Biochemistry ; Questions and Answers PDF

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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/279845428 Biochemistry ; Questions and Answers BOOK · JANUARY 2013 DOI: 10.13140/RG.2.1.3676.0168 READS 732 1 AUTHOR: Nalluri Mallikarjuna Rao Vishnu Dental College 27 PUBLICATIONS 44 CITATI...

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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/279845428

Biochemistry ; Questions and Answers BOOK · JANUARY 2013 DOI: 10.13140/RG.2.1.3676.0168

READS

732

1 AUTHOR: Nalluri Mallikarjuna Rao Vishnu Dental College

27 PUBLICATIONS 44 CITATIONS SEE PROFILE

Available from: Nalluri Mallikarjuna Rao Retrieved on: 03 February 2016

Questions and Answers

Dr. N. MALLIKARJUNA RAO

BIOCHEMISTRY -

Questions and Answers

Questions and Answers

BIOCHEMISTRY -

Questions and Answers

BIOCHEMISTRY -

Questions and Answers

Questions and Answers

Dr. N. MALLIKARJUNA RAO Professor & HOD Department Of Biochemistry Vishnu Dental College, Bhimavaram - 534202.

BIOCHEMISTRY -

Questions and Answers

Published by

HEAD OFFICE: No. 225/B, 9th ‘A’ Main, Vijayanagara, Bangalore - 560 040. Phone : 080 23407999 Mobile : 9980396967, Fax : 080 23302032 Email: [email protected] / [email protected] Website: www.seekaybooks.com

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BIOCHEMISTRY : Questions and Asnwers Dr. N. MALLIKARJUNA RAO

© 2013 SEEKAY Publications

First Edition : 2013

ISBN : 978-81-924169-3-9

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical. Including photocopying, recording, or any information storage and retrieval system without permission, in writing from the author and the publisher.

Printed & Designed by : M.M. PRINTERS, Anjananagara, Bangalore-560091.

BIOCHEMISTRY -

Questions and Answers

Preface This book is written to help student in their preparation for examinations. It meets needs of first year M.B.B.S., B.D.S., B.Sc.(N), B.P.T., M.Sc (Medical) and second year B.Pharm students. Topics prescribed by Various Health Science, Universities in India Vijayawada are included in the book. In this book questions and answers are given for 21 topics. Complex pathways are presented in a easy to remember way. This book is written in such way that learning of questions and answers given in each chapter makes student to acquire concept or theme of that topic simultaneously. The book contains 495 questions. Of this answers are provided to 249 questions remaining are model questions. Answers to 54 essay questions, 110 short questions and 85 very short or brief questions are given in this book. Answers are given in simple language with necessary diagrams or illustrations. Model questions given enhances students ability to answer questions with alteration. I am grateful to Sri K. Prasanna Kumar of Seekay Publications for publishing the book.

BHIMAVARAM

DR. N. MALLIKARJUNA RAO

BIOCHEMISTRY -

Questions and Answers

BIOCHEMISTRY -

Questions and Answers

Contents 1. Cell, Membrane and Transport

001

2. Carbohydrates

007

3. Proteins, Plasma Proteins, Aminoacids and Peptides

013

4. Lipids

029

5. Enzymes

039

6. Nucleotides and Nucleic acids

058

7. Biological oxidation

068

8. Carbohydrate Metabolism

076

9. Lipid Metabolism

102

10. Protein and Amino acid Metabolism

120

11. Porphyrin and hemoglobin Metabolism

141

12. Nucleotide Metabolism

150

13. Replication, Transcription and Translation

159

14. Vitamins

173

15. Minerals

189

16. Water, electrolytes and acid –base balance

199

17. Nutrition and Energy Metabolism

205

18. Hormones

211

19. Organ function Tests

219

20. Xenobiotics

225

21. Cancer

229

BIOCHEMISTRY -

Questions and Answers

CHAPTER - 1 | Cell Membrane & Transport

Chapter

1

Cell Membrane & Transport

1. Describe common structural and functional features of eukaryotic cell. A. 1. Though mammals contain many types of cells which differ in function, shape, size etc., they have common features.

2. All types of cells contain nucleus, membrane and sub cellular components etc. 3. Each cell component has uniqe structure and function. Nucleus 1. It is located in the centre of most of the cells. It is surrounded by double layered membrane in which pores are present.

