Protein Structure and Function: Amino Acids
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Questions and Answers

What are proteins composed of?

Amino acids

Which of the following describes the function of proteins? (Select all that apply)

  • Fight infectious bacteria (correct)
  • Form frameworks in bones (correct)
  • Store genetic information
  • Direct and regulate metabolism (correct)

    • All amino acids are coded for by DNA.

    False

    At physiological pH, what form does the carboxyl group of an amino acid take?

    <p>Dissociated carboxylate ion (–COO–)</p> Signup and view all the answers

    Which amino acid has a secondary amino group?

    <p>Proline</p> Signup and view all the answers

    The phenomenon where nonpolar amino acids cluster together in proteins is known as the ______ effect.

    <p>hydrophobic</p> Signup and view all the answers

    Sickle cell anemia is caused by the replacement of a nonpolar amino acid with a polar one.

    <p>False</p> Signup and view all the answers

    What is the pKa of the α-carboxyl group of alanine?

    <p>2.3</p> Signup and view all the answers

    At which pH does alanine exist predominantly as the dipolar form II?

    <p>5.7</p> Signup and view all the answers

    Which of the following pairs acts as a buffer in the pH region around pK2?

    <p>–NH3+/–NH2</p> Signup and view all the answers

    What is the isoelectric point (pI) of alanine calculated to be?

    <p>5.7</p> Signup and view all the answers

    What occurs when the pH equals pK1?

    <p>Equal amounts of forms I and II exist.</p> Signup and view all the answers

    How does the charge of plasma proteins behave at a pH above their pI?

    <p>They have a net negative charge.</p> Signup and view all the answers

    In which condition is the Henderson-Hasselbalch equation applied to alanine?

    <p>To calculate the titration curve.</p> Signup and view all the answers

    Which form of alanine has a net charge of +1?

    <p>Form I</p> Signup and view all the answers

    What role do cross-links in concept maps serve?

    <p>They identify central concepts relevant to multiple topics.</p> Signup and view all the answers

    Which amino acid is unique in having a secondary amino group?

    <p>Proline</p> Signup and view all the answers

    At physiological pH, what is the charge of the α-carboxyl group in an amino acid?

    <p>Negative charge</p> Signup and view all the answers

    What characterizes the α-carbon of most amino acids?

    <p>It is a chiral carbon due to four distinct substituents.</p> Signup and view all the answers

    Which statement is true about the chemical classification of amino acids?

    <p>The nature of the side chain determines the amino acid's classification.</p> Signup and view all the answers

    What does the Henderson-Hasselbalch equation describe?

    <p>The concentration ratio of a weak acid and its conjugate base.</p> Signup and view all the answers

    Which of the following describes buffering in relation to amino acids?

    <p>Amino acids can serve as buffers near their pKa values.</p> Signup and view all the answers

    Which statement about the L-form of amino acids is accurate?

    <p>The L-form of amino acids is the prevalent form in human proteins.</p> Signup and view all the answers

    What type of interaction stabilizes the three-dimensional shape of proteins by forming covalent bonds between cysteine residues?

    <p>Disulfide bonds</p> Signup and view all the answers

    In which part of a polypeptide molecule are nonpolar side chains typically found?

    <p>In the interior, associating with other nonpolar amino acids</p> Signup and view all the answers

    Which interaction is primarily responsible for enhancing the solubility of proteins in an aqueous environment?

    <p>Hydrogen bonds</p> Signup and view all the answers

    What types of amino acid side chains are likely to interact via ionic interactions?

    <p>Positively and negatively charged</p> Signup and view all the answers

    The interior arrangement of nonpolar amino acids in a polypeptide is a result of which effect?

    <p>Hydrophobic effect</p> Signup and view all the answers

    Which amino acids participate in the formation of disulfide bonds?

    <p>Cysteine</p> Signup and view all the answers

    What is represented by point C in the context of amino acids?

    <p>The pI of the amino acid</p> Signup and view all the answers

    What is the role of hydrogen bonds in the tertiary structure of proteins?

