Biology Unit Test T2 P4 Flashcards
(30 cards)
Amino acids are the building blocks of proteins. Which groups are always part of an amino acid structure?
All amino acids share a common structure consisting of a central carbon atom, known as the alpha (α) carbon. Attached to this carbon are three groups: an amine group (-NH₂), a carboxyl group (-COOH), and a unique side chain called the R-group. The R-group varies among different amino acids and determines their specific properties. This structure allows amino acids to link together and form proteins.
What are essential amino acids defined as?
Essential amino acids cannot be made by the human body and must be obtained through food. There are nine essential amino acids that humans need for proper growth and function. These amino acids are vital because the body relies on them to build proteins and carry out various biological processes. Without enough of these amino acids in the diet, the body cannot maintain healthy tissues.
in the formation of a dipeptide, which bond is formed between two amino acids?
A peptide bond forms when the carboxyl group of one amino acid reacts with the amine group of another amino acid. During this process, a molecule of water is released, making it a condensation reaction. This bond links the two amino acids together, creating a chain called a polypeptide. Peptide bonds are essential for building proteins.
When does denaturation of proteins occur?
Denaturation happens when a protein loses its secondary, tertiary, or quaternary structure because of external factors such as changes in pH or temperature. These changes disrupt the hydrogen bonds and other interactions that maintain the protein’s shape. As a result, the protein unfolds and can no longer function properly. Denaturation is often irreversible and affects the protein’s biological activity.
How is the secondary structure of a protein described as?
The secondary structure of a protein refers to the local folding patterns of its backbone, which are stabilized by hydrogen bonds. The two main types of secondary structures are alpha-helices and beta-pleated sheets. Alpha-helices form a coiled shape, while beta-pleated sheets consist of folded, sheet-like arrangements. These structures contribute to the protein’s overall shape and stability.
Which type of bond stabilises tertiary structure by linking R-groups of amino acids?
Ionic bonds between charged R-groups of amino acids help stabilize the protein’s tertiary structure by forming strong attractions. Other important interactions that contribute to this stability include hydrogen bonds, hydrophobic interactions, and disulfide bridges. Hydrogen bonds form between polar groups, while hydrophobic interactions cause nonpolar R-groups to cluster away from water. Disulfide bridges are strong covalent bonds between cysteine residues that further reinforce the protein’s shape.
What does the R-group of an amino acid determine?
The R-group, or side chain, of an amino acid determines its chemical properties, including whether it is hydrophilic (water-attracting) or hydrophobic (water-repelling). This influences how the amino acid interacts with its surrounding environment and with other amino acids within the protein. Hydrophilic R-groups tend to be found on the protein’s surface, while hydrophobic R-groups usually cluster inside. These interactions help shape the protein’s overall structure and function.
What is an example of a conjugated protein?
Hemoglobin is a conjugated protein because it consists of both polypeptide chains and a non-protein component called the heme group. The heme group contains an iron ion that is essential for binding oxygen. Each hemoglobin molecule has four heme groups, allowing it to carry up to four oxygen molecules. This combination of protein and non-protein parts enables hemoglobin to perform its role in oxygen transport effectively.
What does the primary structure of a protein refer to?
The primary structure of a protein is the specific linear sequence of amino acids in a polypeptide chain. This sequence is determined by the genetic code in the DNA. The order of amino acids is crucial, as it influences how the protein will fold into its functional shape. Even a single change in the sequence can affect the protein’s structure and function.
Fibrous proteins like collagen are what?
Fibrous proteins, such as collagen, are known for their structural role in the body. They are insoluble in water and have high tensile strength, making them ideal for supporting tissues like skin, tendons, and bones. Their structure is built from repetitive amino acid sequences that form long, tightly packed fibers. This organization gives fibrous proteins their durability and resistance to stretching.
Where are hydrophobic amino acids likely found?