2. Pores present in the membrane permits exchange of material between nucleus and other structures of cell.

3. The outer membrane of nucleus is continuous with other membrane. 4. Chromosomes are present in the nucleus of human and other mammalian cells. 5. Chromatin is the substance present in chromosomes. 6. Chromatin is nucleoprotein which consist of DNA and proteins. 7. Nucleus also contain some amount of RNA. 8. DNA and RNA present in nucleus are carriers of genetic information. NUCLEUS

Outer Nuclear Membrane Chromosome

Inner Nuclear Membrane

Nuclear Pore Mitochondria: 1. Like nucleus it is also surrounded by double layered membrane. 2. The inner membrane forms folds which are named as cristae. 3. Knob like structures are present in cristae. 4. Matrix is the name given to space within inner membrane. 001

BIOCHEMISTRY -

Questions and Answers

5. Number of mitochondria varies from one organ to other. 6. Mitochondria is the power house of the cell. 7. Size and shape of mitochondria depends on the function of organ in which they are present. 8. Electron transport chain, citric acid cycle, β-oxidation, ketone body formation, pyruvate oxidation, few of heme biosynthesis and urea cycle enzymes are present in mitochondria. MITOCHONDRIA Outer Membrane

Chistae Knob Inner Membrane Matrix

Endoplasmic reticulum: This membranous net work is divided into smooth endoplasmic

reticulum and rough endoplasmic reticulum.

Smooth endoplasmic reticulum: It is also

known as microsomal fraction of cell. It appears

smooth due to the absence of ribosomes. It is

site of hydroxylation reactions of drugs and steroids etc.

Rough Endoplasmic Reticulum Nucleus

Nucleus

Smooth Endoplasmic Reticulum

Rough endoplasmic reticulum: It is

continuation of outer nuclear membrane. It

appears rough due to presence of ribosomes. It

Ribosome

is the site of protein synthesis.

Golgi complex: It is another membranous net

work present in cell. It is involved in secretion of proteins, formation of other cellular

components and in glycosylation of proteins.

002

Golgi Complex

CHAPTER - 1 | Cell Membrane & Transport

Lysosomes: They are vesicle like membrane surrounded structure present in cytoplasm. They are

involved in hydrolysis of internalized foreign molecules as well as endogenous substances. Since

lysosomes are involved in the removal of endogenous substances they are called as suicide bags of

cell.

Peroxisomes: Are membranous vesicles found in cytosol. They are involved in hydrogen peroxide

metabolism.

Cytosol: Soluble portion of the cell is called as cytosol. It contains enzymes of glycolysis, HMP

shunt, aminoacid and fatty acid activation, fattyacid synthesis, and few enzymes of porphyrins

and urea synthesis.

2. Write note on chemical constituents of cell. A. Chemical constituents of life forms (Cells):Cells contain various organic as well as inorganic molecules and water.

a. Organic substances : They form major part of cell. There are two type of organic

molecules. Macro molecules are nucleic acids, proteins, lipids and carbohydrates.

Amino acids, fatty acids, peptides, vitamins, monosaccharides, nucleotides, hormones

and coenzymes are small organic molecules.

b. Inorganic molecules : They are present as anions and cations. They are sodium, potassium, calcium, magnesium, bicarbonate, chloride, phosphate etc.

c. Water: It is the most predominant molecule of cell.

3. Write about structure of cell membrane. A. 1. Membranes are non covalent assemblies of lipids and proteins with carbohydrates attached.

2. They are gel or semi fluid or semi solid structures. 3. Membrane lipids are organized in a bilayer form in which proteins are embeded. 4.

The two sides of membrane are different i. e. molecular composition of cytosolic side of membrane differs from extra cellular side.

Membrane lipids : 1. Lipids present in membrane are

PROTEIN

Protein Lipid Membrane Bilayer

Cytosol

phospholipids, cholesterol and glycolipids.

2. Phosphalipids and glycolipids form membrane bilayer.

3. The proportion of phospholipid and

glycolipid in membrane is different in

membranes. 4. Membrane lipids are in constant motion.

