Biological Molecules Flashcards
What is the name of the bond that holds water molecules together?
Hydrogen bonding.
Why is water a good solvent?
The molecules in water are polar, so this enables water molecules to bind to solute molecules.
How do properties relating to the density of water contribute to the survival of organisms?
Ice is less dense than water so it floats, creating a habitat for some species as ice insulates the water below. For example, polar bears live on top of ice whilst aquatic animals such as fish move under ice.
What properties of water make it an ideal habitat for an amphibian?
Any two from: High specific heat capacity, Good solvent, Ice is less dense than water, High density so it can float.
Outline the 8 properties of water.
- High boiling point as lots of energy is needed to break hydrogen bonds - important for living organisms- e.g: Stable water temperature for aquatic organisms.
- Ice is less dense than water - important for living organisms as ice insulates the water below creating a habitat for species like polar bears and fish.
- Cohesion due to hydrogen bonding in water - important for living organisms.
- Adhesion due to the water molecules being attracted to the surface/other molecules - important for living organisms.
- Good solvent - e.g: allowing mineral ions to be transported around plants and animals.
- Transport medium - allows the transport of soluble substances.
- Evaporation as a cooling mechanism as the evaporating water takes the heat away from the body e.g: sweating in humans and panting in dogs.
- High specific heat capacity - creates a stable temperature for living organisms so enzymes can work at their optimum temperature.
What is a condensation reaction?
A condensation reaction occurs when a water molecule is removed to form a covalent bond.
What is a hydrolysis reaction?
A hydrolysis reaction occurs when a water molecule is added to break a covalent bond.
How do monomers form polymers?
When lots of monomers join up together in a condensation reaction, they form polymers.
What chemical elements make up carbohydrates?
Carbon (C), Hydrogen (H) and Oxygen (O).
What chemical elements make up nucleic acids?
Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N) and Phosphorous (P).
What are monomers of carbohydrates referred to as?
Monosaccharides.
Describe disaccharides.
Disaccharides are made up of two monosaccharide molecules joined together by a glycosidic bond.
What are polymers of carbohydrates referred to as?
Polysaccharides.
Draw the ring structure of alpha glucose.
Draw the ring structure of beta glucose.
What type of monosaccharide is glucose?
Glucose is a hexose monosaccharide because it contains 6 carbon atoms.
Draw the ring structure of ribose.
What type of monosaccharide is ribose?
Ribose is a pentose monosaccharide because it contains 5 carbon atoms.
What monosaccharides is sucrose made up of?
Alpha glucose and fructose make up the disaccharide: sucrose.
What monosaccharides is lactose made up of?
Beta glucose and galactose make up the disaccharide: lactose.
What monosaccharides is maltose made up of?
Alpha glucose and alpha glucose make up the disaccharide: maltose.
Describe the properties of starch making it ideal for storage in plants.
Starch is a mixture of amylose and amylopectin. Amylose is made up of alpha, 1,4 glycosidic bonds which gives it a coiled and compact structure. Amylopectin is made up of alpha 1,4 and 1,6 glycosidic bonds creating branching. Starch does not dissolve therefore doesn’t affect osmotic/water potential. It holds glucose in chains so it can easily be broken off from the ends.
Describe the properties of glycogen.
Glycogen in animals is made up of alpha 1,4 and 1,6 glycosidic bonds so it is compact, insoluble so doesn’t affect osmotic pressure, has many ends so it can be easily hydrolysed back into glucose monomers used for respiration.
Describe the properties of cellulose.
Cellulose is made up of beta glucose joined together in beta 1,4 glycosidic bonds. They form beta pleated sheets between which hydrogen bonds can form cross links to form bundles called microfibrils. Larger bundles are called macrofibrils. These provide high tensile strength and make up plant cell walls. They allow water to pass through prevents the cell from bursting, determines the cell’s shape. Cellulose also doesn’t affect osmotic potential and is inert.
What is one physical property of glucose that allows it to be easily transported in animals?
Soluble.
Why do mammals store glycogen instead of glucose?
Glycogen is insoluble so has no effect on the water potential of the cell. Glycogen is metabolically inactive. Glycogen is compact. Glycogen is able to store lots of energy. Glycogen is highly branched so can be rapidly broken down to release glucose.
Give three properties of cellulose that make it suitable as the basis of plant cell walls.