    <p>To create interactions that enhance solubility</p> Signup and view all the answers

    Which amino acid in the peptide Val-Cys-Glu-Ser-Asp-Arg-Cys can be phosphorylated?

    <p>Serine</p> Signup and view all the answers

    How do hydrophobic interactions affect the polarity of amino acid arrangements in proteins?

    <p>They cause nonpolar amino acids to aggregate in the interior</p> Signup and view all the answers

    At pH 5, what is the expected charge of the peptide Val-Cys-Glu-Ser-Asp-Arg-Cys?

    <p>Negative</p> Signup and view all the answers

    How does the structure of proteins relate to their function?

    <p>Higher structural levels build upon the primary structure</p> Signup and view all the answers

    What happens to aspartate at a pH of 5 in terms of ionization?

    <p>It is ionized</p> Signup and view all the answers

    What is the ratio of the ionized to un-ionized form of aspirin at a pH of 7.0?

    <p>10,000:1</p> Signup and view all the answers

    Which statement is true about the peptide depending on the side chain of the amino acids?

    <p>Cysteine can form disulfide bonds</p> Signup and view all the answers

    Which of the following best describes the relationship between pK values and buffer regions in amino acids?

    <p>Maximum buffering occurs at pKa values</p> Signup and view all the answers

    What is the primary characteristic of HbF compared to HbA regarding oxygen affinity?

    <p>HbF has a higher oxygen affinity than HbA.</p> Signup and view all the answers

    What percentage of total hemoglobin is composed of HbA2 in normal adults?

    <p>2%</p> Signup and view all the answers

    How is HbA1c formed?

    <p>Through nonenzymatic glycosylation of hemoglobin.</p> Signup and view all the answers

    Where are the genes coding for the α-globin chains located?

    <p>On chromosome 16.</p> Signup and view all the answers

    What effect does 2,3-BPG have on hemoglobin's affinity for oxygen?

    <p>It decreases the affinity for oxygen.</p> Signup and view all the answers

    What is the structure of HbA2?

    <p>Two α-globin and two δ-globin chains.</p> Signup and view all the answers

    What is the main role of HbF during gestation?

    <p>Enhancing oxygen transfer from the mother to the fetus.</p> Signup and view all the answers

    What is glycation in the context of hemoglobin?

    <p>The nonenzymatic addition of glucose to hemoglobin.</p> Signup and view all the answers

    What is the term used for the sequence of amino acids in a protein?

    <p>Primary structure</p> Signup and view all the answers

    What type of bond links amino acids together in a protein chain?

    <p>Peptide bond</p> Signup and view all the answers

    What characterization does the peptide bond exhibit?

    <p>It has a partial double-bond character.</p> Signup and view all the answers

    What happens to proteins with abnormal amino acid sequences?

    <p>They can disrupt normal folding and function.</p> Signup and view all the answers

    In naming a peptide, how are the suffixes of amino acids treated?

    <p>They are replaced with –yl except for the C-terminal.</p> Signup and view all the answers

    What is the effect of prolonged exposure to strong acids or bases on peptide bonds?

    <p>They are broken nonenzymically.</p> Signup and view all the answers

    What structure results from the linkage of many amino acids through peptide bonds?

    <p>An unbranched chain known as a polypeptide</p> Signup and view all the answers

    Why is understanding primary protein structure important in genetic diseases?

    <p>It identifies abnormal amino acid sequences related to diseases.</p> Signup and view all the answers

    What is the role of Edman reagent in the sequencing of peptides?

    <p>To label the N-terminal residue of a peptide</p> Signup and view all the answers

    Which enzyme class is responsible for hydrolyzing peptide bonds within a protein?

    <p>Peptidases</p> Signup and view all the answers

    What allows the determination of a polypeptide's complete amino acid sequence after cleavage into fragments?

    <p>Overlapping fragments from separate cleaving agents</p> Signup and view all the answers

    The analysis of amino acids using an amino acid analyzer is based on which principle?

