Notes on Topic 1 - Molecules, Transport and Health in line with the Carson Edexcel International A-level Spec.
Notes include:
- 1.1 Water
- 1.2 / 1.4 Carbohydrates
- 1.3 Core practical 1
- 1.5 Lipids
- 1.6 / 1.7 / 1.8 Heart and Circulatory System
- Heart dissection
- 1.9 / 1.10 / 1.11 Haemo...
1.1 Water
Learning objectives
1.1 Understand the importance of water:
- As a solvent in transport
- Including its dipole nature
Key terms
- Anion
A negative ion.
- Cation
A positive ion.
- Ionic bonds
Bonds formed when atoms give or receive electrons; they result in charged particles
called ions.
- Covalent bonds
Bonds formed when atoms share electrons; covalent molecules may be polar if the
electrons are not shared equally.
- Dipole
The separation of charge in a molecule when the electrons in covalent bonds are not
evenly shared.
- Polar molecule
A molecule containing a dipole.
- Dissociation
Splitting of a molecule into smaller molecules, atoms, or ions, especially by a
reversible process.
- Hydrogen bonds
Weak electrostatic intermolecular bonds formed between polar molecules
containing at least one hydrogen atom.
Knowledge that leads up to the main learning objectives
Organic molecules
Organic compounds are generally any chemical compounds that contain carbon-hydrogen
bonds.
They are usually composed of:
- Carbon atoms in rings or long chains
- Other elements are then attached to those carbon atoms, such as hydrogen, oxygen, and
..nitrogen.
Overview Bonding
There are 3 main types (in general, to have an overview, the paragraph below is more
important):
- Ionic bonding
Metal + Non-metal
- Covalent
Non-metal + Non-metal
- (Metallic bonding)not really relevant in biology. I just put it in there to be aware of it
(Metal + Metal)
,3 main types of bonds that are important in biology:
- Ionic bonds
- Medium strength
- Atoms give or receive electrons from each other
- Now the atoms become ions (because they either received or gave electrons) and
..have a positive or negative charge.
- Covalent bonds
- The strongest bonds
- The electrons are shared instead of transferred completely to another (now) ion. So
..the electrons orbit both atoms.
- Hydrogen bonds (in this topic we are only going to talk about how they occur in water)
- Very weak bond (but lots of them)
- They occur through specific covalent bonds in which there is a slightly positive
..charge forming on the H atoms.
- This means that H atoms are weakly attracted to slightly positive atoms like oxygen
..or sulphur.
Ionic Bonding
The aim of any atom is to have a stable outer shell. So if they don’t they will try to bonds
with other atoms that don’t either, to basically complete each other.
After one of them gave the other electrons, they will either become positive or negative
according to who gave and who received electrons.
This makes them attracted to each other, ultimately making them bond together.
Here is an example:
,Ions
- Some atoms have fuller outer shells and some don’t. When an atom doesn’t have a
fuller outer shell (which makes it unstable), its goal is to bond with other unstable
atoms, so they all can have a fuller outer shell.
- But when getting a full outer shell, they will automatically change into ions.
- A fuller outer shell is the most stable state they can be in.
- Atoms are always neutral and ions are always either positively or negatively charged.
- Metals always lose electrons to form + ions
Non-metals always gain electrons to form – ions.
- The positive and negative ions have a name:
- Cations
Positive ions
- Anions
Negative ions
Inorganic ions
An inorganic ions is an ion that does not contain carbon.
- When an ionic substance dissolves in water its ions separate. (They would normally
stick together). This creates positive and negative ions. (They existed beforehand in
their solution but because they were together there was no overall charge).
- A common inorganic ion in our human diet is NaCl, which is table salt.
- Our cells are more than half water so most ionic substances in our body are not
together(and neutral) but rather separate (positively and negatively charged)
because they are all dissolved in water they will exist as inorganic ions. In this
separate state they are able to do specific jobs.
- Once they are dissociated from each other they are known as electrolytes (in body
issue).
- Those electrolytes are essential for:
- Electrical activity needed to support muscle contractions and neuron activation.
- They also contribute to osmotic pressure of body fluids
- As well as performing a number of other important functions.
Inorganic ions I need to know about:
Important anion (-):
- Nitrate ions (NO3-)
- Needed in plants
- For the formation of amino acids and therefore proteins
- Also for DNA/RNA
- Phosphate ions (PO43-)
- Needed in all living organisms
- Needed in the formation of ATP and ADP
- As well as DNA/RNA
- Chloride ions (Cl-)
- Needed in animals
- These are needed in nerve impulses
- And in many secretory systems
, Important cations (+):
- Sodium ions (Na+)
- Needed in animals
- Needed in nerve impulses
- And in many secretory systems
- Calcium ions (Ca2+)
- Needed in plants and animals
- The formation of calcium pectate for the middle lamella between two cell walls in -
..plants.
- Bone formation and muscle contraction
- Hydrogen ions (H+)
- Needed in plants and animals
- Needed in cellular respiration and photosynthesis
- And in numerous pumps and systems in organisms as well as the pH balance
- Magnesium ions (Mg2+)
- Needed in plants
- Needed for the production of chlorophyll
Covalent bonding
Electrons are shared in covalent bonding.
- The “holding hands” bond
- The bonds formed are very strong (although between molecules is weak)
- The molecules formed are usually neutral
- However some may be polarised with electron sharing not quite even.
- These are called dipoles (the difference in charge is tiny)
- This is now called a polar molecule all together
- More likely with more hydrogens
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller frankawirtz. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £8.19. You're not tied to anything after your purchase.