Cellulose is insoluble. Cellulose is inert/unreactive. Cellulose has high tensile strength.
How does the structure of glycogen differ from that of amylopectin?
Glycogen is more branched so has more free ends where glucose can be added or removed which speeds up glucose release/hydrolysis. Glycogen is more coiled. Glycogen is more compact.
What chemical elements make up lipids?
Carbon (C), Hydrogen (H) and Oxygen (O).
What covalent bond is formed between lipids in a condensation reaction?
Ester bond.
Describe the structure of a triglyceride molecule.
A triglyceride molecule is made up of one glycerol molecule bonded to three fatty acid chains via ester bonds.
Describe the structure of a phospholipid molecule.
A phospholipid molecule is made up of one glycerol molecule, one phosphate group and two fatty acid chains.
What type of molecules are triglycerides and phospholipids?
Triglycerides and phospholipids are macromolecules as they are not made up of lots of repeating units.
What is the difference between saturated and unsaturated fatty acids?
Saturated fatty acids have only single carbon to carbon bonds whilst unsaturated fatty acids have at least one double carbon to carbon bond. This causes unsaturated fatty acids to kink/bend thus resulting in them being less dense.
Describe the properties and function of triglycerides.
Triglycerides are a good energy store and source. This is because triglycerides are used: A respiratory substrate - they release water once broken down. Insoluble - so don’t affect water potential. Used to make hormones. Water proofing. Buoyancy. Form layers of insulation for warmth or protective layers around organs or nerves (e.g: myelin sheath). Aid fat absorption of fat soluble molecules.
Describe the properties and function of phospholipids.
Phospholipids have a hydrophilic phosphate head but a hydrophobic fatty acid tail. This causes the phosphate head to orientate towards water whilst the fatty acid tails orientate away from water. This creates a micelle when dropped into water. Phospholipids form the phospholipid bilayer which is found in the plasma membrane.
What is cholesterol made of?
Cholesterol is made up of a 4 carbon ring structure.
What is the function of cholesterol?
As cholesterol molecules are hydrophobic, they form part of the cell membrane and help regulate fluidity.
What substances are made using cholesterol?
Vitamin D, Bile, Steroid hormones.
How does the structure of phospholipids allow them to form the bi-layer of a plasma membrane?
Phospholipids are made up of a hydrophilic phosphate head and a hydrophobic fatty acid tail. The hydrophobic fatty acid tail repels water. The hydrophilic phosphate head forms hydrogen bonds with water. The medium outside and inside the plasma membrane is aqueous. The hydrophobic nature of tails results in their facing towards each other.
Name three functions of triglycerides in living organisms.
Energy source for respiration/respiratory substrate, energy storage, thermal insulation.
Describe and explain the pattern of the melting points of polyunsaturated lipids.
More double bonds give lower melting point. There are fewer hydrogens resulting in a more kinked molecule, so less uniformly packed together (so lower temperature needed for melting).
What chemical elements make up proteins?
Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N) and Sulfur (S).
Draw the general structure of an amino acid.
What is formed in a condensation reaction of two amino acids?
dipeptide molecule
Define the primary structure of a protein.
The sequence of amino acids bonded by peptide bonds.
Define the secondary structure of a protein.
The folding of the polypeptide chain, held in place with hydrogen bonds forms alpha helix or beta-pleated sheets.
Define the tertiary structure of a protein.
Further folding of the polypeptide chain which are held in place by hydrogen bonds, disulfide bridges and ionic bonds. Hydrophobic and hydrophilic interactions occur as the amino acids with hydrophobic R groups orientate towards the inside of the protein and the amino acids with hydrophilic R groups orientate towards the outside of the protein.
What is collagen?
Collagen is a fibrous protein which is flexible but does not stretch.
What is insulin?
Insulin is a globular protein with a specific, fixed shape.
What is elastin?
Elastin is a fibrous protein which recoils after being deformed.
What is haemoglobin?
Haemoglobin is a globular protein which can change shape.
What is meant by a conjugated protein?
- Contains non-protein groups. 2. Has prosthetic group. 3. In haemoglobin, (prosthetic group) is iron / Fe ion. 4. (Prosthetic group) is attached by covalent bonds / ionic interactions / hydrogen bonds.
State three properties of a fibrous protein that are different from those of a globular protein.
- Insoluble. 2. Strong. 3. Unreactive.
