Metabolism & Nutrients

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Questions and Answers

What is metabolism?

All of the chemical reactions that take place in cells (and therefore in the organism).

What are the 2 types of metabolic chemical reactions?

Catabolism (catabolic) and Anabolism (anabolic).

What are nutrients and why are they needed?

Nutrients are any substance in food that is used for growth, repair or maintaining the body; or important substances needed for body functions. Reasons they are needed include: providing energy, repairing and building cells, and regulating body processes.

What is the difference between an organic compound and a non-organic compound?

Organic compounds are molecules that have a carbon chain, whereas non-organic (inorganic) compounds do not have a carbon chain. Signup and view all the answers

What are the 6 groups of nutrients? Determine which ones are organic and non-organic.

Organic: 1. Carbohydrates, 2. Lipids, 3. Proteins. Non-Organic: 4. Minerals, 5. Vitamins, 6. Water. Signup and view all the answers

What are Carbohydrates? Describe their function, composition, and types.

Carbohydrates are the main source of energy for cells. Simple sugars, particularly glucose, are used in cellular respiration to release energy. They contain atoms of carbon, hydrogen, and oxygen. Simple sugars include monosaccharides (e.g., glucose, fructose, galactose) which can join to form disaccharides (e.g., sucrose, maltose, lactose). Signup and view all the answers

What are proteins? Describe their function, composition, examples, and peptide bonds.

Proteins are organic compounds made up of many amino acids. They form structural material and enzymes. Excess protein can be converted to carbohydrates or used for energy. They contain carbon, hydrogen, oxygen, nitrogen, and often sulfur and phosphorus. Amino acids join via peptide bonds; two amino acids form a dipeptide, and more than ten form a polypeptide. Signup and view all the answers

What is protein synthesis?

Protein synthesis is the process where cells require amino acids so they can build them up into proteins. Signup and view all the answers

What are lipids?

Lipids are used as an energy source and include fats and oils. They are broken down into fatty acids and glycerol. Glycerol can enter the glycolysis pathway for energy release. Other examples include phospholipids (important for cell membranes). Fat lipids consist of glycerol and one, two, or three fatty acid molecules. A triglyceride is composed of glycerol and three fatty acid molecules and is how fat is stored in the body. Signup and view all the answers

List and describe the 3 main inorganic nutrient compounds discussed.

<ol> <li>Water: Important as a fluid for dissolving substances and for chemical reactions. 2. Minerals: May be part of enzymes or function as cofactors. 3. Vitamins: Act as coenzymes for many metabolic chemical reactions.</li> </ol> Signup and view all the answers

What is a catalyst?

A substance that speeds up a chemical reaction without being consumed in the process. Signup and view all the answers

Define enzymes and state what they do.

Enzymes are organic catalysts, typically proteins, that speed up the rate of biochemical reactions in the body without being used up themselves. They break large molecules (like carbohydrates, lipids, proteins) into smaller molecules for absorption and reduce the activation energy required for reactions. Signup and view all the answers

Explain the lock and key model of enzyme action.

The lock and key model proposes that the enzyme (the key) has a specific shape (the active site) that fits precisely onto its substrate (the lock), allowing the reaction to occur. Only the correctly shaped substrate will fit the enzyme's active site. Signup and view all the answers

List the factors that affect enzyme activity.

Concentration (of enzyme and substrate), temperature, pH, co-factors and co-enzymes, and enzyme inhibitors. Signup and view all the answers

How does enzyme concentration affect reaction rate?

The higher the concentration of enzymes, the faster the rate of the chemical reaction, assuming sufficient substrate is available. Signup and view all the answers

How does temperature affect enzyme activity?

As the temperature increases, the rate at which the enzyme speeds up a reaction generally increases, up to an optimal temperature. Beyond the optimum, high temperatures can cause the enzyme to denature (lose its shape) and lose activity. Signup and view all the answers

How does pH affect enzyme activity?

Enzymes are sensitive to pH. Each enzyme has an optimum pH at which it works best. Extreme pH values can alter the enzyme's structure and reduce or eliminate its activity. Examples of optimum pH: Stomach (around 2), Mouth (around 7), Intestine (around 7-9). Signup and view all the answers

Explain the role of co-factors and co-enzymes in enzyme activity.

Many enzymes require the presence of co-factors or co-enzymes before they can catalyse a reaction. These substances can change the shape of the active site so the enzyme can combine with the substrate. Co-factors are typically metal ions (e.g., Iron), while co-enzymes are organic molecules (e.g., Vitamins). Signup and view all the answers

What are enzyme inhibitors?

Enzyme inhibitors are substances that slow or stop an enzyme's activity. Inhibitors can be used by cells to control reactions so that products are produced in specific amounts. Signup and view all the answers

Explain cellular respiration.

Cellular respiration is the set of metabolic processes by which organic molecules (like glucose) are broken down in cells to release energy for the cell's activities. It is the chemical reaction that makes energy available for the cell. Signup and view all the answers

How is the energy released from cellular respiration used?

Approximately 60% of the energy released from respiration is in the form of heat, which helps maintain body temperature and acts as a catalyst. The remaining 40% is captured in the form of Adenosine Triphosphate (ATP) for cellular work. Signup and view all the answers

Provide the summarized chemical equation for aerobic cellular respiration.

Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP) Chemical formula: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + energy (ATP)$ Signup and view all the answers

List seven uses for the energy (ATP) produced by cellular respiration within a cell.

<ol> <li>Building complex molecules (anabolism). 2. Cell division and growth (mitosis). 3. Movement of organelles. 4. Movement of the whole cell. 5. Maintaining cell organisation. 6. Active transport across membranes. 7. Transmission of nerve impulses.</li> </ol> Signup and view all the answers

What are the 2 types of cellular respiration, and what process do they both begin with?

The two types are: 1. Aerobic respiration (requires oxygen) and 2. Anaerobic respiration (occurs in the absence of oxygen). Both forms begin with the process of glycolysis. Signup and view all the answers

Explain the process of glycolysis.

Glycolysis takes place in the cytoplasm. It involves a series of 10 steps where one molecule of glucose ($C_6H_{12}O_6$) is broken down to form two molecules of pyruvic acid ($C_3H_4O_3$). This process does not require oxygen and releases a small amount of ATP. Signup and view all the answers

Explain the main stages of aerobic respiration after glycolysis.

