SBCH321: Practice questions and answers. Room no. 247, Department of Biochemistry & Microbiology, University of Zululand

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1 SBCH321: Practice questions and answers Prof Khajamohiddin Syed Room no. 247, Department of Biochemistry & Microbiology, University of Zululand Important notice The questions and answers provided in this file are only for students practice purposes. The intention of providing this information is purely to educate and make students aware of the correct way of answering the questions. All the sources used in the preparation of this material are properly cited at the end of this document. Students are requested not to regard this material as a reference, but as guidance on how to answer questions. However, ultimately the onus rests on the student to work hard and to read the books and other material on the topics listed in the module.

2 1. What is metabolism? List and describe the different types of metabolism. 3M 2. What is a metabolic pathway? List and describe the different types of metabolic pathways. 3M 3. List and describe the role of the five most important metabolic pathways in humans. 5M 4. List five advantages of metabolic regulation. 2.5M 5. List five different types of mechanisms of metabolic regulations present in humans. 2.5M 6. What is allosteric regulation? Describe the role of allosteric activators and inhibitors. 2.5M 7. What is covalent modification? 1.5M 8. What is compartmentation in metabolism? Describe three advantages and the main disadvantage of compartmentation of metabolism. 3M 9. Match the cellular space, cytosol, mitochondrial matrix and the interplay of both spaces with the metabolic pathways: Glycolysis, fatty acid synthesis, gluconeogenesis, citric acid cycle, oxidative phosphorylation, beta-oxidation of fatty acids, ketone-body formation, pentose phosphate pathway and urea synthesis. 6M 10. In eukaryotic cells each organelle performs some major or specialized function. List five eukaryotic organelles and their major functions. 5M 11. What is metabolic specialization of organs? How many major organ systems are present in the body? List any five major organ systems and their organs and describe the function of the organ system. 8.5M 12. What are hormones? Give an overview of three different types of hormone classifications and sub-classifications. (or) Present different categories hormones classification in a schematic diagram? 6M 13. Give a detailed classification of hormones based on their chemical structure. Provide one example of a hormone for each category in the format of a schematic diagram. List the three main characteristic of the different categories of hormones. 14.5M 14. List five hormones and describe their one main function. 5M 15. List five neurotransmitters and describe their one main function. 5M 16. Draw a schematic diagram on synthesis of different of steroid hormones along with their category from cholesterol. 5M 17. List the name of two thyroid hormones along with their chemical structures. 4M Draw a schematic diagram showing the enzymatic steps in involved in the synthesis of different catecholamines along with the enzymes involved in the process. 9M 19. Draw a schematic diagram showing the enzymatic steps in involved in the synthesis of different Histamine and Serotonin along with the enzymes involved in the process. 9M 20. What are hormones and neurotransmitters? List five differences between nervous system and endocrine system? 7M 21. List five glands and their two secretions. 7.5M

3 Introduction to metabolic regulation 1. What is metabolism? List and describe the different types of metabolism. (3M) Metabolism is a term that is used to describe all chemical reactions involved in maintaining the living state of the cells and the organism. Metabolism can be conveniently divided into two categories: (i) Catabolism: The breakdown of molecules to obtain energy. (ii) Anabolism: The synthesis of all compounds needed by the cells using the energy generated by catabolism. 2. What is a metabolic pathway? List and describe the different types of metabolic pathways. 3M Comment [ks1]: 0.5M Comment [ks2]: 0.5M Comment [ks3]: 0.5M Comment [ks4]: 0.5M Comment [ks5]: 0.5M Comment [ks6]: 0.5M In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. Metabolic pathways are usually classified into two different categories: 1. Anabolic pathway: Metabolic pathways that are characterized by their ability to synthesize molecules with the utilization of energy. 2. Catabolic pathway: Metabolic pathways that are characterized by their ability to break down complex molecules by releasing energy in the process. Comment [ks7]: 0.5M Comment [ks8]: 0.5M Comment [ks9]: 0.5M Comment [ks10]: 0.5M Comment [ks11]: 0.5M Comment [ks12]: 0.5M 3. List and describe the role of the five most important metabolic pathways in humans. 5M Pathway Glycolysis Citric acid cycle (Krebs' cycle) Oxidative phosphorylation (electron-transport chain) Pentose phosphate pathway Urea cycle Fatty acid β-oxidation Gluconeogenesis Role Glucose oxidation in order to obtain ATP Acetyl-CoA oxidation in order to obtain GTP and valuable intermediates Disposal of the electrons released by glycolysis and citric acid cycle. Much of the energy released in this process can be stored as ATP Synthesis of pentoses and release of the reducing power needed for anabolic reactions Disposal of NH4+ in less toxic forms Fatty acids breakdown into acetyl-coa, to be used by the Krebs' cycle Glucose synthesis from smaller precursors, to be used by the brain Comment [ks13]: 0.5M Comment [ks14]: 0.5M Comment [ks15]: 0.5M Comment [ks16]: 0.5M Comment [ks17]: 0.5M Comment [ks18]: 0.5M Comment [ks19]: 0.5M Comment [ks20]: 0.5M Comment [ks21]: 0.5M Comment [ks22]: 0.5M

