1.1 (1) - Biological Molecules Flashcards
Introduction to biological molecules Carbohydrates and monosaccharides Carbohydrates - disaccharides and polysaccharides Starch, glycogen and cellulose Lipids Proteins Enzyme action Enzyme inhibition
What is a monomer?
1 single unit of a polymer
What is a polymer?
A chain of monomers, making a larger molecule
What is the function of carbohydrates?
- Commonly used as respiratory substrates
- Structural components in plasma membranes and cell walls
What is the function of lipids?
- Insulation
- Energy source
- Help create cell membranes
What is the function of proteins?
Form many cell structures
What is the function of nucleic acid?
Used for production to make genetic material
What is a respiratory substrate?
A molecule that can release energy to produce ATP in a cell
What kind of sugar is a monosaccharide?
Hexose sugar
What is the difference between an ɑ-glucose and a β-glucose?
ɑ-glucoses have their hydroxyl below Carbon 1
β-glucoses have their hydroxyl above Carbon 1
What kind of reaction are monosaccharides formed during?
Condensation reaction
What bond are 2 monosaccharides joined together in a disaccharide by?
Glycosidic bond (covalent)
What is a carbohydrate monomer called?
Monosaccharide
What are the 3 main monosaccharides?
- Glucose
- Fructose
- Galactose
What are 2 monosaccharides joined together called?
Disaccharides
What are the 3 main disaccharides?
- Maltose
- Sucrose
- Lactose
What 2 monosaccharides make up maltose?
2 ɑ-glucoses
What 2 monosaccharides make up sucrose?
1 glucose and 1 fructose
What 2 monosaccharides make up lactose?
1 glucose and 1 galactose
What are many monosaccharides joined together called?
Polysaccharides
What are the 3 main polysaccharides?
- Cellulose
- Glycogen
- Starch
What monosaccharides is cellulose made up of?
Chains of β-glucoses
What monosaccharides is glycogen made up of?
Chains of ɑ-glucoses
What monosaccharides is starch made up of?
Chains of ɑ-glucoses
What is a condensation reaction?
When two monosaccharides join and a water molecule is removed
What is a hydrolysis reaction?
When water is added to a disaccharide to break the glycosidic bond between the 2 monosaccharides
What is a reducing sugar?
One that can donate electrons to another chemical
Describe the Benedict’s Test
1) Add 2cm3 of food sample to a test tube in a paste / liquid form
2) Add 2cm3 of Benedict’s reagent
3) Heat the mixture gently over a water bath for 5 minutes
What are the test results (colours) for the Benedict’s Test?
Blue - None present Green - Trace Yellow - Low Orange/red - Moderate Maroon - High
Is the Benedict’s Test quantitative or semi-quantitative?
Semi-quantitative
What is a semi-quantitative test?
It doesn’t measure the precise quantity of a substance, BUT the result expresses an estimate of how much of a detected substance is present (eg. colour spectrum)
What is the test for non-reducing sugars?
1) Make sure the food sample is liquid
2) Add 2cm3 of food sample to 2cm3 of Benedict’s reagent in a test tube → filter
3) Place test tube in water bath for 5 minutes. If the colour does NOT change, reducing sugars are NOT present
4) In a new test tube, add 2cm3 of food sample to 2cm3 dilute hydrochloric acid (DHA) and put into a water bath for 5 minutes. The DHA will hydrolyse any NON-REDUCING disaccharides present into its REDUCING monosaccharides
5) Slowly add some sodium hydrogen carbonate solution to the test tube (neutralising it). Test with pH paper, the solution should be alkaline
6) Re-test the resulting solution by heating it with 2cm3 Benedict’s reagent in a water bath for 5 minutes
7) If a non-reducing sugar was present in the original sample, the reagent will now turn brown-orange, because of the reducing sugars that were produced from the hydrolysis of the non-reducing sugars
Describe starch
- Plant energy-storage molecule
- It makes it insoluble, so that they don’t draw water into the cell and affect water potential
- Doesn’t dissolve, so there is no effect on osmotic potential, it won’t diffuse
- It can be hydrolysed to ɑ-glucoses, which is easy to transport and good for respiration
- It can take a more-branched structure which has more ends, speeds up its break down
- Forms close spiral structures - allows it to be tightly packed
Describe glycogen
- Found in animals
- Insoluble
- Function - energy storage and release molecule
- Forms a many-branched structure, so that there are lots of ends for glucose to be released from
Describe cellulose
- Structural carbohydrate
- β-glucoses are ALTERNATING (flipped over), forming really strong chains
- Dietary fibre
What three chemical elements are lipids composed of?
Carbon (C), hydrogen (H) and oxygen (O)
Do lipids have a lower or higher proportion of oxygen to carbon and hydrogen than carbohydrates?
Lower proportion
What substances are lipids soluble / insoluble in?
Soluble - organic substances (eg. alcohol and acetone)
Insoluble - water
What are 4 functions of lipids?
- Energy storage molecule
- Waterproofing
- Insulation
- Physical protection
If it is solid between 10°C and 20°C, the lipid is a…
Fat
If it is liquid between 10°C and 20°C, the lipid is an…
Oil
What is the structure of a triglyceride?
3 fatty acids with a glycerol molecule joined via an ester bond
What is the main cause of fatty acid variation?
Saturation
How many double bonds does a monounsaturated fatty acid have?
