SCPBB1 Week 5 Digestive System 2024 PDF

Animal and Plant Biology SCPBB1 Digestive System Eduvos (Pty) Ltd (formerly Pearson Institute of Higher Education) is registered with the Departme...

Animal and Plant Biology SCPBB1 Digestive System Eduvos (Pty) Ltd (formerly Pearson Institute of Higher Education) is registered with the Department of Higher Education and Training as a private higher education institution under the Higher Education Act, 101, of 1997. Registration Certificate number: 2001/HE07/008 Reminders Upcoming: Quiz 2 Quiz 3 to be done in week 7 Deferred block test: 21 August o Please apply via the Assessment Office – NOT your lecturer! Recap Quiz - Circulation What is the correct path through the circulatory system which describes the passage of blood originating in the left leg? A. Vena cava, left atrium, right atrium, lungs, left ventricle, right ventricle, aorta B. Vena cava, right atrium, left atrium, lungs, right ventricle, left ventricle, aorta C. Vena cava, left atrium, left ventricle, lungs, right atrium, right ventricle, aorta D. Vena cava, right atrium, right ventricle, lungs, left atrium, left ventricle, aorta Recap Quiz - Circulation The tissue layer common to all blood vessels is the: A. Circular smooth muscle B. Endothelium C. Longitudinal straited muscle D. Connective tissue Recap Quiz - Circulation The transfer of oxygen to the body's cella take place in the: A. Arteries B. Arterioles C. Capillaries D. Venules E. A, B and C Recap Quiz - Circulation Haemoglobin, contained in leukocytes, transports oxygen throughout the body: A. True B. False Week 4: Digestive System Resources Chapter 42 (Animal digestive systems) (Pages 974 – 1027) myLMS notes, links, articles, etc. Animal nutrition Animal nutrition An adequate diet must satisfy three needs: Chemical energy for cellular processes, Organic building blocks for macromolecules, Essential nutrients. Nutrition constitutes the process by which an animal takes in and makes use of food to meet these needs The activities of cells, tissues, organs, and whole animals depend on sources of chemical energy in the diet. This energy is used to produce ATP, which powers processes ranging from DNA replication and cell division to vision and flight Essential Nutrients Essential nutrients in the diet include: Certain amino acids and Fatty acids Vitamins and minerals. The key functions of essential nutrients include: Serving as substrates of enzymes Coenzymes Cofactors in biosynthetic reactions Can you think of any examples of essential nutrients? Essential Amino Acids 20 amino acids to make Plants and microorganisms normally can produce all 20 Most animals have the enzymes to synthesize about half of these amino acids, but diet must include sulfur and organic nitrogen. Eight essential amino acids: Isoleucine, leucine, Lysine Methionine Phenylalanine, threonine, tryptophan, And valine Essential Fatty Acids Although animals can synthesize many fatty acids, they lack the enzymes to form the double bonds found in certain required fatty acids. In mammals, they include: Linoleic acid α-Linolenic acid Arachidonic acid Eicosapentanoic acid Docosahexanoic acid ω3- Polyunsaturated fatty acids ω3- Polyunsaturated fatty acids Animals typically obtain ample quantities of essential fatty acids from seeds, grains, and vegetables in their diet. Vitamins Vitamins are organic molecules that are required in the diet in very small amounts (0.01-100 mg/day, depending on the vitamin). The 13 vitamins required by humans vary in both chemical properties and function Vitamin B2 e.g. is a water-soluble vitamin that is converted in the body to FAD, an important coenzyme (e.g. cellular respiration) Vitamins Minerals Dietary minerals are inorganic nutrients, such as iron and sulfur Are usually required in small amounts (1 mg to about 2,500 mg/day) Minerals have diverse functions in animal physiology: Some are assembled into the structure of proteins; E.g. iron is incorporated into the oxygen carrier hemoglobin as well as some enzymes Others, such as sodium, potassium, and chloride, are important in the functioning of nerves and muscles and in maintaining osmotic balance between cells and the surrounding body fluid. Animal diet Animals obtain and ingest their food in various ways: Herbivores: