Blood and Body Fluids (BLF) 103 Quiz: Hemoglobin

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Questions and Answers

What is the composition of Adult Hemoglobin A (HbA1)?

2 α and 2 δ chains

2 β and 2 δ chains

2 α and 2 γ chains

2 α and 2 β chains (correct)

How does carbon monoxide affect hemoglobin's affinity for oxygen?

It allows hemoglobin to deliver more oxygen to tissues.

It increases the affinity of hemoglobin for oxygen. (correct)

It decreases the affinity of hemoglobin for oxygen.

It reduces the number of heme sites available for binding.

What is the primary function of 2,3 Bisphosphoglycerate (BPG) in red blood cells?

To enhance the formation of carboxyhemoglobin.

To facilitate the conversion of glucose to ATP.

To stabilize the T-conformation of hemoglobin. (correct)

To increase the affinity of hemoglobin for oxygen.

At what age does fetal hemoglobin begin to be replaced by Adult Hemoglobin A?

At 6 months Signup and view all the answers

What is the significance of glycosylated hemoglobin (HbA1c) in diabetic patients?

It is used for monitoring blood glucose level over the past 3 months. Signup and view all the answers

Which statement about hemeproteins is correct?

Hemoglobin is a hemeprotein specifically designed for oxygen transport. Signup and view all the answers

What role does 2,3 BPG play in hemoglobin function?

It facilitates the release of oxygen from hemoglobin. Signup and view all the answers

Which function of hemoglobin is crucial for maintaining blood pH?

Binding to hydrogen ions (H+). Signup and view all the answers

What is the maximum number of oxygen molecules a single hemoglobin molecule can carry?

4 Signup and view all the answers

How does hemoglobin contribute to the transport of carbon dioxide?

It binds carbon dioxide indirectly while releasing oxygen. Signup and view all the answers

What is the primary role of hemoglobin in oxygen transport?

Binds oxygen in the lungs where concentration is high Signup and view all the answers

How does hemoglobin facilitate the removal of carbon dioxide from the body?

By binding carbon dioxide and buffering hydrogen ions Signup and view all the answers

What is the pH range that hemoglobin helps maintain in the blood?

7.35–7.45 Signup and view all the answers

What component forms protoporphyrin IX in heme?

Four pyrrole rings condensed through methenyl bridges Signup and view all the answers

Which statement about the iron atom in heme is true?

It has six coordination bonds of which two are perpendicular to the ring plane. Signup and view all the answers

What role does the distal histidine (His E7) play in the function of hemoglobin?

It stabilizes the oxygen bound to iron. Signup and view all the answers

What condition can arise from a failure of hemoglobin to properly buffer blood pH?

Acidosis or alkalosis Signup and view all the answers

What role do coordinated nitrogen atoms play in hemoglobin?

They prevent heme iron from converting to ferric state Signup and view all the answers

Which amino acid group is responsible for attaching heme to the polypeptide chain?

Imidazole group of one histidine Signup and view all the answers

What structural change occurs in hemoglobin when O2 binds to heme?

Rupture of some hydrogen and ionic bonds between α2β2 dimers Signup and view all the answers

What are the differences between the T form and R form of hemoglobin?

T form is deoxygenated while R form is oxygenated Signup and view all the answers

What effect does the binding of the first O2 molecule have on the remaining O2 molecules in hemoglobin?

It facilitates the binding of additional O2 molecules Signup and view all the answers

How does cooperative binding influence the dissociation of O2 from hemoglobin?

It facilitates dissociation of other O2 molecules after the first O2 dissociates Signup and view all the answers

What characteristic of the T form of hemoglobin affects its mobility?

Overall structure being less mobile Signup and view all the answers

What is the significance of the sixth coordination position of the ferrous atom in hemoglobin?

It becomes occupied with oxygen upon binding Signup and view all the answers

How does the presence of nonpolar amino acids in the globin chain affect heme?

They utilize hydrophobic interactions to sequester heme Signup and view all the answers

What is the overall effect of the T form on hemoglobin's affinity for oxygen?

