SBI4U – Grade 12 – Biology – Biochemistry Notes

Unit 1: Biochemistry

Importance of Water:

– Water is polar and forms hydrogen bonds with other water molecules

Universal Solvent:

  • –  Dissolves more substances than any other
  • –  Solutes dissolve into the spaces between the molecules

    High Heat Capacity:

– Ensures temperature regulation and homeostasis

  • –  Water requires large amounts of energy to heat it up, and it retains heat very

    well once it has been warmed

  • –  Release of sweat helps expel a source of warmth from the body

    Cohesion and Adhesion:

  • –  Cohesion is two water molecules bonded together (hydrogen bond)
  • –  Adhesion is a water molecule bonding with another substance

    Lower Density as Solid than as Liquid:

– Once water reaches below 4oC, the amount of hydrogen bonds continues to increase; it creates a more structured lattice of water molecules which lowers the density of the water

– Helps to spread the weight of the water out, giving it buoyancy


Types of Molecules:



  • –  Contains carbon, oxygen, hydrogen, nitrogen; carbon is the basis of all life
  • –  Larger in size
  • –  Complex structures containing rings or

    long chains

  • –  Eg. Glucose, Haemoglobin, DNA,


  • –  Usually doesn’t contain carbon (if it does it doesn’t have hydrogen or is simple)
  • –  Smaller in size
  • –  Simple structures containing 2 to 10


  • –  Eg. Carbon dioxide, Oxygen gas,

    Sodium chloride, Calcium phosphate


  • –  A large, complex, molecule (eg. protein, DNA)
  • –  Polymer: a molecule composed of smaller, repeating

    components (individual strand of DNA)

  • –  Monomer: the smallest repeating portion of a polymer (eg.


    Dehydration Synthesis:

  • –  Also known as condensation
  • –  When a water molecule is removed, it forms a new

    bond as a hydrogen and a hydroxyl, creating two new

    and longer polymers


– When a water molecule is formed (from a hydrogen and hydroxyl), it breaks bonds and forms longer polymers

Functional Groups:

  • –  Functional groups are the active sites on molecules
  • –  Responsible for determining the chemical and physical properties of a molecule



Chemical Formula

Chemical Structure

Part of molecules



Alcohols, carbohydrates



Fatty acids and amino acids






Amino acids



Phospholipids, nucleic acid



– Carbohydrates are used for storing energy (glucose), providing structure (cellulose), cell identification and communication

– Monosaccharides are the monomers of carbohydrates; similar ring-like structure, building block of all carbohydrates

– Found in foods like bread, pasta, fruit, vegetables


– The difference between glucose alpha and glucose beta is that on C1​ ​, the hydrogen and the hydroxyl are flipped

  • –  Alpha glucose: hydrogen on top
  • –  Beta glucose: hydroxyl on bottom
  • –  Galactose: C4​ ​has the hydroxyl on top and hydrogen on

    the bottom

    Dehydration Synthesis:

  • –  Water molecules are being removed, which forms new bonds and creates longer polymers
  • –  In carbohydrates, monosaccharides are joined together to form a disaccharide to form a ether bond

– An ether bond is formed by the removal of water from two hydroxyl groups – One water molecule is removed when a disaccharide is formed

Disaccharide Reactions:

  • –  Glucose + Glucose = Maltose + Water
  • –  Glucose + Fructose = Sucrose + Water
  • –  Glucose + Galactose = Lactose + Water





Function of molecule


Alpha glucose


Glucose storage in plants


Alpha glucose

Liver and muscle cells

Glucose storage in animals


Beta glucose

Plant cell walls

Structural support for plant cells


Function of Lipids:

– Used for long-term energy storage (triglycerides), cushioning, protection, vitamin absorption

  • –  Used to make cell membranes (phospholipids)
  • –  Used to make hormones (steroids)
  • –  Used to make waterproof coatings (waxes)


– A bond between glycerol and one fatty acid
– Diglyceride has one glycerol and two fatty

acids, triglyceride has three
– Carboxyl and hydroxyl are responsible for

combining a glycerol to a fatty acid by creating one water molecule (two if diglyceride, three if tri…)

– Forms an ester bond

Saturated and Unsaturated Fatty Acid:

Types of Fats:

Fatty Acids:

– Essential fatty acids are lipids that can’t be produced in the body and therefore must be consumed; they’re found in linoleic acid and omega




Physical State


Saturated Fatty Acid

Only single bonds between atoms

Solid at room temperature

Butter, meat, cream, cheese

Unsaturated Fatty Acid

One or more double bonds between carbon atoms

Liquid at room temperature

Vegetable oil, fish, nuts, avocados


Monomer Units



Glycerol and three fatty acids.

