Topic 2 - Genes and Health Flashcards
What factors increase the rate of gas exchange by diffusion?
- Increased surface area
- Diffusion distance decreases
- Steeper diffusion gradient
These factors enhance the efficiency of gas exchange in biological systems.
What is Fick’s Law?
Rate of diffusion = SA x Concentration difference/ diffusion distance
What does Fick’s Law state regarding the rate of diffusion?
The larger the surface area, difference in concentration, and shorter the diffusion distance, the quicker the rate.
What adaptations do mammal lungs have for rapid gas exchange?
- 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.
What is the primary function of the cell membrane?
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.
Describe the composition of the cell membrane?
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.
What is the fluid mosaic model?
A model describing the structure of the cell membrane - its fluidity and mosaic arrangement of proteins, with dynamic and flexible components
What types of proteins are found in the cell membrane?
- Transport proteins
- Receptor proteins
- Enzymes
- Structural proteins
- Recognition proteins
These proteins play various roles in cell function and communication.
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.
[molecule]
Different molecules have varying abilities to permeate the membrane based on size, polarity, and other characteristics.
What is diffusion?
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
What factors increase the rate of gas exchange by diffusion?
The rate becomes more rapid as:
* Surface area increases
* Diffusion distance decreases
* Diffusion gradient becomes steeper
These factors facilitate faster movement of molecules.
What is facilitated diffusion?
The transport of polar, charged, and water-soluble molecules across the membrane via a channel protein
This process does not require energy.
Define osmosis.
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.
What is active transport?
The transport of all types of molecules through carrier proteins, requiring energy in the form of ATP
It can occur against the concentration gradient.
What is the role of ATP in active transport?
ATP provides energy for the process; hydrolysis of ATP releases energy needed for transport
Phosphorylation of ATP also requires energy.
What is endocytosis?
Large particles are enclosed in vesicles made from the cell surface membrane and transported into the cell
This is an active transport mechanism.
What is exocytosis?
Vesicles containing large particles fuse with the cell surface membrane and are transported out of the cell
This also represents an active transport mechanism.
What are the components of a mononucleotide?
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.
What is the pairing of bases in DNA?
A-T and C-G
This base pairing is essential for DNA structure.
What type of bond forms between the phosphate group and Carbon-5 in a nucleotide?
Phosphodiester bonds
These bonds link nucleotides together in a DNA strand.
What type of bond forms between the bases in DNA?
Hydrogen bonds
These bonds hold the two strands of DNA together.
Fill in the blank: The sugar in DNA is _______.
deoxyribose
This sugar is a pentose sugar.
What type of bonds hold the structure of nucleic acids together?
Hydrogen bonds
Hydrogen bonds are crucial for the stability of DNA and RNA structures.
What is the structure of DNA?
Double-stranded, alpha double helix with a sugar-phosphate backbone
The sugar-phosphate backbone provides structural support to the DNA molecule.
What are the purine bases in nucleic acids?
Adenine, guanine
Purines are one of the two categories of nitrogenous bases found in nucleic acids.
What are the pyrimidine bases in nucleic acids?
Cytosine, uracil
Pyrimidines are the second category of nitrogenous bases, with uracil found only in RNA.
What is the base pairing in RNA?
A-U, C-G
This pairing is crucial for the formation of RNA structures and their function in protein synthesis.
What sugar is found in RNA?
Ribose
Ribose is a five-carbon sugar that is part of the backbone of RNA.
What is the structure of mRNA?
Single-stranded, not usually folded, carries codons
Codons are triplets of bases in mRNA that correspond to specific amino acids.
What is the structure of tRNA?
Single-stranded, folded into a specific pattern
The folded structure allows tRNA to carry anticodons that are complementary to mRNA codons.
What are the two stages of protein synthesis?
Transcription, translation
Transcription occurs in the nucleus, while translation occurs at the ribosomes.
Where does transcription occur?
