Organisation-Digestion

• Multicellular organisms have many levels of organisation
• Cells are the basic building blocks of all living organisms
• Unicellular organisms are made from one cell, whereas multicellular organisms are made up of collections of cells
• In complex multicellular organisms, cells are specialised to carry out particular functions
• Specialised cells form tissues, which form organs in organ systems
• Examples of organ systems in humans are the digestive system (provides the body with nutrients) and the respiratory system (provides the body with oxygen and removes carbon dioxide)
• Cells - Basic functional and structural units in a living organism
• Tissue - A group of cells of similar structure working together to perform a particular function
• Organs - Made from a group of different tissues working together together to perofrm a particular function
• Organ Systems - Made from a group of organs with related functions working together to perform body functions within the organism
• The role of the stomach is to start protein digestion
• The stomach produces proteases like pepsin, which digests proteins into amino acids
• Acid produced by glandular tissue in the stomach aids protein digestion by helping proteins unravel so that enzymes can break the bonds holding the amino acids together
• The stomach is one of the organs that make up the digestive system
• The digestive system's role is to break down large insoluble molecules into smaller, soluble food molecules to provide the body with nutrients
• Three types of tissue found in the stomach are muscular, epithelial, and glandular, which work together to allow the stomach to carry out its role
• Mouth:

  • Begins the digestion of carbohydrates
• Stomach:

  • Begins the digestion of protein
  • Small molecules such as alcohol are absorbed
• Small intestine (duodenum):

  • Continues the digestion of carbohydrate and protein
  • Begins the digestion of lipids
• Small intestine (ileum):

  • Completes the digestion of carbohydrates and proteins into single sugars and amino acids
  • Absorption of single sugars, amino acids, fatty acids, and glycerol
• Large intestine:

  • Absorption of water
  • Egestion of undigested food
• The large intestine is home to hundreds of species of bacteria
• These bacteria form a microbial ecosystem known as the microbiota or gut flora
• The gut flora plays an essential role in human digestion by:

  • Breaking down substances we can't digest, such as cellulose
  • Supplying essential nutrients
  • Synthesising vitamin K
  • Providing competition with harmful bacteria to restrict their growth
• Taking antibiotics can disrupt the gut microbiota, leading to short-term problems with digestion
• Digestive enzymes work outside of cells to digest large, insoluble food molecules into smaller, soluble molecules that can be absorbed into the bloodstream
• Metabolism is the sum of all reactions happening in a cell or organism, involving the synthesis or breakdown of molecules
• Enzymes are biological catalysts made from protein that speed up chemical reactions in cells
• Substrates temporarily bind to the active site of an enzyme, leading to a chemical reaction and the formation of products that are released
• Enzymes remain unchanged at the end of a reaction and can process hundreds or thousands of substrates per second
• Enzymes catalyze specific chemical reactions in living organisms, with each enzyme usually catalyzing one particular reaction
• Enzymes have specific three-dimensional shapes determined by the order of amino acids in the protein chain
• The 'lock and key theory' explains enzyme action, where the enzyme's active site and substrate(s) fit together perfectly like a lock and key
• Enzymes work fastest at their optimum temperature, and denature at high temperatures, losing their shape and activity
• The optimum pH for most enzymes is 7, but some enzymes have different optimum pH levels for activity
• Changes in pH can alter the shape of the enzyme's active site, affecting substrate binding and enzyme activity
• The specific shape of an enzyme is determined by the amino acids that make the enzyme
• The three-dimensional shape of an enzyme is especially important around the active site area; this ensures that the enzyme’s substrate will fit into the active site enabling the reaction to proceed
• Enzymes work fastest at their ‘optimum temperature’ – in the human body, the optimum temperature is around 37⁰C
• Heating to high temperatures (beyond the optimum) will start to break the bonds that hold the enzyme together – the enzyme will start to distort and lose its shape – this reduces the effectiveness of substrate binding to the active site reducing the activity of the enzyme