MCB Flashcards
Active recall questions
1
Q
Describe the molecular structure of water and the type of bonds it forms.
A
Water molecules possess polar covalent bonds within the molecule and hydrogen bonds between molecules.
2
Q
Explain the properties of water and their significance in biological systems.
A
Water exhibits cohesion , adhesion,high surface tension, and high specific heat , crucial for various biological processes such as transport, support, and temperature regulation.
3
Q
Discuss capillary action, surface tension, and their underlying mechanisms.
A
Capillary action is the movement of water through narrow tubes without external forces, facilitated by adhesion and cohesion. Surface tension arises from the cohesive forces between water molecules, creating an inward force on the surface.
4
Q
How does water’s density change as a solid, and what role does this play in its function as an insulator?
A
Water becomes less dense as a solid (ice) due to stable hydrogen bonds, allowing it to float and act as an insulator, preserving aquatic environments during freezing temperatures.
5
Q
Explain the processes of evaporation and the high heat of vaporization in relation to water’s role in temperature regulation.
A
Evaporation is a cooling process where water absorbs heat energy and changes into vapor by breaking hydrogen bonds. The high heat of vaporization, requiring significant energy to vaporize, helps regulate temperatures by dissipating heat through evaporative cooling.
6
Q
How does water act as a universal solvent, and provide an example of its solvent properties in biological systems.
A
Water’s polarity enables it to dissolve a wide range of substances, making it a universal solvent. An example is the dissolution of salt in water, where water molecules interact with the charged ions (sodium and chloride) of the salt, illustrating its solvent properties in biological systems.
7
Q
Define hydrophilic and hydrophobic substances, and explain water’s role in metabolic reactions.
A
Hydrophilic substances are attracted to water, while hydrophobic substances repel it. In metabolism, water participates in condensation reactions (anabolic) by removing water to form bonds between monomers, and hydrolysis reactions (catabolic) by adding water to break down polymers into monomers, facilitating various biochemical processes.
8
Q
What properties of carbon make it essential for the diversity of organic molecules?
A
Carbon’s tetravalence allows it to form up to four covalent bonds, enabling the formation of diverse organic compounds with varied structures and functions.
9
Q
Describe the functions and sources of carbohydrates in biological systems.
A
- Carbohydrates serve as energy stores, structural components, and precursors for other molecules.
- They are obtained from plants through processes like photosynthesis and are essential for various cellular activities and metabolic processes.
10
Q
Explain the structural levels of proteins and the role of enzymes in biochemical reactions.
A
Proteins exhibit primary, secondary, tertiary, and quaternary structures, each crucial for their function. Enzymes, a type of protein, catalyze biochemical reactions by lowering the activation energy required for the reaction to occur, facilitating metabolic processes in cells.
11
Q
Discuss the functions of lipids, vitamins, and minerals in biological systems.
A
Lipids, including fatty acids, triglycerides, phospholipids, and cholesterol, serve as energy stores, structural components of cell membranes, and signaling molecules.
Micronutrients like vitamins and minerals play essential roles in complex biochemical processes.
12
Q
How do fatty acids differ in structure and function between saturated and unsaturated forms?
A
Saturated fatty acids contain only single bonds between carbon atoms and are typically solid at room temperature. In contrast, unsaturated fatty acids contain one or more double bonds, leading to kinks in the hydrocarbon chain and making them typically liquid at room temperature. These structural differences impact their properties and physiological roles in energy storage and membrane fluidity.
13
Q
Describe the structure and function of phospholipids in cell membranes.
A
Phospholipids consist of hydrophobic tails and hydrophilic heads due to the presence of a phosphate group. In cell membranes, they form a lipid bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward, providing a barrier that separates the cell from its external environment. This structure is essential for maintaining cell integrity and regulating the passage of molecules in and out of the cell.
14
Q
What role do enzymes play in biochemical reactions, and how can their activity be regulated?
A
Enzymes catalyze biochemical reactions by lowering the activation energy required for the reaction to proceed, thereby increasing the reaction rate. Their activity can be regulated through mechanisms such as enzyme inhibition, where inhibitors bind to the enzyme and affect its ability to bind substrates. Inhibition can be competitive, where inhibitors compete with substrates for the active site, or non-competitive, where inhibitors bind to allosteric sites and alter the enzyme’s conformation.
15
Q
Explain the significance of micronutrients like vitamins and minerals in maintaining overall health.
A
Micronutrients, including vitamins and minerals, are essential for various physiological functions, such as metabolism, growth, and immune function. They act as cofactors, coenzymes, or structural components in enzymatic reactions, ensuring proper cellular function and overall health. Understanding their importance and sources is crucial for preventing deficiencies and maintaining optimal health and well-being.
16
Q
Describe the structure and function of the nucleus in eukaryotic cells.
A
The nucleus is a membrane-bound organelle containing DNA, involved in DNA replication, repair, transcription. Nuclear pores regulate molecule movement; nucleolus regulates proteins.
17
Q
Compare and contrast the structure and function of smooth endoplasmic reticulum (SER) and rough endoplasmic reticulum (RER) in cells.
A
SER synthesizes lipids, aids carbohydrate metabolism; RER studded with ribosomes, involved in protein synthesis. Both contribute to cellular metabolism and biochemical reactions.
18
Q
Discuss the role of ribosomes in protein synthesis.
A
Ribosomes are composed of RNA and proteins, catalyze peptide bond formation in translation, following genetic code from mRNA.
19
Q
Explain the structure and function of the Golgi apparatus in eukaryotic cells.
A
The Golgi apparatus processes, modifies, packages proteins and lipids for secretion or delivery within the cell. Generates secretory vesicles for transport.
20
Q
Describe the structure and function of vesicles and explain how lysosomes fit under this category.
A
- Vesicles are hollow spheres which are made of membranes. they have many functions but their main function is that they help transport materials and recycle waste material.
