1
Q
What name is given to the small molecular subunits that join together to form larger biological molecules?
A
Monomers
Small repeating building blocks that can be chemically joined to form larger molecules.
2
Q
What term describes a large molecule formed when many repeating subunits are chemically bonded together?
A
Polymer
Polymers consist of many monomers linked in long chains or complex structures.
3
Q
Glucose and other simple sugars belong to which class of biological monomer?
A
Monosaccharides
These single sugar units can combine to form disaccharides and polysaccharides.
4
Q
Which type of monomer joins together to form proteins?
A
Amino acids
Amino acids link via peptide bonds during protein synthesis.
5
Q
DNA and RNA are built from repeating units known as what?
A
Nucleotides
Each nucleotide contains a sugar, phosphate group, and nitrogen-containing base.
6
Q
What type of reaction joins two molecules together while releasing a molecule of water?
A
Condensation reaction
Also called a dehydration reaction, it commonly forms glycosidic, peptide, and ester bonds.
7
Q
Fill in the blank:
A condensation reaction forms a chemical bond between molecules and releases a molecule of _______.
A
Water
Water is removed when the bond forms between the monomers.
8
Q
What type of reaction breaks a bond between two molecules using a molecule of water?
A
Hydrolysis
The reverse of condensation; it is common in digestion of biological polymers.
9
Q
True or False:
Hydrolysis reactions build polymers from monomers.
A
False
Hydrolysis breaks polymers into smaller units; condensation builds them.
10
Q
What class of biological molecule includes sugars, starch and glycogen?
A
Carbohydrates
Carbohydrates are organic molecules composed of carbon, hydrogen and oxygen, often used for energy storage or structural roles.
11
Q
What type of monomer forms larger carbohydrate molecules?
A
Monosaccharides
Monosaccharides are single sugar units that act as building blocks for disaccharides and polysaccharides.
12
Q
Name three common monosaccharides found in biological systems.
A
- Glucose
- Galactose
- Fructose
These are hexose sugars with the same molecular formula but slightly different structures.
13
Q
What type of chemical bond forms when two monosaccharides join together?
A
Glycosidic bond
This bond forms during a condensation reaction between two sugar molecules.
14
Q
Fill in the blank:
Two monosaccharides join together through a _______ reaction to form a glycosidic bond.
A
Condensation
The reaction removes a molecule of water as the bond forms.
15
Q
What carbohydrate is produced when two glucose molecules join together?
A
Maltose
Maltose is a disaccharide commonly produced during starch digestion.
16
Q
Which disaccharide forms when glucose combines with fructose?
A
Sucrose
Sucrose is the main sugar transported in the phloem of plants.
17
Q
Which disaccharide is formed from glucose and galactose?
A
Lactose
Lactose is the sugar found in milk.
18
Q
Glucose exists in two structural forms known as what?
A
Isomers
The two forms are α-glucose and β-glucose, which differ in the arrangement of atoms around one carbon.
19
Q
What two specific structural forms of glucose exist in solution?
A
- α-glucose
- β-glucose
They differ in the orientation of the hydroxyl group on carbon 1.
20
Q
What term describes carbohydrates formed by many glucose units joined together?
A
Polysaccharides
These are large polymer molecules built from many monosaccharides.
21
Q
Which two polysaccharides are formed from α-glucose in living organisms?
A
Starch and glycogen
Both are energy storage molecules in plants and animals respectively.
22
Q
Which polysaccharide is formed from β-glucose?
A
Cellulose
Cellulose forms strong fibres used in plant cell walls.
23
Q
What is the main storage carbohydrate in animals?
A
Glycogen
Glycogen is stored mainly in the liver and muscles and can be rapidly broken down to release glucose.
24
Q
What is the main storage carbohydrate in plants?
A
Starch
Starch is stored in plant cells and consists of amylose and amylopectin molecules.
25
What is the main **structural carbohydrate** found in **plant cell walls**?
Cellulose
## Footnote
Cellulose forms strong microfibrils that provide structural support to plant cells.
26
Which **reagent** is used to test for **reducing sugars**?
Benedict's solution
## Footnote
When heated to near boiling (≈95 °C) with a reducing sugar, the solution changes from blue to green, yellow, orange or brick-red depending on the concentration of reducing sugar.
27
What **colour change** occurs when **Benedict's test** gives a positive result for reducing sugars?