    <p>Measurement of light absorption</p> Signup and view all the answers

    Which property of the phenylthiohydantoin (PTH) derivative facilitates the sequencing process?

    <p>Instability of the N-terminal peptide bond</p> Signup and view all the answers

    What is the primary method for determining a protein's primary structure from its DNA sequence?

    <p>Translation of nucleotide sequence</p> Signup and view all the answers

    What defines the role of carboxypeptidases in polypeptide analysis?

    <p>They determine the C-terminal amino acid</p> Signup and view all the answers

    Which of the following statements about sequencing large polypeptides is accurate?

    <p>Overlapping fragments are crucial for correct ordering.</p> Signup and view all the answers

    What is the primary function of a buffer in a solution?

    <p>To resist changes in pH</p> Signup and view all the answers

    What relationship does the Henderson-Hasselbalch equation describe?

    <p>The relationship between pH, pKa, and concentration of acid and conjugate base</p> Signup and view all the answers

    At what pH does a buffer achieve maximum buffering capacity?

    <p>At pH equal to the pKa</p> Signup and view all the answers

    What happens to the weak acid HA when a strong acid like HCl is added to a buffer solution?

    <p>HA decreases and A– increases</p> Signup and view all the answers

    Which statement accurately describes the dissociation constant Ka of an acid?

    <p>A larger Ka indicates a stronger acid</p> Signup and view all the answers

    What effect does buffering have on the pH of a solution when both a weak acid and its conjugate base are present?

    <p>It maintains the pH within a specific range</p> Signup and view all the answers

    How does the pH of a solution relate to the equilibrium of weak acids and their conjugate bases?

    <p>Equilibrium shifts depend on the ratio of acid to conjugate base</p> Signup and view all the answers

    What defines a weak acid in terms of its dissociation in solution?

    <p>It partially ionizes, yielding limited H+ and A–</p> Signup and view all the answers

    Which interaction is characterized by the formation of covalent links between cysteine side chains?

    <p>Disulfide bonds</p> Signup and view all the answers

    What stabilizing interaction is primarily responsible for keeping nonpolar amino acids in the interior of a protein structure?

    <p>Hydrophobic interactions</p> Signup and view all the answers

    Which type of interaction increases the solubility of proteins in aqueous environments?

    <p>Hydrogen bonds</p> Signup and view all the answers

    Which amino acid is primarily involved in the formation of ionic interactions within proteins?

    <p>Aspartate</p> Signup and view all the answers

    What effect does the presence of disulfide bonds have on protein stability?

    <p>They stabilize the three-dimensional structure.</p> Signup and view all the answers

    In the context of protein folding, where are hydrophobic amino acids typically located?

    <p>In the interior of the polypeptide</p> Signup and view all the answers

    What role do hydrogen bonds play in protein structure?

    <p>They stabilize interactions between side chains and solvents.</p> Signup and view all the answers

    Which type of interaction is described as occurring between positively and negatively charged side chains?

    <p>Ionic interactions</p> Signup and view all the answers

    What characteristic of the sigmoidal oxygen-dissociation curve allows hemoglobin to carry and deliver oxygen efficiently?

    <p>The steep slope over a specific range of oxygen concentrations</p> Signup and view all the answers

    Which factor enhances the release of oxygen from hemoglobin according to the Bohr effect?

    <p>Lower pH due to higher CO2 concentration</p> Signup and view all the answers

    What occurs to the oxygen-dissociation curve when the pH is raised?

    <p>It shifts to the left, indicating higher affinity for oxygen</p> Signup and view all the answers

    Which reaction occurs in metabolically active tissues that contributes to lowering the pH?

    <p>CO2 + H2O -&gt; H2CO3 -&gt; HCO3– + H+</p> Signup and view all the answers

    What function does bicarbonate serve in the blood?

    <p>As a major blood buffer</p> Signup and view all the answers

    How does the pH differential between the lungs and tissues affect hemoglobin's oxygen binding?