- Lysosomes are an example of vesicles they are responsible for breaking down contents - a molecular recycling center.
21
Q
Discuss the structure and function of mitochondria in eukaryotic cells.
A
Mitochondria produce ATP through cellular respiration, have double membrane with inner membrane folded into cristae. Contain own DNA inherited maternally.
22
Q
Explain the role of chloroplasts in photosynthesis.
A
Chloroplasts are organelles in plant cells responsible for photosynthesis, containing chlorophyll pigments within thylakoid membranes, converting light energy into sugars.
23
Q
Describe the structure and function of vacuoles in plant cells.
A
Vacuoles store water, maintain pressure, store chemicals, waste. Contribute to cell structure, especially in maintaining rigidity and supporting growth.
24
Q
Compare and contrast the structure and composition of cell walls in plant cells and other organisms.
A
Cell walls provide support, protection in plants; composed of cellulose, lignin. Other organisms have different types of cell walls.
25
Explain the structure and function of the plasma membrane in animal cells.
The plasma membrane regulates molecule movement in/out of cell. Phospholipids, proteins, cholesterol maintain fluidity, permeability, and integrity of the membrane.
26
Discuss the fluid mosaic model of the cell membrane.
The fluid mosaic model describes dynamic nature of the cell membrane, with phospholipids forming a fluid bilayer and embedded proteins. Regulated by phospholipids, proteins, cholesterol.
27
Describe the structure of phospholipids and their role as the primary molecules in cell membranes.
Phospholipids consist of hydrophilic phosphate heads, hydrophobic fatty acid tails, forming bilayer. Amphipathic nature creates membranes with selective permeability.
28
Define epithelial tissue and its main functions. Provide examples of where epithelial tissue is found.
Epithelial tissue forms linings, acts as a barrier, regulates molecule passage. Found in skin, digestive tract, blood vessels, and hormone-secreting glands.
29
Describe the characteristics and functions of connective tissue. List examples of connective tissue components.
Connective tissue connects other tissues, provides support, elasticity, and energy storage. Includes extracellular matrix, fat cells, bones, cartilage, and tendons.
30
Explain the structure and function of muscle tissue. Differentiate between the types of muscle tissue and their roles.
Muscle tissue consists of contractile fibers generating force for movement. Types include skeletal (voluntary), smooth (involuntary), and cardiac (heart contractions).
31
Discuss the composition and function of nervous tissue. Describe the primary cell type found in nervous tissue.
Nervous tissue is primarily composed of neurons transmitting electrical impulses for information transfer. Found in the brain, spinal cord, and nerves.
32
Explain the different mechanisms of cellular transport.
Simple diffusion, facilitated diffusion, osmosis, and active transport are mechanisms of transport, involving movement of molecules across membranes with or without energy input.
33
Describe the process of diffusion and the factors influencing diffusion rates.
Diffusion is movement of molecules from high to low concentration. Factors affecting diffusion rates include concentration gradient, surface area, molecule size and nature, and temperature.
34
Define osmosis and discuss the concept of tonicity. Provide examples of osmosis in biological systems.
Osmosis is diffusion of water across a semipermeable membrane. Tonicity describes solute-solvent ratios: hypertonic (high solute), hypotonic (low solute), isotonic (equilibrium). Example: osmosis occurs in the intestine, where water enters the blood.
35
Explain the process and significance of active transport.
Active transport requires energy (ATP) to move molecules against their concentration gradient, often utilizing protein pumps. It is essential for maintaining cellular homeostasis and transporting essential molecules.
36
Differentiate between endocytosis and exocytosis. Describe the types of endocytosis and their respective functions.
Endocytosis brings materials into the cell, including phagocytosis (solids), pinocytosis (liquids), and receptor-mediated endocytosis (triggered by molecular signals). Exocytosis releases materials from the cell.
37
How are molecules transported around the cell?
Motor proteins transport cargo along microtubules to the Golgi apparatus, facilitating intracellular transport.
38
Compare and contrast the processes of meiosis and mitosis.
Meiosis occurs in gametes, resulting in haploid cells, while mitosis occurs in somatic cells, producing diploid cells.
39
Describe the stages of the cell cycle in mitosis.
The cell cycle consists of G1 (cell growth), S (DNA replication), G2 (additional growth), and M (mitotic phase).
40
Explain the role of checkpoints and cyclins in the cell cycle.
Checkpoints ensure accurate cell cycle progression, and cyclins regulate the activity of cyclin-dependent kinases, controlling cellular activities such as DNA replication and mitosis.
41
Outline the stages of meiosis and their significance.
Meiosis involves prophase 1 (homologous chromosome pairing), metaphase 1 (random chromosome orientation), anaphase 1 (chromosome separation), telophase 1 (haploid nuclei formation), and subsequent phases similar to mitosis.
42
What are chromosomal abnormalities, and provide an example?
Chromosomal abnormalities result from nondisjunction, leading to gametes with an incorrect number of chromosomes. Down syndrome, caused by trisomy of chromosome 21, is an example of a chromosomal abnormality.
43
Describe the different modes of signaling in the endocrine system.
Endocrine signaling involves releasing hormones into the bloodstream to target distant cells. Autocrine signaling occurs when a cell releases ligands that bind to its own surface receptors. Paracrine signaling involves the release of chemicals to affect nearby cells locally.
44
List the different types of hormones, their functions and their half-lives
Hormones are categorized into amines, peptides, and steroids based on their half-life. Steroid hormones, derived from cholesterol, and its half life is hours-days. amines are amino acids with modified groups, and its half life 1-3 minutes. Peptides are short chains of amino acids, and its half life is minutes - hour
45
How do feedback mechanisms regulate hormonal levels in the body?
Feedback loops, such as negative and positive feedback, regulate hormone levels to maintain homeostasis. Negative feedback loops involve a change in a variable triggering hormone release to return the variable to its normal range. Positive feedback loops amplify the initial stimulus, further increasing hormone secretion or activity.
