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Biology A Level > Topic 2 - Genes and Health > Flashcards

Topic 2 - Genes and Health Flashcards

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1
Q

What factors increase the rate of gas exchange by diffusion?

A
  • Increased surface area
  • Diffusion distance decreases
  • Steeper diffusion gradient

These factors enhance the efficiency of gas exchange in biological systems.

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2
Q

What is Fick’s Law?

A

Rate of diffusion = SA x Concentration difference/ diffusion distance

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3
Q

What does Fick’s Law state regarding the rate of diffusion?

A

The larger the surface area, difference in concentration, and shorter the diffusion distance, the quicker the rate.

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4
Q

What adaptations do mammal lungs have for rapid gas exchange?

A
  • Large surface area due to many alveoli
  • Good supply of circulating blood
  • Short diffusion distance as alveoli are one cell thick

These adaptations ensure efficient oxygen uptake and carbon dioxide removal.

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5
Q

What is the primary function of the cell membrane?

A

Controlling the movement of substances in and out of the cell/organelle.

The cell membrane also contains receptors for other molecules and facilitates cell adhesion.

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6
Q

Describe the composition of the cell membrane?

A

A partially permeable membrane composed of a sea of phospholipids with protein molecules between them.

The arrangement of proteins and lipids gives the membrane its unique properties.

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7
Q

What is the fluid mosaic model?

A

A model describing the structure of the cell membrane - its fluidity and mosaic arrangement of proteins, with dynamic and flexible components

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8
Q

What types of proteins are found in the cell membrane?

A
  • Transport proteins
  • Receptor proteins
  • Enzymes
  • Structural proteins
  • Recognition proteins

These proteins play various roles in cell function and communication.

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9
Q

Fill in the blank: The movement of molecules through the cell membrane depends on the properties of the _______ as well as the requirements of the cell.

A

[molecule]

Different molecules have varying abilities to permeate the membrane based on size, polarity, and other characteristics.

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10
Q

What is diffusion?

A

The passive movement of small, non-polar, lipid-soluble molecules from an area of high concentration to low concentration through the phospholipid bilayer

Examples include carbon dioxide and oxygen

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11
Q

What factors increase the rate of gas exchange by diffusion?

A

The rate becomes more rapid as:
* Surface area increases
* Diffusion distance decreases
* Diffusion gradient becomes steeper

These factors facilitate faster movement of molecules.

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12
Q

What is facilitated diffusion?

A

The transport of polar, charged, and water-soluble molecules across the membrane via a channel protein

This process does not require energy.

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13
Q

Define osmosis.

A

The net movement of water molecules from an area of low solute concentration to high solute concentration through a partially permeable membrane

This process is crucial for maintaining cell turgor.

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14
Q

What is active transport?

A

The transport of all types of molecules through carrier proteins, requiring energy in the form of ATP

It can occur against the concentration gradient.

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15
Q

What is the role of ATP in active transport?

A

ATP provides energy for the process; hydrolysis of ATP releases energy needed for transport

Phosphorylation of ATP also requires energy.

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16
Q

What is endocytosis?

A

Large particles are enclosed in vesicles made from the cell surface membrane and transported into the cell

This is an active transport mechanism.

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17
Q

What is exocytosis?

A

Vesicles containing large particles fuse with the cell surface membrane and are transported out of the cell

This also represents an active transport mechanism.

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18
Q

What are the components of a mononucleotide?

A

A mononucleotide consists of:
* A base (purine or pyrimidine)
* A sugar (deoxyribose)
* A phosphate group

Purines include adenine and guanine; pyrimidines include cytosine and thymine.

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19
Q

What is the pairing of bases in DNA?

A

A-T and C-G

This base pairing is essential for DNA structure.

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20
Q

What type of bond forms between the phosphate group and Carbon-5 in a nucleotide?

A

Phosphodiester bonds

These bonds link nucleotides together in a DNA strand.

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21
Q

What type of bond forms between the bases in DNA?

A

Hydrogen bonds

These bonds hold the two strands of DNA together.

