Chapter 8

• All living organisms share key characteristics:

  • Made up of one or more cells
  • Require energy for cell function (light energy or chemical energy)
  • Need matter (gases, nutrients, ions) to support life processes
  • Have the ability to respond to stimuli
  • Must remove wastes
• Energy comes from either:

  • Photosynthesis: capturing light to produce usable energy
  • Cellular Respiration: converting chemical energy from food (carbohydrates, fats) into energy cells can use
• Chemosynthesis

  A process where bacteria (nitrogen-fixing bacteria, chemotrophs) make energy from inorganic compounds, found in places with no sunlight (e.g. deep sea trenches)
• Metabolism 


  is all of the chemical reactions that take place inside a cell or organism: the total sum of the reactions.
• Some organisms use metabolism to maintain stable internal conditions
• Nutrients are essential for all living things

  
  

  • Autotrophs: make their own nutrients through photosynthesis or chemosynthesis
  • Heterotrophs: obtain nutrients by eating autotrophs or heterotrophs
• Cellular processes such as building and breaking down complex molecules occur though chemical reactions
• Assimilation

  Process where an organism converts absorbed nutrients into complex molecules to be used in the body
• Absorption

  Transport nutrients into the organism, followed by assimilation into the organism's structure
• Cell theory

  • The cell is the basic unit of life
  • Cell arise from pre-existing cells
  • Early living organisms is made up of one or more cells
• Discovery of Cells

  • Cells were first discovered and names by Robert Hooke in 1655
  • Hooke said they looked like "cellula" -- small rooms that monks lived in
  • Thats where the term cells comes from
• Notable Scientists for Cell Theory

  • Three scientists are notable for cell theory; Robert Hooke, Matthias, Jakob Schleiden, and Theodor Schwann
  • Shleiden and Schwann developed the first cell theory in the late 1830s
• Microscopy

  Is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye
• The quality of an image depends on:

  Magnification: a scaling up of an object's size; a measure of a degree of enlargement

  Resolution: the measure of the clarity of the image; the minimum distance between two distinguishable but seperate points
• Light Microscopes

  • Uses light to create the image
  • Glass lenses are used for magnifying
  • Magnification up to 400x
  • Can see cell membranes, cell membrane walls nuclei, chloroplasts, cytoplasm
  • Specimen can be alive
• Electron Microscopes

  • Uses electrons to create the image
  • Electromagnets used for magnifying
  • Magnification up to 1 000 000x or more
  • Can see small organelles or atoms
  • Specimen can not be alive
• Common Anatomical Features of all Cell

  • The contents of the cell are enclosed in a cell membrane
  • There is a semi-fluid substance inside the cell membrane called the cytosol
  • Cells contain chromosomes, which contains genes
  • All cells have ribosomes, which function to make proteins
• Cells are classified into two main groups:

  Prokaryotes: single celled organisms (unicellular) that lack membrane-bound organelles, do not have a nucleus, are significantly smaller than eukaryotes and have a single, circular chromosome made of DNA -- grouped within two domains, Bacteria and Archaea

  Eukaryotes: can be unicellular or multicellular, have internal membrane-bound organelles, has nucleus, relatively larger, have linear chromosomes -- found in Kingdown Protista, Fungi, Plantae, Animalia
• Key Structures in Prokaryotic Cells

  1. Cytoplasm -- make up internal bulk of the cell, site of chemical reactions necessary for cell survival, made up of cytosol and structures like chromosomes, plasmids and ribosomes
  2. Ribosomes -- scattered through cytosol, site of protein synthesis, essential for cell growth, repair and function
  3. Genetic Material -- prokaryotes have a single, circular chromosome (DNA) located in cytoplasm, carries instruction for protein synthesis, contains plasmids which are small rings of DNA
• Eukaryotic Cells

  • contains various membrane-bound organelles that perform specialised function
  • organelles allow different chemical reactions to occur simultaneously
  • membrane-bound compartments increase efficiency by maximising surface for biochemical processes
• Key Structures in Eukaryotic Cells 


  1. Organelles -- membrane-bound compartments that carry out special tasks
  2. Nucleus -- contains DNA arranged in linear chromosomes, it coordinates activities of the cell by controlling protein production, it is surrounded by membrane that separates the DNA from cytoplasm and aids in cell division
• What is the structure of the cell membrane?

  It is a flexible phospholipid bilayer.
• What is the function of the cell membrane?


  It controls the entry and exit of substances, enclosing the cell.
• What is cytoplasm?


  It is the cell contents between the nucleus and membrane, including organelles.
• What is the role of cytosol?


  Cytosol is the semi-liquid part of the cytoplasm where metabolic activity occurs.
• What are the two types of Endoplasmic Reticulum (ER) and their functions?


  • Smooth ER: Lacks ribosomes, involved in lipid production.
  • Rough ER: Has ribosomes, site for protein synthesis.
• What is the function of the Golgi apparatus?


  It modifies, sorts, and packages proteins from the ER for transport.
• What do lysosomes contain and what is their function?


  Lysosomes contain sacs of enzymes that break down foreign substances and macromolecules.
• What is the primary function of mitochondria?


  Mitochondria are the site of aerobic respiration, producing ATP.
• What is contained within the nucleus?


  The nucleus contains DNA and controls cell activities.
• Where are ribosomes found and what is their function?

  Ribosomes are found in the cytosol or rough ER and are the site of protein synthesis.
• What is the role of centrosomes and centrioles in animal cells?

  They play a major role in cell division by organizing spindle fibers.
• What is the function of chloroplasts in plant cells?


  Site of photosynthesis, converting light energy into chemical energy stored in carbohydrates
• What is the composition of the cell wall in plant cells?

  Made up of cellulose
• How does the cell wall benefit plant cells?

  It protects the plant cell, maintains its shape, and prevents water uptake
• What is the role of the large vacuole in plant cells?

  Stores water, nutrients, wastes, and toxins, and provides rigidity for plants
• What are the main structures found in plant cells and their functions?

  • Chloroplast: Site of photosynthesis, converting light energy into chemical energy
  • Cell Wall: Made of cellulose, protects the cell, maintains shape, prevents water uptake
  • Large Vacuole: Stores water, nutrients, wastes, and toxins; provides rigidity
• Specialised and unspecialised cells 


  Cells in our body (e.g blood, liver, brain and nerve cells) are specialised to perform particular function

  Stem cells are unspecialised cells that have the potential to develop into many different kinds of cell

  Unspecialised cells can keep dividing -- specialised cells cant do this
• Endosymbiotic Theory 


  Proposes that mitochondria and chloroplasts originated from free-living bacteria that were ingested by ancient prokaryotes

  Evidence:

  • Both have their own DNA
  • Both can replicate independently of the host cell
  • Both have double membranes (suggesting they were engulfed by another cell)

  This theory suggests that mitochondria and chloroplasts evolved from bacteria and established a symbiotic relationship with their host cells