Structure and Functions in Living Organisms

• Levels of Organisation:

  1. Organelles
  2. Cells
  3. Tissues
  4. Organs
  5. Organ Systems
• Nucleus: contains genetic material that controls cells activities
• Cell membrane: controls substances that enter and leave cell
• Cytoplasm: where chemical reactions take place and contains enzymes that control reactions
• Mitochondria: where aerobic respiration takes place
• Ribosomes: site of protein synthesis
• Chloroplasts: contain chlorophyll which absorbs sunlight for photosynthesis
• Cell wall: supports and strengthens the cell
• Vacuole: stores cell sap and supports the cell
• Organelle: structures within a cell
• Tissue: same cells working together to carry out a same specific function.
• Organs: different tissues working to carry out same function
• Organ system: different organs working to carry out same function
• Specialised cell: adapted to carry out a particular function
• Differentiation: process that cell becomes specialised
• Stem cells: cells that are undifferentiated. They are found in human embryos
• Advantages of using stem cells:

  • they are easy to extract
  • they can be turned into any type of cell
  • they can help cure ill humans
• Disadvantages of using stem cells:

  • they are a potential human life so could be moral issue
  • the body will reject them without the use of drugs
  • they may produce cancer cells
• Advantages of using adult stem cells:

  • No human embryo will be destroyed
  • The cell will not be rejected from body
  • They have ability to cure ill human
• Disadvantages of using adult stem cells:

  • They are difficult to extract
  • They can only be turned into one cell
• Chemical elements in Biological Molecules:

  • Carbohydrates: Carbon, Hydrogen, Oxygen
  • Proteins: Carbon, Hydrogen, Oxygen, Nitrogen, Sulphur
  • Lipids: Carbon, Hydrogen, Oxygen
• Carbohydrate monosaccharides: Glucose, Galactose, Fructose
• Carbohydrate disaccharides:

  Maltose - Glucose and Glucose

  Sucrose - Glucose and Fructose

  Lactose - Glucose and Galactose
• Disaccharide: two monosaccharides covalently bonded together
• Carbohydrate polysaccharides: Starch, Glycogen, Cellulose
• Protein monomer: amino acid

  Protein polymer: polypeptide

  20 amino acids exist naturally in organisms
• Lipid monomer: Glycerol and 3 fatty acids

  Lipid polymer: Lipid

  Structure is called a triglyceride
• Food Tests:

  Benedict solution - tests glucose, starts blue and goes to red if there is lots of glucose (blue to green to yellow to orange to red)

  Biuret solution: tests protein, starts blue and goes pink if present

  Sudan III solution: tests lipids, separate red layer forms if present

  Iodine solution: tests starch, starts brown and goes blue-black
• Enzyme: biological catalyst that speeds up metabolic reactions
• Enzymes have an active site that matches shape of the substrate. They are specific to only one substrate. They work best at body temperature which is 37 degrees C and at the right pH. If they are at too high a temperature or the wrong pH, they will denature.
• Diffusion: net movement of particles from high concentration to low concentration down a concentration grdient
• Osmosis: net movement of water molecules from a region of high water potential to a region of low water potential down a water potential gradient across a partially permeable membrane
• Factors affecting diffusion:

  Temperature - as it increases, kinetic energy increases and therefore there are more successful collisions of particles

  Concentration gradient - the bigger the gradient, the faster diffusion occurs

  Diffusion distance - the shorter the distance, the faster diffusion occurs

  Surface Area: Volume - the bigger the SA:Vol, the faster diffusion can occur
• Osmosis in an animal cell:

  If surrounding solution has a high water potential, then the animal cell will swell and burst as water will move into the cell across the partially permeable cell membrane.

  If the surrounding solution has a lower water potential than the animal cell, it will shrink and shrivel as water moves out of cell across partially permeable membrane.

  
• Osmosis in a plant cell:

  If the surrounding solution has a higher water potential than the plant cell, the cell will swell and become turgid as water moves in.

  If the surrounding solution has a lower water potential than the plant cell, the cytoplasm will shrink from the cell wall and the cell will become plasmolysed.

  
• Active Transport: particles move from a low concentration to a high concentration against a concentration gradient across a partially permeable membrane
• Components in a Balanced Diet:

  • Carbohydrates
  • Protein
  • Lipids
  • Water
  • Vitamin A, B, C, D
  • Calcium
  • Iron
  • Fibre
• The function of carbohydrates in the diet is as an energy source. Carbohydrates are found in bread and pasta.
• The function of proteins in the diet is growth and repair of cells. It can be found in meat.
• The function of lipids in the diet is to provide insulation and as an energy source. It is found in butter and fish.