In the nucleus
Transcription is the process of creating mRNA from a DNA template.
What happens during transcription?
DNA uncoils, complementary bases pair to form mRNA
The antisense strand of DNA serves as a template for the mRNA synthesis.
What is the role of the antisense strand during transcription?
It serves as a template to make the mRNA molecule
The antisense strand is complementary to the mRNA produced.
What occurs during translation?
Amino acids are assembled to form a polypeptide chain/protein
Translation is the second stage of protein synthesis where mRNA is decoded by tRNA.
What is the process by which free nucleotides line up and form a molecule of mRNA?
Catalyzed by RNA polymerase
This involves complementary base pairing and the joining of adjacent nucleotides by phosphodiester bonds.
What does mRNA do after it is formed?
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.
During translation, what do amino acids join together to form?
A polypeptide chain
What is the role of tRNA in translation?
Binds to specific amino acids from the cytoplasm depending on its anti-codon
This process is known as activation.
How do tRNA anticodons interact with mRNA codons?
They bind to mRNA codons and are held in place by hydrogen bonds.
What type of bond is formed between amino acids during translation?
Peptide bond
What happens to tRNA molecules after the ribosome joins the amino acids?
They detach from the amino acids.
What indicates the end of the formation of a polypeptide chain?
A stop codon is reached on mRNA.
What is a gene?
A series of bases on a DNA molecule coding for a series of amino acids in a polypeptide chain.
What is the order of bases on DNA referred to as?
The genetic code
What is the structure of the genetic code?
Consists of triplets of bases, each coding for a particular amino acid.
What are the non-coding sections of DNA called?
Introns
What are the coding regions of DNA called?
Exons
What does it mean that the genetic code is non-overlapping?
Each triplet is only read once and triplets don’t share any bases.
What does it mean that the genetic code is degenerate?
More than one triplet codes for the same amino acid.
What is the genetic code classified as?
A triplet code
What are start and stop codons?
They either start or stop protein synthesis.
What are the monomers from which proteins are made?
Amino acids
Amino acids contain an amino group, a carboxyl group, and a variable R group.
How many different amino acids are there?
20
Each amino acid has a different R group.
What type of bond joins amino acids together?
Peptide bonds
Formed in condensation reactions.
What is a dipeptide?
A molecule containing two amino acids
What is a polypeptide?
A chain containing three or more amino acids
What determines the structure of proteins?
The order and number of amino acids
What is the primary structure of a protein?
The sequence of amino acids in a protein
What is the secondary structure of a protein?
The 2D arrangement of the chain of amino acids
Can be either alpha helix or beta pleated sheet.
What is the tertiary structure of a protein?
The 3D folding of the secondary structure into a complex shape
What types of bonding determine the tertiary structure?
Hydrogen bonding, ionic bonds, and disulphide bridges
What is the quaternary structure of a protein?
The 3D arrangement of more than one polypeptide
Do all proteins have all levels of structure?
No
What are fibrous proteins characterized by?
Long parallel polypeptides and very little tertiary/quaternary structure
What is a key feature of fibrous proteins?
Insoluble
Used for structural purposes such as collagen.
What are globular proteins characterized by?
Complex tertiary/quaternary structures
What is a key feature of globular proteins?
Form colloids in water
Name two uses of globular proteins.
Hormones and antibodies
Fill in the blank: Amino acids are joined by _______.
Peptide bonds
What type of protein is collagen?
Fibrous protein
Collagen has high tensile strength due to hydrogen and covalent bonds.
What is the structure of collagen molecules?
Three polypeptides forming an alpha triple helix
This structure leads to the formation of fibrils and strong collagen fibers.
What is the primary function of collagen in the body?
Forms the structure of bones, cartilage, and connective tissue
Collagen is a main component of tendons which connect muscles to bones.
What type of protein is hemoglobin?
Water-soluble globular protein
Hemoglobin consists of four beta polypeptide chains and a haem group.