46
Provide examples of specific hormonal pathways and disorders associated with hormonal imbalances.
Examples include thyroid hormone regulation through negative feedback, leptin signaling in appetite control and obesity, melatonin regulation of circadian rhythms, growth hormone influence on growth and metabolism, and insulin and glucagon regulation of blood glucose levels. Disorders like dwarfism, gigantism, obesity, and diabetes can result from hormonal imbalances affecting these pathways.
47
What is the alimentary canal?
The alimentary canal is the continuous tube through which food passes in the body, consisting of the mouth, esophagus, stomach, small intestine, and large intestine, ultimately leading to the expulsion of waste.
48
What are the primary processes involved in digestion?
Digestion involves both mechanical and enzymatic actions to break down food. Mechanical digestion physically breaks down food into smaller pieces, while enzymatic digestion involves the use of digestive enzymes to chemically break down complex molecules into simpler ones.
49
Why is digestion important?
Digestion is essential to break down large, insoluble polymer molecules (e.g., carbohydrates, lipids, proteins, nucleic acids) into smaller, soluble monomers that can be absorbed by cells in the small intestine.
This process allows the body to extract nutrients and energy from food for various cellular functions and metabolic processes.
50
What is hydrolysis, and how is it involved in digestion?
Hydrolysis is a chemical reaction in which a molecule of water is added to a substance, causing it to split into two parts. In digestion, hydrolysis reactions, catalyzed by enzymes, break down complex macromolecules into simpler subunits, facilitating their absorption by the body.
51
What are the main enzymes involved in carbohydrate digestion?
Carbohydrate digestion primarily involves the enzyme amylase, which breaks down complex carbohydrates (starches) into smaller subunits (e.g., maltose, glucose) that can be absorbed by the body.
52
How are proteins digested in the body?
Proteins are broken down into smaller peptides and amino acids by proteases, enzymes secreted in an inactive form called zymogens. These proteases become active in the stomach due to low pH and continue digestion in the small intestine.
53
What role do lipases play in lipid digestion?
Lipases, along with bile salts, emulsify lipid globules, breaking them down into smaller components that can be chemically digested by pancreatic lipases. This process facilitates the absorption of lipids in the small intestine.
54
What are the functions of saliva in digestion?
Saliva contains enzymes like amylase, which initiate the breakdown of carbohydrates. It also helps in lubricating food for easy passage down the esophagus and maintains a slightly alkaline pH in the mouth.
55
How does the stomach contribute to digestion?
The stomach churns food with its muscular walls, mixing it with gastric juices containing hydrochloric acid (HCl) and enzymes like pepsin. Mechanical digestion physically breaks down food, while chemical digestion involves enzymes breaking down proteins into smaller peptides.
56
What causes stomach ulcers, and how do they develop into cancer?
Stomach ulcers can result from erosion of the stomach's protective mucus layer, exposing the stomach wall to gastric acids and enzymes. Helicobacter pylori infection is a common cause. Over time, prolonged ulcers may lead to stomach cancer, often through a process involving inflammation, cell damage, and changes in the stomach lining's structure.
57
How does the small intestine contribute to nutrient absorption?
The small intestine, with its villi and microvilli, greatly increases the surface area for nutrient absorption. Nutrients are absorbed into the bloodstream through the epithelial cells lining the small intestine, facilitated by transport mechanisms like cotransport with sodium ions and facilitated diffusion.
58
What are the main functions of the large intestine (colon)?
The large intestine absorbs water and electrolytes from undigested food, forming feces. It also houses beneficial bacteria that produce vitamins like K and folic acid. Additionally, the large intestine plays a role in the storage and subsequent expulsion of waste material from the body.
59
How does dietary fiber benefit digestion and overall health?
Dietary fiber, being indigestible, adds bulk to stool, promoting regular bowel movements and reducing the risk of constipation. It also absorbs water, keeping stools soft and easy to pass. Furthermore, dietary fiber has been associated with lower cholesterol levels, better blood sugar regulation, and reduced risk of colon cancer, making it an essential component of a healthy diet.
60
What substances are egested as feces during the process of egestion?
Feces primarily contain undigested material such as bile pigments, epithelial cells, lignin, cellulose, and bacteria from the gut flora. These substances, along with water, are expelled from the body through the rectum and anus during defecation.
61
How does the process of absorption occur in the small intestine?
Absorption in the small intestine involves the uptake of digested nutrients (e.g., glucose) from the lumen into epithelial cells lining the villi. This process may include co-transport with ions, facilitated diffusion, or active transport mechanisms. Once absorbed, nutrients enter the bloodstream and are transported to various tissues and organs for utilization or storage, such as the liver storing excess glucose as glycogen.
62
What is an infectious disease, and what are its primary causes?
An infectious disease is a spreadable illness that disrupts the normal function of the body. It is caused by pathogens, which are agents capable of colonizing and living in or on the host, replicating using host resources, evading immune responses, and spreading to new hosts. Pathogens include bacteria, viruses, parasites, fungi, and other microorganisms.
63
What are some examples of parasitic worms and parasitic protozoa?
Parasitic worms are large multicellular eukaryotes that live and feed off living hosts, entering through skin surfaces or holes. Parasitic protozoa, on the other hand, are microscopic, single-celled organisms that can be free-living or parasitic. Examples of diseases caused by parasitic worms include giardiasis and amoebic dysentery, while diseases caused by parasitic protozoa include malaria and toxoplasmosis.
64
How do fungi contribute to infectious diseases?
Fungi, although only a few hundred species can cause illness in humans, can lead to a range of infections from mild fungal skin conditions like ringworm to more severe lung infections resulting from inhaling fungal spores.
65
What are some common bacterial infections and the diseases they cause?