<ol> <li>Krebs cycle: The two pyruvic acid molecules enter the mitochondria. Here, pyruvic acid is broken down, releasing carbon dioxide ($CO_2$) as waste and hydrogen ions ($H^+$), generating a small amount of ATP. 2. Electron transport chain: The hydrogen ions ($H^+$) formed in the Krebs cycle are passed along an electron transport chain within the mitochondria. At each step, energy is released and used to produce a large amount of ATP. Finally, hydrogen combines with oxygen to form water ($H_2O$).</li> </ol> Signup and view all the answers

At the end of aerobic respiration, what is the theoretical maximum number of ATP molecules made, and how many are produced in each major stage?

The theoretical maximum is 38 ATP molecules formed per glucose molecule. The breakdown is: 2 ATP from glycolysis, 2 ATP from the Krebs cycle, and 34 ATP from the electron transport system. Signup and view all the answers

Explain the Krebs cycle.

Following glycolysis, the two pyruvic acid molecules enter the mitochondria. In the Krebs cycle (also known as the citric acid cycle), pyruvic acid is further broken down, releasing carbon dioxide ($CO_2$) as waste and transferring high-energy electrons and hydrogen ions ($H^+$) to electron carriers, generating 2 ATP molecules per glucose. Signup and view all the answers

Explain the electron transport system (chain) in aerobic respiration.

Hydrogen ions ($H^+$) and high-energy electrons, primarily from the Krebs cycle, are passed along a series of protein complexes (the electron transport chain) embedded in the inner mitochondrial membrane. As electrons move down the chain, energy is released and used to pump $H^+$ ions, creating a gradient. This gradient drives ATP synthesis as $H^+$ ions flow back across the membrane. Finally, oxygen acts as the final electron acceptor, combining with $H^+$ ions to form water ($H_2O$). Signup and view all the answers

Explain anaerobic respiration in humans.

Anaerobic respiration begins with glycolysis, producing 2 pyruvic acid molecules and 2 ATP. Since oxygen isn't available, the pyruvic acid is then converted into lactic acid. Accumulation of lactic acid can cause muscle fatigue. During this process, an oxygen debt is built up, requiring increased oxygen intake after exercise (recovery oxygen) to break down the lactic acid. Signup and view all the answers

What is the digestive system?

The digestive system is a continuous tube, the alimentary canal, that runs from the mouth to the anus, along with accessory organs that aid digestion. Signup and view all the answers

Define digestion.

Digestion is the breakdown of large, complex nutrient molecules (food) into products small enough to be absorbed into the blood and utilized by cells. Signup and view all the answers

What are the 6 main activities of the digestive system?

<ol> <li>Ingestion of food. 2. Mechanical digestion. 3. Chemical digestion. 4. Movement of food along the alimentary canal. 5. Absorption of digested food into blood and lymph. 6. Elimination of material that is not absorbed.</li> </ol> Signup and view all the answers

What does the alimentary canal consist of?

The alimentary canal consists of the Mouth, Pharynx, Oesophagus, Stomach, Small Intestine, Large Intestine, Rectum, and Anus. Signup and view all the answers

What are the 2 types of digestion?

<ol> <li>Mechanical digestion: The physical break up of food into smaller particles (e.g., chewing by teeth, churning in the stomach). 2. Chemical digestion: The chemical breakdown of complex molecules into simpler molecules using enzymes and acids (e.g., saliva breaking down starch, stomach acid digesting proteins).</li> </ol> Signup and view all the answers

How is ATP formed from ADP?

ATP (Adenosine Triphosphate) is formed when a third phosphate molecule bonds to ADP (Adenosine Diphosphate), storing energy in that bond. Signup and view all the answers

What do ATP and ADP stand for?

ATP stands for Adenosine Triphosphate. ADP stands for Adenosine Diphosphate. Signup and view all the answers

How is energy released from ATP?

Energy required for cellular processes like building molecules (anabolism) is stored in the bond between the 2nd and 3rd phosphate groups of ATP. When this energy is needed, the bond is broken, converting ATP back into ADP + P (inorganic phosphate) and releasing the stored energy. Signup and view all the answers

How many ATP molecules are typically made per stage in aerobic respiration?

Approximately 2 ATP molecules in the glycolysis stage, 2 ATP in the Krebs cycle, and 34 ATP in the electron transport system. Signup and view all the answers

What is mastication?

Mastication is the process of chewing food in the mouth, breaking it down into smaller particles. Signup and view all the answers

What are the 4 types of teeth in the human mouth and their function?

<ol> <li>Incisors (4 front): Chisel-shaped for biting or cutting. 2. Canines (1 on each side of incisors): Pointed for tearing. 3. Premolars (2 on each side behind canines): For grinding. 4. Molars (3 on each side at the back): For crushing and grinding.</li> </ol> Signup and view all the answers

Describe the chemical digestion that occurs in the mouth.

Saliva, secreted by three pairs of salivary glands, contains mucous for lubrication and forming the bolus, and the digestive enzyme salivary amylase, which begins the chemical digestion of starch into smaller polysaccharides or disaccharides. Signup and view all the answers

Besides digestion, what are other functions of the mouth?

Ingestion of food, dissolving food with saliva so taste receptors can be stimulated, and forming the chewed food into a round lump called a bolus by the tongue, which is then pushed towards the pharynx for swallowing. Signup and view all the answers

What is the oesophagus?

The oesophagus is a muscular tube that carries the bolus (lump of food) from the pharynx (throat) to the stomach. It passes through the diaphragm. Movement of food is lubricated by mucous secreted by its lining. Signup and view all the answers

How is the bolus pushed along the oesophagus?

The bolus is pushed along the oesophagus by waves of muscular contractions of the circular muscles in its wall. This process is called peristalsis. Signup and view all the answers

What mechanical digestion occurs in the stomach?

Mechanical digestion in the stomach involves waves of muscular contractions (churning) of the stomach wall. Signup and view all the answers

What are the 3 layers of muscle surrounding the stomach?

A circular layer, a longitudinal layer, and an additional oblique layer. Signup and view all the answers

What do the stomach contractions achieve?

The contractions allow the stomach to churn food, mixing it with gastric juices until it becomes a thick, soupy liquid called chyme. Signup and view all the answers

Describe other functional features of the stomach lining and outlet.

