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biological molecules Flashcards

1
Q

What makes water a polar molecule?

A

Unequal charge distribution due to oxygen being slightly negative and hydrogen being slightly positive, leading to hydrogen bonding.

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2
Q

How does water act as a solvent?

A

Dissolves polar substances, allowing metabolic reactions to occur in solution

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3
Q

What is latent heat of vaporisation?
+ give 2 examples

A

The energy required to turn water into vapor; provides a cooling effect in sweating and transpiration.

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3
Q

Why does water have a high specific heat capacity?

whats a use of this?

A

Hydrogen bonding absorbs energy, minimises temperature fluctuations in organisms.

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4
Q

Why is ice less dense than liquid water?

whats a use of this?

A

Water molecules are held further apart when frozen

creating an insulating layer that protects aquatic life.

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4
Q

What are monosaccharides?

give 3 examples

A

Single sugar molecules (glucose, fructose, galactose) used for energy.

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5
Q

How does cohesion benefit organisms?

A

Water molecules stick together, enabling transport in xylem.

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6
Q

How do monosaccharides join together?

A

Condensation reactions forming glycosidic bonds.

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7
Q

What is a disaccharide?

give 3 examples

A

Two monosaccharides joined by a glycosidic bond (e.g., maltose, sucrose, lactose).

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8
Q

How is a glycosidic bond broken?

A

Hydrolysis reaction using water.

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9
Q

What are polysaccharides?

what are the ones used for storage?
what are the ones used for structure

A

Long chains of monosaccharides used for storage (starch, glycogen) or structure (cellulose, chitin).

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10
Q

How is starch structured?

A

Made of amylose (unbranched, coiled for compact storage) and amylopectin (branched for quick energy release).

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11
Q

What is the function of glycogen?

A

Highly branched for rapid glucose release, stored in animals.

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12
Q

What is the function of cellulose?

A

Provides structural support in plant cell walls due to hydrogen bonding.

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13
Q

What are triglycerides composed of?

A

Glycerol and three fatty acids linked by ester bonds.

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14
Q

What is cholesterol’s role in membranes?

A

Provides stability and reduces permeability.

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14
Q

What is the difference between saturated and unsaturated fats?

A

Saturated fats have no double bonds (solid at room temp), unsaturated fats have double bonds (liquid at room temp).

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14
Q

How are triglycerides adapted for energy storage?

A

High energy-to-mass ratio, insoluble in water.

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15
Q

What is the function of phospholipids?

A

Form cell membranes due to hydrophilic heads and hydrophobic tails.

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16
Q

What are amino acids?

A

Monomers of proteins, containing an amino group, carboxyl group, and R-group.

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16
Q

How are amino acids joined?

A

Peptide bonds through condensation reactions.

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17
Q

What is an example of a fibrous protein?

A

Collagen—strong due to hydrogen and covalent bonding.

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18
Q

What are the four levels of protein structure?

A

Primary: Sequence of amino acids.

Secondary: Alpha-helix or beta-sheet (hydrogen bonds).

Tertiary: 3D shape (disulfide, ionic, hydrogen bonds).

Quaternary: Multiple polypeptides (e.g., hemoglobin).

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19
Q

What is an example of a globular protein?

A

Hemoglobin—soluble, carries oxygen in red blood cells.

