Cells

• Biology


  The study of life (bio = life; logos = study)
• Characteristics of living things (vital functions)

  • Movement
  • Reproduction
  • Sensitivity
  • Growth
  • Respiration
  • Excretion
  • Nutrition
• All organisms are made up of one or more cells
• Unicellular organisms


  Made up of only one cell
• Multicellular organisms


  Made up of many cells
• Cell


  The basic building block of all living things
• Cells


  • Provide structure for the body
  • Take in nutrients from food
  • Convert nutrients into energy
  • Carry out specialized functions
• Organelles


  Specialized structures that perform certain tasks within the cell
• Animal cell


  • Consists of an outer cell membrane, a jelly-like cytoplasm, a nucleus and many mitochondria
• Cell membrane


  Surrounds the cytoplasm and holds the cell contents inside, is thin and flexible, and is selectively permeable
• Cytoplasm


  Jelly-like transparent material which fills the cell and holds several organelles
• Nucleus


  The controlling centre of the cell, contains the genetic material (DNA)
• Mitochondrion


  The organelle where respiration takes place, supplies energy to the cells
• Plant cell


  • Has a cell wall, vacuole and chloroplasts in addition to the structures found in animal cells

  
• Cell wall


  Thick, rigid outer layer made up of cellulose that gives strength and protection to the cell
• Vacuole


  Space inside the plant cell filled with cell sap, creates turgor pressure to maintain cell shape
• Chloroplasts


  Organelles that contain chlorophyll and are important for photosynthesis
• Food granules


  Glucose stored as glycogen in animal cells and starch in plant cells
• Differences between animal and plant cells

  • Animal cell lacks cell wall, vacuole, and chloroplasts
  • Plant cell has cell wall, large vacuole, and chloroplasts

  
• Development of multicellular organisms

  Single-celled organisms evolved into multicellular organisms over millions of years
• Cell differentiation/specialization


  Cells within a multicellular organism have different shapes, structures, and functions
• Examples of specialized cells

  • Red blood cell (transports oxygen)
  • Ciliated epithelial cell (traps dust and microbes)
  • Muscle cell (helps in movement)
  • Nerve cell (carries messages)
  • Ovum/egg cell (female reproductive cell)
  • Sperm cell (male reproductive cell)
  • White blood cell (defends body against microbes)
  • Palisade (leaf) cell (carries out photosynthesis)
  • Root hair cell (absorbs water from soil)
  • Xylem cell (transports water in a plant)
• Levels of organization


  Cells → Tissues → Organs → Systems → Organism