Bacterial infections caused by eubacteria, which are prokaryotic organisms, include streptococcus (sore throat, pneumonia), Vibrio cholerae (cholera), Salmonella (gastrointestinal diseases), Staphylococcus (food poisoning), and Haemophilus influenzae (lung infections).
66
What are the characteristics and examples of viruses as pathogens?
Viruses are non-living particles that reproduce by hijacking living cells. Examples of viral infections include rhinovirus (common cold), HIV (causing AIDS), and papillomavirus (warts). Viruses are challenging to treat because they can adapt, making them resistant to traditional treatments.
67
What are the two types of immune systems, and how do they differ?
The immune system comprises the innate immune system and the adaptive immune system. The innate immune system provides non-specific defense mechanisms against pathogens, while the adaptive immune system offers specific defense mechanisms and forms immunological memory upon exposure to pathogens.
68
What are physical barriers in the body's defense against pathogens?
Physical barriers include the skin, which forms a waterproof barrier and secretes chemical substances to inhibit bacterial growth, and mucous membranes lining the body's openings, such as the respiratory and gastrointestinal tracts. These membranes contain goblet cells that secrete mucus to trap microbes, along with mechanical actions like shedding of skin cells, mucociliary action, and bodily fluid flushing, which help remove pathogens from the body.
69
How do internal defenses, such as phagocytosis and fever, combat infections?
Internal defenses involve phagocytic white blood cells that engulf and digest pathogens, along with fever, an elevated body temperature that accelerates tissue metabolism and immune response activity. Phagocytosis entails the attachment of microbes to phagocytes, engulfment, digestion within phagolysosomes, and removal of indigestible material. Fever is triggered by the release of cytokines and helps enhance immune response efficiency.
70
What role do mast cells and histamine play in inflammation?
Mast cells detect tissue injury and release histamine, a chemical that causes increased blood vessel dilation and permeability, leading to redness, heat, and swelling typical of inflammation. Histamine also facilitates the migration of phagocytes to the site of infection and initiates various immune responses against pathogens.
71
How does the adaptive immune system respond to pathogens?
The adaptive immune system mounts responses through humoral immunity, involving B cells and antibodies, and cell-mediated immunity, involving T cells and cytokines. Both responses are antigen-specific and require exposure to antigens. B cells produce antibodies that bind to antigens, while T cells release cytokines that regulate immune responses or directly kill infected cells. The adaptive immune system forms immunological memory for rapid and specific responses upon subsequent exposure to the same pathogens.
72
What is the role of vaccination in preventing infectious diseases?
Vaccination stimulates the immune system to produce immunity to specific diseases without causing illness symptoms. It introduces antigens, mimicking pathogens, to trigger primary and memory immune responses. Different types of vaccines, such as live attenuated, inactivated, subunit, DNA/RNA, and viral vector vaccines, offer various approaches to disease prevention. Vaccination has been instrumental in eradicating diseases, reducing deaths and disabilities, and improving public health globally.
73
What are the benefits and risks associated with vaccination?
Vaccination offers numerous benefits, including disease eradication, reduced mortality and morbidity, fewer workdays lost due to illness, and cost-effectiveness. However, vaccine immunity may vary in effectiveness, and some individuals may experience side effects. There's also a risk of complacency and reduced vaccination rates leading to disease resurgence. It's essential to weigh the benefits against potential risks when considering vaccination programs and individual immunization decisions.
74
What are the main components and functions of the respiratory system?
The respiratory system includes the pharynx, larynx, trachea, bronchi, and lungs. These organs work together to facilitate breathing and gas exchange. The pharynx is a membrane-lined cavity connecting the nose and mouth to the esophagus or trachea. The larynx is a hollow muscular tube housing the vocal cords and serving as a passage to the lungs. The trachea, reinforced by cartilage rings, conveys air to and from the lungs, while the bronchi branch into smaller tubes called bronchioles. The lungs, enclosed in the thorax, contain numerous alveoli for gas exchange.
75
What is gas exchange, and where does it primarily occur in the respiratory system?
Gas exchange refers to the process of oxygen (O2) and carbon dioxide (CO2) exchange between the lungs and the bloodstream or body tissues. It primarily occurs in the alveoli, which are tiny air sacs in the lungs surrounded by capillaries.
76
What are the structural features and functions of alveoli?
Alveoli are spherical-shaped structures in the lungs with a high surface area to optimize gas exchange. They are covered by a dense network of capillaries, facilitating the diffusion of gases into and out of the bloodstream. Type 1 pneumocytes, thin cells lining the alveoli, are responsible for gas exchange, while type 2 pneumocytes produce and secrete surfactant, a substance that prevents alveoli from collapsing during exhalation.
77
How does gas exchange occur in the alveoli?
Gas exchange in the alveoli involves the diffusion of gases across a short diffusion pathway with a large surface area-to-volume ratio. Ventilation and circulation maintain large diffusion gradients, ensuring efficient gas exchange. About 80% of the alveolar surface contacts capillaries, and blood cells move through capillaries in a single file to increase contact time. Surfactant on the alveolar surfaces aids in the dissolution of gases and prevents alveoli from collapsing.
78
What laws govern the process of ventilation?
Boyle's law states that pressure increases as volume decreases in a gas. Newton's second law dictates that air moves from areas of high pressure to low pressure due to acting forces. During inhalation, the diaphragm contracts, increasing lung volume and decreasing pressure to allow air to flow into the lungs. During exhalation, the diaphragm relaxes, reducing lung volume and increasing pressure to expel air from the lungs.
79
What is emphysema, its causes, effects, and treatment?
Emphysema is a respiratory condition characterized by the weakening and rupture of alveoli, resulting in larger air spaces and reduced gas exchange surface area. Long-term exposure to airborne irritants such as tobacco smoke, air pollution, and chemical fumes contributes to its development. Symptoms include shortness of breath, coughing, wheezing, and chest tightness. Treatment focuses on managing symptoms and preventing further damage, including smoking cessation, bronchodilator medications, and in severe cases, lung transplantation.