Blue to brick-red precipitate
## Footnote
The colour may vary depending on sugar concentration.
28
How can a **non-reducing sugar** be tested using **Benedict's solution**?
Hydrolysis
## Footnote
The sugar is first hydrolysed with dilute acid, neutralised, then tested with Benedict’s solution.
29
Which **reagent** is used to test for **starch**?
Iodine solution
## Footnote
Iodine/potassium iodide turns from brown/orange to blue-black in the presence of starch.
30
# True or False:
**Glycogen** is the main **storage carbohydrate** in plants.
False
## Footnote
Plants store carbohydrates mainly as starch, while animals store glycogen.
31
# Fill in the blank:
**Iodine solution** turns _\_\_\_\_\_\_ in the presence of **starch**.
Blue-black
## Footnote
This colour change is used in qualitative food tests for starch.
32
Which two major **groups of biological lipids** are required in the **AQA specification**?
Triglycerides and phospholipids
## Footnote
Both are important biological lipids but have different structures and functions in organisms.
33
What type of **molecule** combines with **fatty acids** to form triglycerides?
Glycerol
## Footnote
Glycerol is a three-carbon alcohol that forms the backbone of triglycerides.
34
How many **fatty acid molecules** are present in one **triglyceride molecule**?
Three
## Footnote
Each fatty acid attaches to glycerol via an ester bond.
35
# Fill in the blank:
A **triglyceride** forms when one **glycerol molecule** reacts with three _\_\_\_\_\_\_ molecules.
Fatty acid
## Footnote
This occurs through condensation reactions.
36
What type of **chemical bond** forms between **glycerol and fatty acids** in triglycerides?
Ester bond
## Footnote
Each ester bond forms during a condensation reaction that releases water.
37
# Fill in the blank:
An **ester bond** forms between **glycerol** and a **fatty acid** during a _\_\_\_\_\_\_ reaction.
Condensation
## Footnote
Water is released when the ester bond forms.
38
What term describes a **fatty acid** that contains no **carbon–carbon double bonds**?
Saturated
## Footnote
Saturated fatty acids contain the maximum number of hydrogen atoms.
39
What term describes a **fatty acid** that contains one or more **carbon–carbon double bonds**?
Unsaturated
## Footnote
Double bonds introduce bends in the fatty acid chain.
40
# True or False:
**Unsaturated fatty acids** contain at least one **carbon–carbon double bond**.
True
## Footnote
These double bonds affect the shape and physical properties of the lipid.
41
In **phospholipids**, what **group** replaces one of the fatty acids found in a triglyceride?
Phosphate group
## Footnote
This substitution creates a molecule with different chemical properties.
42
Which **lipid type** is a major component of **cell membranes**?
Phospholipids
## Footnote
Their structure allows them to form bilayers in aqueous environments.
43
Which **lipid type** is primarily used for **long-term energy storage** in organisms?
Triglycerides
## Footnote
They have a high energy content and are stored in adipose tissue in animals.
44
Why are **triglycerides** good **energy storage molecules**?
They have high energy content.
## Footnote
They contain many C–H bonds and are insoluble, so they do not affect water potential.
45
Why are **phospholipids** suited to forming **cell membranes**?
They are amphipathic.
## Footnote
They have a hydrophilic phosphate head and hydrophobic fatty acid tails.
46
What **qualitative test** is used to detect **lipids** in a food sample?
Emulsion test
## Footnote
The test uses ethanol and water to detect lipids.
47
# Fill in the blank:
A **positive emulsion test** for **lipids** produces a _\_\_\_\_\_\_ white emulsion.
Milky
## Footnote
Lipids dissolve in ethanol and form a cloudy emulsion when water is added.
48
What **reagent** is first added to a sample during the **emulsion test for lipids**?
Ethanol
## Footnote
The mixture is shaken and then water is added to observe the emulsion.
49
What type of biological **monomer** joins together to form **proteins**?
Amino acids
## Footnote
Proteins are polymers formed from chains of amino acids linked together.
50
What **functional group** is represented by **NH₂** in the general structure of an amino acid?
Amine group
## Footnote
This basic group contains nitrogen and can accept a hydrogen ion.
51
What **functional group** is represented by **COOH** in an amino acid?
Carboxyl group
## Footnote
This acidic group can donate a hydrogen ion in solution.
52
# Fill in the blank:
The part of an amino acid that differs between different **amino acids** is the \_\_\_\_\_\_ **group**.