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20
What is the function of enzymes?
Biological catalysts that speed up reactions without being consumed.
21
How do enzymes lower activation energy?
providing an alternative reaction pathway with a lower energy requirement
22
What is the lock and key model?
substrate fits exactly into the active site.
23
What is the induced fit model?
Active site changes shape slightly to accommodate substrate.
24
How does temperature affect enzyme activity?
Increases rate until denaturation at high temperatures.
25
How does substrate concentration affect enzyme activity?
Increases rate until saturation point. When the amount of available substrate exceeds the amount of enzymes, then no more substrate can be broken down.
25
How does pH affect enzyme activity?
Hydrogen and ionic bonds hold the tertiary structure of the protein (ie. the enzyme) together Below and above the optimum pH of an enzyme, solutions with an excess of H+ ions (acidic solutions) and OH- ions (alkaline solutions) can cause these bonds to break The breaking of bonds alters the shape of the active site, which means enzyme-substrate complexes form less easily Eventually, enzyme-substrate complexes can no longer form at all At this point, complete denaturation of the enzyme has occurred
26
What are competitive inhibitors?
Molecules that bind to the active site, blocking substrate binding.
27
What are non-competitive inhibitors?
Bind on alternitive binding site on enzyme, altering active site shape. substrate can no longer bind.
28
What are nucleotides?
Monomers of nucleic acids, composed of a phosphate group, pentose sugar, and nitrogenous base.
29
explain how do DNA and RNA differ? | 6 marks
**1. Structure** **DNA** Strands Double-stranded (forms a double helix) Deoxyribose Larger more stable Adenine (A), Thymine (T), Cytosine (C), Guanine **RNA** (G) Adenine (A), Uracil (U), Cytosine (C), Guanine (G) Smaller, less stable Ribose Single-stranded **2. Function** **DNA:** Stores genetic information and acts as a blueprint for proteins. **RNA:** Helps transfer genetic information for protein synthesis. **3. Types of RNA** mRNA (Messenger RNA): Carries genetic code from DNA to ribosomes. tRNA (Transfer RNA): Brings amino acids for protein synthesis. rRNA (Ribosomal RNA): Forms ribosomes, which assemble proteins.
30
How are nucleotides joined?
Phosphodiester bonds between phosphate and sugar groups.
31
What is complementary base pairing?
A-T and C-G in DNA; A-U and C-G in RNA.
32
What is ATP composed of?
Adenine, ribose, and three phosphate groups.
33
How is energy released from ATP?
Hydrolysis of the terminal phosphate group.
34
What enzyme catalyses ATP hydrolysis?
ATP hydrolase.
35
How is ATP resynthesised?
ADP + Pi → ATP via ATP synthase during respiration and photosynthesis.
36
How is reducing sugar detected?
Benedict’s test—red precipitate forms.
37
How is non-reducing sugar tested?
Acid hydrolysis followed by Benedict’s test.
38
How is starch detected?
Iodine test—turns blue-black.
39
How is protein detected?
Biuret test—turns lilac in presence of peptide bonds.
40
How is lipid detected?
Emulsion test—milky-white emulsion forms if lipids are present.
41
What is the general formula for a monosaccharide?
(CH₂O)n, where n = usually 3 to 7.
42
Draw α-glucose and β-glucose?
In α-glucose, the OH group on carbon 1 is below the ring; in β-glucose, it is above the ring. remember down up down when placing the OH groups
43
What are the three common disaccharides and their monosaccharide components?
Maltose = Glucose + Glucose Sucrose = Glucose + Fructose Lactose = Glucose + Galactose
44
What are the two components of starch?
Amylose and Amylopectin.
45
What is the structure of amylose?
Unbranched polymer of α-glucose. Coiled into a helix for compact storage. 1,4 glycosidic bonds only.
46
What is the structure of amylopectin?
Branched polymer of α-glucose. Contains 1,4 and 1,6 glycosidic bonds (allows faster breakdown).
47
Why is starch a good storage molecule?
Insoluble (does not affect water potential). Compact (lots of glucose stored in a small space). Easily hydrolysed for energy release.
48
What is the structure of glycogen?
Highly branched polymer of α-glucose. More 1,6 glycosidic bonds than amylopectin (faster energy release). Found in animals (stored in liver and muscle cells).
49
What is the structure of cellulose?
Unbranched polymer of β-glucose. Every other β-glucose is flipped to form straight chains. Chains are held together by hydrogen bonds, forming microfibrils for structural support.
50
Why is cellulose strong?
Many hydrogen bonds between chains. Forms fibres for structural support in plant cell walls
51
How do you test for reducing sugars?
Add Benedict’s reagent to the sample. Heat in a water bath at 80°C. A brick-red precipitate indicates a reducing sugar.
52
Which sugars are reducing sugars?
All monosaccharides and some disaccharides (e.g., maltose, lactose).
53
How do you test for non-reducing sugars (e.g., sucrose)?
First boil with hydrochloric acid to hydrolyse glycosidic bonds. Neutralise with sodium hydrogen carbonate. Then perform Benedict’s test as normal.
54
What is the structure of a triglyceride?
1 glycerol molecule. 3 fatty acids. Joined by ester bonds in a condensation reaction.
55
What is the difference between saturated and unsaturated fatty acids?
Saturated = No C=C double bonds (solid at room temp). Unsaturated = At least one C=C double bond (liquid at room temp).
56
What bond forms between glycerol and fatty acids?
Ester bond (formed by a condensation reaction).
57
How do triglycerides act as a good energy store?
High energy content due to many C-H bonds. Insoluble (does not affect water potential).
58
Why do phospholipids form a bilayer in water?
The phosphate head is hydrophilic (attracts water). The fatty acid tails are hydrophobic (repel water). This creates a bilayer with hydrophobic tails facing inwards.
59
How does the phospholipid bilayer control what enters and leaves the cell?
Small, non-polar molecules (e.g., oxygen, CO₂) diffuse through easily. Ions and large molecules require transport proteins.
60
How do you test for lipids?
Add ethanol and shake. Pour into water. A milky-white emulsion indicates lipids.
61
What is the monomer of a protein?
Amino acid.
62
What is the general structure of an amino acid?
Amino group (-NH₂). Carboxyl group (-COOH). R group (varies between amino acids).
63
What is the primary structure of a protein?
A sequence of amino acids in a polypeptide chain.
64
What is the secondary structure of a protein?
Hydrogen bonds form, creating an α-helix or β-pleated sheet.
65
What is the tertiary structure of a protein?
Further folding of the polypeptide. Bonds involved: Hydrogen bonds (weak). Ionic bonds (between R groups). Disulfide bridges (strong covalent bonds between cysteine).
66
What is the quaternary structure of a protein?
Two or more polypeptide chains joined together (e.g., haemoglobin).
67
What are the key properties of a globular protein?
Spherical and soluble. Hydrophilic R groups on the outside. Example: Haemoglobin (carries oxygen in the blood).
68
What are the key properties of a fibrous protein?
Long, strong, and insoluble. Used for structural purposes. Example: Collagen (found in skin and connective tissues).
69
How do you test for proteins?
Add Biuret reagent (sodium hydroxide + copper sulfate). A purple colour indicates protein.
76
beta pleated sheet
folds
77
alpha helix
curve
78
what can a beta sheet also be represented as?
arrow
79
quaternary structure
protein made up of two or more poly peptide bonds

biology (28 decks)

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