80
How does hemoglobin facilitate oxygen transport in the bloodstream?
Hemoglobin, present in red blood cells, binds with oxygen in the lungs and transports it to tissues throughout the body. It consists of four polypeptide chains—two alpha and two beta chains—arranged in a tetrameric structure. Hemoglobin exhibits cooperative binding, meaning it readily associates with oxygen in areas of high oxygen concentration and releases it where oxygen is needed, such as body tissues undergoing cellular respiration.
81
What factors affect hemoglobin's affinity for oxygen?
Factors influencing hemoglobin's affinity for oxygen include pH levels, carbon dioxide (CO2) levels, and temperature. A decrease in pH (acidic conditions) or an increase in CO2 levels reduces hemoglobin's affinity for oxygen, promoting oxygen release to tissues. Conversely, a rise in pH (alkaline conditions) or a decrease in CO2 levels increases hemoglobin's affinity for oxygen, facilitating oxygen uptake in the lungs. Temperature changes can also influence hemoglobin's oxygen-binding capacity.
82
How is carbon dioxide transported in the bloodstream?
Carbon dioxide (CO2) is transported in the bloodstream in three forms: as dissolved gas in plasma (5%), as bicarbonate ions in blood plasma (85%), and bound to hemoglobin as carbaminohemoglobin (10%). In red blood cells, CO2 reacts with water to form carbonic acid, which dissociates into bicarbonate ions and hydrogen ions. Bicarbonate ions are exchanged for chloride ions to maintain cell neutrality. In the lungs, this process is reversed, allowing CO2 to be exhaled.
83
How does the respiratory system regulate blood pH?
The respiratory system regulates blood pH by adjusting ventilation rates to control carbon dioxide (CO2) levels. Chemoreceptors in the brainstem detect changes in blood pH and trigger adjustments in ventilation to expel excess CO2 or increase CO2 levels as needed. Additionally, kidneys can regulate blood pH by reabsorbing bicarbonate ions or clearing excess bicarbonate through urine. This pH regulation ensures the maintenance of physiological homeostasis in the body.
84
What are the mechanisms behind oxygen dissociation from hemoglobin?
Oxygen dissociation from hemoglobin depends on factors such as partial pressure of oxygen (PO2), pH, and temperature. Hemoglobin exhibits cooperative binding, meaning it undergoes conformational changes upon oxygen binding, increasing its affinity for subsequent oxygen molecules. As PO2 decreases, hemoglobin releases oxygen more readily, facilitating oxygen delivery to tissues. Changes in pH and temperature also affect hemoglobin's affinity for oxygen, influencing oxygen dissociation in response to metabolic demands.
85
What are the functions of nucleic acids?
Nucleic acids serve as macromolecules that store genetic information and encode instructions for protein synthesis.
86
What is a nucleotide?
A nucleotide is the monomeric unit of nucleic acids, comprising three main components: a nitrogenous base (adenine, thymine, cytosine, guanine, or uracil), a five-carbon sugar (ribose or deoxyribose), and a phosphate group (PO4-).
87
What are the three parts of a nucleotide?
Nucleotides consist of a nitrogenous base (A, T, C, G, or U), a five-carbon sugar (ribose or deoxyribose), and a phosphate group (PO4-).
88
What is the structure of a nucleotide?
In the structure of a nucleotide, the phosphate group and nitrogenous base connect at the correct corners of a pentagon. Nucleotides contain either ribose or deoxyribose as the five-carbon sugar, with the nitrogenous base attached to carbon-1 and the phosphate group attached to carbon-5.
89
What is the process of DNA replication, and what are its stages?
DNA replication involves several stages: initiation, elongation, and termination. Initiation begins with helicase separating the DNA strands at replication bubbles, forming Y-shaped replication forks. DNA polymerases synthesize new strands, with the leading strand elongating continuously and the lagging strand synthesized in segments called Okazaki fragments. Termination occurs when replication forks meet, and DNA ligase joins the Okazaki fragments.
90
What are the proteins involved in DNA replication, and what are their functions?
Proteins involved in DNA replication include helicase, which unwinds the DNA double helix, and primase, which synthesizes RNA primers. DNA polymerase III adds nucleotides to the RNA primers, while DNA polymerase I removes RNA nucleotides and replaces them with DNA. DNA ligase joins Okazaki fragments, and proofreading mechanisms correct errors in replication.
91
What are the potential errors in DNA replication, and how are they corrected?
Errors in DNA replication occur rarely but can lead to mutations. Proofreading mechanisms involve DNA polymerase checking each incorporated nucleotide against its template and correcting mismatches. Mismatch repair mechanisms involve repair proteins detecting mispaired nucleotides, nucleases cutting out the incorrect base, DNA polymerases filling in missing nucleotides, and DNA ligases joining the repaired DNA strands.
92
What is RNA?
RNA, or ribonucleic acid, is a nucleic acid consisting of a single polynucleotide chain, unlike DNA which is double-stranded. RNA contains a ribose sugar, a phosphate group, and one of four nitrogenous bases: adenine (A), uracil (U), cytosine (C), or guanine (G). RNA serves various roles in cellular processes, including carrying genetic information from DNA to the protein synthesis machinery and acting as a catalyst in certain biochemical reactions.
93
How is RNA copied from DNA, and what is this process called?
RNA is synthesized from DNA through a process called transcription. During transcription, a specific segment of DNA, containing the gene for a particular protein, is copied into a complementary RNA molecule, usually messenger RNA (mRNA). Transcription involves RNA polymerase binding to the promoter region of the DNA, unwinding the DNA double helix, and synthesizing an RNA molecule by adding complementary ribonucleotides. This process results in the formation of an RNA molecule that carries the genetic information encoded in the DNA to the ribosomes for translation into protein.