4 4. List five advantages of metabolic regulation. 2.5M (i) To maintain cell components in precise and correct amounts (metabolic balance) (ii) To respond effectively to environmental changes (iii) To conserve energy and material (iv) To adjust the need of cell/organisms (v) To maximize efficiency of operation by regulating the catabolic and anabolic pathways Comment [ks23]: 0.5M Comment [ks24]: 0.5M Comment [ks25]: 0.5M Comment [ks26]: 0.5M Comment [ks27]: 0.5M 5. List five different types of mechanisms of metabolic regulations present in humans. 2.5M (i) Allosteric regulation (ii) Covalent modification (iii) Adjustment of enzyme levels (iv) Compartmentation (v) Metabolic specialization of organs Comment [ks28]: 0.5M Comment [ks29]: 0.5M Comment [ks30]: 0.5M Comment [ks31]: 0.5M Comment [ks32]: 0.5M 6. What is allosteric regulation? Describe the role of allosteric activators and inhibitors. 2.5M Allosteric regulation (or allosteric control) is the regulation of an enzyme by binding an effector molecule at a site other than the enzyme's active site. The site to which the effector binds is termed the allosteric site. Allosteric sites allow effectors to bind to the protein, often resulting in a conformational change involving protein dynamics. Effectors that enhance the protein's activity are referred to as allosteric activators, whereas those that decrease the protein's activity are called allosteric inhibitors. 7. What is covalent modification? 1.5M Comment [ks33]: 0.5M Comment [ks34]: 0.5M Comment [ks35]: 0.5M Comment [ks36]: 0.5M Comment [ks37]: 0.5M Covalent modifications are enzyme catalyzed alterations of synthesized proteins and include the addition or removal of chemical groups. Usually this occurs through the addition and removal of a particular group, one form of the enzyme being more active than the other. Phosphorylation and dephosphorylation are the most common but not the only means of covalent modification. Comment [ks38]: 0.5M Comment [ks39]: 0.5M Comment [ks40]: 0.5M

5 8. What is compartmentation in metabolism? Describe three advantages and the main disadvantage of compartmentation of metabolism. 3M All reactions occurring in cells take place in certain spaces known as compartments, which are separated from other compartments by means of semi-permeable membranes. Comment [ks41]: 0.5M Advantages: (i) Compartmentation helps to separate even chemically quite heterogeneous environments and thus to optimize the course of chemical reactions. (ii) Compartmentation provides optimal conditions for individual enzymatically catalysed reactions. (iii) Compartmentation protects cell organelles from the activity of lytic enzymes. Comment [ks42]: 0.5M Comment [ks43]: 0.5M Comment [ks44]: 0.5M (iv) Compartmentation helps in regulation of metabolic pathways, making them more accurate and targeted and less interfering with one another. Disadvantage: Despite its advantages, compartmentation puts greater demand on energy consumption. This arises from a frequent need to use ATP-dependent transporters, transporting substances across membranes against the concentration gradient and thus creating different environments in different compartments. Comment [ks45]: 1M 9. Match the cellular space, cytosol, mitochondrial matrix and the interplay of both spaces with the metabolic pathways: Glycolysis, fatty acid synthesis, gluconeogenesis, citric acid cycle, oxidative phosphorylation, beta-oxidation of fatty acids, ketone-body formation, pentose phosphate pathway and urea synthesis. 6M Comment [ks46]: MARKS WILL BE ALLOCATED ONLY IF YOU ARRANGE PROPERLY Cytosol Mitochondrial matrix Interplay of above spaces Glycolysis, pentose phosphate pathway, fatty acid synthesis Citric acid cycle, oxidative phosphorylation, betaoxidation of fatty acids, ketone-body formation Gluconeogenesis, urea synthesis Comment [ks47]: 0.5M Comment [ks48]: 1.5M (0.5M FOR EACH PATHWAY) Comment [ks49]: 0.5M Comment [ks50]: 2M (0.5M FOR EACH PATHWAY) Comment [ks51]: 0.5M Comment [ks52]: 1M (0.5M FOR ECH PATHWAY)

