lactose is made up of galactose and glucose and is bound via a beta 1,4 glycosidic bond.
the enzyme lactase cleaves this bond to break down the sugar lactose. Maltose is glucose- alpha 1,4- glucose, and sucrose is glucose- alpha, 1,2- fructose.
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Which of the following statements about carbohydrates is true?
Which of the following statements about carbohydrates is true?
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Glucose has five (not six) hydroxyl groups. Reducing sugars either have an aldehyde group or can form one through isomerism; sucrose doesn’t fit either description. Although there are more amylose molecules than amylopectin in starch, amylose is a minor component by mass; amylopectin makes up 70-80% of starch by mass. Polysaccharides are indeed joined in the union of two oses, which form glycosidic bonds.
Glucose has five (not six) hydroxyl groups. Reducing sugars either have an aldehyde group or can form one through isomerism; sucrose doesn’t fit either description. Although there are more amylose molecules than amylopectin in starch, amylose is a minor component by mass; amylopectin makes up 70-80% of starch by mass. Polysaccharides are indeed joined in the union of two oses, which form glycosidic bonds.
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What functional groups are present on carbohydrates?
What functional groups are present on carbohydrates?
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Carbohydrate chains contain aldehyde or ketone functional groups, which are types of carboxyl groups. Remember the general formula for a carbohydrate is: 
since they are hydrates (water) of carbon.
Carbohydrate chains contain aldehyde or ketone functional groups, which are types of carboxyl groups. Remember the general formula for a carbohydrate is:
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Which of the following is not an example of a compound that contains carbohydrate in its structure?
Which of the following is not an example of a compound that contains carbohydrate in its structure?
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To identify the answer choice that is NOT a polysaccharide, let's go delve into each answer choice a bit.
Cellulose is a polysaccharide and also a very important component of the cell wall of plants. It consists of many glucose sugars bound together via beta (1-4) linkages.
Peptidoglycan is also a polysaccharide and a very important component of the cell wall of bacteria. Its structure consists of alternating N-acetylglucosamine and N-acetylmuramic acid connected via beta (1-4) linkages. Both of these are modified sugar molecules.
Chitin is a polysaccharide that plays an important role in the structure of the exoskeleton of many fungi, arthropods, and insects. Its structure consists of a long chain of N-acetylglucosamine, which is a derivative of the sugar glucose.
Collagen is the only answer choice that does not represent a carbohydrate. Rather, collagen is a protein that plays a very important role in the extracellular matrix of various connective tissues found in animals.
Glycogen is a branched form of glucose that is the storage form in animals. It contains beta (1-4) and beta (1-6) linkages.
To identify the answer choice that is NOT a polysaccharide, let's go delve into each answer choice a bit.
Cellulose is a polysaccharide and also a very important component of the cell wall of plants. It consists of many glucose sugars bound together via beta (1-4) linkages.
Peptidoglycan is also a polysaccharide and a very important component of the cell wall of bacteria. Its structure consists of alternating N-acetylglucosamine and N-acetylmuramic acid connected via beta (1-4) linkages. Both of these are modified sugar molecules.
Chitin is a polysaccharide that plays an important role in the structure of the exoskeleton of many fungi, arthropods, and insects. Its structure consists of a long chain of N-acetylglucosamine, which is a derivative of the sugar glucose.
Collagen is the only answer choice that does not represent a carbohydrate. Rather, collagen is a protein that plays a very important role in the extracellular matrix of various connective tissues found in animals.
Glycogen is a branched form of glucose that is the storage form in animals. It contains beta (1-4) and beta (1-6) linkages.
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Both cellulose and starch are polymers of glucose; why can't and enzyme that breaks down starch also break down cellulose?
Both cellulose and starch are polymers of glucose; why can't and enzyme that breaks down starch also break down cellulose?
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Cyclized monosaccharides can exist in two different stereoisomers that depend on the orientation of the hydroxyl group on the anomeric carbon. If this 
group is on the opposite side of the ring as the 
group, the sugar as the alpha anomer. The opposite orientation is referred to at the beta anomer. Cellulose is a polymer of beta glucose while starch is a polymer of alpha glucose, and the bonds between these glucose monomers differ depending on their anomer. This makes it so an enzyme can recognize one or the other but not both. Note that D-sugars are biologically relevant.
Cyclized monosaccharides can exist in two different stereoisomers that depend on the orientation of the hydroxyl group on the anomeric carbon. If this
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