The mucosa (lining) is specialised for secreting gastric juices from gastric glands located in gastric pits. At the bottom of the stomach, the pyloric sphincter, a thickening of circular muscle, controls the flow of chyme into the duodenum (the first part of the small intestine), preventing backflow unless pushed by peristalsis. Signup and view all the answers

Describe the structure and mechanical action of the small intestine.

The small intestine is about 6m long and consists of three sections: the duodenum (receives material from the stomach), the jejunum, and the ileum. Mechanical action includes segmentation, which involves circular muscle contractions that break up the bolus, mix contents with juices and bile, and bring food into contact with the lining for absorption. Signup and view all the answers

What role does bile play in the small intestine?

Bile, produced by the liver and stored in the gallbladder, contains bile salts. These act like detergents to emulsify lipids (fats), breaking large fat globules into tiny droplets. This increases the surface area for lipase enzymes to work on and digest the fats more efficiently. Signup and view all the answers

Where does pancreatic juice come from and where is it released?

The pancreas produces and secretes pancreatic juice, which contains digestive enzymes. It is released into the duodenum (first part of the small intestine) via the pancreatic duct. Signup and view all the answers

List the main digestive enzymes found in pancreatic juice and their actions.

<ol> <li>Pancreatic amylase: Digests starch/polysaccharides into disaccharides (like maltose). 2. Pancreatic protease (trypsin): Digests proteins/polypeptides into smaller dipeptides. 3. Pancreatic lipase: Digests lipids (fats) into fatty acids and glycerol. 4. Pancreatic ribonuclease and deoxyribonuclease: Digest RNA and DNA.</li> </ol> Signup and view all the answers

What does the pancreas produce relevant to digestion?

The pancreas produces and secretes pancreatic juices, which contain a variety of digestive enzymes and bicarbonate to neutralize stomach acid. Signup and view all the answers

How is the small intestine adapted for absorption?

The small intestine is the primary site for nutrient absorption. It achieves an enormous surface area through: its long length (approx. 6m), extensive folding of the inner lining (mucosa), and the presence of numerous finger-like projections called villi, which are themselves covered in microscopic projections called microvilli. Signup and view all the answers

Describe the structure and function of the large intestine.

The small intestine joins the large intestine at the caecum, a small pouch with the appendix attached (which has no known digestive function). The large intestine primarily absorbs excess water, making the remaining contents more solid (faeces). Contents are pushed into the rectum by peristalsis. Stretching of the rectal walls triggers the defecation reflex. Signup and view all the answers

What are the two layers of muscle found in the wall of the oesophagus (and much of the alimentary canal)?

<ol> <li>Longitudinal muscle layer: Runs along the length of the canal. 2. Circular muscle layer: Arranged in circles around the canal.</li> </ol> Signup and view all the answers

Describe the structure and function of a villus in the small intestine.

A villus is a small, finger-like projection extending from the folded inner surface (mucosa) of the small intestine. Villi dramatically increase the surface area for absorption. Each villus contains a network of capillaries (small blood vessels) and a lacteal (a small lymph vessel). Absorptive cells on the surface take up nutrients, which then enter the capillaries (sugars, amino acids, water-soluble vitamins, minerals) or the lacteal (fatty acids, glycerol, fat-soluble vitamins). Signup and view all the answers

What is excretion?

Excretion is the removal from the body of metabolic wastes, which are waste products generated by chemical reactions within cells. Signup and view all the answers

What are the 4 main excretory organs in humans?

Lungs, liver, kidneys, and skin. Signup and view all the answers

Define Elimination (or Egestion).

Elimination is the removal of undigested or unabsorbed material (faeces) from the digestive tract via the anus. Signup and view all the answers

Explain the excretory functions of the lungs, skin, liver, and kidneys.

Lungs: Remove carbon dioxide ($CO_2$) produced during cellular respiration. Skin: Sweat glands remove excess water, salts, urea, and lactic acid through perspiration (sweat), primarily for cooling but also contributing to excretion. Liver: Processes many substances for excretion, detoxifies harmful compounds (like alcohol), breaks down excess amino acids (producing urea), and forms bile pigments from haemoglobin breakdown. Kidneys: Regulate blood composition and volume (water balance, electrolytes) and remove the primary nitrogenous waste, urea, along with uric acid, creatinine, and excess salts and water, forming urine. Signup and view all the answers

Where is bile produced, stored, and released?

Bile is produced by the liver, stored and concentrated in the gall bladder, and released into the duodenum (first part of the small intestine) through the common bile duct. Signup and view all the answers

What is deamination, where does it occur, and why?

Deamination is the removal of the amino group (-NH2) from an amino acid molecule. It primarily occurs in the liver, aided by enzymes. It happens when there are excess amino acids beyond the body's needs for protein synthesis, allowing the remaining carbon skeleton of the amino acid to be used for energy or converted into carbohydrates or fats. Signup and view all the answers

Explain the 5 main steps in the process of deamination and urea formation.

<ol> <li>The amino group (-NH2) is removed from the amino acid in the presence of oxygen, aided by liver enzymes. 2. The amino group is initially converted to highly toxic ammonia (NH3). 3. The remaining part of the amino acid (carbon skeleton) is converted into a carbohydrate (like glucose or glycogen) or used in cellular respiration. 4. The toxic ammonia (NH3) is quickly converted into urea, which is much less toxic to the body. 5. Urea is transported via the bloodstream to the kidneys and excreted from the body in urine.</li> </ol> Signup and view all the answers

Provide a simplified summary equation for deamination.

Amino acid + Oxygen → (Hydrogen + Carbon component) + Ammonia → Carbohydrate/Energy + Urea (excreted) Signup and view all the answers

Describe the main parts of the kidney and their basic functions.

Cortex: The outer layer containing glomeruli and convoluted tubules. Medulla: The inner part containing renal pyramids (formed by loops of Henle and collecting ducts). Renal Artery: Carries blood into the kidney. Renal Vein: Carries filtered blood away from the kidney. Renal Pelvis: A funnel-shaped structure that collects urine from the collecting ducts and channels it into the ureter. Ureter: The tube that carries urine from the kidney to the bladder. Signup and view all the answers

What is a nephron and what is its function?

The nephron is the microscopic functional unit of the kidney. It is responsible for removing wastes from the blood and regulating blood composition (water, salts, pH). Signup and view all the answers

List the main structures of a nephron in the order that filtrate passes through.