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22
Q

Fill in the blank: The sugar in DNA is _______.

A

deoxyribose

This sugar is a pentose sugar.

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23
Q

What type of bonds hold the structure of nucleic acids together?

A

Hydrogen bonds

Hydrogen bonds are crucial for the stability of DNA and RNA structures.

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24
Q

What is the structure of DNA?

A

Double-stranded, alpha double helix with a sugar-phosphate backbone

The sugar-phosphate backbone provides structural support to the DNA molecule.

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25
Q

What are the purine bases in nucleic acids?

A

Adenine, guanine

Purines are one of the two categories of nitrogenous bases found in nucleic acids.

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26
Q

What are the pyrimidine bases in nucleic acids?

A

Cytosine, uracil

Pyrimidines are the second category of nitrogenous bases, with uracil found only in RNA.

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27
Q

What is the base pairing in RNA?

A

A-U, C-G

This pairing is crucial for the formation of RNA structures and their function in protein synthesis.

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28
Q

What sugar is found in RNA?

A

Ribose

Ribose is a five-carbon sugar that is part of the backbone of RNA.

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29
Q

What is the structure of mRNA?

A

Single-stranded, not usually folded, carries codons

Codons are triplets of bases in mRNA that correspond to specific amino acids.

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30
Q

What is the structure of tRNA?

A

Single-stranded, folded into a specific pattern

The folded structure allows tRNA to carry anticodons that are complementary to mRNA codons.

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31
Q

What are the two stages of protein synthesis?

A

Transcription, translation

Transcription occurs in the nucleus, while translation occurs at the ribosomes.

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32
Q

Where does transcription occur?

A

In the nucleus

Transcription is the process of creating mRNA from a DNA template.

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33
Q

What happens during transcription?

A

DNA uncoils, complementary bases pair to form mRNA

The antisense strand of DNA serves as a template for the mRNA synthesis.

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34
Q

What is the role of the antisense strand during transcription?

A

It serves as a template to make the mRNA molecule

The antisense strand is complementary to the mRNA produced.

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35
Q

What occurs during translation?

A

Amino acids are assembled to form a polypeptide chain/protein

Translation is the second stage of protein synthesis where mRNA is decoded by tRNA.

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36
Q

What is the process by which free nucleotides line up and form a molecule of mRNA?

A

Catalyzed by RNA polymerase

This involves complementary base pairing and the joining of adjacent nucleotides by phosphodiester bonds.

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37
Q

What does mRNA do after it is formed?

A

Moves out of the nucleus through a pore and attaches to a ribosome in the cytoplasm

This is where the next stage of protein synthesis occurs.

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38
Q

During translation, what do amino acids join together to form?

A

A polypeptide chain

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39
Q

What is the role of tRNA in translation?

A

Binds to specific amino acids from the cytoplasm depending on its anti-codon

This process is known as activation.

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40
Q

How do tRNA anticodons interact with mRNA codons?

A

They bind to mRNA codons and are held in place by hydrogen bonds.

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41
Q

What type of bond is formed between amino acids during translation?

A

Peptide bond

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42
Q

What happens to tRNA molecules after the ribosome joins the amino acids?

A

They detach from the amino acids.

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43
Q

What indicates the end of the formation of a polypeptide chain?

A

A stop codon is reached on mRNA.

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44
Q

What is a gene?

A

A series of bases on a DNA molecule coding for a series of amino acids in a polypeptide chain.

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45
Q

What is the order of bases on DNA referred to as?

A

The genetic code

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46
Q

What is the structure of the genetic code?

A

Consists of triplets of bases, each coding for a particular amino acid.

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47
Q

What are the non-coding sections of DNA called?

A

Introns

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48
Q

What are the coding regions of DNA called?

A

Exons

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49
Q

What does it mean that the genetic code is non-overlapping?

A

Each triplet is only read once and triplets don’t share any bases.

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50
Q

What does it mean that the genetic code is degenerate?

A

More than one triplet codes for the same amino acid.

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51
Q

What is the genetic code classified as?

