B1.1

• A tissue is a group of cells with a similar structure and function working together
• Organs are collections of tissues, with each organ containing several tissues that work together to perform a specific function
• Muscular tissue churns food and the digestive stomach juices together
• Glandular tissue produces digestive juices in the stomach
• Epithelial tissue covers the inside and outside of organs
• The Pancreas produces hormones that control blood sugar and enzymes that digest food
• The digestive system is a muscular tube that starts at the mouth and ends at the anus, squeezing food through it
• Enzymes produced by pancreatic and salivary glands break down food in the small intestine
• In the small intestine, large insoluble molecules are broken down into soluble ones for absorption into the blood
• The small intestine is where food is digested and absorbed into the blood, with a large surface area covered in villi, a good blood supply, and short diffusion distances to blood vessels for increased diffusion and active transport
• The liver produces bile which helps with digestion
• Carbohydrates are a fuel that provides energy for metabolic reactions in cells, and will be broken down into glucose
• Cellulose is a carbohydrate material found in plants and is important for support
• In the large intestine, water is absorbed from undigested food into the blood
• carbohydrates are a fuel that makes all other reactions in life possible, containing carbon, hydrogen, and oxygen, and are important for energy storage in the body
• Lipids are crucial for cell membrane structure, hormones, and the nervous system
• Lipids are divided into fats (solid) and oils (liquid) and are the most efficient energy store in your body and an important source of energy in your diet
• Lipids are crucial in your cell membrane, as hormones, and in your nervous system
• Proteins are good for:

  • Structural components of tissues like muscles and tendons
  • Acting as catalysts
  • Acting as enzymes, which act as catalysts to speed up chemical reactions but are not used up in the reaction so can be used repeatedly
  • Acting as hormones, such as insulin
  • Acting as antibodies, which destroy pathogens and are part of the immune system
• Enzymes are biological catalysts made up of large protein molecules:

  • The shape of the enzyme is vital for it to work because its active site has to be the correct and unique shape to bind to a substrate molecule
• Amino acids make up proteins in long chains, with 20 different amino acids joined together by special bonds:

  • Different arrangements of amino acids give different proteins, which are folded, coiled, and twisted to create specific shapes allowing other molecules to interact
• Lipids are made up of carbon, hydrogen, and oxygen, are insoluble in water, and are made up of glycerol and fatty acids:

  • Glycerol is always the same, but the fatty acids vary, determining whether the lipid will be a solid (fat) or liquid (oil)
• Proteins are used for building up the cells and tissues of the body and are the basis of all enzymes:

  • Between 15% to 20% of body mass is protein, made up of long chains of amino acid units containing carbon, hydrogen, oxygen, and nitrogen
• Bile is not an enzyme as it does not break down fat molecules; it emulsifies the fat into tiny droplets, increasing the surface area for the enzyme lipase to work on, which enhances the rate of digestion
• Once food is digested into glucose, amino acids, and fatty acids in the small intestine, they pass into the bloodstream to be carried around the body to the cells that need them
• In the digestive system, the stomach lining produces pepsin, a protease enzyme that works best in acidic conditions; the same glands also produce hydrochloric acid to allow the protease enzymes to work effectively and kill bacteria in the food
• Proteins are broken down into amino acids by enzymes called proteases, produced in the stomach, pancreas, and small intestine
• Lipids are broken down into fatty acids and glycerol in the small intestine by the enzyme lipase, produced in the pancreas
• Digestive enzymes work outside of cells and are produced by specialized cells in glands and the lining of the digestive system, enhancing digestion on the system's large surface area
• Carbohydrases are enzymes that break down carbohydrates; starch is broken down into sugars by amylase, produced in the mouth and pancreas
• Enzymes are crucial for metabolic reactions, speeding up specific types of reactions like building large molecules from smaller ones, changing one molecule into another, and breaking down large molecules into smaller ones
• A change in pH can affect enzyme action by altering the forces that hold the protein molecule in place, changing the shape of the active site, and potentially stopping the enzyme from working completely
• The rate of enzyme-controlled reactions increases with temperature up to a point, usually around 40°C, after which high temperatures can denature the enzyme, affecting its structure and decreasing the rate of reaction