<ol> <li>Glomerular (Bowman's) capsule surrounding the glomerulus (renal corpuscle). 2. Proximal convoluted tubule. 3. Loop of Henle (descending limb and ascending limb). 4. Distal convoluted tubule. 5. Collecting duct (receives filtrate from multiple nephrons). Filtrate then flows into the Renal Pelvis and Ureter.</li> </ol> Signup and view all the answers

What is urine formation, and what are the three main processes involved?

Urine formation is the process by which the kidneys filter blood, reabsorb essential substances, secrete additional wastes, and produce urine. The three main processes are: 1. Glomerular Filtration, 2. Selective Reabsorption, 3. Tubular Secretion. Signup and view all the answers

Explain Glomerular Filtration.

Glomerular filtration is the first step in urine formation, occurring in the renal corpuscle (glomerulus and Bowman's capsule). High blood pressure in the glomerulus forces water and small dissolved substances (like salts, glucose, amino acids, urea) out of the blood, across the capillary walls and into the Bowman's capsule. The collected fluid is called filtrate. Large components like blood cells and proteins remain in the blood. Signup and view all the answers

Which arteriole connected to the glomerulus is larger, and why is this significant?

The afferent arteriole (carrying blood into the glomerulus) has a larger diameter than the efferent arteriole (carrying blood away). This difference in diameter increases resistance to blood flow out of the glomerulus, resulting in higher blood pressure within the glomerular capillaries, which enhances the process of filtration. Signup and view all the answers

Explain Selective Reabsorption.

Selective reabsorption is the process where useful substances are transported out of the filtrate in the renal tubules and back into the bloodstream. This occurs along the proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. Cells lining the tubule actively and passively reabsorb essential materials that the body needs to keep, preventing their loss in urine. Signup and view all the answers

What types of materials are selectively reabsorbed from the filtrate?

Materials reabsorbed include most of the water, all of the glucose, amino acids, and various ions (like sodium, potassium, chloride, bicarbonate) depending on the body's needs. Signup and view all the answers

How is an effective surface area for reabsorption achieved in the nephron?

A large surface area for reabsorption is achieved by the long length and convoluted (twisted) nature of the nephron tubules, specifically the proximal and distal convoluted tubules, and the long loop of Henle. Additionally, the cells lining the proximal tubule have microvilli. Signup and view all the answers

Explain Tubular Secretion.

Tubular secretion is the process where certain waste products and excess ions are actively transported from the blood in the capillaries surrounding the tubules directly into the filtrate within the renal tubules (mainly the distal convoluted tubule and collecting duct). This process adds materials to the filtrate, removes additional wastes not filtered at the glomerulus, and helps maintain the blood's pH by secreting hydrogen ions ($H^+$) or bicarbonate ions ($HCO_3^-$) as needed. Signup and view all the answers

What are the four main enzymatic components of pancreatic juice, and what role do they play in digestion besides breaking down nutrients?

<ol> <li>Pancreatic Amylase: breaks down starch into maltose. 2. Trypsin (a protease): splits proteins into peptides. 3. Pancreatic Lipases: breaks down fats into fatty acids and glycerol. 4. Ribonuclease and Deoxyribonuclease: digest RNA and DNA. Besides enzymatic digestion, pancreatic juice contains bicarbonate ions which neutralize the acidic chyme entering the duodenum from the stomach, creating an optimal pH environment for these enzymes to function.</li> </ol> Signup and view all the answers

Identify enzymes present in the small intestine (secreted by intestinal glands or acting there) that break down peptides, sucrose, and lipids, and state what they break them down into.

<ol> <li>Peptidases: Break down peptides (from protein digestion) into individual amino acids. 2. Sucrase: Breaks down the disaccharide sucrose (table sugar) into the monosaccharides glucose and fructose. 3. Lipases (including pancreatic lipase acting in the intestine): Break down lipids (fats) into fatty acids and glycerol.</li> </ol> Signup and view all the answers

What are Carbohydrates? Include their function, what they contain, and examples of simple and complex sugars.

Carbohydrates are the main source of energy for cells. Simple sugars, particularly glucose, are used in cellular respiration to release energy. They contain atoms of carbon, hydrogen and oxygen. <ul> <li>Simple sugars (monosaccharides): e.g., glucose, fructose, galactose.</li> <li>Disaccharides (two simple sugars joined): e.g., sucrose, maltose, lactose.</li> </ul> Signup and view all the answers

What are proteins? Include their function, composition, and describe peptide bonds.

Proteins are organic compounds made up of many amino acids. Many important proteins are enzymes, and they also make up structural material of the cell. Excess protein may be converted to carbohydrates for energy. Proteins contain carbon, hydrogen, oxygen, nitrogen, and often sulfur and phosphorus. <ul> <li>When 2 amino acids bond, they form a peptide bond.</li> <li>A dipeptide is 2 amino acids joined by a peptide bond.</li> <li>Polypeptides are made up of more than 10 amino acids.</li> </ul> Signup and view all the answers

List and describe the 3 main types of inorganic compounds mentioned as nutrients.

Water: Important as its a fluid that other substances dissolve in. Some chemical reactions occur in water. Minerals: May be part of enzymes, may function as cofactors. Vitamins: Act as coenzymes for many of the chemical reactions of metabolism. Signup and view all the answers

Define enzymes and explain what they do.

Enzymes are organic catalysts, usually proteins, that speed up the rate of biochemical reactions in the body without being used up themselves. Enzymes break large molecules of carbohydrates, lipids and proteins into smaller molecules that can be absorbed. Enzymes reduce the activation energy required for the reaction to occur (to get started and take place). Signup and view all the answers

How does concentration affect enzyme activity?

The higher the concentration of enzymes (up to a point, relative to substrate), the faster the rate of chemical reactions. Signup and view all the answers

How does pH affect enzyme activity? Provide examples.

Enzymes are sensitive to pH. Each enzyme has an optimum pH at which it works best. <ul> <li>Stomach (e.g., pepsin): optimum pH around 2</li> <li>Mouth (e.g., salivary amylase): optimum pH around 7</li> <li>Intestine (e.g., trypsin): optimum pH around 7-9</li> </ul> Signup and view all the answers

How is the energy from cell respiration distributed?