A

A triplet code

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52
Q

What are start and stop codons?

A

They either start or stop protein synthesis.

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53
Q

What are the monomers from which proteins are made?

A

Amino acids

Amino acids contain an amino group, a carboxyl group, and a variable R group.

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54
Q

How many different amino acids are there?

A

20

Each amino acid has a different R group.

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55
Q

What type of bond joins amino acids together?

A

Peptide bonds

Formed in condensation reactions.

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56
Q

What is a dipeptide?

A

A molecule containing two amino acids

57
Q

What is a polypeptide?

A

A chain containing three or more amino acids

58
Q

What determines the structure of proteins?

A

The order and number of amino acids

59
Q

What is the primary structure of a protein?

A

The sequence of amino acids in a protein

60
Q

What is the secondary structure of a protein?

A

The 2D arrangement of the chain of amino acids

Can be either alpha helix or beta pleated sheet.

61
Q

What is the tertiary structure of a protein?

A

The 3D folding of the secondary structure into a complex shape

62
Q

What types of bonding determine the tertiary structure?

A

Hydrogen bonding, ionic bonds, and disulphide bridges

63
Q

What is the quaternary structure of a protein?

A

The 3D arrangement of more than one polypeptide

64
Q

Do all proteins have all levels of structure?

A

No

65
Q

What are fibrous proteins characterized by?

A

Long parallel polypeptides and very little tertiary/quaternary structure

66
Q

What is a key feature of fibrous proteins?

A

Insoluble

Used for structural purposes such as collagen.

67
Q

What are globular proteins characterized by?

A

Complex tertiary/quaternary structures

68
Q

What is a key feature of globular proteins?

A

Form colloids in water

69
Q

Name two uses of globular proteins.

A

Hormones and antibodies

70
Q

Fill in the blank: Amino acids are joined by _______.

A

Peptide bonds

71
Q

What type of protein is collagen?

A

Fibrous protein

Collagen has high tensile strength due to hydrogen and covalent bonds.

72
Q

What is the structure of collagen molecules?

A

Three polypeptides forming an alpha triple helix

This structure leads to the formation of fibrils and strong collagen fibers.

73
Q

What is the primary function of collagen in the body?

A

Forms the structure of bones, cartilage, and connective tissue

Collagen is a main component of tendons which connect muscles to bones.

74
Q

What type of protein is hemoglobin?

A

Water-soluble globular protein

Hemoglobin consists of four beta polypeptide chains and a haem group.

75
Q

What is the main function of hemoglobin?

A

Carries oxygen in the blood

Oxygen binds to the haem (Fe2+) group and is released when required.

76
Q

What are enzymes?

A

Biological catalysts

Enzymes increase the rate of reaction by lowering the activation energy.

77
Q

What model describes how substrates fit into enzymes?

A

Lock and key model

This model illustrates enzyme specificity to substrates.

78
Q

What is the induced-fit theory?

A

The enzyme changes shape to fit the substrate

The structure of the enzyme is distorted upon forming a complex with the substrate.

79
Q

How can the initial rate of reaction be measured?

A

By calculating the gradient of a concentration-time graph

This measurement helps in understanding enzyme kinetics.

80
Q

What effect does increasing enzyme concentration have on the rate of reaction?

A

Increases the rate until substrate concentration becomes limiting

Beyond a certain point, more active sites than substrates exist.

81
Q

What happens to the rate of reaction as substrate concentration increases?

A

Increases until enzyme concentration becomes limiting

Beyond a certain point, the formation of enzyme-substrate complexes plateaus.

82
Q

What is the optimum temperature for enzyme activity?

A

The temperature at which enzymes work best

Rate of reaction decreases beyond this temperature due to enzyme denaturation.

83
Q

How does pH affect enzyme activity?

A

Alters the bonds within its structure, affecting the active site shape

Enzymes work within a narrow range of specific pH values.

84
Q

What is the main purpose of semi-conservative replication of DNA?

A

To ensure genetic continuity between generations of cells.

85
Q

Who proved the semi-conservative model of DNA replication?

