Cells as the Basis of Life

• Cell metabolism is a biochemical process that takes place in the cell
• cell metabolism synthesises proteins, carbohydrates, lipids, and nucleic acids
• cell metabolism is critical to the survival of cells
• the internal membranes of the mitochondria is folded to form cristae
• cristae increases the SA:V for attachment of ATP synthase
• ATP synthase is important for aerobic respiration
• the internal membranes of chloroplast have:

  • membranous flattened sacs called thylakoids
  • photosynthetic pigments (chlorophyll) within the thylakoid membranes
  • host the first stage of photosynthesis (where pigments are able to trap light energy)
• biochemical processes are influenced by specific enzymes
• in a metabolic pathway there are:

  • many regulated steps
  • each step loses energy as heat energy
  • some steps produce intermediate compounds
  • specific enzymes are required at each step
• cell theory states that all cells arise from pre-existing cells
• Cells contain DNA(hereditary material) which is passed onto daughter cells
• Cells are the units of structure and function in all organisms
• The cell membrane:

  •separates the cell from its surroundings

  •controls the exchange of materials

  •nutrients and wastes, between the cell and its environment
• the mitochondria plays a role in:

  •cell communication

  •cell adhesion

  •the binding of hormones.
• The cell is fluid, rather than being a rigid or solid structure.
• Proteins and lipids move sideways throughout the membrane for the requirements of the cell
• The fluid mosaic model:

  The term mosaic is used to describe the various molecules (embedded protein, carbohydrate, cholesterol etc.) that are scattered throughout the membrane.
• Membrane Components:

  Integral proteins:

  •permanently in the bilayer

  •typically span across the bilayer
• Membrane Components:

  Peripheral proteins:

  •tend to attach temporarily

  •associate with one surface of the membrane
• Membrane Components:

  Cholesterol:

  •component of animal cells

  •Helps to maintain stability of the membrane
• Membrane Components:

  Glycoproteins:

  •Membrane proteins with carbohydrate chains attached
• Membrane Components:

  Glycolipids:

  •Phospholipids with carbohydrate chains attached
• membrane protein functions:

  •Hormone binding sites

  •Cell communication

  •Cell adhesion

  •Channel proteins and pump proteins

  •Cholesterol
• Hydrophobic

  •non-polar

  •are repelled by water
• Hydrophilic (dissolves in water)

  •charged polar end

  •attracts water molecules
• The cell membrane consists of a phospholipid bilayer

  
• Prokaryotic Cells:

  •Unicellular

  •Size: 1- 10 µm

  •One circular chromosome located in the cytoplasm

  •No membrane-bound organelles

  •Contains ribosomes

  •Reproduce by binary fission

  •Cell wall present

  •Cell membrane and cytoplasm present
• Eukaryotic Cells:

  •Mostly 10-100µm

  •Unicellular or multicellular

  •Multiple linear chromosomes located in the nucleus

  •Many different types of membrane-bound organelles

  •Contain ribosomes

  •Reproduce via mitotic division

  •Cell membrane and cytoplasm present

  •Plants have a cell wall present
• Evolutionary theory:

  •Chloroplasts and mitochondria were once ‘free-living’ prokaryotic organisms
• Mitochondria and chloroplasts:

  •have their own DNA

  •circular DNA similar to prokaryotes

  •are similar in size to prokaryotic cells

  •can divide independently- own protein synthesis system including ribosomes similar in size to prokaryotic cell ribosomes.

  •divide by binary fission – not produced directly by genes from the nucleus

  •have inner membranes that resemble the cell membranes of prokaryotes more than the cell membranes of eukaryotes in which they are found.
• Nucleus:

  •Controls all cell activities

  •contains DNA

  •determines which proteins are to be made via protein synthesis, therefore, determine the structure and function (enzymes) of the cells.
• Nucleus:

  nuclear envelope – a double membrane boundary

  •contains many nuclear pores

  •allows some substances to move into or out of the nucleus eg mRNA
• Nucleus:

  •nucleoli (singular (nucleolus))

  •Found within the nucleus (one or more)

  •Appears as a dark mass

  •no membrane

  •Location of ribosomal RNA (rRNA) synthesis.
• Mitochondria:

  •Location of the latter stages of aerobic respiration (energy production).

  •Cells such as muscle cells and sperm cells require a large number of mitochondria.

  •it has a double membrane

  •Inner membrane folded forming a structure called cristae.

  •This structure increases surface area, allowing for the efficient synthesis of ATP (energy).
• Chloroplast:

  Chloroplasts are a type of plastid - double membrane bound organelle involved in the synthesis and storage of food, and is commonly found within the cells of photosynthetic organisms, like plants.
• Chloroplasts have a double membrane
• chlorophyll is a photosynthetic pigment
• Grana are stacks of thylakoids
• stroma is the fluid surrounds grana
• Vacuoles are fluid filled spaces surrounded by a membrane