Approximately 60% of the energy released from respiration is in the form of heat, which is useful in maintaining body temperature and acts as a catalyst for reactions. The remaining 40% of the energy is captured in the form of Adenosine Triphosphate (ATP). Signup and view all the answers

Provide the summarised equation for aerobic cellular respiration.

Word Equation: Glucose + Oxygen → Carbon Dioxide + Water + Energy Chemical Equation: $C_6H_{12}O_6 + 6O_2 → 6CO_2 + 6H_2O + energy (ATP + heat)$ Signup and view all the answers

List what energy (ATP) is used for in the cell.

<ol> <li>Building complex molecules (anabolism)</li> <li>Cell division and growth (mitosis)</li> <li>Movement of organelles</li> <li>Movement of whole cell</li> <li>Maintaining cell organisation</li> <li>Active transport</li> <li>Transmission of nerve impulses</li> </ol> Signup and view all the answers

What are the 2 types of cellular respiration?

<ol> <li>Aerobic respiration: requires oxygen.</li> <li>Anaerobic respiration: occurs in the absence of oxygen. Both forms begin with the process of glycolysis.</li> </ol> Signup and view all the answers

At the end of aerobic respiration, approximately how many ATP molecules are theoretically made per glucose molecule, and how are they distributed across the stages?

The theoretical maximum yield is 38 ATP molecules per glucose: <ul> <li>2 net ATP in the glycolysis stage</li> <li>2 ATP in the Krebs cycle stage</li> <li>34 ATP in the electron transport system phase The actual yield is often less than this theoretical maximum.</li> </ul> Signup and view all the answers

Explain the electron transport system (or chain).

Hydrogen ions (H+) and electrons, carried by NADH and FADH2 from glycolysis and the Krebs cycle, are passed along a series of protein complexes in the inner mitochondrial membrane (the electron transport chain). At several steps, energy is released and used to pump H+ into the intermembrane space. Finally, electrons combine with oxygen (the final electron acceptor) and H+ to form water. The flow of H+ back into the matrix through ATP synthase drives the synthesis of large amounts of ATP. Signup and view all the answers

Explain anaerobic respiration in humans (lactic acid fermentation).

<ol> <li>Glycolysis occurs, breaking glucose into 2 pyruvic acid molecules and producing 2 net ATP.</li> <li>Since oxygen isn't available for the subsequent stages (Krebs cycle, Electron Transport Chain), the 2 pyruvic acid molecules are converted into lactic acid. This conversion regenerates NAD+ needed for glycolysis to continue. Accumulation of lactic acid can contribute to muscle fatigue. During recovery after exercise, extra oxygen is required (recovery oxygen or oxygen debt) to process the accumulated lactic acid, often converting it back to pyruvic acid or glucose in the liver.</li> </ol> Signup and view all the answers

What structures does the alimentary canal consist of?

<ul> <li>Mouth</li> <li>Pharynx</li> <li>Oesophagus</li> <li>Stomach</li> <li>Small Intestine</li> <li>Large Intestine</li> <li>Rectum</li> <li>Anus</li> </ul> Signup and view all the answers

What are the 2 types of digestion? Provide examples.

Mechanical digestion: Physical break up of food into smaller particles. E.g., Teeth grinding up food, stomach churning. Chemical digestion: Chemical break down of complex molecules into their simpler molecules using enzymes. E.g., Salivary amylase breaking down starch, pepsin breaking down protein, hydrochloric acid aiding protein digestion. Signup and view all the answers

How is energy stored and released using ATP and ADP?

Building molecules (anabolism) requires energy. Energy obtained from processes like cellular respiration is used to attach a third phosphate group to ADP, forming ATP. This energy is stored in the high-energy bond between the 2nd and 3rd phosphate groups. When the cell requires energy for activities, the terminal phosphate bond in ATP is broken (hydrolysis), releasing the stored energy and forming ADP + P (inorganic phosphate). Signup and view all the answers

Describe mastication.

Mastication is the process of chewing food in the mouth, breaking it down into smaller particles. Signup and view all the answers

What are the 4 types of teeth in the mouth and their functions?

Incisors: 4 front teeth per jaw - chisel shaped for biting or cutting. Canines: 1 on each side of incisors per jaw - pointed, tearing teeth. Pre-molars: 2 on each side behind canines per jaw - grinding teeth. Molars: 3 on each side behind pre-molars per jaw - crushing or grinding teeth. Signup and view all the answers

Describe the chemical digestion that occurs in the mouth, including the role of saliva components.

Saliva is secreted by 3 pairs of salivary glands. It contains: <ul> <li>Mucous: for lubricating the food (bolus) and helping it stick together.</li> <li>Digestive enzyme salivary amylase: which begins the digestion of starch into smaller polysaccharides or disaccharides.</li> </ul> Signup and view all the answers

What are other functions of the mouth besides digestion?

Ingestion of food. Saliva dissolves food so taste receptors can be stimulated. After chewing, food is formed into a round lump called a bolus by the tongue and is pushed towards the pharynx for swallowing (deglutition). Signup and view all the answers

Describe mechanical digestion in the stomach.

Mechanical digestion in the stomach involves waves of muscular contractions (churning) of the stomach walls. Signup and view all the answers

What do the contractions allow the stomach to do, and what is the resulting mixture called?

Contractions allow the stomach to contract in a variety of ways to churn food. Food becomes a thick, soupy liquid called chyme. Signup and view all the answers

Describe the components of chemical digestion in the stomach.

Gastric juice contains: <ul> <li>Hydrochloric acid (HCl): Destroys bacteria and provides the optimum acidic pH (around 2) for pepsin.</li> <li>Mucus: Protects the stomach lining from digesting itself by the acid and enzymes.</li> <li>Pepsinogen: The inactive form of the digestive enzyme pepsin.</li> <li>Pepsin: When pepsinogen contacts HCl, it is converted to its active form, pepsin. Pepsin begins the chemical digestion of proteins by breaking them down into smaller polypeptides.</li> </ul> Signup and view all the answers

Describe other features of the stomach related to its function.

Mucosa: The lining of the stomach, specialized for the secretion of gastric juices. Gastric glands: Located in narrow tube-like structures called gastric pits within the mucosa, these glands secrete gastric juice. Pyloric sphincter: A thickening of circular muscle at the junction between the stomach and the duodenum (start of the small intestine). It controls the flow of chyme out of the stomach. Signup and view all the answers

Describe the structure of the small intestine, including its sections and segmentation.

