Biomolecules - Introduction

Biomolecules
- Molecules involved in maintenance and metabolic processes of living organisms
- Organic biomolecules contain:
   - Hydrogen
   - Carbon
   - Oxygen
   - Nitrogen
   - Sulphur
- Formed by condensation reaction
   - The forming of covalent bonds by removing a water molecule
 - Split by hydrolysis
   - The splitting of covalent bonds by adding a water molecule
- 4 main types:
   - Carbohydrates
   - Lipids
   - Proteins
   - Water


Overview of Condensation Reaction

Monomer	Polymer Formed	By-product	Bond Name
Monosaccharide (simple sugar)	Disaccharide --> Polysaccharide	Water	Glycosidic Bond (-O-)
Amino acid	Dipeptide --> Polypeptide	Water	Peptide Bond  (C-N)
Glycerol Fatty acids	Monoglycerides Diglycerides Triglycerides (Glyrcerol attached to fatty acids)	Water	Ester bond (-O-) [amino acids]
DNA/RNA	DNA	Water	Phosphodiester bond

Homeostasis + Cell Structure + Feedback Loop

What is homeostasis?

It is the controlled stability of the internal environment of cells and tissues.
Some examples include:
- Water regulation (osmoregulation)
- Temperature regulation (thermoregulation)
- Glucose regulation

Why is there a need for homeostasis?

It is so that a state of dynamic equilibrium can be achieved. A dynamic equilibrium means a state of balance achieved within an environment as a the result of internal control mechanisms that continuously oppose outside forces that tend to change that environment.


Cell Structure

Component	Organelle Name	Function
A	Nuclear Membrane	- Controls entry and exit of substances
B	Nuclear Pore	- Allows transport of water-soluble substances
C	Nucleolus	- Contains chromatin that controls cell activity; DNA, genetic material - Compartmentalized to increase efficiency of processes and protection
D	Lysosome	- Breaks down worn out organelles - Digests materials
E	Rough Endoplasmic Reticulum	- Isolate and transport proteins synthesized by attached ribosomes - Proteins may undergo further folding
F	Smooth Endoplasmic Reticulum	- Synthesis and transport lipids
G	Cytoplasm	- Contains the cell organelles - Site of cellular reactions - Means of transport for substances in cell
H	Golgi Apparatus	- Process and package complex molecules - Transports proteins and fat molecules to cytoplasm for secretion
I	Cell plasma membrane	- Compartmentalize - Controls entry and exit - Increase surface area - Cell recognition - Cell communication - Site of chemical reactions
J	Vesicle/Vacuole	- Sacs for storage (plant cell), digestion and waste removal (animal cell)
K	Mitochondria	- Produce adenosine triphosphate (ATP) from cellular respiration - Energy currency of cell
L	Ribosome	- Sites of protein synthesis

Cell Plasma Membrane

Organelle	Function
Phospholipid	- Major component of the membrane - When they come into contact with water, they tend to line up heads in water and hydrophobic tails away from the water
Proteins	- Extrinsic    - Loosely attach at hydrophilic surface of phospholipid bilayer - Intrinsic (partially or completely)    - Contain both hydrophilic and hydrophobic regions
Glycoproteins	- Interspersed among phospholipids - Consists of carbohydrate chains bound to peripheral proteins and hydrophilic regions of internal proteins that occur on surface of outer membrane    - Cell recognition or cell adhesion for immune response
Glycolipids	- Interspersed among phospholipids - Consists of carbohydrate chains bound to the head of phospholipid - Involved in cell recognition or cell signalling pathways
Cholesterol	- Interspersed among phospholipids - Essential in maintaining membrane fluidity    - Allow protein movement within cell membrane

Cell Transport

	Transport Mechanism	Type of substances	Energy input	Examples of substances	Importance of mechanism
Simple Diffusion	Across the phospholipid bilayer directly, following a concentration gradient.	Small, lipid soluble and hydrophobic in order to be able to interact with the hydrophobic tails of the bilayer	Passive transport, ATP input not required	Oxygen gas, carbon dioxide, minerals in soil (in high concentration)	To allow for the absorption of small, lipid soluble substances into living cells for essential processes like respiration
Facilitated Diffusion - Ion Channel	Across the phospholipid bilayer through a water, filled pore, following a concentration gradient	Water and water-soluble substances and small lipids	Passive Transport, ATP input not required	Urea, glycerol	To allow for the absorption of water, water-soluble substances and small lipids into living cells for essential processes
Facilitated Diffusion - Carrier Protein	Across the phospholipid bilayer through a carrier protein that has a specific binding site, following a concentration gradient	Too large and too hydrophilic substances	Passive transport, ATP input not required	Amino acids, glucose, fructose	To allow for absorption of too large and too hydrophilic substances into living cells for essential processes
Osmosis	Across a partially permeable membrane, following a concentration gradient	Water	Passive Transport, ATP input not required	Water molecules	To allow for absorption of water into living cells for essential processes such as hydrolysis and condensation and a medium for transport within the cell
Active Transport	Across the phospholipid bilayer through a specific protein pump, against the concentration gradient	Particles	Active Transport, ATP input is required as substances go against the concentration gradient	Amino acids and glucose (in low concentration)	To allow for absorption of large particles against the concentration gradient into living cells for essential processes.
Bulk Transport - Endocytosis	Ingestion of fluids/solids from outside the cell into the cell	Fluid, solids	Active Transport, ATP input is required as substances go against the concentration gradient	Bacteria, food	To allow for the ingestion of fluids and/or solids into living cells for essential processes such as processing food and digestion
Bulk Transport - Exocytosis	Expelling contents from inside of the cell to outside the cell	Waste materials, excess materials	Active Transport, ATP input is required as substances go against the concentration gradient	Enzymes, hormones and antibodies	To allow for the expelling of waste and excess materials from the cell into the outside of the cell
Pinocytosis	Encloses fluid and pinches off to form vesicle	Fluid or suspensions	Active Transport, ATP input is required as substances go against the concentration gradient	-	To allow ingestion of fluid or suspension into the cell
Phagocytosis	Encloses particles and buds off to form vacuole	Bio-organisms	Active Transport, ATP input is required as substances go against the concentration gradient	Food molecules	To allow ingestion of solids from outside the cell

Feedback Loop

It is a self-regulated system in which feedback to the input a part of a system's output so as to reverse or enhance the direction of change.

Positive Feedback Loop (Rare)

- Increases the output of a system, further enhancing deviation from internal equilibrium

eg. Giving birth, rashes, blood clotting

Negative Feedback Loop (Common)

- Reduces the output of a system in order to stabilize or re-establish internal equilibrium

eg. Body temperature, osmoregulation, glucose level

Keywords:

Increase in ____ is detected by the receptors and insulin is released into the blood.