    <p>Lower pH in tissues favors unloading of oxygen</p> Signup and view all the answers

    What would happen if hemoglobin maintained a hyperbolic oxygen-dissociation curve?

    <p>It would be unable to release oxygen effectively</p> Signup and view all the answers

    What stabilizes the deoxy form (T form) of hemoglobin according to the Bohr effect?

    <p>Higher CO2 concentration and lower pH</p> Signup and view all the answers

    What is the primary function of muscle spindles in skeletal muscles?

    <p>To detect changes in muscle length</p> Signup and view all the answers

    What percentage of a mixed nerve is composed of sensory fibers?

    <p>40%</p> Signup and view all the answers

    Which type of nerve fibers primarily regulate blood flow to the muscles?

    <p>Sympathetic fibers</p> Signup and view all the answers

    What role do Golgi Tendon Organs play in muscle function?

    <p>They regulate muscle stiffness</p> Signup and view all the answers

    Where does the nerve typically enter a muscle?

    <p>At about the midpoint on its deep surface</p> Signup and view all the answers

    What is the primary function of the epimysium in skeletal muscle organization?

    <p>Binds fascicles together.</p> Signup and view all the answers

    What role does the endomysium play in muscle tissue?

    <p>Surrounds and supports individual muscle cells.</p> Signup and view all the answers

    Which connective tissue structure separates muscles from other organs?

    <p>Fascia</p> Signup and view all the answers

    What is the significance of the Golgi Tendon Organ (GTO) in muscle function?

    <p>Inhibits muscle contraction.</p> Signup and view all the answers

    What is the main composition of the perimysium in muscle tissue?

    <p>Irregular dense connective tissue</p> Signup and view all the answers

    In skeletal muscle, what is a fascicle?

    <p>A group of muscle fibers.</p> Signup and view all the answers

    What describes an aponeurosis in relation to muscle tissue?

    <p>A tough, sheet-like structure connecting muscle to muscle.</p> Signup and view all the answers

    Which connective tissue structure allows activation of specific subsets of muscle fibers within a fascicle?

    <p>Perimysium</p> Signup and view all the answers

    What is the primary function of Broca's area?

    <p>Motor control for speech production</p> Signup and view all the answers

    A lesion in the primary motor cortex (Area 4) would most likely lead to which condition?

    <p>Contralateral hemiplegia</p> Signup and view all the answers

    What primary sensation is processed by the primary somatosensory cortex (Areas 1, 2, 3)?

    <p>Touch and pain</p> Signup and view all the answers

    What condition is characterized by an inability to interpret sensations such as touch or vibration?

    <p>Sensory agnosia</p> Signup and view all the answers

    What symptom is most commonly associated with a destructive lesion in Area 8 (frontal eye field)?

    <p>Eye deviation towards the lesion</p> Signup and view all the answers

    Which area is associated with Wernicke's aphasia following damage?

    <p>Area 21, 22</p> Signup and view all the answers

    What condition does a lesion in the supplementary motor cortex (Area 6) primarily cause?

    <p>Apraxia</p> Signup and view all the answers

    Which area is involved in processing auditory information?

    <p>Area 41, 42</p> Signup and view all the answers

    What effect does a lesion in Area 39 (angular gyrus) have on language?

    <p>Difficulty with reading and writing</p> Signup and view all the answers

    What is the significance of the primary visual cortex (Area 17)?

    <p>Initial processing of visual information</p> Signup and view all the answers

    Study Notes

    Overview of Proteins

    • Proteins are abundant and diverse macromolecules essential for life processes.
    • Functions include acting as enzymes, hormones, contractile proteins in muscles, and providing structural support in bones through collagen.
    • Proteins play critical roles in the bloodstream (e.g., hemoglobin shuttling oxygen, immunoglobulins fighting pathogens).
    • Proteins are linear polymers made of amino acids, which are the building blocks of these macromolecules.