The small intestine is about 6m long and is made up of 3 sections: <ul> <li>Duodenum: Receives chyme from the stomach and secretions from the pancreas, liver, and gallbladder; continues digestion.</li> <li>Jejunum: Middle section, primary site for nutrient absorption.</li> <li>Ileum: Final section, absorbs remaining nutrients (like Vitamin B12, bile salts) and connects to the large intestine. Segmentation involves circular muscle contractions that break up the chyme further, mix it with digestive juices and bile, and bring it into contact with the intestinal lining for absorption.</li> </ul> Signup and view all the answers

Explain the role of bile in mechanical digestion within the small intestine.

Bile, produced by the liver and stored in the gallbladder, contains bile salts. Bile salts act like detergents and emulsify lipids (fats), breaking large fat globules into tiny droplets. This emulsification dramatically increases the surface area upon which lipases (fat-digesting enzymes) can work to break down the lipids chemically. Signup and view all the answers

How does the pancreas contribute to chemical digestion in the small intestine?

The pancreas produces and secretes pancreatic juice, which contains digestive enzymes and bicarbonate. This juice is released into the duodenum via the pancreatic duct. Signup and view all the answers

List four major enzymes found in pancreatic juice and their functions.

<ol> <li>Pancreatic amylase: Digests starch/polysaccharides into disaccharides (like maltose).</li> <li>Pancreatic protease (Trypsin): Digests proteins/polypeptides into smaller peptides.</li> <li>Pancreatic lipase: Digests lipids (fats) into fatty acids and glycerol.</li> <li>Pancreatic ribonuclease and deoxyribonuclease: Digest RNA and DNA into nucleotides.</li> </ol> Signup and view all the answers

What main substance does the pancreas produce for digestion?

The pancreas produces and secretes pancreatic juice, containing enzymes and bicarbonate. Signup and view all the answers

Explain how the small intestine is adapted for efficient absorption.

The small intestine is the primary site for absorption of digested nutrients. It has an enormous surface area to allow for efficient absorption, achieved by: <ul> <li>Long length (approx. 6 meters).</li> <li>Folding of the inner lining (mucosa) into plicae circulares.</li> <li>Presence of villi (finger-like projections of the mucosa).</li> <li>Presence of microvilli (microscopic projections on the surface of epithelial cells lining the villi).</li> </ul> Signup and view all the answers

Describe the structure and main functions of the large intestine.

The small intestine joins the large intestine at the caecum, a small pouch. The appendix is a small tube attached to the caecum (thought to have minimal function in humans). The large intestine absorbs excess water from the remaining indigestible food matter, making the contents (faeces) more solid. It also absorbs some electrolytes and vitamins produced by gut bacteria. Contents are pushed into the rectum by peristalsis. As the rectal walls stretch, they trigger the defecation reflex to eliminate faeces through the anus. Signup and view all the answers

What are the two layers of muscle found throughout most of the alimentary canal, such as in the oesophagus?

Longitudinal muscle: runs along the length of the canal. Circular muscle: arranged in circles around the canal. Signup and view all the answers

Describe villi and their role in absorption. What structures are typically found within a villus?

Villi are small, finger-like projections that extend from the folded inner surface (mucosa) of the small intestine. They vastly increase the surface area for the absorption of digested food. Structures within a villus typically include: <ul> <li>A network of capillaries (tiny blood vessels)</li> <li>A lacteal (a small lymphatic vessel)</li> <li>Absorptive epithelial cells covering the surface</li> <li>An arteriole and venule supplying the capillaries</li> <li>Nerve fibres</li> <li>Connective tissue</li> </ul> Signup and view all the answers

What is excretion? Provide examples of metabolic waste.

Excretion is the removal from the body of metabolic waste products - substances produced by the chemical reactions within cells. Examples of metabolic waste: water, carbon dioxide, nitrogenous compounds (like urea), bile pigments, excess salts, and hormones. Signup and view all the answers

Define Elimination.

Elimination is the removal of indigestible material (faeces) from the body, primarily via the anus. Signup and view all the answers

Explain what bile is, where it is produced, stored, and released.

Bile is a substance produced by the liver. It is secreted by the liver into the gall bladder, where it is stored and concentrated. Bile enters the duodenum (first part of the small intestine) through the common bile duct. Signup and view all the answers

Define deamination: what is it, where does it occur, and why does it happen?

What: Deamination is the removal of an amino group (-NH2) from an amino acid molecule. Where: It occurs primarily in the liver, aided by enzymes. Why: It happens when there are excess amino acids beyond what's needed for protein synthesis, or when the body needs to use amino acids for energy. The remaining part of the amino acid can then be converted into carbohydrates or fats. Signup and view all the answers

Explain the 5 main steps involved in the process of deamination and subsequent urea formation.

<ol> <li>The amino group (-NH2) is removed from the amino acid, often requiring oxygen and enzymes.</li> <li>The removed amino group is initially converted to ammonia (NH3).</li> <li>The remaining part of the amino acid (containing carbon and hydrogen, sometimes called a keto acid) can be converted into a carbohydrate (like glucose or glycogen) or fat, or used in cellular respiration.</li> <li>The toxic ammonia (NH3) is quickly converted by the liver into urea, which is much less toxic.</li> <li>Urea is released into the bloodstream, transported to the kidneys, and excreted from the body in urine.</li> </ol> Signup and view all the answers

Provide the word equation summarizing deamination and the fate of its products.

amino acid + oxygen → keto acid + ammonia ↓ ↓ (carbohydrate/fat → cellular respiration) (urea → excreted) Signup and view all the answers

Describe the main parts of the Kidney and their general functions.

Cortex: The outer layer of the kidney, containing glomeruli and convoluted tubules. Medulla (containing Renal Pyramids): The inner part of the kidney, containing loops of Henle and collecting ducts. Renal Artery: Carries oxygenated blood containing waste products into the kidney. Renal Vein: Carries filtered, deoxygenated blood away from the kidney. Renal Pelvis: A funnel-shaped structure that collects urine from the collecting ducts and channels it into the ureter. Ureter: A tube that carries urine from the renal pelvis of the kidney to the urinary bladder. Signup and view all the answers

What is a Nephron and what is its function? List its main structures in order.