6 10. In eukaryotic cells each organelle performs some major or specialized function. List five eukaryotic organelles and their major functions. 5M Comment [ks53]: AT LEAST REMEMBER FIVE ORGANNELLE AND THEIR ONE FUNCTION Mitochondria Organelle Major function Critic acid cycle, electron transport and oxidative phosphorylation, fatty acid oxidation, amino acid breakdown Comment [ks54]: 2.5M (FIVE ORGANELLE--- EACH 0.5M) Comment [ks55]: 2.5M (ONE FUNCTION FOR EACH ORGANELLE: 0.5M EACH) Cytosol Glycolysis, pentose phosphate pathway, fatty acid biosynthesis, many reactions of gluconeogenesis Lysosome Enzymatic digestion of cell components and ingested matter Nucleus DNA replication and transcription, RNA processing Golgi apparatus Posttranslational processing of membrane and secretory proteins; formation of plasma membrane and secretory vesicles Rough endoplasmic reticulum Smooth endoplasmic reticulum Peroxisome (glyoxysome in plants) Synthesis of membrane-bound and secretory proteins Lipid and steroid biosynthesis Oxidative reactions catalyzed by amino acid oxidases and catalases; glyoxylate cycle reactions in plants 11. What is metabolic specialization of organs? How many major organ systems are present in the body? List any five major organ systems and their organs and describe the function of the organ system. 8.5M (i) In humans, each organ is specialized or evolved to perform a specific metabolic role in the body. This fact is known as metabolic specialization of organs. (ii) There are ten major organ systems in the human body. Comment [ks56]: 0.5M Comment [ks57]: 0.5M

7 (iii) The table below lists the major organ systems, their organs and the role of the organ system in the human body. Organs System Role Circulatory system Heart, blood, blood vessels and lymphatics It is the body s delivery system, concerned with circulating blood to deliver oxygen and nutrients to every part of the body. Mouth, stomach and intestines Digestive system The purpose of the digestive system is to turn the food one eats into something useful for the body. When one eats, one s body uses this system to digest food so one s cells can use it to make energy. Collection of glands, including the pituitary and thyroid glands, as well as the ovaries and testes Endocrine system It regulates, coordinates, and controls a number of body functions by secreting chemicals into the bloodstream. These secretions help control moods, growth and development, and metabolism. Skin, hair, nails and sweat glands Integumentary system Its main function is to act as a barrier to protect the body from the outside world. It also functions to retain body fluids and to protect against disease, eliminate waste products and regulate body temperature. Muscle tissue Muscular system This system is made up of muscle tissue that helps move the body and move materials through the body. Quite simply, muscles move the body. Muscles are bundles of cells and fibers that work in a simple way: they tighten up and relax. Brain, spinal cord, and nerves Nervous system The nervous system is the control center of the human body. It receives and interprets stimuli and transmits impulses to organs. One s brain uses the information it receives to coordinate all one s actions and reactions. Uterus, penis, ovaries and testes Reproductive system The human reproductive system ensures that humans are able to reproduce and survive as a species. Nose, larynx, trachea, diaphragm, bronchi and lungs Respiratory system The primary function of the respiratory system is to supply the blood with oxygen to enable the blood to deliver oxygen to all parts of the body. The respiratory system does this through breathing. Bones, cartilage and joints Skeletal system The skeletal system provides the shape and form for human bodies in addition to supporting and protecting the bodies, allowing bodily movement, producing blood cells, and storing minerals. Comment [ks58]: 2.5M (FIVE ORGANS EACH 0.5M) Comment [ks59]: 2.5M (FIVE SYSTEMS BELONG TO EACH ORGANS 0.5M EACH) Comment [ks60]: 2.5M (ONE ROLE FOR EACH FIVE ORGANS -0.5M EACH)

8 Kidneys, ureters, urinary bladder, and urethra Urinary system The purpose of the urinary system is to filter out excess fluid and other substances from the bloodstream. Some fluid is reabsorbed by the body but most is expelled as urine.