Used for long-term energy storage in plants and animals


Glycerol, two fatty acids, phosphate group

Cell membranes (phospholipid bilayer); phospholipids have a polar head (hydrophilic) and nonpolar tails (hydrophobic) which causes them to form layers


Synthesized from cholesterol, composed of four carbon-based rings
Don’t contain glycerol or fatty acids, but they’re hydrophobic

Cholesterol in the cell membranes
Estrogen and testosterone (sex hormones)

– Trans-fatty acids are unsaturated fatty acids that have undergone hydrogenation in order to become saturated and solid at room temperature

  • –  The body can’t dispose of trans-fatty acids properly so it sits in the body
  • –  Hydrogenation is the process of breaking the double carbon bonds in unsaturated acids so that they only contain single bonds and can bond with more hydrogen to become saturated


– Found in foods like meat, tofu, eggs, nuts


  • –  Structure components of all cells (support, movement, transport)
  • –  Enzymes (catalysts in chemical reactions)
  • –  Regulators of cell processes (hormones, gene control)
  • –  Defense from disease (antibodies)

    Amino Acids:

  • –  Amino acids are the monomers of all proteins
    – There are twenty different varieties of amino acids, differing

    only by their R groups
    – R-groups are side chains that affect bonding and make each

    amino acid unique from one another

  • –  When two amino acids undergo dehydration synthesis, they produce a

    dipeptide and one water molecule

– Held together by a peptide bond of the amino and carboxyl

functional groups

Protein Structure:

  • –  Primary: the order of amino acids
  • –  Secondary: Alpha helix or beta-pleated sheet
  • –  Tertiary: Bends and kinds in secondary structure

    due to interaction of R groups

  • –  Quaternary: two or more polypeptide chains join

    together to make a globular-shaped structure

    Essential Amino-Acids:

– These are proteins that are needed by the body but can’t be synthesized in it

– Non-essential amino acids can be produced in the body

Complete Protein Foods:

– A complete protein food contains all 9 essential amino acids; it doesn’t require you to eat any other food in order to reach this full balance



Nucleic Acid:

– Includes DNA, RNA and adenosine triphosphate (ATP)


  • –  DNA: makes up genetic material, making instructions for proteins
  • –  RNA: involved in making proteins
  • –  ATP: energy used for the cell (created in the mitochondria

    through cellular respiration)


  • –  Monomer unit for all nucleic acid
  • –  Composed of sugar, phosphate group, and nitrogen base

    (adenine, thymine, guanine, cytosine)

    • –  Adenine and guanine are similar in shape, as are thymine

      and cytosine

    • –  Adenine and thymine bond through a double hydrogen


    • –  Guanine and cytosine bond through a triple hydrogen bond

      DNA and RNA:

      Adenosine Triphosphate (ATP):

  • –  Composed of three phosphate groups, one ribose (sugar) and one nitrogen base
  • –  Dehydration synthesis of ATP from ADP + P uses energy since bonds are created (endergonic reaction)
  • –  Hydrolysis of ADP + P from ATP releases energy since bonds are broken (exergonic) reaction


    Biochemical Reaction:

– Process that changes biochemical substances into others



  • –  Double-stranded helix
  • –  Composed of deoxyribose sugar
  • –  Contain nitrogen bases of adenine,

    cytosine, guanine and thymine

  • –  Single-stranded helix
  • –  Composed of ribose sugar
  • –  Contain nitrogen bases of adenine,

    guanine, cytosine and uracil

  • –  Reactant: starts the chemical reaction
  • –  Product: result from the chemical reaction


  • –  Substances that speed up chemical reactions without being consumed in the reaction
  • –  Enzymes are protein catalysts that reduce the activation energy required in biological


– Orient molecules towards each other or apart so that they

can synthesize/decompose by using less energy

Exergonic Reaction:

– There’s a net-release of energy during the chemical reaction
– Energy is consumed during the activation of the reaction,

but more energy is released during the process of breaking bonds

Endergonic Reaction:

– There’s a net-input of energy into the chemical reaction
– Energy is absorbed so the reaction can occur, with some

being released after the formation of bonds

Functioning of Enzymes:

  • –  Enzymes lower activation energy by reducing the amount of energy needed for the reactants to come together and react
  • –  Bind substrates tightly and specifically to an active site on

    the enzyme

– Forms an enzyme-substrate complex

– Products are released from the active site, allowing the enzyme to continue catalyzing additional reactions

Influences on Enzymes:

– Have optimal temperatures and pH
– Any changes to these conditions will change the

shape of the enzyme, altering the shape of the active site and their ability to

catalyze reactions
– Denaturation can be caused by heat, extreme cold, change in pH, chemicals

  • –  Bonding between R-groups is disrupted (eg. hydrogen bonds are disrupted in acidic environments since [H+​ ​] is high, meaning additional hydrogen are bonded to molecules)
  • –  Secondary, tertiary, and quaternary structures are modified
  • –  Protein loses its 3D shape and becomes non-functional

    Enzyme Inhibition:

– Competitive Inhibitors: Substances that compete with a substrate for a spot on the enzyme’s active site (eg. CO bonds stronger to haemoglobin than oxygen does).