The nephron is the functional unit of the kidney, responsible for removing wastes from the blood and regulating blood composition to form urine. Structures (in order of filtrate flow): <ol> <li>Renal Corpuscle (Glomerular/Bowman's capsule surrounding the Glomerulus)</li> <li>Proximal convoluted tubule</li> <li>Loop of Henle (Descending limb and Ascending limb)</li> <li>Distal convoluted tubule</li> <li>Collecting duct (receives filtrate from several nephrons) *The collecting duct then leads to the Renal Pelvis and Ureter.</li> </ol> Signup and view all the answers

Explain what Glomerular Filtration is and where it occurs.

Glomerular filtration is the process where fluid and small solutes are forced out of the blood in the glomerulus and collected by the glomerular (Bowman's) capsule. This takes place in the renal corpuscle. High blood pressure within the glomerulus forces water and dissolved blood components (like glucose, amino acids, ions, urea) through the filtration membrane into the capsule. The collected fluid is called filtrate. Approximately 20% of the blood plasma entering the glomerulus becomes filtrate. Signup and view all the answers

Explain Selective Reabsorption in the nephron.

Selective reabsorption is the process by which useful substances from the filtrate are transported back into the blood as the filtrate flows through the renal tubules (proximal tubule, loop of Henle, distal tubule, collecting duct). This process is carried out by the cells lining the renal tubule. It ensures that essential substances needed by the body (like water, glucose, amino acids, ions) are recovered from the filtrate and not lost in the urine. Signup and view all the answers

What materials are typically reabsorbed from the filtrate back into the blood?

Water, glucose, amino acids, ions (such as sodium, potassium, chloride, bicarbonate), and some vitamins. Signup and view all the answers

How is an effective surface area for reabsorption achieved in the nephron tubule?

A large surface area for reabsorption is achieved by: <ul> <li>The long length of the renal tubule.</li> <li>The presence of two convoluted sections (proximal and distal convoluted tubules).</li> <li>The long Loop of Henle.</li> <li>Microvilli on the surface of cells, especially in the proximal convoluted tubule.</li> </ul> Signup and view all the answers

Explain what Tubular Secretion is and its main purposes.

Tubular secretion is the process where certain materials are actively transported from the blood in the capillaries surrounding the tubules into the filtrate within the tubule. This typically occurs in the proximal and distal convoluted tubules and collecting duct. Main purposes: <ul> <li>Removing certain waste products or foreign substances (like drug metabolites, excess potassium ions, creatinine) that were not filtered efficiently at the glomerulus.</li> <li>Helping to regulate blood pH by secreting hydrogen ions (H+) or bicarbonate ions ($HCO_3^-$) into the filtrate.</li> <li>This helps maintain the urine's pH as well.</li> </ul> Signup and view all the answers

Identify four components/enzymes in pancreatic juice and state their function in digestion.

<ol> <li>Pancreatic Amylase: Breaks down starch (a polysaccharide) into the disaccharide maltose.</li> <li>Trypsin (a protease): Splits proteins and large peptides into smaller peptides.</li> <li>Pancreatic Lipases: Break down fats (triglycerides) into fatty acids and glycerol.</li> <li>Ribonuclease and Deoxyribonuclease: Digest RNA and DNA (nucleic acids) into nucleotides.</li> </ol> Signup and view all the answers

Identify three enzymes found in the small intestine (often within intestinal juice) and state their roles.

<ol> <li>Peptidases: Break down peptides (from protein digestion) into individual amino acids.</li> <li>Sucrase: Breaks down sucrose (table sugar, a disaccharide) into glucose and fructose (monosaccharides).</li> <li>Lipases (intestinal lipase): Break down lipids (fats) into fatty acids and glycerol (supplementing pancreatic lipase).</li> </ol> Signup and view all the answers

What are Carbohydrates? Describe their function, components, and types.

What are proteins? Describe their function, components, and structure.

Proteins are organic compounds made up of many amino acids. Enzymes are important proteins. They also make up structural material of the cell. Excess protein may be converted to carbohydrates. They contain carbon, hydrogen, oxygen, nitrogen, and often sulfur and phosphorus. Amino acids bond via peptide bonds. A dipeptide is 2 amino acids joined by a peptide bond; polypeptides are made of more than 10 amino acids. Signup and view all the answers

List and describe the 3 main inorganic compounds acting as nutrients.

Water: Important as a fluid in which other substances dissolve; some chemical reactions occur in water. Minerals: May be part of enzymes or function as cofactors. Vitamins: Act as coenzymes for many metabolic chemical reactions. Signup and view all the answers

Define enzymes and describe what they do.

Enzymes are organic catalysts that speed up the rate of biochemical reactions in the body without being used up themselves. They break large molecules (carbohydrates, lipids, proteins) into smaller molecules for absorption and reduce the activation energy needed for reactions. Signup and view all the answers

How does enzyme concentration affect the rate of reaction?

The higher the concentration of enzymes, the faster the rate of the chemical reaction, assuming substrate is not limiting. Signup and view all the answers

What are co-factors and co-enzymes, and what is their role?

Many enzymes require co-factors or co-enzymes to catalyze a reaction. These substances can change the shape of the active site so the enzyme can combine with the substrate. Co-factors are typically metal ions (e.g., Iron), while co-enzymes are organic molecules (e.g., Vitamins). Signup and view all the answers

How is energy from cellular respiration utilized?

Approximately 60% of the energy released from respiration is in the form of heat, useful for maintaining body temperature and acting as a catalyst. The remaining 40% is captured as Adenosine Triphosphate (ATP). Signup and view all the answers

Provide the summarized equation for cellular respiration.

<code>Glucose + Oxygen → Carbon Dioxide + Water + Energy</code> or chemically: <code>$C_6H_{12}O_6 + 6O_2 → 6CO_2 + 6H_2O$ + energy (ATP)</code> Signup and view all the answers

List some uses for energy (ATP) within the cell.

Building complex molecules, cell division and growth (mitosis), movement of organelles, movement of the whole cell, maintaining cell organization, active transport, and transmission of nerve impulses. Signup and view all the answers

Explain the process of aerobic respiration.

Aerobic respiration follows glycolysis if oxygen is present. It involves: 1. Glycolysis (in cytoplasm). 2. Krebs cycle (in mitochondria): The 2 pyruvic acid molecules enter the mitochondria and are broken down, producing hydrogen ions ($H^+$), waste carbon dioxide ($CO_2$), and some ATP. 3. Electron transport chain (in mitochondria): Hydrogen ions ($H^+$) are passed along a chain, releasing energy at each step to produce a large amount of ATP. Hydrogen eventually combines with oxygen to form water. Signup and view all the answers

At the end of aerobic respiration, theoretically how many ATP molecules are made per glucose molecule?