R group
## Footnote
The R group (side chain) determines the chemical properties of the amino acid.
53
What type of **bond** forms when two **amino acids** join together?
Peptide bond
## Footnote
This bond forms during a condensation reaction between the amine group of one amino acid and the carboxyl group of another.
54
# Fill in the blank:
A \_\_\_\_\_\_ **reaction** occurs when two **amino acids** join to form a peptide bond.
Condensation
## Footnote
A molecule of water is released when the bond forms.
55
What **molecule** is formed when two **amino acids** join together?
Dipeptide
## Footnote
A dipeptide contains two amino acids linked by one peptide bond.
56
What name is given to a long chain of many **amino acids** joined together?
Polypeptide
## Footnote
Polypeptides may fold to form functional proteins.
57
A functional **protein** may consist of one or more what type of **chain**?
Polypeptides
## Footnote
Some proteins contain multiple polypeptide subunits.
58
What level of **protein structure** refers to the **sequence of amino acids** in a polypeptide chain?
Primary structure
## Footnote
The order of amino acids is determined by the DNA sequence.
59
What level of **protein structure** forms when a polypeptide chain coils into an **α-helix** or folds into a **β-pleated sheet**?
Secondary structure
## Footnote
Stabilised mainly by hydrogen bonds between peptide bonds in the backbone.
60
What level of **protein structure** describes the overall **three-dimensional folding** of a polypeptide?
Tertiary structure
## Footnote
Stabilised by hydrogen bonds, ionic bonds and disulfide bridges between R groups.
61
What level of **protein structure** occurs when multiple **polypeptide chains** combine to form a functional protein?
Quaternary structure
## Footnote
Examples include haemoglobin, which contains multiple polypeptide subunits.
62
Which type of **bond** forms between **sulfur atoms** in some amino acid side chains?
Disulfide bridge
## Footnote
These strong covalent bonds help stabilise the tertiary structure of proteins.
63
Which type of **bond** forms between **oppositely charged side chains** in proteins?
Ionic bonds
## Footnote
These interactions contribute to stabilising tertiary structure.
64
Which relatively weak **bonds** help stabilise both **secondary and tertiary protein structures**?
Hydrogen bonds
## Footnote
Many hydrogen bonds together help maintain protein shape.
65
Why is **protein structure** important for **protein function**?
They have a specific shape.
## Footnote
The precise 3D structure determines how the protein interacts with other molecules.
66
What **chemical test** is used to detect **proteins** in a sample?
Biuret test
## Footnote
The test detects peptide bonds present in proteins.
67
# Fill in the blank:
A positive **Biuret test** changes the **solution** from blue to \_\_\_\_\_\_.
Purple
## Footnote
The colour change indicates the presence of peptide bonds in proteins.
68
# True or False:
All **proteins** consist of only one **polypeptide chain**.
False
## Footnote
Many proteins contain multiple polypeptide chains forming quaternary structure.
69
What type of **biological molecule** acts as a **catalyst** in living organisms?
Enzymes
## Footnote
Enzymes are proteins that speed up biochemical reactions without being used up.
70
What effect does an **enzyme** have on the **activation energy** of a reaction?
Lowers activation energy
## Footnote
By lowering activation energy, enzymes increase the rate of reactions.
71
What model describes how **enzyme active sites** change shape to fit a **substrate** during binding?
Induced-fit model
## Footnote
The active site becomes more complementary to the substrate as binding occurs.
72
What region of an **enzyme** binds to the **substrate** during a reaction?
Active site
## Footnote
The active site has a specific tertiary structure that allows substrate binding.
73
# Fill in the blank:
When a **substrate** binds to an **enzyme**, an _\_\_\_\_\_\_ complex is formed.
Enzyme-substrate complex
## Footnote
This temporary complex allows the reaction to occur more easily.
74
Why are enzymes considered highly **specific**?
They have an active site with a complementary shape which is coded for by the specific sequence of amino acids.
## Footnote
The shape of the active site only fits particular substrates.
75
# True or False:
Each **enzyme** usually catalyses only **one specific reaction**.
True
## Footnote
Enzyme specificity arises from the precise structure of the active site.
76
What happens to the **rate** of an **enzyme-controlled reaction** when enzyme concentration increases (if substrate is abundant)?
Increases
## Footnote
More enzyme molecules mean more available active sites.