Lower affinity for oxygen Signup and view all the answers

Study Notes

Course Information

Academic Year: 2024-2025
Year: 1
Semester: 1
Module: Blood and Body Fluids (BLF) 103

Hemoglobin Structure & Function

Lecturer: Manar Yehia
Department: Biochemistry and Molecular Biology

Objectives

Identify hemeproteins
Explain general structure of hemoglobin and myoglobin
Explain different functions of hemoglobin
Explain structure of heme group
Describe biochemical effect of 2, 3 BPG
Illustrate importance of inosine in blood banks

Introduction

Hemoglobin and myoglobin are hemeproteins, crucial for binding oxygen
Their physiological importance relates to oxygen binding ability

Hemoproteins

Hemeproteins are specialized proteins containing heme as a prosthetic group
Examples include hemoglobin, myoglobin, catalase, peroxidase, cytochromes, and cytochrome P-450
Each protein has a specific function

Hemoglobin

Hemoglobin is composed of heme and globin
Heme contains an iron atom that binds oxygen
Globin is a protein that surrounds the heme group
Each hemoglobin molecule can carry up to four oxygen molecules

Hemoglobin Functions

Oxygen Transport: Hemoglobin binds oxygen in the lungs and transports it to tissues and organs, where it's released for cellular respiration.
Carbon Dioxide Transport: Hemoglobin helps transport carbon dioxide, a waste product, from tissues to the lungs. It binds CO2 directly or indirectly through buffering hydrogen ions. This facilitates removal through exhalation.
Buffering Blood pH: Hemoglobin acts as a buffer by binding hydrogen ions (H+), maintaining blood pH within a narrow range and preventing acidosis or alkalosis.

Structure and Properties of Heme

Heme consists of a complex organic ring structure known as protoporphyrin IX, which is bound to a single iron atom (ferrous state, Fe2+)
The iron atom has six coordination bonds, four of which bind to nitrogen atoms in the porphyrin ring, in the same plane. The fifth and sixth bind to other molecules, including oxygen.

Binding of Heme to the Polypeptide Chain

Heme is attached to its polypeptide chain through the imidazole group of a histidine and other hydrophobic interactions with amino acids
This binding sequesters the heme, preventing interactions that would occur with free heme.

Cooperative Binding of Oxygen

The first oxygen binding to deoxyhemoglobin (weakly to a subunit in T state) makes it easier for oxygen to bind to other subunits, this is cooperative bonding
Conversely, dissociation of the first oxygen molecule facilitates the dissociation of other oxygen molecules

Different Forms of Hemoglobin

Fetal Hemoglobin: Composed of two alpha and two gamma chains, has a higher affinity for oxygen.
Adult Hemoglobin (HbA1): Composed of two alpha and two beta chains.
Adult Hemoglobin (HbA2): Composed of two alpha and two delta chains.
HbA1c: Proportional to average blood glucose over the past three months, used to monitor long-term blood sugar control in diabetes

Effect of Carbon Monoxide (CO)

CO binds to hemoglobin with high affinity, reducing the amount of oxygen transported to tissues, leading to tissue anoxia.

2,3-Bisphosphoglycerate (BPG)

BPG is a glycolytic intermediate in red blood cells that binds in the cavity between the two beta-globin chains of hemoglobin
BPG stabilizes the T-state conformation, thereby decreasing hemoglobin's affinity for oxygen.
This facilitates oxygen delivery to tissues.
In stored blood, inosine is needed to restore the quantity of BPG

Hemoglobin vs. Myoglobin

Hemoglobin: Tetrameric, oxygen transport, higher affinity
Myoglobin: Monomeric, oxygen reservoir, higher affinity

Interactive Questions (Examples)

Question: What is the heme group in hemoglobin responsible for?
- Answer: Oxygen binding
Question: How many polypeptide chains does a hemoglobin molecule have?
- Answer: Four
Question: What is the primary function of hemoglobin in the body? -Answer: Oxygen transport

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Description

This quiz focuses on the structure and function of hemoglobin and myoglobin, key hemeproteins essential for oxygen binding. Participants will identify hemeproteins, explain their structures, and understand the biochemical effects of various factors on their functions.