Compare the properties and functions of fibrous proteins and globular proteins in the human body.
Fibrous proteins properties include: insoluble, elongated / long / rods / filaments / ropes / strands, strong / tough, flexible. Fibrous proteins are important for: protection - keratin in hair, nails and skin, structure - collagen in bone / cartilage / connective tissue / tendons / ligaments / skin / blood vessels, elasticity - elastin in alveoli / cartilage, mechanical movement - actin/myosin in muscle, microtubules in flagella / cilia / spindle / cytoskeleton. Globular proteins properties include: soluble, spherical / ball-shaped, have 3D / tertiary / 3o shape / structure, specific / complementary (to another molecule), ref. conjugated / contain prosthetic group, temperature / pH sensitive, hydrophilic on outside. Globular proteins are important for: enzymes / metabolic role / to catalyse reaction(s) / to lower activation energy - e.g: pepsin that helps digest proteins in the stomach, transporting substances in blood haemoglobin e.g. carries oxygen, hormones / receptors / for cell signalling e.g. insulin which binds to glycoprotein receptors to increase uptake of glucose from the blood, organise/package DNA.
Describe and explain why collagen is a fibrous protein.
Insoluble - has many non-polar amino acids. Little to no tertiary structure. Has a structural function.
Why is collagen a strong molecule?
Collagen has many covalent bonds/cross-links between collagen molecules. Collagen has many hydrogen bonds between polypeptides. Polypeptides overlap.
How do hydrophilic and hydrophobic interactions contribute to the spherical shape of a globular protein?
Hydrophobic regions/R groups are on the inside of the protein and hydrophilic regions/groups are on the outside of the protein.
What is the chemical symbol for a calcium ion?
Ca^2+.
What is the chemical symbol for a sodium ion?
Na^+.
What is the chemical symbol for a potassium ion?
K.
What type of bonds are present between collagen molecules?
Collagen has many hydrogen bonds between polypeptides.
How do hydrophilic and hydrophobic interactions contribute to the shape of a globular protein?
Hydrophobic regions/R groups are on the inside of the protein, and hydrophilic regions/groups are on the outside.
What is the chemical symbol for a calcium ion?
Ca^2+
What is the chemical symbol for a sodium ion?
Na^+
What is the chemical symbol for a potassium ion?
K^+
What is the chemical symbol for a hydrogen ion?
H^+
What is the chemical symbol for an ammonium ion?
NH4^+
What is the chemical symbol for a nitrate ion?
NO3^-
What is the chemical symbol for a hydrogencarbonate ion?
HCO3^-
What is the chemical symbol for a chloride ion?
Cl^-
What is the chemical symbol for a phosphate ion?
PO4^3-
What is the chemical symbol for a hydroxide ion?
OH^-
What processes are calcium ions (Ca2+) involved in?
Muscle contraction, synapses, and the Bohr effect.
What processes are sodium ions (Na+) involved in?
Nerve impulses and selective reabsorption.
What processes are potassium ions (K+) involved in?
Nerve impulses.
What processes are hydrogen ions (H+) involved in?
Translocation and chemiosmosis.
What processes are ammonium ions (NH4+) involved in?
Nitrogen cycle.
What processes are nitrate ions (NO3-) involved in?
Nitrogen cycle.
What processes are hydrogencarbonate ions (HCO3-) involved in?
Nitrogen cycle.
What processes are chloride ions (Cl-) involved in?
Bohr effect.
What processes are phosphate ions (PO4^3-) involved in?
DNA, RNA, phospholipids, ATP.
What processes are hydroxide ions (OH-) involved in?
Photosynthesis.
How do you test for proteins?
Add sample to a test tube, add Biuret’s solution. If protein is present, you get a purple/lilac color.
How do you test for reducing sugars?
Heat sample with Benedict’s solution. If a reducing sugar is present, you get a yellow/orange/brick-red color.
How do you test for non-reducing sugars?
Heat sample with Benedict’s solution. If no change, heat with hydrochloric acid, then add excess NaOH to neutralize. Heat with Benedict’s solution again. If present, a yellow/orange/brick-red color appears.
How do you test for starch?
Add sample to a test tube, add iodine solution. If starch is present, iodine solution will change from brown to blue-black color.
How do you test for lipids?
Add sample to test tube, add few drops of ethanol, shake, pour over water. If lipids are present, you will get a white emulsion.