    Amino Acid Structure

    • Over 300 different amino acids are described in nature, but only 20 are common in mammalian proteins, coded by DNA.
    • Each amino acid consists of:
      • A carboxyl group.
      • A primary amino group (except proline which has a secondary amino group).
      • A distinctive side chain ("R group") attached to the α-carbon.
    • At physiological pH (around 7.4), carboxyl groups dissociate to form negatively charged carboxylate ions, and amino groups become protonated.

    Amino Acid Classification

    • Amino acids can be classified based on the properties of their side chains:
      • Nonpolar Side Chains: Do not engage in hydrogen or ionic bonding, characterized as "oily" or lipid-like, promoting hydrophobic interactions.
      • Nonpolar amino acids cluster in the interior of proteins in polar environments, known as the hydrophobic effect, maintaining the protein's three-dimensional shape.
      • In hydrophobic environments, nonpolar R groups are found on the protein's exterior, interacting with lipids.

    Significance of Side Chains

    • The nature and properties of side chains dictate the functional roles of amino acids within proteins.
    • Examples include the role of specific amino acids in diseases, such as sickle cell anemia, where a polar glutamate is replaced by a nonpolar valine in hemoglobin.

    Proline as an Exception

    • Proline's side chain and α-amino nitrogen form a rigid five-membered ring, resulting in its classification as a secondary amino acid, differing from the primary amino group of other amino acids.

    General Protein Structure Considerations

    • The hydrophobic interactions play a crucial role in stabilizing protein structures, influencing their functionalities and location within different environments.

    pKa of Alanine

    • Sequential dissociation of protons from alanine's carboxyl (–COOH) and amino (–NH3+) groups follows specific pKa values: pK1 is approximately 2, and pK2 is approximately 9.
    • pKa denotes the pH where half of the protons have been removed; for alanine, pK1 = 2.3 and pK2 = 9.1.

    Titration Curve of Alanine

    • The Henderson-Hasselbalch equation helps generate the titration curve of weak acids, illustrating pH changes during base addition.
    • Buffer regions:
      • –COOH/–COO– pair buffers around pK1.
      • –NH3+/–NH2 pair buffers near pK2.
    • At pH equal to pK1, both protonated (form I) and deprotonated forms (form II) are present in equal amounts; the same concept applies at pK2 with forms II and III.
    • The isoelectric point (pI) for alanine, when it is neutral, is calculated as the average of pK1 and pK2, resulting in pI = 5.7.

    Characteristics of Amino Acids

    • All amino acids possess a primary α-amino group and a α-carboxyl group; proline has a secondary amino group.
    • These groups allow amino acids to act as buffers, with buffering capacity maximal within ±1 pH unit of their pKa values.
    • Each amino acid has a chiral α-carbon except glycine, with the L-form predominating in proteins.

    Protein Structure

    • Proteins are formed from 20 standard amino acids linked by peptide bonds, leading to a unique three-dimensional structure.
    • Protein structure is categorized into four levels: primary, secondary, tertiary, and quaternary.
    • Key interactions stabilizing tertiary structures include:
      • Disulfide bonds: Covalently link cysteine residues, enhancing stability in extracellular environments.
      • Hydrophobic interactions: Nonpolar side chains typically cluster inward, while polar/charged groups face outward.
      • Hydrogen bonds: Hydrogen from amino acid side chains can interact with electronegative atoms, improving protein solubility.
      • Ionic interactions: Charged groups can attract or repel each other, affecting structure and solubility.

    Hemoglobin Variants

    • Hemoglobin A2 (HbA2) represents a minor form of hemoglobin, comprising α-globin and δ-globin chains, constituting about 2% of total hemoglobin.
    • Hemoglobin A1c (HbA1c) results from non-enzymatic glycosylation, significant in monitoring diabetes due to its association with blood glucose levels.

    Gene Organization of Globins

    • Hemoglobin genes for α-globin and β-globin are located in separate clusters (families) on different chromosomes, with two genes coding for α-globin on chromosome 16.

    Amino Acids and Their Configurations

    • All amino acids in proteins are predominantly of the L configuration; D-amino acids are found in some antibiotics and bacterial cell walls.