A

Meselson and Stahl.

86
Q

What are the three models of DNA replication?

A
  1. Semi-conservative replication
  2. Conservative replication
  3. Dispersive replication
87
Q

In the Meselson-Stahl experiments, what isotopes of nitrogen were used?

A

N15 and N14.

88
Q

What happens to DNA after one generation in N14 culture following growth in N15?

A

The DNA contains one strand with 15-N and one strand with 14-N.

89
Q

What is the outcome after two generations in N14 culture?

A

Half of the DNA molecules are the same as in generation one, and the other half contains entirely 14-N.

90
Q

What is the first step of semi-conservative replication of DNA?

A

The double helix unwinds and hydrogen bonds between complementary bases break, catalyzed by DNA helicase.

91
Q

What occurs during the second step of DNA replication?

A

One of the strands is used as a template for complementary base pairing with free nucleotides.

92
Q

What is formed during the third step of DNA replication?

A

Phosphodiester bonds are formed between adjacent nucleotides in condensation reactions, catalyzed by DNA polymerase.

93
Q

What is a mutation?

A

A permanent change in the DNA of an organism.

94
Q

What are the types of gene mutations?

A
  1. Substitution
  2. Insertion
  3. Deletion
  4. Duplication
95
Q

Fill in the blank: Substitution is a change in _______.

A

one base.

96
Q

Fill in the blank: Insertion involves _______ another base in.

A

adding.

97
Q

Fill in the blank: Deletion involves _______ a base out.

A

taking.

98
Q

Fill in the blank: Duplication involves _______ the same base more than once.

A

adding.

99
Q

What is inversion in genetics?

A

Swapping the order of bases around

This change affects the mRNA, tRNA, and the primary structure of proteins.

100
Q

What genetic disorder is caused by a mutation of a single gene coding for the CFTR protein?

A

Cystic fibrosis

CFTR protein is a channel protein that transports chloride ions out of respiratory tract cells.

101
Q

What role does the CFTR protein play in mucus consistency?

A

Transports chloride ions, making mucus watery

Water moves into mucus by osmosis due to chloride ion transport.

102
Q

What effect does a mutation in the CFTR gene have on mucus?

A

Makes the mucus very thick

A mutant CFTR protein is less efficient at transporting chloride ions.

103
Q

How does thick mucus affect the respiratory system?

A

Traps bacteria, increasing infection risk

It also decreases the surface area of alveoli for gas exchange.

104
Q

What is one impact of thick mucus on the reproductive system?

A

Cervical mucus prevents sperm from reaching the egg

In men, the sperm duct can be blocked with mucus.

105
Q

How does thick mucus affect the digestive system?

A

Blocks the pancreatic duct, preventing enzyme delivery

This leads to improper digestion and nutrient absorption.

106
Q

What happens to the mucus lining in the duodenum in cystic fibrosis?

A

Becomes very thick, reducing nutrient absorption

Thick mucus can also lead to cyst formation in the pancreas.

107
Q

What is a gene?

A

A piece of DNA with a specific sequence of bases

Each gene codes for a specific protein.

108
Q

Define allele.

A

One of the different forms of a particular gene

Alleles can result in different traits.

109
Q

What does genotype refer to?

A

All the alleles of an organism

It represents the genetic makeup.

110
Q

Define phenotype.

A

The set of observable characteristics of an individual

Resulting from the interaction of its genotype with the environment.

111
Q

What is inversion in genetics?

A

Swapping the order of bases around

This change affects the mRNA, tRNA, and the primary structure of proteins.

112
Q

What genetic disorder is caused by a mutation of a single gene coding for the CFTR protein?

A

Cystic fibrosis

CFTR protein is a channel protein that transports chloride ions out of respiratory tract cells.

113
Q

What role does the CFTR protein play in mucus consistency?

A

Transports chloride ions, making mucus watery

Water moves into mucus by osmosis due to chloride ion transport.

114
Q

What effect does a mutation in the CFTR gene have on mucus?

A

Makes the mucus very thick

A mutant CFTR protein is less efficient at transporting chloride ions.