94
What are the different bases found in RNA?
RNA contains four different nitrogenous bases: adenine (A), guanine (G), cytosine (C), and uracil (U). Unlike DNA, which contains thymine (T), RNA contains uracil, which pairs with adenine (A) during RNA synthesis. The base pairing between adenine and uracil allows RNA to faithfully transcribe the genetic information encoded in DNA.
95
What is the mechanism of RNA transcription, and what are its key steps?
-RNA transcription begins with the binding of RNA polymerase to the promoter region of the DNA. Once bound, RNA polymerase unwinds the DNA double helix to expose the template strand, which serves as a blueprint for RNA synthesis.
- RNA polymerase then assembles an RNA molecule by adding complementary ribonucleotides to the growing RNA chain.
- The process of transcription includes initiation, elongation, and termination stages.
- During initiation, RNA polymerase binds to the promoter, and the DNA double helix is partially unwound to create a transcription bubble.
- Elongation involves RNA polymerase synthesizing an RNA molecule by adding ribonucleotides in the 5' to 3' direction, complementary to the DNA template.
- Termination occurs when RNA polymerase reaches a terminator sequence, signaling the end of transcription.
96
How is mRNA processed before leaving the nucleus?
Before leaving the nucleus, mRNA undergoes several modifications. These include the addition of a guanine cap at the 5' end and a polyadenine tail at the 3' end. Additionally, non-coding regions called introns are removed from the mRNA transcript in a process called splicing. The resulting mature mRNA molecule contains only the protein-coding sequences, known as exons, which will be translated into protein. mRNA transcripts are then transported out of the nucleus and into the cytoplasm, where they serve as templates for protein synthesis.
97
How does RNA serve as a genetic messenger in protein synthesis?
RNA serves as a genetic messenger by carrying the genetic information encoded in DNA to the protein synthesis machinery in the cytoplasm.
98
What is translation in DNA, and where does it occur?
Translation is the process of converting the nucleotide sequence of mRNA into an amino acid sequence to synthesize proteins. While DNA is stored in the nucleus, translation occurs in the cytoplasm, specifically at ribosomes. Ribosomes can be found freely in the cytoplasm or attached to the rough endoplasmic reticulum (RER).
99
How is the mRNA codon translated into an amino acid sequence?
mRNA contains a sequence of three-nucleotide codons that specify particular amino acids. During translation, transfer RNA (tRNA) molecules act as adaptor molecules, recognizing mRNA codons and delivering the corresponding amino acids. Each tRNA molecule carries a specific amino acid and has an anticodon sequence that is complementary to the mRNA codon. The ribosome facilitates the binding of tRNA molecules to mRNA codons and catalyzes the formation of peptide bonds between adjacent amino acids, resulting in the synthesis of a polypeptide chain.
100
What are the key steps in the translation process?
Translation can be divided into three main stages: initiation, elongation, and termination. During initiation, the small ribosomal subunit binds to the mRNA upstream of the start codon (AUG), and an initiator tRNA carrying methionine binds to the start codon. In elongation, amino acids are added one by one to the growing polypeptide chain as tRNA molecules recognize and bind to the mRNA codons in the ribosome's A site, and peptide bonds are formed between adjacent amino acids. Ribosomes move along the mRNA in the 5' to 3' direction, and the process continues until a stop codon is reached. Termination occurs when a stop codon (UAA, UAG, or UGA) is encountered, and a release factor binds to the A site, causing the release of the completed polypeptide chain. Finally, the translation apparatus is disassembled, and the newly synthesized protein is released.
101
What is the role of tRNA in translation, and how does it work?
Transfer RNA (tRNA) molecules play a crucial role in translation by bringing amino acids to the ribosome according to the mRNA codon sequence. Each tRNA molecule carries a specific amino acid and has an anticodon sequence that base pairs with the complementary mRNA codon. This allows tRNA to recognize the codons on the mRNA and deliver the corresponding amino acids to the ribosome, where peptide bond formation occurs. tRNA molecules undergo a cycle of binding to mRNA codons, delivering amino acids, and then being released from the ribosome to repeat the process.
102
What is a polyribosome, and how does it function in translation?
A polyribosome, or polysome, is a cluster of ribosomes simultaneously translating the same mRNA molecule. Up to 50 ribosomes can bind to the mRNA template, allowing for the simultaneous synthesis of multiple copies of the same protein. Polyribosomes increase the efficiency of protein synthesis by maximizing the use of mRNA transcripts and speeding up the production of proteins. This coordinated assembly of multiple ribosomes on a single mRNA molecule ensures rapid and efficient protein synthesis within the cell.
103
What are mutations, and what are the types of mutations?
Mutations are alterations in the genetic information, which can lead to changes in the DNA sequence. There are two basic types of mutations: gene mutations and chromosomal mutations. Gene mutations involve changes in single genes and can be further categorized into point mutations, which include substitutions, insertions, and deletions. Chromosomal mutations affect larger segments of DNA and can involve changes in the structure or number of chromosomes.
104
What are the effects of mutations on transcription and translation?
Mutations can alter the sequence of nucleotides in DNA, which in turn affects the mRNA transcribed from it. These changes can lead to differences in the amino acid sequence during translation, ultimately influencing the structure and function of the resulting protein. Depending on the type and location of the mutation, its effects on transcription and translation can vary.
105
What are the different types of point mutations, and how do they impact translation?
Point mutations involve changes in a single nucleotide and can manifest as substitutions, insertions, or deletions. Substitutions involve replacing one base with another, potentially leading to no effect (silent mutation), a change in a single amino acid (missense mutation), or the premature termination of translation (nonsense mutation). Insertions and deletions can cause frameshift mutations, where the reading frame of the mRNA shifts, affecting the entire sequence of amino acids translated from it.
106
What are the characteristics and effects of silent, missense, and nonsense mutations?