    Acidic and Basic Properties of Amino Acids

    • Amino acids possess weakly acidic α-carboxyl groups and weakly basic α-amino groups in aqueous solutions.
    • Acidic and basic amino acids have ionizable side chains, allowing them to function as buffers.
    • Weak acids and bases ionize to limited extents, with acidity defined as proton donors and alkalinity as proton acceptors.
    • pH quantifies proton concentration, defined by the equations pH = log(1/[H+]) or pH = -log[H+].
    • The Henderson-Hasselbalch equation relates pH to concentrations of weak acids and their conjugate bases.

    Buffers

    • Buffers resist pH changes when acids or bases are added, achieved by mixing weak acids (HA) with their conjugate bases (A–).
    • Buffers can neutralize added acids (A– converts to HA) or bases (HA converts to A–).
    • Maximum buffering occurs when pH equals pKa, effective within approximately ±1 pH unit of pKa.

    Primary Structure of Proteins

    • The primary structure of proteins is the linear sequence of amino acids, critical for understanding genetic diseases linked to amino acid abnormalities.
    • Peptide bonds form covalently between the α-carboxyl group of one amino acid and the α-amino group of another.
    • Peptide bonds are stable under conditions that denature proteins, requiring strong acids or bases for hydrolysis.
    • Peptides are read from N-terminal (left) to C-terminal (right), with residues denoting remaining parts of amino acids post-peptide bond formation.

    Peptide Bond Characteristics

    • Peptide bonds exhibit partial double-bond character, making them rigid and planar.
    • Amino acid composition can be determined using spectrophotometry and amino acid analyzers.

    Sequencing of Peptides

    • Sequencing begins at the N-terminal end using Edman reagent, which labels the terminal residue for identification.
    • Large polypeptides are cleaved at specific sites for sequencing, with overlapping fragments allowing for complete sequence reconstruction.
    • Enzymes that hydrolyze peptide bonds are classified as peptidases, with categories including exopeptidases and endopeptidases.

    Tertiary Structure of Proteins

    • Four major interactions stabilize the tertiary structure:
      • Disulfide Bonds: Covalent linkages between cysteine residues enhance protein stability.
      • Hydrophobic Interactions: Nonpolar amino acids cluster inward, while polar/charged ones are exposed to the aqueous environment.
      • Hydrogen Bonds: Form between polar groups, increasing protein solubility.
      • Ionic Interactions: Occur between positively and negatively charged side chains.

    Oxygen-Dissociation Curve and Bohr Effect

    • The sigmoidal oxygen-dissociation curve of hemoglobin efficiently transports oxygen from lungs to tissues.
    • The Bohr effect describes increased oxygen release from hemoglobin in lower pH or higher pCO2 conditions, shifting the curve to the right.
    • CO2 in metabolically active tissues lowers pH by forming carbonic acid, enhancing oxygen unloading.
    • This gradient supports efficient gas exchange, with different affinities for oxygen at varying pH levels between lungs and tissues.

    Muscle Structure and Connective Tissues

    • Fascia surrounds individual skeletal muscles, providing separation from other muscles.
    • Muscles are encased in superficial and deep fascia, particularly in large muscle groups such as limbs.
    • Tendons form from the fascia extending beyond muscles, functioning as tough cord-like structures.
    • Aponeurosis connects muscles by forming tough sheet-like structures.

    Connective Tissue Coverings

    • Epimysium:

      • Dense connective tissue surrounding an entire skeletal muscle.
      • Binds fascicles together and separates muscles from other organs.
      • Allows muscles to contract effectively while maintaining structural integrity.

    • Perimysium:

      • Connective tissue that divides the muscle into fascicles.
      • Facilitates the activation of specific muscle fiber subsets within each fascicle.

    • Endomysium:

      • Composed of collagen and reticular fibers, surrounds individual muscle fibers.
      • Plays a vital role in transferring the force produced by muscle fibers to tendons.