003

BIOCHEMISTRY -

Questions and Answers

Membrane proteins: 1. There are two types of membrane proteins. 2. They are peripheral membrane proteins and integral membrane proteins. 3. The protein content is different in membranes. 4. The peripheral membrane proteins are present on membrane surface. 5. The integral membrane proteins occupy membrane bilayer. Fluid mosaic model: 1. It is model proposed for membrane structure. 2. Membrane is of fluid in nature. 3. Lipids forms bilayer. 4. The membrane proteins float in the lipid bilayer. 5. Membrane proteins interact extensively with lipids present in bilayer. 6. Surface of the membrane appears as that of mosaic surface. Mosaic Surface

Lipid Bilayer Proteins

Protein Fluid Mosaic Model

4. Describe transport of molecules across cell membrane with examples. A. For the trans port of molecules across membrane several mechanisms exist. Membrane transport: Two or more types of transport mechanism are involved in

movement of molecules across membrane.

They are A. Simple or passive diffusion B. Mediated transport A. Simple diffusion: It is transport of molecules down the concentration gradiant. It does not require either energy or carrier.

Examples : Absorption of xylose and mannose. B. 1. Facilitated or mediated transport: This type of transport requires carrier molecule.

The carrier molecule is responsible for moving molecules from out side of cell to in

side or vice versa. It does not require energy.

Mechanism of transport of molecules by carrier involves conformational change in carrier

molecule. The carrier molecule exist in two states and has binding site for solute molecule. In

the native state the binding site of carrier molecule is exposed to high concentration of solute. 004

CHAPTER - 1 | Cell Membrane & Transport

The solute molecule binds to carrier molecule at its binding site. This is followed by

conformational change in the carrier molecule which exposes solute to low concentration.

Solute molecule is released and carrier molecule comes back to native state. Membrane Conformational

Solute Outside

Carrier

Examples:

inside

Change

Binding Site

1. Glucose uptake by adipocytes, erythrocytes

2. Fatty acid uptake by enterocytes

3. Transport of glucose from enterocyte into blood 2. Active transport: It transport solute molecules against concentration gradient i. e. from low concentration to high concentration. It is accompanied by hydrolysis of ATP.

Examples:

1. Na+/K+ – ATPase 2. Ca2+-ATPase of muscle. 3. H+/K+-ATPase of stomach.

3. Secondary active transport: In this type of transport energy required for movement of

solute molecule is derived from movement of another solute molecule down concentration

gradient. Hence it is called as cotransport. Carrier is symporter. Examples:

1. Glucose uptake by enterocyte

2. Aminoacid uptake by enterocyte

5. Define ionophores and ion channels. Give examples. A. Ionophores: Ionophores form pores in membrane which allows movement of ions across membranes.

Examples: 1. Gramicidin. 2. Valinomycin. 3. Diphtheria toxin. Ion channels: Ion channels are pores (channels) present in membrane that allow

movement of ions across membrane.

Examples : 1. Sodium (Na+) channel. 2. Pottasium (K+) channel. 3. Calcium (Ca2+) channel. 4. Cholirde (Cl-)channel.

6. Write differences between facilitated transport and active transport. A. Differences between facilitated transport and active transport:

005

BIOCHEMISTRY -

Questions and Answers

Facilitated transport

Active transport

1. Transport molecules down the concentration

1. Transport molecules against gradient.

2. Requires no energy.

2. Requires energy.

3. Carrier is saturated

3. No carrier saturation.

4. Influenced by hormones

4. Not under hormonal influence.

concentration gradient.

7. What are the functions of cell membrane? A. 1. Membranes separates cell from its surroundings. 2. Shape of cell depends on membrane.

3. Cell interacts with environment through the membrane. 4. Membranes act as permeability barriers.

5. Membranes are involved in energy production.

6. Flow of molecules form cell into surroundings and vice versa is regulated by membranes.

7. Formation of various cell organelles requires membrane. Other model questions are

8. Write note on mitochondria structure and functions. 9. Write briefly on nucleus/ nucleolus. 10. Write about cytomembranes of a eukaryotic cell. 11. Define facilitated transport and active transport. Give examples for each. 12. Write about membrane lipids and membrane proteins. 13. Explain features of fluid mosaic membrane model with help of a diagram 14. Facilitated transport.

