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Flashcards in Topic 2 Deck (73):

What factors effect gas exchange

Surface area to volume ratio
Consideration gradient


How do you fins surface area to volume ratio



How does thickness effect gas exchange

If the surface is thicker it will take longer for molecules to diffuse through it as they have more distance to travel through a medium


Why does the human body have alveoli

provides a larger surface area for diffusion between air and blood and have numerous capillaries and thin walls


How does Concentration gradient effect gas exchange
and what is it directly proportional too

The greater more rapid the faster the exchange

Concentration gradient is directly proportional to surface area
Rate of diffusion is directly proportional to Concentration gradient

Thickness of gas exchange surface inversely proportional to Concentration gradient and there for rate as well


What does Fick's law state

Rate of diffusion ∝ (surface area * diffusion gradient) / thickness of surface


How does lung structure allow breathing to take place

• The movement of the diaphragm and intercostals moving the ribs creates a low pressure in the lungs causing air to move in rapidly
• When the diaphragm and intercostals relax the pressure in the lungs increases, this forces the air out of the lungs


What are epithelial cells, where are they and what is there basic structure

• Cells work as a tissue
• In walls of alveoli and capillaries
• Very thin flat cells less than 0.2ɲm


How man aminos can be in a protein

50-2000 amino acids


How many different amino acids are there

There are 20 different amino acids


What is the primary structure of proteins

• Two aminos form a dipeptide with a peptide bond from a condensation reaction
• Polypeptide chains make the protein


What components make up the lungs from top to bottom



What are the three groups that make up the primary structure of proteins in order from left to right

Amino group
Residual group
Carboxylic group


What are the two types of secondary structure, and which groups are involved

α – helix
β – pleated sheet --> chains fold back on themselves and forms hydrogen bonds, achoher

Hydrogen bonds for both form between the slightly negative C=O (from carboxylic group)and the slightly positive -NH (Amine group)


How do α – helix form and how long are they

• Hydrogen bonds between the negative O and the positive H while chains are under eachother
• Can be up to 35 aminos long


How do β – pleated sheet form and how long are they

• Chains fold back on themselves
• Bonds between H and O
• Can be up to 15 aminos long
chains are parallel to e


What are tertiary and quaternary structure and how do they from, and what group is involved

• Chains bend or fold to produce a 3D shape
• Chemical bonds and hydrophobic interactions with the R groups
• Some R groups are polar and hydrophilic and some are non-polar and hydrophobic
• Hydrophilic (polar) are on the outside while the hydrophobic (non-polar) is forced to the inside keeping the water out
• Ionic bonds and covalent disulphide bonds between the R groups
• Hydrogen bonding between the O of the carboxylic acid group and the amine group
• To have a quaternary structure more than one amino chain is needed


What are Globular proteins and how are they made

• Polypeptide chain folds to make a spherical shape
• Soluble which is important for metabolic reactions
• Globular proteins include --> enzymes, pigment in haemoglobin and myoglobin, and antibodies


What are Conjugated proteins

Proteins in tertiary and quaternary structure that contain another chemical group


What are fibrous proteins

• Long chains
• Crosslinked = more strength
• Insoluble
• Examples --> skin, hair, collagen, tendons, bones + cartilage and blood vessel walls


What are cell membranes made of

Phospholipid bilayer, proteins and cholesterol


What is the structure of a phospholipid bilayer

• 7ɲm wide
• Two distinct lines
Three fatty acids and one phosphate group or is it something els lol?


What is the mosaic model

• Not only a phospholipid bilayer
• Also contains proteins, cholesterol, glycolipids and glycoproteins
• Some proteins are as wide/or long as the bilayer, others are only on one of the sides
• Some proteins are fixed, others can move around


What is the evidence for the mosaic model

1. An electron micrograph showed three-layer-protein-lipid sandwich, the dark outer layers being the proteins and the inner layer light region being the lipid. However this model does not allow the hydrophilic heads to be in contact with water
2. Was later changed as the heads are more electron dense than the tails so they appeared darker
3. Ionic experiments showed two different types of protein were present
1. The first type of proteins were spherical proteins which could be removed, this means that they were on the outsides of the membrane (by increasing the ionic strength of a solution)
2. The other protein (integral proteins) must have been imbedded in the membrane layer (detergents were needed to extract these)
4. Freeze-fracture electron microscopy  this fractures the membrane and cuts it in half, once that is done heavy metal is added to it and scanned for observation, it showed the smooth surface of the lipid tails and the bumps from the proteins
5. Molecule labelling was used to show that the inner layer and the outer layer are different as the label only attached to one side this means that membranes are asymmetric
6. A final experiment showed that membranes are indeed a liquid, as a mouse cell was fused with a human cell and the proteins mixed into one cell, the proteins from each cell were given a different fluorescent label


Name the ways which substances pass through cell membranes

Facilitated diffusion
Active transport
Exocytosis and Endocytosis


What is diffusion

• Net movement from high concentration to low concentration
• Small uncharged particles can pass through the lipids


What is facilitated diffusion

• Ions and molecules crossing the membrane with the help of carrier proteins (that bind to a specific site on the membrane) or channel proteins (have specific shapes to allow specific molecules or ions through
• Gated proteins open or close in response to a stimulus such as a p.d (potential difference) or a hormone
• No metabolic energy is required (passive transport)


What is osmosis

• The net movement of water molecules from a solution of low concentration of solute to a high concentration of solute (H2O moves to the solute)