– Noncompetitive Inhibitors: Substances that attach to a binding site on an enzyme other than the active site; results in change of the enzyme’s shape and its loss of affinity for substrate

Allosteric Regulation:

  • –  Allosteric Site: Receptor sites, located far away from the active site, which binds substances that inhibits or stimulates an enzyme’s activity
  • –  Allosteric Activator: substance that binds to an allosteric site on an enzyme and stabilizes the protein conformation that keeps all the active sites available for their substances
  • –  Allosteric Inhibitor: A substance that binds to an allosteric site on an enzyme and stabilizes the inactive form of the enzyme
  • –  Feedback Inhibition: When a product of a sequence of reactions inhibits an enzyme that catalyzed it in an earlier reaction
  • –  Cofactors: Non-protein components that are needed for some enzymes to function (often ions, et Zn+​ 2​, Mn+​ 2​)
  • –  Coenzymes: Organic nonprotein cofactors that are needed for some enzymes to function (eg. NAD+​ ​from vitamin B​3)​

    Cell Structure and Organelles:

    Cell Wall:

  • –  Not vital to cells (not all cells have them, eg. animal cells)
  • –  Responsible for determining cell shape, controlling turgor

    pressure (outward water pressure), adds strength to cell

    • –  High turgor pressure (turgid) is when the cell walls are

      pushed out and the cell is filled with water

    • –  Low turgor pressure (flaccid) is when the cell walls

      shrivel with little water inside the cell

  • –  Cell walls are composed of cellulose (β glucose) in plants,

    chitin in fungi and protists, glycoprotein in bacteria

    Cell Membrane:

  • –  Protects the cell from the outside environment, keeps cell contents in place, controls which substances can enter and exit the cell
  • –  Phospholipids:
    • –  Hydrophilic, polar head (phosphate and glycerol)
    • –  Hydrophobic, nonpolar tails (fatty acids)
    • –  Form a phospholipid bilayer


– Proteins:

  • –  Float around within or on the surface of the membrane
  • –  Used for structural support, surface binding sites for molecules (eg.

    hormones), recognition sites for cell to cell communication and interaction, transport molecules through the
    membrane, transport electrons and
    protons within the membrane

    – Glycocalyx:

  • –  Carbohydrate chains attached to proteins


  • –  Used for recognition and

    communication of proteins, site for cell

    to cell attachment – Cholesterol:

– Keeps the phospholipids stable and retains the membrane’s shape; too much cholesterol makes the membrane solid, too little makes it liquid


  • –  Region of the cell containing the genetic information
  • –  Nucleolus

– A dense area within the nucleus containing RRNA (ribosome RNA) and proteins; ribosomes are produced here

– Nuclear pore:
– Openings in the nuclear membrane allowing for

the passage of molecules in and out of the

nucleus – Chromatin:

– Stringy material made of proteins and DNA that takes up the majority of the nucleus

– Chromosomes:
– Condensed chromatin; condenses into chromosomes shortly before cell

division begins
– DNA is important since it contains all the instructions to make



  • –  Microscopic spheres attached to the endoplasmic reticulum or free-floating in the cytoplasm
  • –  Protein factories: make primary protein structures by stringing amino acids together

    Endoplasmic Reticulum:

– Twisting network of canals and sacs extending through the cytoplasm and connecting the cell membrane to the nuclear membrane


  • –  Rough Endoplasmic Reticulum:
    • –  Has ribosomes attached to it
    • –  Produces, modifies, and transports proteins
  • –  Smooth Endoplasmic Reticulum:
    • –  No ribosomes on it
    • –  Produces lipids (cholesterol and phospholipids) and steroid hormones

      Golgi Apparatus:

  • –  Sacs of membranous plate-like bags which produce vesicles (sacs)
  • –  Produce and store cellular secretions (eg. fighting off infections)
  • –  Many proteins and lipids undergo final processing in the golgi


– Apparatus helps to fold molecules into final shape

completing tertiary and quaternary structures (eg. attaching cofactors to enzymes)


– Membrane-bound sacs that are used for digestion of various structures within the cell – Have acidic environment and hydrolytic enzymes to help digest foreign cells,

damaged organelles, macromolecules


  • –  Site of aerobic cellular respiration (converts sugar energy into adenosine triphosphate, ATP)