77
How does increasing **substrate concentration** affect the **rate** of an enzyme-controlled reaction?
Increases, then plateaus.
## Footnote
The rate rises until all enzyme active sites become occupied.
78
What type of **inhibitor** competes with the **substrate** for the active site of an enzyme?
Competitive inhibitor
## Footnote
These inhibitors have a similar shape to the substrate.
79
What type of **inhibitor** binds to an enzyme at a site other than the **active site**?
Non-competitive inhibitor
## Footnote
This binding alters the enzyme's shape and reduces its activity.
80
How does a **competitive inhibitor** affect **enzyme activity**?
Competes with the substrate.
## Footnote
It reduces reaction rate by blocking substrate binding to the active site.
81
How does a **non-competitive inhibitor** affect **enzyme activity**?
Alters the shape of the active site.
## Footnote
This prevents the substrate from binding effectively.
82
Why does **temperature** affect **enzyme-controlled reactions**?
It changes kinetic energy and enzyme structure.
## Footnote
High temperatures can denature enzymes by breaking bonds that maintain their tertiary structure.
83
What happens to an **enzyme** when it becomes **denatured**?
Active site changes shape.
## Footnote
The substrate can no longer bind, so the enzyme stops functioning.
84
Why does **pH** affect **enzyme activity**?
It alters bonds that maintain enzyme structure.
## Footnote
Changes in pH can disrupt bonds that maintain the enzyme’s tertiary structure.
85
What formula can be used to calculate **pH** from **hydrogen ion concentration**?
pH = −log10[H⁺]
## Footnote
This logarithmic relationship shows that small changes in pH represent large changes in H⁺ concentration.
86
What practical **investigation** is commonly used to study **enzymes** in AQA Biology?
Enzyme rate investigation
## Footnote
Students measure how changing a variable affects the rate of an enzyme-controlled reaction.
87
What **mathematical method** can be used to determine the **initial rate** of an enzyme reaction from a graph?
Tangent method
## Footnote
A tangent drawn at the start of the curve allows calculation of the initial rate.
88
What type of biological molecule carries **genetic information** in almost all living cells?
DNA
## Footnote
Stores hereditary information and forms chromosomes in eukaryotic cells.
89
Which molecule carries genetic instructions from **DNA** to **ribosomes** during protein synthesis?
mRNA
## Footnote
Acts as an intermediary between DNA and ribosomes.
90
What type of **macromolecule** are both **DNA and RNA** classified as?
Polynucleotides
## Footnote
They are long chains of repeating nucleotide monomers.
91
What is the **monomer unit** that builds both **DNA and RNA polymers**?
Nucleotide
## Footnote
Each nucleotide consists of a pentose sugar, phosphate group and nitrogen-containing base.
92
What three **components** make up a **nucleotide**?
* Pentose sugar
* Phosphate group
* Nitrogen-containing base
## Footnote
These components form the basic unit of nucleic acids.
93
Which **pentose sugar** is present in **DNA nucleotides**?
Deoxyribose
## Footnote
Deoxyribose lacks one oxygen atom compared with ribose.
94
Which **pentose sugar** is present in **RNA nucleotides**?
Ribose
## Footnote
Ribose contains one more oxygen atom than deoxyribose.
95
Which four **organic bases** occur in **DNA nucleotides**?
* Adenine
* Cytosine
* Guanine
* Thymine
## Footnote
Often abbreviated as A, C, G and T.
96
Which **organic base** is found in **RNA instead of thymine**?
Uracil
## Footnote
RNA contains A, C, G and U.
97
What type of **reaction** joins two **nucleotides** together when forming a nucleic acid polymer?
Condensation reaction
## Footnote
Water is released during the formation of the bond.
98
What is the name of the **covalent bond** formed between **nucleotides** in DNA and RNA chains?
Phosphodiester bond
## Footnote
Forms between the phosphate group of one nucleotide and the sugar of another.
99
What is the overall **three-dimensional shape** of a **DNA molecule**?
Double helix
## Footnote
Two polynucleotide strands twist around each other.
100
What type of **bond** holds the two **DNA strands** together?
Hydrogen bonds
## Footnote
These occur between complementary bases.
101
How are **bases paired** between the two **DNA strands**?
Complementary base pairing
## Footnote
Adenine pairs with thymine and cytosine pairs with guanine.