    Muscle Fiber Organization

    • Skeletal muscle fibers are organized into bundles called fascicles, which are bound by connective tissues.
    • Each fascicle contains muscle fibers composed of myofibrils made up of thick and thin filaments.

    Autogenic Inhibition

    • Stimulated by the Golgi Tendon Organ (GTO), leading to muscle relaxation by interrupting contraction.
    • Serves to prevent excessive contraction and potential injury to the muscle.

    Nerve Supply

    • The nerve supplying a muscle is a mixed nerve, containing motor and sensory components.

    • Motor Component (60%):

      • Supplied by alpha fibers from the anterior gray horn and gamma fibers from smaller spinal cord cells.

    • Sensory Component (40%):

      • Provided by myelinated fibers from specialized sensory endings within the muscle or tendon.
      • Muscle Spindles act as stretch receptors detecting changes in muscle length, contributing to proprioception for body position awareness.
      • Tendon Spindles (Golgi Tendon Organ) work with muscle spindles to reflexively regulate muscle stiffness.

    Sympathetic Fibers

    • Nonmyelinated fibers regulate blood flow to muscle walls, playing a role in muscle function.

    Frontal Lobe

    • Area 4: Primary motor cortex located in the precentral gyrus. Lesions result in contralateral hemiplegia and hemiparesis. Receives input from the ventrolateral nucleus of the thalamus.
    • Area 6: Comprised of the premotor cortex (lateral frontal) and supplementary motor cortex (medial superior frontal). Crucial for planning and programming movements. Lesions lead to apraxia and receive projections from the ventral-anterior nucleus of the thalamus.
    • Area 8: Frontal eye field. Destructive lesions result in eyes deviating towards the lesion, while irritative lesions cause eyes to look away.
    • Areas 44, 45: Known as Broca’s area, located in the inferior frontal gyrus (opercularis and parts of triangularis).
    • Areas 9 to 14, 46, 47: Together form the prefrontal cortex, involved in higher-level functions including decision-making and social behavior.

    Parietal Lobe

    • Areas 1, 2, 3: Primary somatosensory cortex located in the postcentral gyrus. Responsible for processing touch, pain, temperature, vibration, and proprioception from both face (via VPM) and body (via VPL).
    • Areas 5, 7: Somatosensory association cortex in the superior parietal lobule. Interprets sensory information; lesions lead to sensory agnosia, including:
      • Astereognosis: Inability to interpret object shape by touch.
      • Abarognosia: Impaired perception of weight.
      • Agraphesthesia: Inability to recognize numbers and letters by touch.
    • Area 39 & 40: Angular and supramarginal gyri, part of Wernicke’s area, important for language comprehension. Damage may result in contralateral neglect.

    Temporal Lobe

    • Areas 41, 42: Primary auditory cortex found in the superior temporal lobe (Heschl’s gyrus). Connected to the medial geniculate body, responsible for sound processing.
    • Areas 21, 22: Auditory association area leading to Wernicke’s aphasia. Positioned in the inferotemporal lobe and involved in memory (hippocampus) and emotional processing (amygdala).

    Occipital Lobe

    • Area 17: Primary visual cortex. Lesions can cause cortical blindness and contralateral hemianopia.
    • Areas 18, 19: Visual association areas associated with visual agnosia, resulting in difficulties in recognizing and interpreting visual stimuli.

    Blood Supply of the Brain

    • Vertebral arteries ascend posteriorly and unite to form the basilar artery at the pons, terminating as the posterior cerebral artery which supplies the occipital lobe.
    • Common carotid artery bifurcates at the angle of the mandible into external and internal carotid arteries. Palpating both can lead to loss of consciousness.
    • The Circle of Willis is formed collectively by the vertebral arteries and major cerebral arteries, ensuring collateral circulation within the brain.

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    Description

    Delve into the fundamentals of protein structure and their vital functions in living organisms. This quiz covers amino acids and their roles in enzymes, hormones, and muscle contraction. Test your knowledge on how these macromolecules are essential for various life processes.

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