    – Sugar + O​2​ → CO​2​ + H​2O​ + ATP

  • –  ATP is used by other organelles and cell processes for


  • –  Mitochondrial Structures:
    • –  Cristae: site of chemical reactions using embedded proteins
    • –  Matrix: mitochondria cytosol (liquid portion of cytoplasm)
    • –  Mitochondrial DNA: self replicating organelle, producing its own unique



  • –  Found only in green and photosynthetic organisms
  • –  Convert sunlight to energy via photosynthesis

    – CO​2​ + H​2O​ → C​6H​ ​12O​ ​6​ + O​2

  • –  Chloroplast Structures:
    • –  Stroma: chloroplast cytosol
    • –  Lamella: membrane that attaches inner chloroplast


    • –  Thylakoid disc: have a specialized membrane for photosynthesis
    • –  Grana: stack of thylakoid discs (connected by lamella)
    • –  Chloroplast DNA: self-replicating organelle


Cilia and Flagella:

  • –  Made of protein fibres
  • –  Used for locomotion
  • –  Cilia: short and numerous on cell surface
  • –  Flagella: long and usually few in numbers on cell surface


– Structures that give the cell its shape and help organize its parts – Provide a basis for movement and cell division (allows

for organelles to move along them) – Made of filamentous proteins

  • –  Microtubules: anchor organelles
  • –  Actin filaments: contract muscle cells


  • –  Fluid-filled sac
  • –  In protozoa, vacuoles perform functions such as storage,

    ingestion, digestion, excretion, and expulsion of excess water

  • –  In plants, the large central vacuole help regulate water: turgor pressure is controlled

    by vacuole

    Theory of Endosymbiosis:

  • –  Explains the origin of eukaryotic cell organelles like mitochondria and chloroplasts
  • –  Works were advanced by Lynn Margulis in the 1960s

    Passive Transport:

– The movement of molecules through the cell membrane without the use of cellular energy


– Process by which particle move naturally from areas of high concentration to areas of low concentration until the dynamic equilibrium is reached

– Moving with the concentration gradient


  • –  Molecules are in constant motion (until equilibrium)
  • –  Small molecules are capable of passing through the phospholipids in the cell

    membrane(eg.O​2,​ CO​2,​ H​2O​ ,alcohol,smalllipids)

  • –  Rate of diffusion
    • –  Concentration of particles (increased concentration increases the rate of diffusion)
    • –  Temperature of particles (increased temperature increases the rate of diffusion)
    • –  Pressure (increase in pressure increases the rate of diffusion)
    • –  Agitation (increase in agitation increases the rate of diffusion)


  • –  The diffusion of water through a semipermeable membrane
    • –  Solute: dissolved substance (eg. sugar)
    • –  Solvent: able to dissolve things (eg. water)
    • –  Solution: mixture of solvent and solute
  • –  Types of membranes:
    • –  Impermeable: nothing can move across it
    • –  Semi-permeable: only some molecules can cross it (eg. cell membrane)
    • –  Permeable: any molecules can pass through it

      Types of Solutions:

  • –  Hypertonic Solution: The solution surrounding the cell has a higher concentration of solute than the cell’s cytoplasm, causing water to leave the cell
  • –  Hypotonic Solution: The solution surrounding the cell has a lower concentration of solute than the cell’s cytoplasm, causing water to enter the cell
  • –  Isotonic Solution: The concentration of the solute is the same on the inside and the outside of the cell

    Turgor Pressure:

– The rigid cell wall of the plant prevents it from bursting when it’s filled with water, causing outward water pressure called turgor pressure

– Plant cells full with water are called turgid


– When plant cells are placed in a salt solution, the cells shrink, resulting in plasmolysis

Facilitated Diffusion:

– Some molecules are too large or are hydrophilic so they cannot pass through the phospholipid bilayer (eg. glucose) – Transport proteins assist in getting these molecules

through the cell membrane
– Transport occurs within the concentration gradient (no

energy is required)


Active Transport:

– The movement of molecules through the cell membrane against the concentration gradient using transport ions

– Movement from low concentration to high concentration

  • –  Requires the use of cellular energy (ATP)
  • –  Transport proteins are highly selective (eg. Na+​ ​and

    K+​ ​pump) Endocytosis:

– Transports materials into the cells by the means of vesicles

– Energy is required

  • –  Cell engulfs the materials by folding a portion of

    its membrane around it

  • –  Types of endocytosis:
    1. Phagocytosis: movement of large and whole molecules into the cell’s interior
    2. Pinocytosis: transport of liquids into vesicles inside the cell
    3. Receptor-mediated endocytosis: molecules bind to receptors on the cell’s

      surface and are folded into vesicles within the cell


  • –  Transport of macromolecules (eg. hormones) out of a cell by means of vesicles made by the Golgi complex
  • –  Energy is required