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Ch.3 Biological molecules
Tags
3.1 Biological element
Important biological elements - all living things are made primarily from these four key elements:
carbon (C)
hydrogen (H)
oxygen (O)
nitrogen (N)
→ phosphorus (P), sulfur (S) and other elements e.g. sodium (Na), potassium (K), calcium (Ca) and iron (Fe) have
important roles in biochemistry.
Key biological molecules that contain these biological elements:
C + H + O = carbohydrates
C + H + O = lipids
C + H + O + N + S = proteins
C + H + O + N + P = nucleic acids
Carbon
→ very important biological element
It can bond together to form long chains or rings → other atoms can bond with these chains and rings as carbon
act as a framework
Carbon has a valency of 4 i.e. can form covalen bonds (strong bonds involving the sharing of electrons) with 4
other atoms
Alkanes are examples of hydrocarbons - chains of carbons together with hydrogen
Covalent bonding - strong bond formed when two atoms share a pair of electrons
atoms connect to each other by forming bonds
When two or more atoms are bonded together, the complex is called a molecule
→ Bonding follows simple rules determined by the number of unpaired electrons in the outer shell
carbon atoms - 4 bonds with other atoms
nitrogen atoms - 3 bonds with other atoms
oxygen atoms - 2 bonds with other atoms
Ch.3 Biological molecules 1
, hydrogen atoms - 1 bond with another atom
Ionic bonding - one atom in the pair donates an electron and the other receives it → forms positive and negative ions
held together by the attraction of opposite charges
ion = an atom/molecule where the total number of electrons is not equal to the total number of protons
cations - positive ions, attracted to a negative cathode
gains a positive charge as an atom/molecule loses one or more electrons
anions - negative ions, attracted to a positive anode
gain negative charge as an atom/molecule gains one or more electrons
Key inorganic ions that are involved in biological processes:
Cation -
1. calcium ions (Ca2+)
transmission of impulses across synapses → allow rapid signals to be sent around the body
muscle contraction
2. sodium ions (Na+)
regulate osmotic pressure - help plant cells remain turgid
kidney - taking in sodium ions allow the body to take back water
allow nerve impulses to move along the axon
help maintain pH at approx. 7 in the body
active transport - involved in the co-transport of glucose and amino acids across the membrane
3. potassium ions (K+)
similar to Na+:
regulate osmotic pressure
kidney
nervous impulses
pH
active transport
synthesis of proteins and glycogen
involved in the breakdown of glucose
4. hydrogen ions (H+)
photosynthesis and respiration - drive production of ATP (energy)
pH of fluids - blood must have a stable pH - enzymes denature if not
Ch.3 Biological molecules 2
, pH of cytoplasm - so enzymes don’t denature
5. ammonium ions (NH4+)
amino acids - making proteins
bases in DNA and RNA
Vitamins - vitamin B
Chlorophyll
pH levels - NH3 (ammonia) is converted to NH4+ (ammonium) which mops up excess H+ ions and help
maintaining the pH
nitrogen cycle - nitrifying bacteria convert ammonium to nitrite and then to nitrate
Anions -
1. nitrate ions (NO3-)
amino acids - making protein → absorbed by plant roots to make amino acids and other nitrogen-containing
compounds
bases in DNA and RNA
Vitamins
Chlorophyll
Nitrogen cycle
2. hydrogen carbonate ions (HCO3-)
formed when CO2 dissolves in blood - important way of transporting CO2 in the blood as it can’t be
transported as a gas
regulation of blood pH
3. chloride ions
balance positive charge of sodium and potassium ions in cells
regulation of electrical potential across blood cell membranes
combine with hydrogen ions in the stomach to produce hydrochloric acid
4. phosphate ions (PO4-)
nucleotides - DNA and RNA
ATP (energy) - similar structure to nucleotide
Phospholipids
breakdown of glucose in respiration
5. hydroxide ions
Ch.3 Biological molecules 3
Ch.3 Biological molecules
Tags
3.1 Biological element
Important biological elements - all living things are made primarily from these four key elements:
carbon (C)
hydrogen (H)
oxygen (O)
nitrogen (N)
→ phosphorus (P), sulfur (S) and other elements e.g. sodium (Na), potassium (K), calcium (Ca) and iron (Fe) have
important roles in biochemistry.