Silent mutations occur when a nucleotide substitution does not alter the amino acid sequence, usually due to redundancy in the genetic code. Missense mutations result in the substitution of one amino acid for another, potentially affecting the structure and function of the protein. Nonsense mutations introduce a premature stop codon, leading to the truncation of the protein, often resulting in non-functional or dysfunctional proteins.
107
How do frameshift mutations, additions, and removals of amino acids impact translation?
Frameshift mutations occur when nucleotide insertions or deletions disrupt the reading frame of the mRNA, leading to extensive missense or premature termination of translation. Additions of amino acids result from nucleotide insertions in multiples of three, while removals of amino acids occur due to nucleotide deletions in multiples of three, both affecting the final protein structure and function.
108
What is sickle cell anemia, and how does it relate to mutations?
Sickle cell anemia is a genetic disorder characterized by abnormal, crescent-shaped red blood cells that can cause blockages in blood vessels and lead to various health complications. It is caused by a specific missense mutation in the beta globin subunit of hemoglobin, resulting in the substitution of glutamic acid with valine. This mutation alters the structure of hemoglobin, leading to the characteristic sickle shape of red blood cells and the associated symptoms of the disease.
109
What is metabolism, and what are its types?
Metabolism refers to the sum total of all chemical reactions occurring within a cell, including those involved in obtaining energy from food and those involved in building macromolecules. There are two main types of metabolic processes: catabolic processes, which involve breaking down molecules to release energy, and anabolic processes, which involve building new macromolecules and require energy input.
110
How do cells control their metabolism?
Cells control their metabolism through various mechanisms, including regulating substrate concentration, adjusting enzyme levels through gene expression, and using enzyme inhibitors. By modulating these factors, cells can regulate the rates of specific metabolic pathways to meet their current metabolic requirements.
111
What are enzymes, and how do they function?
Enzymes are globular proteins that act as biological catalysts, speeding up chemical reactions by lowering the activation energy required for the reactions to occur. Enzymes achieve this by binding to specific substrates at their active sites, where catalysis takes place. Enzymes undergo conformational changes upon binding with substrates, resulting in induced fit and precise substrate-enzyme interactions.
112
What are coenzymes and cofactors, and how do they contribute to enzyme function?
Coenzymes and cofactors are nonprotein components that aid in enzyme function. Coenzymes are organic molecules, such as NAD+ and FAD+, while cofactors are inorganic molecules, such as metal ions. These molecules assist enzymes by facilitating specific chemical reactions, such as electron transfer, during catalysis. They help enzymes perform their functions efficiently and are essential for many metabolic pathways.
113
How do enzymes regulate metabolic pathways?
Enzymes play a crucial role in regulating metabolic pathways through feedback mechanisms, including feedback inhibition. In feedback inhibition, high levels of the end product of a metabolic pathway inhibit the activity of enzymes at the beginning of the pathway, preventing overproduction of the product. Additionally, enzymes can control the rate of metabolic pathways by modulating the activity of key enzymes or regulating the rate-determining steps of the pathways.
114
What is ATP, and how does it contribute to cellular energy metabolism?
Adenosine triphosphate (ATP) is the primary energy currency of cells, providing the energy necessary for various cellular processes. ATP consists of adenine, a ribose sugar, and three phosphate groups. The hydrolysis of ATP to adenosine diphosphate (ADP) and inorganic phosphate (Pi) releases energy that can be used by cells to perform work. ATP is continuously generated through cellular respiration, where sugars like glucose are oxidized to produce ATP, carbon dioxide (CO2), and water (H2O).
115
What are NAD+ and NADP+, and how do they function in cellular metabolism?
- NAD+ and its phosphorylated form, NADP+ are coenzymes.
- NAD+ primarily functions in catabolic reactions, such as glycolysis and the citric acid cycle, where it serves as an electron carrier, accepting electrons from substrates during oxidation reactions.
- NADP+ is primarily involved in anabolic reactions, such as fatty acid synthesis and nucleotide synthesis, where it serves as a reducing agent, accepting electrons to become NADPH.
- Both NAD+ and NADP+ play crucial roles in cellular metabolism by facilitating electron transfer reactions essential for energy production and biosynthesis.
116
What are metabolic pathways, and how are they organized?
Metabolic pathways are sequences of enzymatically catalyzed reactions that occur within cells, collectively contributing to metabolism. These pathways are often organized into chains or cycles, with each step controlled by specific enzymes. Chains involve sequential reactions, while cycles involve repeating reactions. This organization allows for the efficient processing of substrates and products in a controlled manner.
117
How does feedback inhibition regulate metabolic pathways?
Feedback inhibition, also known as end-product inhibition, is a regulatory mechanism that negatively controls metabolic pathways. In this process, the final product of a pathway inhibits an enzyme involved in its own synthesis. By binding to an allosteric site on the enzyme, the product reversibly inhibits its activity, ensuring tight regulation of product levels within the cell. An example is the inhibition of threonine deaminase by isoleucine, preventing excessive production of isoleucine from threonine.
118
What are the key functions of ATP in cellular metabolism?
Adenosine triphosphate (ATP) serves two crucial functions in cellular metabolism: First, it acts as an immediate source of energy when hydrolyzed to adenosine diphosphate (ADP) and inorganic phosphate (Pi), releasing energy that can be used for cellular work. Second, ATP can transfer its phosphate group to other molecules, making them less stable and more reactive, which is essential for various metabolic processes requiring energy input.
119
What are the key steps and events in glycolysis and how many are generated overall?
Glycolysis is a universal metabolic pathway that breaks down glucose into pyruvate, generating ATP.
- Step 1: hexokinase adds a phosphate group, consuming 1 ATP.
- Step 3(RDS): phophofructokinase adds another phosphate, consuming another ATP.
- Step 7: phosphoglycerate Kinase removes a phosphate, generating 1 ATP.