What is the main function of hemoglobin?
Carries oxygen in the blood
Oxygen binds to the haem (Fe2+) group and is released when required.
What are enzymes?
Biological catalysts
Enzymes increase the rate of reaction by lowering the activation energy.
What model describes how substrates fit into enzymes?
Lock and key model
This model illustrates enzyme specificity to substrates.
What is the induced-fit theory?
The enzyme changes shape to fit the substrate
The structure of the enzyme is distorted upon forming a complex with the substrate.
How can the initial rate of reaction be measured?
By calculating the gradient of a concentration-time graph
This measurement helps in understanding enzyme kinetics.
What effect does increasing enzyme concentration have on the rate of reaction?
Increases the rate until substrate concentration becomes limiting
Beyond a certain point, more active sites than substrates exist.
What happens to the rate of reaction as substrate concentration increases?
Increases until enzyme concentration becomes limiting
Beyond a certain point, the formation of enzyme-substrate complexes plateaus.
What is the optimum temperature for enzyme activity?
The temperature at which enzymes work best
Rate of reaction decreases beyond this temperature due to enzyme denaturation.
How does pH affect enzyme activity?
Alters the bonds within its structure, affecting the active site shape
Enzymes work within a narrow range of specific pH values.
What is the main purpose of semi-conservative replication of DNA?
To ensure genetic continuity between generations of cells.
Who proved the semi-conservative model of DNA replication?
Meselson and Stahl.
What are the three models of DNA replication?
- Semi-conservative replication
- Conservative replication
- Dispersive replication
In the Meselson-Stahl experiments, what isotopes of nitrogen were used?
N15 and N14.
What happens to DNA after one generation in N14 culture following growth in N15?
The DNA contains one strand with 15-N and one strand with 14-N.
What is the outcome after two generations in N14 culture?
Half of the DNA molecules are the same as in generation one, and the other half contains entirely 14-N.
What is the first step of semi-conservative replication of DNA?
The double helix unwinds and hydrogen bonds between complementary bases break, catalyzed by DNA helicase.
What occurs during the second step of DNA replication?
One of the strands is used as a template for complementary base pairing with free nucleotides.
What is formed during the third step of DNA replication?
Phosphodiester bonds are formed between adjacent nucleotides in condensation reactions, catalyzed by DNA polymerase.
What is a mutation?
A permanent change in the DNA of an organism.
What are the types of gene mutations?
- Substitution
- Insertion
- Deletion
- Duplication
Fill in the blank: Substitution is a change in _______.
one base.
Fill in the blank: Insertion involves _______ another base in.
adding.
Fill in the blank: Deletion involves _______ a base out.
taking.
Fill in the blank: Duplication involves _______ the same base more than once.
adding.
What is inversion in genetics?
Swapping the order of bases around
This change affects the mRNA, tRNA, and the primary structure of proteins.
What genetic disorder is caused by a mutation of a single gene coding for the CFTR protein?
Cystic fibrosis
CFTR protein is a channel protein that transports chloride ions out of respiratory tract cells.
What role does the CFTR protein play in mucus consistency?
Transports chloride ions, making mucus watery
Water moves into mucus by osmosis due to chloride ion transport.
What effect does a mutation in the CFTR gene have on mucus?
Makes the mucus very thick
A mutant CFTR protein is less efficient at transporting chloride ions.
How does thick mucus affect the respiratory system?
Traps bacteria, increasing infection risk
It also decreases the surface area of alveoli for gas exchange.
What is one impact of thick mucus on the reproductive system?
Cervical mucus prevents sperm from reaching the egg
In men, the sperm duct can be blocked with mucus.
How does thick mucus affect the digestive system?
Blocks the pancreatic duct, preventing enzyme delivery
This leads to improper digestion and nutrient absorption.
What happens to the mucus lining in the duodenum in cystic fibrosis?