Key biological molecules that contain these biological elements:
C + H + O = carbohydrates
C + H + O = lipids
C + H + O + N + S = proteins
C + H + O + N + P = nucleic acids
Carbon
→ very important biological element
It can bond together to form long chains or rings → other atoms can bond with these chains and rings as carbon
act as a framework
Carbon has a valency of 4 i.e. can form covalen bonds (strong bonds involving the sharing of electrons) with 4
other atoms
Alkanes are examples of hydrocarbons - chains of carbons together with hydrogen
Covalent bonding - strong bond formed when two atoms share a pair of electrons
atoms connect to each other by forming bonds
When two or more atoms are bonded together, the complex is called a molecule
→ Bonding follows simple rules determined by the number of unpaired electrons in the outer shell
carbon atoms - 4 bonds with other atoms
nitrogen atoms - 3 bonds with other atoms
oxygen atoms - 2 bonds with other atoms
Ch.3 Biological molecules 1
, hydrogen atoms - 1 bond with another atom
Ionic bonding - one atom in the pair donates an electron and the other receives it → forms positive and negative ions
held together by the attraction of opposite charges
ion = an atom/molecule where the total number of electrons is not equal to the total number of protons
cations - positive ions, attracted to a negative cathode
gains a positive charge as an atom/molecule loses one or more electrons
anions - negative ions, attracted to a positive anode
gain negative charge as an atom/molecule gains one or more electrons
Key inorganic ions that are involved in biological processes:
Cation -
1. calcium ions (Ca2+)
transmission of impulses across synapses → allow rapid signals to be sent around the body
muscle contraction
2. sodium ions (Na+)
regulate osmotic pressure - help plant cells remain turgid
kidney - taking in sodium ions allow the body to take back water
allow nerve impulses to move along the axon
help maintain pH at approx. 7 in the body
active transport - involved in the co-transport of glucose and amino acids across the membrane
3. potassium ions (K+)
similar to Na+:
regulate osmotic pressure
kidney
nervous impulses
pH
active transport
synthesis of proteins and glycogen
involved in the breakdown of glucose
4. hydrogen ions (H+)
photosynthesis and respiration - drive production of ATP (energy)
pH of fluids - blood must have a stable pH - enzymes denature if not
Ch.3 Biological molecules 2
, pH of cytoplasm - so enzymes don’t denature
5. ammonium ions (NH4+)
amino acids - making proteins
bases in DNA and RNA
Vitamins - vitamin B
Chlorophyll
pH levels - NH3 (ammonia) is converted to NH4+ (ammonium) which mops up excess H+ ions and help
maintaining the pH
nitrogen cycle - nitrifying bacteria convert ammonium to nitrite and then to nitrate
Anions -
1. nitrate ions (NO3-)
amino acids - making protein → absorbed by plant roots to make amino acids and other nitrogen-containing
compounds
bases in DNA and RNA
Vitamins
Chlorophyll
Nitrogen cycle
2. hydrogen carbonate ions (HCO3-)
formed when CO2 dissolves in blood - important way of transporting CO2 in the blood as it can’t be
transported as a gas
regulation of blood pH
3. chloride ions
balance positive charge of sodium and potassium ions in cells
regulation of electrical potential across blood cell membranes
combine with hydrogen ions in the stomach to produce hydrochloric acid
4. phosphate ions (PO4-)
nucleotides - DNA and RNA
ATP (energy) - similar structure to nucleotide
Phospholipids
breakdown of glucose in respiration
5. hydroxide ions
Ch.3 Biological molecules 3