The theoretical maximum is 38 ATP molecules: 2 from glycolysis, 2 from the Krebs cycle, and 34 from the electron transport system. Signup and view all the answers

Explain anaerobic respiration.

Anaerobic respiration starts with glycolysis. Since oxygen isn't available, the 2 pyruvic acid molecules are converted into lactic acid in animals (or ethanol and CO2 in yeast). Accumulation of lactic acid can be harmful. During strenuous exercise leading to anaerobic respiration, an 'oxygen debt' is built up, requiring extra oxygen intake after exercise (recovery oxygen) to process the lactic acid. Signup and view all the answers

How many ATP molecules are typically made per stage in aerobic respiration from one glucose molecule?

2 ATP (net) in the glycolysis stage, 2 ATP in the Krebs cycle stage, and approximately 34 ATP in the electron transport system stage. The theoretical maximum is 38 ATP, but the actual yield is often less. Signup and view all the answers

What is mechanical digestion in the mouth called?

Mastication, which is the process of chewing food, breaking it down into smaller particles. Signup and view all the answers

Describe chemical digestion in the mouth.

Saliva is secreted by three pairs of salivary glands. Saliva contains mucous for lubricating the bolus and helping food stick together, and the digestive enzyme salivary amylase, which begins the digestion of starch into smaller polysaccharides or disaccharides. Signup and view all the answers

What is the oesophagus and its function?

The oesophagus is a muscular tube that carries the bolus from the pharynx to the stomach. It passes through the diaphragm. Movement of food is lubricated by mucous secreted by its lining. Signup and view all the answers

Describe the components involved in chemical digestion in the stomach.

Gastric juice contains: Hydrochloric acid (HCl), which destroys bacteria and provides an optimum acidic pH (around 2) for pepsin; Mucus, which protects the stomach lining from digesting itself; and Pepsinogen, the inactive form of the digestive enzyme pepsin. When pepsinogen contacts HCl, it converts to active pepsin, which begins the breakdown of proteins into smaller polypeptides. Signup and view all the answers

Describe other features and functions of the stomach.

The mucosa is the lining of the stomach, specialised for secreting gastric juices from gastric glands located in gastric pits. The pyloric sphincter is a ring of muscle at the bottom of the stomach that controls the flow of chyme into the duodenum (the first part of the small intestine). Signup and view all the answers

Describe the structure and movement in the small intestine.

The small intestine is about 6m long and has three sections: the duodenum (receives material from the stomach), the jejunum, and the ileum. Segmentation involves circular muscle contractions that break up the bolus, mix it with digestive juices and bile, and bring it into contact with the lining for absorption. Signup and view all the answers

How does bile aid mechanical digestion in the small intestine?

What role does the pancreas play in chemical digestion in the small intestine?

The pancreas produces and secretes pancreatic juice, which contains several digestive enzymes and bicarbonate. This juice is released into the duodenum through the pancreatic duct. Signup and view all the answers

Describe the structure of a villus and its role in absorption.

A villus is a small, finger-like projection extending from the folded surface of the small intestine lining. Each villus contains a network of capillaries (small blood vessels) and a lacteal (a lymphatic capillary). Absorptive cells on the villus surface take up digested nutrients. Monosaccharides, amino acids, water-soluble vitamins, and minerals enter the capillaries. Fatty acids and glycerol are reassembled into fats within the cells, enter the lacteal, and are transported via the lymphatic system. Signup and view all the answers

What is deamination, where does it occur, and why is it necessary?

Deamination is the removal of an amino group (-NH2) from an amino acid molecule. It occurs primarily in the liver with the aid of enzymes. It is necessary because excess amino acids cannot be stored as protein; removing the amino group allows the remaining part of the molecule to be used for energy (converted to carbohydrate or fat) or stored. Signup and view all the answers

Summarize the overall transformation during deamination using the simplified equation/flowchart provided.

<code>amino acid + oxygen → carbohydrate + ammonia</code> <code>ammonia → urea</code> <code>carbohydrate → cellular respiration</code> <code>urea → excreted</code> Signup and view all the answers

Describe the main structures of the kidney and their functions.

Cortex: Outer layer containing renal corpuscles. Medulla: Inner part, arranged in renal pyramids containing tubules and collecting ducts. Renal artery: Carries blood into the kidney. Renal vein: Carries filtered blood away from the kidney. Renal pelvis: Funnel-shaped structure that collects urine from the pyramids. Ureter: Tube that carries urine from the renal pelvis to the bladder. Signup and view all the answers

Which arteriole entering/leaving the glomerulus is larger, and why is this significant?

The afferent arteriole (carrying blood into the glomerulus) has a larger diameter than the efferent arteriole (carrying blood away). This difference in diameter increases resistance to blood flow out of the glomerulus, thus raising the blood pressure within the glomerular capillaries, which enhances filtration. Signup and view all the answers

What types of materials are reabsorbed during selective reabsorption?

Most of the water, all of the glucose, amino acids, and various ions (like sodium, potassium, chloride, bicarbonate) are reabsorbed. Signup and view all the answers

What are the four main enzyme components of pancreatic juice and their functions in digestion?

<ol> <li>Pancreatic Amylase: Breaks down starch (polysaccharides) into the disaccharide maltose. 2. Trypsin (a protease): Splits proteins and polypeptides into smaller peptides. 3. Pancreatic Lipases: Break down fats (lipids) into fatty acids and glycerol. 4. Ribonuclease and Deoxyribonuclease: Digest RNA and DNA into nucleotides.</li> </ol> Signup and view all the answers

Identify three enzymes found in the digestive system (as per the card) and state their roles in breaking down macromolecules.

<ol> <li>Peptidase: Breaks down peptides (from protein digestion) into amino acids. 2. Sucrase: Breaks down sucrose (a disaccharide) into monosaccharides (glucose and fructose). 3. Lipases: Break down lipids (fats) into fatty acids and glycerol.</li> </ol> Signup and view all the answers

Flashcards

What is metabolism?

All chemical reactions in cells.

Two types of metabolic reactions?

Catabolism breaks down; anabolism builds up.