Hydrophobic amino acids tend to cluster in the interior regions of membrane-bound proteins, away from the surrounding water-based environment. This positioning helps stabilize the protein within the lipid bilayer of the cell membrane. By avoiding contact with water, these nonpolar amino acids interact with the hydrophobic interior of the membrane. This arrangement is crucial for maintaining the protein’s structure and proper function in the membrane.
What is the quaternary structure a feature of?
Quaternary structure refers to the way multiple polypeptide chains, or subunits, come together to form one functional protein. These subunits are held together by various interactions such as hydrogen bonds, ionic bonds, and hydrophobic interactions. The arrangement and interaction of these subunits are essential for the protein’s overall function. An example of a protein with quaternary structure is hemoglobin, which consists of four subunits working together to transport oxygen.
What are the alpha-helix and beta-pleated sheet structures stabilised by?
Both alpha-helices and beta-pleated sheets are common secondary structures in proteins, stabilized by hydrogen bonds. These hydrogen bonds form between the amino hydrogen of one peptide bond and the carboxyl oxygen of another within the backbone. In alpha-helices, the bonding creates a coiled structure, while in beta-pleated sheets, it forms a folded, sheet-like arrangement. These patterns contribute to the overall stability and shape of the protein.
What does the tertiary structure dependent on?
Tertiary structure refers to the overall three-dimensional shape of a single polypeptide chain. It is determined by interactions between the R-groups (side chains) of amino acids. These interactions include hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges. Together, they fold the polypeptide into a specific shape that is essential for the protein’s function.
What are conjugated proteins characterised by?
Conjugated proteins are proteins that contain non-protein components, known as prosthetic groups, along with their amino acid chains. These non-protein parts are essential for the protein’s function. For example, hemoglobin contains heme groups that help bind oxygen, and lipoproteins include lipid components that assist in transporting fats. The combination of protein and prosthetic group allows conjugated proteins to carry out specialized roles in the body.
Which protein is a globular protein with a specific role in regulating blood sugar?
Insulin is a globular protein hormone that plays a key role in regulating blood sugar levels. It has a compact, spherical shape, which is characteristic of globular proteins. This structure allows insulin to be soluble in water and easily transported through the bloodstream. Insulin binds to receptors on cell surfaces, enabling cells to absorb glucose from the blood.
Disulfide bridges are particularly important in stabilising what?
Disulfide bridges are strong covalent bonds that form between the sulfur atoms of two cysteine residues in a protein. These bonds create links between different parts of the polypeptide chain, helping to stabilize the protein’s tertiary structure. Disulfide bridges are especially important in proteins that function in harsh environments, as they provide extra structural support. Their presence helps maintain the protein’s specific shape, which is crucial for its function.
Where are non-polar amino acids most likely found?
Non-polar (hydrophobic) amino acids are typically located in the interior regions of membrane proteins. This positioning allows the protein to interact favorably with the hydrophobic core of the lipid bilayer. By avoiding water, these amino acids help stabilize the protein’s structure within the membrane. This arrangement is essential for the protein’s proper function and integration in the cell membrane.
In a beta-pleated sheet what does the polypeptide chain do?
In a beta-pleated sheet, the polypeptide chain folds back and forth, creating a flat, sheet-like structure. This arrangement allows adjacent strands to lie side by side. Hydrogen bonds form between the amino hydrogen of one strand and the carboxyl oxygen of a neighboring strand, stabilizing the sheet. This structure contributes to the protein’s overall stability and strength.
Cysteine forms strong covalent bonds called what?
Cysteine residues contain sulfur in their side chains, which can form strong covalent bonds called disulfide bridges. These bridges link different parts of a protein chain or different chains together. Disulfide bridges play a crucial role in stabilizing the protein’s three-dimensional structure. This added stability is especially important for proteins exposed to harsh conditions.
What term have interactions between R-groups determining the protein’s overall 3D shape?
Tertiary structure
What term have hydrogen bonds between polypeptide backbones resulting in zigzag structures?
Beta-pleated sheet
What term is the basic sequence of amino acids in a polypeptide?
Primary structure
What term is a protein with a non-protein component?
Conjugated protein