115
Q

How does thick mucus affect the respiratory system?

A

Traps bacteria, increasing infection risk

It also decreases the surface area of alveoli for gas exchange.

116
Q

What is one impact of thick mucus on the reproductive system?

A

Cervical mucus prevents sperm from reaching the egg

In men, the sperm duct can be blocked with mucus.

117
Q

How does thick mucus affect the digestive system?

A

Blocks the pancreatic duct, preventing enzyme delivery

This leads to improper digestion and nutrient absorption.

118
Q

What happens to the mucus lining in the duodenum in cystic fibrosis?

A

Becomes very thick, reducing nutrient absorption

Thick mucus can also lead to cyst formation in the pancreas.

119
Q

What is a gene?

A

A piece of DNA with a specific sequence of bases

Each gene codes for a specific protein.

120
Q

Define allele.

A

One of the different forms of a particular gene

Alleles can result in different traits.

121
Q

What does genotype refer to?

A

All the alleles of an organism

It represents the genetic makeup.

122
Q

Define phenotype.

A

The set of observable characteristics of an individual

Resulting from the interaction of its genotype with the environment.

123
Q

What is a recessive allele?

A

An allele that produces a feature only if two copies are present

Recessive alleles are expressed phenotypically only when an individual is homozygous for that allele.

124
Q

What is a dominant allele?

A

An allele that produces a feature even if only one copy of the allele is present

Dominant alleles can mask the presence of recessive alleles in heterozygous individuals.

125
Q

Define incomplete dominance.

A

A form of intermediate inheritance where one allele is not completely expressed over its paired allele, resulting in a third phenotype

This third phenotype is a blend of the dominant and recessive traits.

126
Q

What is a homozygote?

A

An individual having two identical alleles of a particular gene

Homozygotes can be either homozygous dominant or homozygous recessive.

127
Q

What is a heterozygote?

A

An individual having two different alleles of a particular gene

Heterozygotes can express dominant alleles while masking recessive alleles.

128
Q

What is monohybrid inheritance?

A

The inheritance of just one characteristic

Monohybrid crosses analyze the inheritance patterns of a single trait.

129
Q

In a monohybrid cross where both parents are heterozygous (Aa), what are the expected genotypic ratios?

A

1 Homozygous dominant (AA) : 2 Heterozygous (Aa) : 1 Homozygous recessive (aa)

This results in a 1:2:1 genotypic ratio.

130
Q

What is the purpose of genetic screening?

A

To determine if an individual’s DNA contains alleles for genetic disorders

It can identify carriers and assist in prenatal testing.

131
Q

What is pre-implantation genetic diagnosis?

A

Testing embryos created through IVF for genetic disorders before implantation

This helps ensure that only healthy embryos are implanted.

132
Q

What is chorionic villus sampling?

A

A test carried out at 8 to 12 weeks of pregnancy to analyze DNA from a sample of embryonic tissue from the placenta

It is quicker than amniocentesis.

133
Q

What is amniocentesis?

A

A procedure carried out at 14-16 weeks of pregnancy to obtain a sample of amniotic fluid for DNA analysis

Results take 2-3 weeks as fetal cells need to be cultured.

134
Q

True or False: Genetic testing has no social and ethical issues.

A

False

There are various concerns, including risks to the fetus, potential for abortion, and costs associated with raising a child with a genetic disorder.

135
Q

Fill in the blank: The risk of _______ to the fetus is a concern associated with genetic testing.

A

harm

This includes the possibility of miscarriage due to invasive procedures.

136
Q

What is a potential risk associated with genetic testing?

A

Risk of harm to foetus or miscarriage

137
Q

What ethical concern arises from the outcomes of genetic testing?

A

Might lead to an abortion - right to life

138
Q

What financial consideration is mentioned regarding genetic disorders?

A

Cost of bringing up a baby with a genetic disorder

139
Q

What emotional issues may arise from caring for a baby with a genetic disorder?

A

Emotional and mental issues

Biology A Level (4 decks)

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