human bio

  • Living things are made up of cells whose activities allow the organism to function.
    Cells are made up of:

  • a cell membrane

  • a cytoplasm made up of the jelly-like cytosol and the organelles suspended within it

  • the nucleus

  • a cytoskeleton

  • inclusions.

  • Each organelle has a specific role within the cell.
    Organelles include:

  • the nucleus, which controls the functioning of the cell

  • ribosomes, which are the site of protein synthesis

  • endoplasmic reticulum, which form channels and are involved in storing and transporting molecules

  • the Golgi body, which modifies and packages proteins

  • vesicles, which are membrane-bound
    SaCs

  • lysosomes, which contain digestive enzymes

  • mitochondria, which are the site of cellular respiration

  • cilia and flagella, which are important in moving particles or cells.

  • Cells need to take in their requirements, including glucose and oxygen, and remove wastes produced, including carbon dioxide.

  • The cell membrane provides a physical barrier, controls the movement of substances into and out of the cell, and provides sensitivity and support for the cell.

  • The cell membrane is described by the fluid mosaic model, with a phospholipid bilayer arranged with the hydrophilic heads on the outside and the hydrophobic tails on the inside.

  • Substances are able to move across the cell membrane by various means.

  • With simple diffusion, they move with the concentration gradient directly across the membrane. If the substance is water, the movement is called osmosis.

  • Facilitated transport uses membrane proteins. Channel proteins allow facilitated diffusion, while carrier proteins allow facilitated diffusion or active transport. Facilitated diffusion is a passive process as the movement is with the concentration gradient, whereas active transport is an active process as it is against the concentration gradient.

  • Vesicular transport involves membrane-bound sacs called vesicles.
    Endocytosis brings substances into the cell, whereas exocytosis removes substances.

  • The size of cells is limited by the surface area required to supply the needs of the volume. As the cell gets larger, the surface-area-to-volume ratio decreases, and therefore larger organisms are made up of many cells rather than one large cell.

  • The structure of the body is organised into systems, which are made of organs, which are made of tissues, which are made of cells.
    Tissue is classified as follows:

  • Epithelial: lines and covers organs.

  • Connective: provides support and connection - includes bone, cartilage, tendon, ligaments and fat storage.

  • Muscular: tissue that is able to contract either voluntarily (skeletal muscle) or involuntarily (cardiac or smooth muscle).

  • Nervous: makes up the brain and nerves, carries messages around the body.

  • Each body system is made up of organs that allow it to fulfil a specific function within the organism.