Becomes very thick, reducing nutrient absorption
Thick mucus can also lead to cyst formation in the pancreas.
What is a gene?
A piece of DNA with a specific sequence of bases
Each gene codes for a specific protein.
Define allele.
One of the different forms of a particular gene
Alleles can result in different traits.
What does genotype refer to?
All the alleles of an organism
It represents the genetic makeup.
Define phenotype.
The set of observable characteristics of an individual
Resulting from the interaction of its genotype with the environment.
What is inversion in genetics?
Swapping the order of bases around
This change affects the mRNA, tRNA, and the primary structure of proteins.
What genetic disorder is caused by a mutation of a single gene coding for the CFTR protein?
Cystic fibrosis
CFTR protein is a channel protein that transports chloride ions out of respiratory tract cells.
What role does the CFTR protein play in mucus consistency?
Transports chloride ions, making mucus watery
Water moves into mucus by osmosis due to chloride ion transport.
What effect does a mutation in the CFTR gene have on mucus?
Makes the mucus very thick
A mutant CFTR protein is less efficient at transporting chloride ions.
How does thick mucus affect the respiratory system?
Traps bacteria, increasing infection risk
It also decreases the surface area of alveoli for gas exchange.
What is one impact of thick mucus on the reproductive system?
Cervical mucus prevents sperm from reaching the egg
In men, the sperm duct can be blocked with mucus.
How does thick mucus affect the digestive system?
Blocks the pancreatic duct, preventing enzyme delivery
This leads to improper digestion and nutrient absorption.
What happens to the mucus lining in the duodenum in cystic fibrosis?
Becomes very thick, reducing nutrient absorption
Thick mucus can also lead to cyst formation in the pancreas.
What is a gene?
A piece of DNA with a specific sequence of bases
Each gene codes for a specific protein.
Define allele.
One of the different forms of a particular gene
Alleles can result in different traits.
What does genotype refer to?
All the alleles of an organism
It represents the genetic makeup.
Define phenotype.
The set of observable characteristics of an individual
Resulting from the interaction of its genotype with the environment.
What is a recessive allele?
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.
What is a dominant allele?
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.
Define incomplete dominance.
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.
What is a homozygote?
An individual having two identical alleles of a particular gene
Homozygotes can be either homozygous dominant or homozygous recessive.
What is a heterozygote?
An individual having two different alleles of a particular gene
Heterozygotes can express dominant alleles while masking recessive alleles.
What is monohybrid inheritance?
The inheritance of just one characteristic
Monohybrid crosses analyze the inheritance patterns of a single trait.
In a monohybrid cross where both parents are heterozygous (Aa), what are the expected genotypic ratios?
1 Homozygous dominant (AA) : 2 Heterozygous (Aa) : 1 Homozygous recessive (aa)
This results in a 1:2:1 genotypic ratio.
What is the purpose of genetic screening?
To determine if an individual’s DNA contains alleles for genetic disorders
It can identify carriers and assist in prenatal testing.
What is pre-implantation genetic diagnosis?
Testing embryos created through IVF for genetic disorders before implantation
This helps ensure that only healthy embryos are implanted.
What is chorionic villus sampling?
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.
What is amniocentesis?
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.
True or False: Genetic testing has no social and ethical issues.
False
There are various concerns, including risks to the fetus, potential for abortion, and costs associated with raising a child with a genetic disorder.
Fill in the blank: The risk of _______ to the fetus is a concern associated with genetic testing.
harm
This includes the possibility of miscarriage due to invasive procedures.
What is a potential risk associated with genetic testing?
Risk of harm to foetus or miscarriage
What ethical concern arises from the outcomes of genetic testing?
Might lead to an abortion - right to life
What financial consideration is mentioned regarding genetic disorders?
Cost of bringing up a baby with a genetic disorder
What emotional issues may arise from caring for a baby with a genetic disorder?
Emotional and mental issues