1 double bond
How many double bonds does a saturated fatty acid have?
0 double bonds
How many double bonds does a polyunsaturated fatty acid have?
More than 1 double bond
How is a phospholipid different to a triglyceride?
One of the fatty acids is replace with a hydrophilic phosphate molecule
What do phospholipid bilayers help to make?
Cell membrane
What is the significance of phospholipids being polar?
They can form bilayers in aqueous solutions, forming a barrier between the intercellular and extracellular fluid
Phospholipid structure aids with the formation of…
Glycolipids
Describe the emulsion test for lipids
1) Take a clean, dry test tube
2) Add 5cm3 ethanol to 2cm3 of food sample
3) Shake the tube thoroughly to dissolve any lipid in the sample
4) Add 5cm3 water, shake gently
5) A cloudy-white emulsion indicates the presence of a lipid
6) As a control, repeat the procedure using water instead of the food sample; the control should remain clear
What are the monomers of proteins called?
Amino acids
What is the generic structure of a protein?
- Central ɑ-carbon
- Amino group (left - H-N-H)
- Solitary hydrogen (above)
- Carboxyl group (right - OH-C=O)
- R-group (varies the protein)
How many types of amino acids are proteins made of?
All 20 amino acids
What is the name of a polymer of amino acids joining together?
Polypeptide
What is the joining of many monomers to make a polymer called?
Polymerisation
What bond are amino acids joined by?
Peptide bond
What molecule is formed between the -OH from the carboxyl group when 2 amino acids join?
Water molecule
Describe a protein’s primary structure
- A chain of amino acids
- It is determined by the type, sequence and number of amino acids
- It determines the shape, structure and function of the protein because of the r-group and different molecular structure
Describe a protein’s secondary structure
- Occurs as H bonds form between the +charged H of the -NH and the -charged oxygen of the -C=O group
- The H bonds tend to be weak, but they are strong enough to twist the polypeptide chain into a 3D shape (ɑ helix OR β-pleated sheet)
Describe a protein’s teritary structure
- It is determined by the primary structure
- It’s the result of further twisting of the secondary structure
- Plays a significant role in determining the protein’s behaviour
- Maintained by:
- Disulfide bonds
- Hydrogen bonds
- Ionic bonds
Describe a protein’s quaternary structure
- Consists of 2 or more polypeptide chains bonded together
- Some large proteins also include a non-peptide part, called a prosthetic group (eg. inorganic iron ions are the prosthetic group in haemoglobin)
What 5 factors affect the rate of enzyme-controlled reactions?
- Enzyme concentration
- Substrate concentration
- Concentration of competitive and non-competitive inhibitors
- Temperature
- pH
What 3 things are needed for chemical reactions to occur naturally?
- Reactants must collide with enough energy to change their atom arrangement
- The free energy of the products must be less than that of the reactants (substrates)
- There must be enough activation energy
What kind of protein is an enzyme?
Globular protein
What is the shape of an enzyme’s active site detemined by?
The protein’s tertiary structure
What is a protein’s primary structure determined by?
- Which amino acids are present
- How many are present
- What order they’re arranged in
In the Induced Fit Model (IFM), how to enzymes, substrates and active sites fit together?
- The active site of an enzyme only takes the shape of the substrate when they collide
- The flexibility of the polypeptide chains in the enzyme allows it to change the shape of its active site around the substrate, if all the right bonds can be formed in all the right places
- If this happens, the reaction can happen
How is the enzyme able to shape its active site around a substrate?
The flexibility of the polypeptide chains allows the active site to shape the substrate, only if all the right bonds can be formed in all the right places
What is the molecule called that forms between an enzyme and a substrate when they bond?
Enzyme-substrate complex
How does temperature affect the rate of enzyme-catalysed reactions?
If the temperature is increased, the active site starts to denature, so the enzyme can’t fit withe the substrate, so it can’t catalyse the reaction
How does pH affect the rate of enzyme-catalysed reactions?
- The hydrogen and ionic bonds (in the enzyme) will be disrupted by the presence of H+ or OH- ions
- If the ionic bonds are swamped with H+ or OH- ions, the electrostatic forces of attraction will be interfered with and they’ll weaken
- Changes in pH away from the enzyme’s optimum pH will interfere with the hydrogen and ionic bonds in the enzyme’s tertiary structure
- The shape changes and the active site no longer matches the substrate, so the enzyme can’t react with it
What does a higher concentration of substrates mean for the reaction?
Means that it’s more likely for a substrate to bind with an active site
What does ‘inhibition’ mean?
Certain “inhibitor molecules” can prevent an enzyme from working
What are the 2 types of enzyme inhibition?
- Competitive inhibition
- Non-competitive inhibition
Describe competitive inhibition
When a molecule, other than an enzyme-specific substrate, is complementary to the active site of the enzyme and stops the reaction from being catalysed
Describe non-competitive inhibition
- Doesn’t occupy the active site
- They attack the allosteric site, distorting the shape of the active site so that it’s not longer complementary to the substrate
Describe how inhibitors affect enzymes
- Competitive inhibitor mimics substrate and competes for the active site
- Non-competitive inhibitor alters conformation of enzyme so active site is no longer fully functioning
Which type of lipid is a good energy-storage molecule? Why?
Triglyceride - there is a higher ratio of carbon-hydrogen bonds to oxygen bonds