9 Introduction to hormones 1. What are hormones? Give an overview of three different types of hormone classifications and sub-classifications. 6M Or Present different categories hormones classification in a schematic diagram? 6M (i) A hormone is any member of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behavior. (ii) Hormones can be classified into three different categories based on solubility; their function and based on their chemical structure as shown in the figure. Comment [ks61]: 1M Comment [ks62]: O.5M Comment [ks63]: O.5M Comment [ks64]: O.5M Comment [ks65]: O.5M Comment [ks66]: PICTURE COMPONENTS EACH 0.5M X12=6M; components likes hormones, solubility, where they function, chemicals structure, fat soluble.etc., should be presented in a correct format (iii) Based on their solubility, hormones are classified into two categories, fat-soluble hormones and water-soluble hormones. Based on the site of function, hormones are classified into three different categories: endocrine hormones, autocrine hormones and paracrine hormones. Based on chemical structure, hormones are classified into three different categories: proteins/polypeptide hormones, steroid hormones and amino acid derivative hormones. Comment [ks67]: 1M Comment [ks68]: 1M Comment [ks69]: 1M 2. Give a detailed classification of hormones based on their chemical structure. Provide one example of a hormone for each category in the format of a schematic diagram. List the three main characteristic of the different categories of hormones. 4M+6M+4.5M=14.5M Comment [ks70]: 4M Comment [ks71]: 6M Comment [ks72]: 4.5M Based on chemical structure, hormones are classified into three different categories: Protein/polypeptide hormones, steroid hormones and amino acid derivative hormones. Steroid hormones are classified into five major classes based on the number of carbon, hydrogen and oxygen Comment [ks73]: 1M

10 atoms: Progestagens, glucocorticoids, mineralocorticoids, androgens and estrogens. Amino acid derivative hormones are further classified into three different categories based on the type of amino acid: Tyrosine derivative hormones, histidine derivative hormones and tryptophan derivative hormones. The tyrosine derivative hormones, based on the mechanisms of signal transduction, are further classified into thyroid hormones and catecholamine hormones. Comment [ks74]: 1M Comment [ks75]: 1M Comment [ks76]: 1M The diagram below shows the classification of hormones based on chemical structure and also shows an example of a hormone in each category/sub-category. Comment [ks77]: 1M Comment [ks78]: 6M

11 ALLOCATION OF MARKS FOR FIGURE: Comment [ks79]: 24 COMPONENTS (0.25M X 24=6M) Characteristics of different categories of hormones: Hormone Protein/polypeptide hormones Steroid hormones Amino acid derivative hormones Characteristic (i) Made up of amino acids ( 3 amino acids) (ii) Water-soluble and charged (iii) Cannot cross the biological membrane (iv) Need receptors present in/on the cell surface to pass the signal (i) Made up of lipids, mainly cholesterol (ii) Need carrier proteins to reach the target site (iii) Can cross the cell membrane (iv) Receptors inside the cell (cytoplasm or nucleus) (v) Affect transcription or translation (i) Made up of a single amino acid (ii) Amino acid modified in the side chain (iii) Capable of dual signalizing as proteins/polypeptide hormones and steroid hormones Comment [ks80]: ANY OF THE BELOW THREE CHARACTERSITC FO REACH HORMONE: 3 CHARACTERSITISC FOR 3 HORMONES.MEANS TOTAL 9.SO. 9X0.5M=4.5M