- Step 10: pyruvate kinase removes another phosphate, generating 1 ATP.
overall 2 ATP are generated per glycolysis
120
What is the link reaction, and how does it connect anaerobic and aerobic processes?
The link reaction connects anaerobic glycolysis in the cytoplasm with aerobic respiration in the mitochondria. It involves the conversion of pyruvate to acetyl coenzyme A (acetyl CoA) in the mitochondrial matrix. During this process, pyruvate is oxidized to produce NADH and carbon dioxide (CO2), and the resulting acetyl group is attached to coenzyme A to form acetyl CoA. This compound then enters the citric acid cycle, facilitating the further breakdown of glucose to produce ATP.
121
What are the key events and products of the citric acid cycle (Krebs cycle)?
The citric acid cycle, also known as the Krebs cycle or TCA cycle, is a series of oxidation and decarboxylation reactions occurring in the mitochondrial matrix. Key events include the combination of acetyl CoA with a 4-carbon compound to form a 6-carbon compound, its subsequent breakdown back to the original 4-carbon compound, and the production of ATP, NADH, FADH2, and CO2. This cycle generates energy-rich molecules and molecular building blocks necessary for cellular functions.
122
How does the electron transport chain contribute to ATP synthesis?
The electron transport chain (ETC) is located in the inner mitochondrial membrane and plays a crucial role in ATP synthesis through oxidative phosphorylation. High-energy electrons carried by hydrogen carriers (e.g., NADH, FADH2) are shuttled through the ETC, losing energy as they move between electron carriers. This energy is used to pump protons into the intermembrane space, creating an electrochemical gradient. Chemiosmosis then drives protons back into the matrix through ATP synthase, generating ATP from ADP and Pi.
123
What is the role of oxygen in cellular respiration?
Oxygen is essential for aerobic respiration, serving as the final electron acceptor in the electron transport chain. It combines with de-energized electrons and protons to form water molecules, facilitating the removal of electrons and maintaining the proton gradient necessary for ATP synthesis. Additionally, oxygen binds to hydrogen ions in the mitochondrial matrix, ensuring a higher concentration of protons in the inter-membrane space, which drives ATP synthesis through chemiosmosis. Aerobic respiration results in the complete breakdown of glucose into carbon dioxide and water, producing ATP as a form of cellular energy.
124
What are the differences between the circulatory systems of mammals and fish?
Mammals have double circulatory systems with separate pathways for oxygenated and deoxygenated blood, reflecting their higher metabolic activity. Fish, on the other hand, typically have a single circulatory path due to their lower metabolic demands.
125
How do arteries and veins differ in structure and function?
Arteries and veins have similar structures, including a central lumen, endothelium, muscle/elastin layer, and collagen fibers. However, veins have larger lumens, thinner walls, more collagen, and valves to prevent backflow, whereas arteries have smaller lumens, thicker walls, thicker muscle layers, less collagen, and lack valves.
126
What are the structural characteristics and functions of capillaries?
Capillaries are the thinnest blood vessels, consisting of only an endothelial layer, a basement membrane, and pericytes. Their thinness facilitates the exchange of gases, nutrients, and waste products between blood and tissues.
127
Describe the phases of the cardiac cycle and how it is coordinated.
The cardiac cycle includes diastole (relaxation), atrial systole (atrial contraction), and ventricular systole (ventricular contraction). It is coordinated by the heart's electrical system, starting with impulses generated by the sinoatrial node (SAN), followed by the atrioventricular node (AVN), bundle of His, and Purkinje fibers.
128
What are some common cardiovascular diseases and their associated risk factors?
Cardiovascular diseases include hypertension, atherosclerosis, thrombosis, embolism, and myocardial infarction (heart attack). Risk factors include genetics, age, gender, smoking, obesity, and diet. Dietary cholesterol, while relevant, is not the sole contributor to cardiovascular disease, with genetics playing a significant role.
129
What causes edema, and what are its potential causes?
Edema, characterized by fluid buildup in tissues, can be caused by heart failure, venous insufficiency, or other factors. Capillary leakiness allows blood plasma to leak out, increasing hydrostatic pressure. Lymph nodes help remove waste fluid.
130
How is the heartbeat coordinated, and what role do valves play?
The heartbeat is coordinated by the heart's electrical system, starting with impulses generated by the sinoatrial node (SAN). Valves prevent the backflow of blood and produce the "lubb-dubb" sounds. The tricuspid and aortic valves are semilunar, while the pulmonary and mitral valves are atrioventricular.
131
What are the components and significance of an ECG (electrocardiogram)?
An ECG represents one cardiac cycle. It shows the P wave (atrial activation), QRS complex (ventricular activation), and T wave (recovery wave). Patterns in an ECG can reveal whether a heartbeat is normal, fast, slow, or abnormal based on their frequency.
132
What are the key types of cardiovascular diseases and their mechanisms?
Cardiovascular diseases include hypertension, atherosclerosis, thrombosis, embolism, and myocardial infarction (heart attack). These diseases result from factors such as plaque buildup, blood clots, and occlusions in blood vessels.
133
What are some factors that can increase the risk of cardiovascular disease, and what are the different types of cholesterol?
Genetics, age, gender, smoking, obesity, and diet influence cardiovascular disease risk. High-density lipoprotein (HDL) is considered good cholesterol, while low-density lipoprotein (LDL) is considered bad cholesterol. However, genetics play a significant role in cholesterol levels.
134
What causes edema, and how can it be attributed to cardiovascular conditions?
Edema can result from heart failure, venous insufficiency, or liver and kidney diseases. Increased hydrostatic pressure in veins and capillaries can lead to fluid buildup in tissues.
135
What are the functions of peripheral resistance and how does it influence blood pressure?
Peripheral resistance, determined by the contact between blood and blood vessel walls, affects blood pressure by causing friction. Ventricular systole and diastole phases also contribute to fluctuations in blood pressure.