006

CHAPTER - 2 | Carbohydrates

Chapter

2

Carbohydrates

1. Classify carbohydrates. Give examples for each class. Add note on the function of each example. A. Carbohydrates classification: Carbohydrates are classified into a. Monosaccharides.

b. Oligo saccharides,

c. Polysaccharides based on their carbon chain length. Monosaccharides: 1. Monosaccharides are carbohydrates which

H–C

can not be hydrolyzed to small molecules.

H – C – OH

2. Monosaccharide containing three to seven

CH2OH

carbons with functional aldehyde or keto

group are present in nature.

O

Glyceraldehyde

CH2OH C

O

CH2OH Dihydroxy Acetone

3. They are aldotriose, keto triose, aldo tetrose,

keto tetrose, aldopentose, ketopentose,

aldohexose, ketohexose and aldoheptose, ketoheptose. 4. Glyceraldehyde and dihydroxy acetone are aldotriose and ketotriose respectively. The phosphorylated forms are metabolic intermediates.

5. Erythrose is an example for aldotetrose and erythrulose is an example for ketotetrose. Erythrose phosphate is metabolic intermediate.

6. Aldopentose and ketopentose are ribose and

ribulose respectively. Ribose is constituent of nucleic acids. Ribulosephosphate is metabolic

intermediate.

7. Aldohexoses are glucose, galactose and mannose. Fructose and sedoheptulose are ketohexose and

ketoheptose respectively.

8. Glucose is present in our blood and gives rise to energy on oxidation.

CHO H – C – OH HO – C – H

CH2OH C–O HO – C – H

H – C – OH

H – C – OH

H – C – OH

H – C – OH

CH2OH

CH2OH

Glucose

Fructose 007

BIOCHEMISTRY -

Questions and Answers

9. Galactose is a constituent of lactose and has function like glucose. 10. Phosphorylated sedoheptulose is metabolic intermediate. Oligosaccharides :

They consist of few monosaccharides.

They are disaccharides, trisaccharide etc.

Monosaccharide

Monosaccharide Glycosidic Bond Disaccharide

Monosaccharide

Monosaccharide

Monosaccharide

Tri Saccharide Glycosidic Bond Disaccharides: 1. Disaccharide consist of two monosaccharide units. 2. Glycosidic bond joins individual monosaccharides. Maltose, lactose and sucrose are examples. Name

Composition

Linkage

Source

Maltose

Glucose+Galactose

β (1→ 4)

Milk

Sucrose

Glucose+Fructose

α, β (1→ 2)

Sugarcane, honey, fruit juices.

Lactose

Glucose+ Glucose

α (1→4)

Malt, barley

Functions: All disaccharides yields energy after their hydrolysis to constituent

monosaccharides.

Polysaccharides: 1. Polysaccharides are made up of more than ten monosaccharide units. 2. They are polymers of monosaccharides. 3. They are divided into a. Homopolysaccharides b. Heteropolysaccharides.

Homopolysaccharides: 1. They are made up of only one type of monosaccharide. 2. So building block of homopolysaccharide is only one type. 3. They are glycogen, starch, cellulose, inulin, dextrin etc. Starch: 1. It consist of two components. A major amylose and minor amylopectin components. 008

CHAPTER - 2 | Carbohydrates

2. Amylose is a linear polymer of glucose in which monomeric glucose units are joined by α (1, 4) linkages. It has helical secondary structure.

3. Amylopectin has branched structure. 4. In the linear part glucose units are joined by α (1, 4) linkage. At the branch point glucose units are held by α (1→6) linkage.

5. For every 20-30 glucose units a branch point is present in amylopectin. 6. The secondary structure of amylopectin is random coil due to branches. 7. Starch is common polysaccharide in our diet. It is a storage polysaccharide present in our food stuffs like rice, wheat, pulses, tubers, grains etc.

AMYLOPECTIN Glu

Glu

Glu

Glu

Glu

Glu

Glu

a (1 Z 4) Glycosidic Bond

Glu

Glu

Glu

Glu

Glu

Glu

Glu

Glu

Glu

Glu

a (1 Z 6) Glu Glycosidic Bond Glu

a (1 Z 4) Glycosidic Bond Glu

Glu-Glucose Glycogen: 1. The structure of glycogen is like that of amylopectin part of starch. 2. Glucose units are held by α (1→4) likages in straight chain part and at branch point α (1→6) glycosidic bond is present between glucose units. 3. Though the glycogen structure ...