The Cell

• Open system: exchange matter and energy with their surroundings
• Closed system: exchange energy, but not matter with their surroundings
• Isolated systems: do not exchange matter or energy with their surroundings
• Cells are efficient open systems able to carry out all of the life processes:

  • intake nutrients
  • removal of waste
  • growth and reproduction
  • exchange of gases
• Cells maintain life processes within specialized membrane-bound structures called organelles.
• Ribosomes are the only organelle not enclosed by a membrane
• Cell membrane: protective barrier for the cell: it allows the transport of materials into and out of the cell

  • most important for cell communication
• Nucleus: contains DNA -- the genetic material of the cell that directs all cellular activities.

  • surrounded by the nuclear envelope, which has pores to allow the transport of materials

  
• Cytoplasm: gel-like substance inside the cell membrane where the organelles are suspended.

  • contains the nutrients required by the cell to carry on the life processes

  
• Cell wall: found in plant cells -- rigid frame around the cell that provides strength and support
• Chloroplasts: contain a pigment called chlorophyll that produces a green colour

  • found inly in plants
  • sites of photosynthesis
• Vacoules: membrane-bound vesicles that store water

  • plant cells have a large central vacoule
• Vesicles: membrane-bound structures that store nutrients, products of secretion, and fats

  • transport substances throughout and out of the cell
• Ribosomes: granules that may be attached to the endoplasmic reticulum or free-floating in the cytoplasm

  • sites of protein synthesis
• Endoplasmic reticulum: series of interconnected small tubes that branch from the nuclear envelope

  • materials are transported through these tubes

  
• Rough Endoplasmic Reticulum: has ribosomes attached to it and it associated with protein synthesis

  
• Smooth endoplasmic reticulum: associated with lipid (fat and oil) production
• Lysosomes: sacs in the cell where digestion of a substance occurs. roles of include:

  • defense against invading bacteria
  • destruction of damaged cell organelles
  • programmed cell death
• Golgi Apparatus: consists of flat, disc-shaped sacs involved in secretion

  • receives substances from the endoplasmic reticulum and packages them into vesicles for transport
• Mitochondria: rod-like structure where reactions occur to convert chemical energy in sugars into energy that the cells can use
• Similarities between plant and animal cells:

  • have the same basic chemical composition
  • both have genetic material in the form of DNA that directs cellular activities
  • share may of the same organelles
• Differences between the plant and animals cells:

  • animals cells have centriole which are involved in cell division; plant cells do not
  • plant cells have a rigid cell wall made of cellulose, a type of carbohydrate, while animals cells do not have a cell wall
  • plant cells contain chloroplast
  • plant cells have a large central vacuole; animal cells tend to have small vacuoles