Bio 1.1

• There are three units of length.

  1. Milimeter
  2. Micrometer
  3. Nanometer
• There are 2 types of cells.

  1. Eukaryote cell (has a true nucleus)
  2. Prokaryote cell (lacks a true nucleus)
• Each cell can release their own energy.

  1. Cells contain mitochondria
  2. Mitochondria produces ATP
  3. ATP hydrolyses to release energy
• The 3 principles of cell theory

  1. All living organisms consist of one cell or more
  2. Cells are the basic units of life
  3. All cells come from pre-existing cells
• Cells cannot grow to be very large.

  Reason:

  1. Volume of cell determines the level of metabolic activity occuring in the cell
  2. When surface area increases, surface area to volume ratio of cell will decrease. This will decrease the rate of movement of substances in/out of cell through cell membrane, and may not be able to keep up with the cell requirments
• Eukaryotic cells are compartmentalized by single or double membranes.

  Single membrane: Golgi Apparataus, Lysosome

  Double membrane: Mitochondria, Chloroplast, Nucleus

  No membrane: Nucleolus, Cell membrane, Ribosomes, Centriole
• Advantages of being compartmentalized

  1. Increased efficiency
  2. Localized Conditions
  3. Damage Containment
  4. Increase concentration of substrates
  5. Regulation of metabolic pathways
• Cell Surface Membrane

  Structure:

  1. Lipid bilayer made of phospholipids with proteins embedded in it
  2. It is selectively permeable

  Function:

  1. It seperates the cell from extra-cellular environment
  2. It only allows selected substances to move in/out of cell(charged ions or polar molecules cannot move into cell)
• Nucleus structure:

  • Bordered by a double membrane nuclear envelope
  • Contains nucleoplasm, a fluid-like substance
  • Nucleoplasm contains genetic material (DNA), ribonucleic acid (RNA), associated proteins, and enzymes required for replication and transcription of DNA
  • DNA containing ribosomal RNA genes cluster together to form the nucleolus, the site of RNA replication
• Nucleus function:

  • Controls all cellular activities
  • DNA contains genes that allow certain traits to be passed down to the next generation as it carries hereditary information
  • DNA is closely associated with histones to form chromatin
  • DNA usually occurs in the form of chromosomes, but in non-dividing cells, DNA is in the form of chromatin
  • Chromatin condenses to form chromosomes, which are highly condensed
• There are 2 types of chromatin

  1. Euchromatin (less condensed DNA)(more transcribed)
  2. Heterochromatin (more condensed DNA) (less transcribed)
• Nuclear Envelope:

  • Structure:
  • A double membrane that borders the nucleus
  • The outer membrane is continuous with the rough endoplasmic reticulum
  • The inner membrane is smooth and in contact with the nucleoplasm
  • Contains multiple nuclear pores ranging from 40-100nm in diameter
• Nuclear envelope

  Function:

  • Enables compartmentalization of eukaryotic DNA, allowing DNA to carry out its function without interruption from processes in other parts of the cell
  • Regulates the export of mRNA from nucleolus to cytoplasm and import of ribosomal proteins into the nucleus
  • Prevents DNA from moving out of nucleus
• Nucleolus

  Structure:

  Tiny, rounded, darky-stained structure.

  Function:

  1. Site of rRNA synthesis, by transcription of rRNA genes
  2. Ribosomal sub-units are assembled, by associating ribosomal proteins with ribosomal ribonucleic acid
• Endomembrane system

  1. System where internal membranes of a eukaryotic cell work together for protein and lipid synthesis and transport

  The membranes are related by

  1. Direct physical touch
  2. Transfer of membrane segments as vescicles
• Organelles involved in endomembrane system:

  1. Golgi Apparataus
  2. Outer membrane of nuclear envelope
  3. Vescicles
  4. Endoplasmic Rectiulum
  5. Cell surface membrane
  6. Lysosome
• Endoplasmic recticulum:

  Structure:

  1. Contains an extensive network of membranes folded into sheets, tubes, sacs
  2. The ER membrane is enclosed to form cisternae
  3. It is continuous with the outer membrane of nuclear envelope
• Rough endoplasmic recticulum:

  Structure:

  1. Cisternae usually flattened
  2. It has membrane-bound ribosomes and proteins embedded on the membrane giving it a granular look

  Function:

  1. Synthesises proteins that will be sent to other parts of cells by transport vescicles
  2. Channel proteins provide binding sites for ribosomes to dock and sythesise polypeptides directly into cisternae
  3. Chaperon proteins help with folding of polpeptides into 3-d proteins conformation
  4. Enzymes involved in glycosylation of proteins to form glycoproteins.
• Smooth Endoplasmic Recticulum:

  Structure:

  1. Cisternae usually tubular
  2. No membrane-bound organelles giving it a smooth appearance

  Functions:

  1. Production and transportation of cellular lipids, membrane phospholipids and steroid hormones
  2. Stores calcium ions in muscle cells
  3. Helps liver cells with metabolism of carbohydrates
  4. Helps with detoxification of drugs in liver cells by hydroxlyation
• Golgi Apparataus:

  Structure:

  1. Flattened membranes(cisternae) stacked on top of each other
  2. Cis-face(facing nucleus)
  3. Trans-face(facing cell membrane)
  4. Associated with golgi vescicles

  Functions:

  1. Sorting and packaging of proteins to be transported to different parts of cell via addition of molecular identification tag.
  2. Restores cell membrane lost by endocytosis
  3. Productions of plant polysaccharides(pectin)
  4. Forms lysosomes that contain hydrolytic enzymes
  5. Modification of proteins and lipids by chemical modification
• Lysosomes:

  Structure:

  1. Vescicles that range from 0.2um to 0.5um in diameter
  2. Contain high concentration of hydrolytic enzymes
  3. Internal environment is acidic

  Functions:

  1. Binds with old/damaged organelles and hydrolyses them for recycling of components
  2. Breaks down substances that enter the cell due to phagocytosis
  3. Carries out intra-cellular hydrolysis in which it breaks down carbohydrates, nucleic acids, lipids, proteins, by hydrolysis, by action of hydrolytic enzymes.
• Synthesis of polypeptides by rER

  1. Ribosomes translate mRNA to form a single short peptide bond, complimentary to SRP
  2. SRP binds with complimentary SRP protein receptor on the membrane of endoplasmic recticulum, allowing ribosomes to dock onto the membrane.
  3. Ribosomes can continue synthesis of polypeptides, directly into cisternae
  4. Synthesised polypeptides are folded into 3-d proteins conformation with help of chaperon proteins in cisternae.
• Mitochondria structure:

  • Cylindrical in shape under electron micrograph
  • Generally large, ranging from 0.5um to 1.5 um in width, 3.0um to 10.0um in length
  • Contain their own DNA, circular chromosome, and 70S ribosomes
  • Double membrane: outer membrane is smooth, while inner membrane is folded, forming cristae
  • Between the membranes is a space called intra-membrane space
  • The inner-membrane contains a semi-fluid substance known as matrix
• Mitochondria functions:

  • Most processes involve production of ATP by cellular aerobic respiration
  • Cristae hugely increases surface area to volume ratio for oxidative phosphorylation to occur
  • Inner membrane embedded with respiratory proteins and enzymes
  • Matrix contains enzymes required for link reactions and Krebs Cycle
• Thylakoid membrane


  A membrane system in the chloroplast where photosynthetic pigments and proteins are embedded
• Chloroplast


  Large organelle in the cells of plants and algae that contains a green pigment called chlorophyll
• The chloroplast acts as a site for photosynthesis
• The chloroplast contains its own circular DNA and 70S ribosomes
• Chloroplast

  • Double membrane
  • Interior contains a third membrane system called the thylakoid membrane
  • Thylakoid membranes fold and stack to form grana
  • Grana are connected by intergranal membranes
  • Photosynthetic pigments and proteins are embedded into the thylakoid membrane
  • Contains its own circular DNA and 70S ribosomes
  • Suspension of a fluid substance called stroma
  • Divides independently of the cell
  • Expresses proteins unique to chloroplast
  • Acts as a site for photosynthesis
  • Involved in both light-dependent and light-independent reactions of photosynthesis
• Stroma


  A fluid substance in the chloroplast where many enzymes and compounds necessary for independent reactions are located
• The chloroplast expresses proteins unique to chloroplast
• Calvin cycle


  A series of light-independent reactions that convert carbon dioxide and other compounds into glucose
• Ribosomes


  Tiny structures, approximately 25 nm in diameter, that act as the site for protein synthesis
• Eukaryotes ribosomes

  20 nm in diameter, with a large 60S subunit and a small 40S subunit
• Functions

  • Produce intracellular proteins
  • Produce extracellular secretory and membrane proteins
• Each subunit

  Made up of ribosomal protein and ribosomal ribonucleic acid (RNA)
• Subunits

  Formed in the nucleolus
• Ribosomes have two subunits
• Prokaryotes ribosomes

  70S ribosome, with a large 50S subunit and a small 30S subunit
• Ribosome diameter

  Approximately 25 nm