102
# True or False:
**DNA** consists of two **polynucleotide chains** that twist to form a double helix.
True
## Footnote
The strands run in opposite directions and are joined by hydrogen bonds.
103
# True or False:
**RNA** usually forms a long **double-stranded helix** like DNA.
False
## Footnote
RNA is usually a shorter single polynucleotide chain.
104
What **structure in cells** is made partly from **RNA** and is responsible for protein synthesis?
Ribosome
## Footnote
Ribosomes consist of ribosomal RNA (rRNA) and proteins.
105
# Fill in the blank:
A **DNA molecule** consists of two \_\_\_\_\_\_ chains held together by **hydrogen bonds** between bases.
Polynucleotide
## Footnote
Each chain is made from many nucleotides joined by phosphodiester bonds.
106
Why did early scientists doubt that **DNA** carried **genetic information**?
DNA appeared too simple.
## Footnote
DNA has only four bases and a repeating structure, appearing too simple to encode complex information.
107
If **30% of the bases** in a **DNA strand** are adenine, what percentage must be thymine?
30%
## Footnote
Complementary base pairing means A pairs with T in equal proportions.
108
How does **DNA replication** ensure that **genetic information** is maintained when a cell divides?
Semi-conservative replication
## Footnote
Each daughter DNA molecule contains one original strand and one newly synthesised strand.
109
What type of **structure** must be unwound at the start of **DNA replication**?
Double helix
## Footnote
The two antiparallel polynucleotide strands must separate so their bases can be copied.
110
Which enzyme separates the two **DNA strands** during replication by breaking the **bonds between bases**?
DNA helicase
## Footnote
This enzyme unwinds the helix and breaks hydrogen bonds between complementary bases.
111
What type of **bond** between complementary bases must be broken to separate the **DNA strands**?
Hydrogen bonds
## Footnote
These weak bonds hold base pairs together between the two strands.
112
During replication, exposed bases on the original strand attract free nucleotides according to which **rule** of **base pairing**?
Complementary base pairing
## Footnote
Adenine pairs with thymine and cytosine pairs with guanine.
113
# Fill in the blank:
Free DNA nucleotides align with bases on the original strand because it acts as a \_\_\_\_\_\_.
Template strand
## Footnote
Each original strand guides the order of nucleotides in the new strand.
114
Which enzyme joins adjacent nucleotides together to build the **new DNA strand** during **DNA replication**?
DNA polymerase
## Footnote
It catalyses the formation of phosphodiester bonds during strand synthesis.
115
What type of **reaction** joins neighbouring nucleotides together during **DNA replication**?
Condensation reaction
## Footnote
A molecule of water is released when the sugar-phosphate backbone forms.
116
# True or False:
Each **new DNA molecule** formed after replication contains **two completely new strands**.
False
## Footnote
Each DNA molecule contains one original strand and one newly synthesised strand.
117
What process occurs when the **DNA strands separate** and the **helix opens** up during replication?
DNA unwinding
## Footnote
This step allows the bases to become exposed for complementary pairing.
118
# Fill in the blank:
The enzyme that builds the new strand forms bonds between nucleotides to create the **sugar-phosphate** \_\_\_\_\_\_.
Backbone
## Footnote
The backbone consists of alternating deoxyribose sugars and phosphate groups.
119
Which classic experiment provided strong evidence supporting the **Watson–Crick model** of **DNA replication**?
Meselson–Stahl experiment
A-Level Biology (OCR)
flashcards
Decks in class (28)
# Cards
-
2: Biological Molecules119
-
2: Water & Inorganic Ions19
-
2: Cells52
-
2: Cell Division20
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2: Membranes & Transport20
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2: Exchange Surfaces37
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2: Transport Systems39
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2: Immune system36
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2: Enzymes & Digestion16
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3: Plant Transport20
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4: Biodiversity & Classification32
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4: Investigating Diversity12
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4: Evolution42
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4: Disease24
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5: Photosynthesis23
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5: Respiration17
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5: Energy & Ecosystems35
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5: Homeostasis57
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5: Nervous & Hormonal Communication115
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5: Muscles14
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6: DNA & Protein Synthesis27
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6: Meiosis & Genetic Diversity14
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6: Inheritance12
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6: Populations (Hardy–Weinberg)15
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6: Ecosystems & Population Dynamics24
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6: Gene Mutations & Expression58
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6: Biotechnology & Genomics46
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6: ATP & Energy Transfer (Integration)11