12 3. List five hormones and describe their one main function. 5M Hormone Insulin Glucagon Cortisol Aldosterone Testosterone Major function (i) Primary regulator of blood glucose concentration (ii) Promotes glucose uptake in muscles and adipose tissue (iii) Inhibits hepatic glucose production and promotes glycogen synthesis and lipogenesis (iv) Stimulates cell growth and differentiation by increasing the synthesis of glycogen, proteins and triacylglycerols (i) Helps make glucose available to other tissues when the concentration of circulating glucose drops (ii) Promotes glycogenolysis and inhibits glycogen synthesis in liver (iii) Promotes lipolysis in adipose tissue (i) Promotes gluconeogenesis and the formation of glycogen (ii) Enhances the degradation of fat and protein (iii) Inhibits the inflammatory response (iv) Enables animals to respond to stress (i) Regulates the excretion of salt and water by the kidneys (ii) Acts on the distal tubules of the kidney to increase the reabsorption of Na + and the excretion of K + and H + (iii) Increases blood volume and blood pressure (i) Regulates development of male reproductive tissues such as testis and prostate (ii) Promotes secondary sexual characteristics such as increased muscle and bone mass, and the growth of the body hair (iii) Prevents osteoporosis Comment [ks81]: Five hormones (0.5Mx5=2.5M) Five biological functions (0.5Mx5=2.5M) Beta-estradiol (estrogen) Thyroxine (i) Controls development and regulation of the female reproductive system (ii) Promotes female secondary sex characteristics, such as breasts (iii) Regulates menstrual cycle (i) Essential hormone in the body (ii) Controls basic metabolic rate and energy production (iii) Controls cardiovascular system, central nervous system and reproductive system (iv) Controls growth and development system and digestive system (v) Enhances hydration of skin and growth of hair 4. List five neurotransmitters and describe their one main function. 5M Hormones and or neurotransmitters Major known function Dopamine Critical for memory and motor skills. Comment [ks82]: Five neurotransmitters (0.5Mx5=2.5M) Five biological functions (0.5Mx5=2.5M) Norepinephrine Deficiency in dopamine production is associated with Parkinson s disease, a degenerative condition causing shaking palsy Neuromodulator that optimizes brain function. As part of the

13 Epinephrine Histamine Serotonin body s fight or flight response, norepinephrine quickly provides an accurate assessment of danger or stressful situations. Activates muscle adenylate cyclase, thereby stimulating glycogen breakdown. Its role in promoting lipolysis in muscle cells is not clear. Involved in allergic responses as well as in the control of acid secretion by the stomach It is popularly thought to be a contributor to feelings of wellbeing and happiness. Important factor in mood, depression, anxiety, sleep quality, emotions and regulation of appetite and body temperature. However, the biological functional role of serotonin is not clear.

14 5. Draw a schematic diagram on synthesis of different of steroid hormones along with their category from cholesterol. 5M Comment [ks83]: Marks allocation 7 arrows in right direction = 7x 0.25M= 1.75M 8 components = 8 x 0.25M= 2M Five categories (in brackets) = 5x 0.25M= 1.25M 6. List the name of two thyroid hormones along with their chemical structures. 4M Comment [ks84]: Marks allocation: For names of T3 and T4 = 0.5M + 0.5M = 1M Two correct structures = 1.5M + 1.5M = 3M

15 7. Draw a schematic diagram showing the enzymatic steps in involved in the synthesis of different catecholamines along with the enzymes involved in the process. 9M Comment [ks85]: Marks allocation: 8 components 8 x 0.5=4M (components means: tyrosine; dopa, dopamine, norepinephrine and epinephrine + 4 enzymes) Chemical structures 5 x 1 = 5M

16 8. Draw a schematic diagram showing the enzymatic steps in involved in the synthesis of different Histamine and Serotonin along with the enzymes involved in the process. 9M Histamine: Comment [ks86]: Marks: 3.5M Two chemical structures = 2 M Three components = 3 x 0.5M = 1.5M Comment [ks87]: Marks: 5.5M Three chemical structures = 3 M Five components 5 x 0.5M = 2.5M Serotonin:

17 9. What are hormones and neurotransmitters? List five differences between nervous system and endocrine system? 7M Hormones: A hormone is any member of a class of signaling molecules produced by glands in multicellular organisms that are transported by the circulatory system to target distant organs to regulate physiology and behaviour. Neurotransmitters: Neurotransmitters, also known as chemical messengers, are endogenous chemicals that enable neurotransmission. Comment [ks88]: 1M Comment [ks89]: 1M Nervous System Neurons release neurotransmitters A neurotransmitter acts on specific cell right next to it. Neurotransmitters have their effects within milliseconds. The effects of neurotransmitters are short-lived. Performs short term crisis management Endocrine System Endocrine cells release hormones Hormones travel to another nearby cell or act on cell in another part of the body. Hormones take minutes or days to have their effects. The effects of hormones can last hours, days, or years. Regulates long term ongoing metabolic function Comment [ks90]: 5 X 0.5M + 5 X 0.5M = 5M 10. List five glands and their two secretions. 7.5M Comment [ks91]: Marks allocation. Five glands: 5 x 0.5M = 2.5M 10 secretions: 10 x 0.5M = 5M