plant based diet Carnivores: meat based diet Omnivores: plant and meat based diet Can you give any examples? Most animals are opportunistic feeders. Deer are herbivores, but occasionally eat insects, worms, or bird eggs. Similarly, herring gulls eat marine invertebrates, insects, and small fishes, but also human refuse. Note that microorganisms are an unavoidable “supplement” in every animal’s diet. Animal Ingestion – Class activity Mode of feeding Meaning Examples (3) Suspension feeder Substrate feeder Fluid feeder Bulk feeder Animal ingestion Suspension Sift small organisms or food Feeders particles from water Substrate Live in or on their food source and Feeders eat their way through it Fluid Suck nutrient-rich fluids from a Feeders living host Bulk Ingest large pieces of food Feeders Animal digestion Digestion Food is broken down into molecules small enough for the body to absorb. Both mechanical and chemical processes Mechanical digestion: chewing or grinding, breaks food into smaller pieces, increasing surface area. Food particles then undergo chemical digestion, cleaving large molecules into smaller components. This is necessary because animals cannot directly use the proteins, carbohydrates, nucleic acids, fats, and phospholipids in food. These molecules are too large to pass through cell membranes and also are not all identical to those the animal needs for its particular tissues Intracellular Digestion Food vacuoles: Cellular organelles in which hydrolytic enzymes break down food Simplest digestive compartment Hydrolysis of food inside vacuoles, called intracellular digestion Cell engulfs solid food by phagocytosis or liquid food by pinocytosis Newly formed food vacuoles fuse with lysosomes, organelles containing hydrolytic enzymes. Brings food in contact with these enzymes, allowing digestion to occur safely within a compartment enclosed by a protective membrane A few animals, such as sponges, digest all their food in this way Extracellular Digestion In most animal species, hydrolysis occurs largely by extracellular digestion Breakdown of food in compartments that are continuous with the outside of the animal’s body. One or more extracellular compartment for digestion enables ingestion of larger pieces of food than can be ingested by phagocytosis. Simple body plans typically have a digestive compartment with a single opening. Known as a gastrovascular cavity Small freshwater cnidarians called hydras provide a good example Digestive system – a map Digestive system – a map Anus Large intestine Small intestine Stomach Oesophagus Spinchters Oral cavity Peristalsis 4 stages of food processing ❑ Ingestion is the act of eating ❑ Digestion is the break down of food into molecules small enough for the body to absorb ❑ Absorption is the uptake of the products of digestion by cells lining the digestive tract ❑ Elimination is the removal of undigested materials out of the digestive tract. The four main stages of food processing. 1. Ingestion Ingested and chewed in the mouth or oral cavity Forms a bolus via mechanical digestion Humans are bulk feeders! 2. Digestion Mechanical ❑ Teeth have special shapes – cut, mash and grind ❑ Saliva released by salivary glands ❑ Saliva contains mucus – a vicious mixture of water, salts, cells and glycoproteins ❑ This lubricates the food for easy swallowing, facilitates taste and smell, protect gums against abrasion ❑ During chewing, tongue movement acts on saliva and food – shape it into bolus ❑ Smaller pieces are easier to swallow ❑ Smaller pieces have more surface area exposed to digestive fluids 2. Digestion Chemical ❑ Breaks down large organic molecules into their components ❑ Proteins split into amino acids ❑ Polysaccharides into monosaccharides ❑ Nucleic acids into nucleotides ❑ Fats are broken down into glycerol and fatty acids ❑ Animals cannot use large molecules: ✓ Cannot cross the plasma membrane ✓ Small molecules needed as building blocks for molecules for their own body 2. Digestion – Class Activity Chemical Happens via enzymes Complete the table below Macromolecule Broken into Enzyme Enzyme Location of secreted by chemical digestion Carbohydrates Lipids Protein Nucleic acids  2. Digestion Chemical Oral cavity Stomach Small intestine ❑ Releases salivary amylase ❑ Stores food – elastic ❑ Duodenum – chyme mixes with ❑ Digestion of polysaccharides ❑ Process food into a liquid digestive juices from pancreas,, and disaccharides suspension liver, gall bladder and intestinal ❑ Forms a chyme using gastric gland cells juice ❑ Epithelium of duodenum – ❑ Gastric juice contains HCl and source of digestive enzymes pepsin enzyme ❑ Bile secreted from liver – assists ❑ Stomach cells release inactive in digestion of lipids pepsinogen, which is activated into pepsin by HCl ❑ Hugh muscular activity of stomach 3. Absorption Contents move to jejunum and ileum via peristalsis Finger shaped projections “villi” – epithelial cells of which have further projections “microvilli” face lumen of intestine Enormous surface area Transportation: active or passive Hepatic portal vein – capillaries carrying nutrient rich blood ends up in liver first ✓ Liver regulates distribution of nutrients ✓ Allows removal of toxic substances Fat digestion and absorption Role of bile and enzyme lipase Fatty acids and monoglycerides get absorbed into intestinal cell Come together to form triglycerides – incorporated into chylomicrons Enter lacteals an carried away via lymph 4. Elimination Large intestine Rectum and anus Waste and undigested material – feces Water reclaimed by large intestine Evolutionary adaptations Dental adaptations Stomach and intestinal adaptations Mutualistic adaptations Evolutionary adaptation How can animals digest food without digesting its own cells and tissues? Evolutionary adaptation Digestive enzymes hydrolyse the same biological molecules that animals are made of – yet they don’t end up digesting themselves!! Evolutionary adaptation: chemical digestion takes place within specialised compartments. Sponges No compartments, digest food in vacuoles Cnidarians and flatworms Gastrovascular cavity with single opening of mouth Food enters mouth, enzyme breaks it, food moves into cells lining the compartment and digestion is completed in vacuoles. Undigested material expelled from mouth Evolutionary adaptation Alimentary canal Most animals have an alimentary canal with mouth, anus and special regions with one-way flow of food One way flow: pharynx, esophagus, stomach, intestine, anus Humans have a stomach Some animals have a crop and gizzard Hence alimentary canal allows compartmentalization Flow of food in sequence Gastrovascular cavity vs Alimentary canal Gastrovascular cavity has a single opening. Its purpose is digestion. Alimentary canal is a tube-like structure with multiple compartments, it does not have a single opening, but mouth and anus. Purpose includes absorption of nutrients Feedback Circuits Regulation of Digestion No need for digestive system to be active between meals Processing is activated step-wise As food reaches each new compartment, it triggers the next stage of processing Nervous reflexes stimulate the release of saliva when food enters oral cavity and orchestrates swallowing when a bolus reaches the pharynx. The arrival of food in the stomach stimulates churning and releasing of gastric juice. These events, as well as peristalsis, is controlled by the enteric nervous system Regulation of Digestion Regulation of Digestion Regulation of Digestion Regulation of Energy Storage When more energy-rich molecules are ingested than metabolically needed, the energy needs to be stored. In humans, excess energy is stored as glycogen in muscle and liver cells – excess beyond this is stored in fat in adipose tissues. During times of energy deficit, liver glycogen is used first, then drawing on muscle glycogen and fat. Fats are especially high in energy – liberating 1 cell of fat provides nearly twice the energy of carbohydrates! Regulation of Energy Storage Glucose homeostasis o Synthesis and breakdown of glycogen is important for: ▪ Energy storage ▪ Maintaining metabolic balance o Normal range for glucose in humans: 70 – 1100mg/100mL o Glucose is vital for cellular respiration and key for carbon skeletons in biosynthesis – maintaining blood glucose is essential! o Glucose homeostasis relies on the antagonistic effects of 2 hormones: insulin and glucagon Glucose homeostasis Regulation of Appetite and Consumption  SELF - STUDY Describe the specialised digestive systems of an earthworm, a grasshopper and a bird. Reminders