What is active transport

• Molecules are moving against the concentration gradient
• Requires ATP
• Binds to a carrier protein, energy released from the conversion of ATP  ADP+Pi causes the protein to change shape and pass through the membrane
• These channel proteins can be referred to as pumps


What is exocytosis and endocytosis

• Bulk transport
• Rely on the fluid nature of the membrane
• Vesicles containing a large quantity of substances forces through the cell membrane
• Exo = out of cell
• Endo = into cell


What are the two enzyme function theories

Lock and key theory
Induced fit theory


What is the lock and key theory

• A complementary shape will fit into the active site, the substrate molecule will form temporary hydrogen bonds with the active site to produce an enzyme-substrate complex


What are enzymes

• Globular proteins can act as catalysts
• Have an active site --> the part of the protein with the catalytic function


What is the Induced fit theory

• Flexible active site that changes shape slightly to fit more closely around the substrate
• Substrate must still be a very similar size, the slight change will allow for the reaction to take place


What is the activation energy

• Enzymes reduce activation energy
• Charged groups form substrate active site assist the breaking and forming of bonds between the substrate and the enzyme, or provide conditions favourable to the reaction


What is a gene

a sequence of base DNA that codes for amino acids


What is a genome

all genes in an individual or species


What is DNA

(deoxyribose nucleic acid) is a long chain polymer made from nucleotides and mononucleotides


What is the structure of mononucleotides

One phosphate group, one deoxyribose and one organic base


What are the organic bases in mononucleotides

Have 5 different bases --> T = thymine, U = uracil (replaces T in RNA), C = cytosine, A = adenine and G = guanine


How do mononucleotides make DNA

• Mononucleotides link together via a condensation reaction creating a phosphodiester bond (also for RNA)
• Two polynucleotide strands link together with hydrogen bonding to form a double helix strand, the two strands are anti parallel (because they run in opposite directions)


Where does transcription take place

In the nucleus


What takes place in transcription

1. RNA polymerase attaches to the DNA, hydrogen bonds are broken causing the double helix to unwind and unzip
2. One side is coding strand and the other the template. The template strand is used to make the mRNA meaning the mRNA has the same base sequence as the coding strand (sense strand)
3. mRNA leaves through the nuclear envelope


What is translation

This stage turns base sequences into a sequence of amino acids


What is transcription

The process of copying the DNA


Where does translation take place

In the cytoplasm


How is translation carried out

1. In the cytoplasm mRNA attaches to the smaller subunit of a ribosome
2. tRNA molecules which have a three-base sequence of the anticodon from the template strand (antisense strand) binds to a larger subunit of the same ribosome complimentary to the mRNA strand already there
3. (AUG = start codon) The tRNA + the amino on top line up next to each other on top of the mRNA strand so peptide bonds can form between the amino acids
4. Once the peptide bond is formed the ribosome moves along the mRNA and the tRNA is released to go collect another amino acid
5. This will continue until a stop codon is present (UAG, UAA and UGA)


What is the nature of genetic code

• Triplet code (codon) is three bases that code for one amino acid
• The codes are non-overlapping, 64 possible triplet codes for 20 aminos
• One start codon and three stop codons (chain terminators)
• Several triplet codes code for the same amino acid (degenerate)
• Mutation = change in base sequence = possible wrong amino = incorrect protein


What were the three theories for DNA replication

Fragmentary replication
Conservative replication
Semi-conservative replication


What is semi-conservative replication

1. Entire double helix unwinds and hydrogen bonds between bases break
2. Complementary free nucleotides link to the two strands with the help of DNA polymerase (this enzyme links the nucleotides together with phosphodiester bonds)


Why does DNA replicate

When a cell divides for growth or repair, DNA must be copied for the daughter cells so they have all the genetic material


What is fragmentary replication

a mix of new nucleotides and parent nucleotides


What is conservative replication

one DNA molecule original and one new one with only new nucleotides


How did Meselson and Stahl’s carry out there experiment

1. E.coli (bacteria) was grown in a medium containing the heavy isotope of nitrogen (N¹⁵) = heavier DNA
2. This bacterium was moved to a new medium only containing the lighter isotope of nitrogen (N¹⁴), this means all the new nucleotides made will be lighter than the old ones
3. Once the DNA is given time to replicate, the bacteria is centrifuged causing the heavy DNA to sink, the medium to stay in the middle and the light DNA to rise closer to the top
4. The result was that all the DNA stayed in the middle of the test tube meaning all the DNA had an equal amount of light and heavy DNA (this means it could have been fragmentary or semi-conservative)
5. The bacterium was left to replicate a second time in the light nitrogen and was then centrifuged again
6. The result showed that the DNA was now medium and light DNA meaning that the only explanation for this was if the DNA replicated semi-conservatively


What mutation causes CF

• Chromosome 7 (which has the code to make the CFTR protein)
• Hundreds of mutations can lead to the genetic disorder of CF the main three are:
1. ATP unable to bind and open the ion channel
2. Channel opens but changes the protein shape and releases chloride
3. DF508 deletion of three nucleotides which causes CFTR to miss fold


What is a homologous pair

A pair of chromosomes


What is a lotus

The location of a gene on the chromosome


What is homologous and what is heterozygous

Homo = Both dominant or both recessive
Hetero = One dominant one recessive


What is a phenotype

a characteristic caused by a genome


What is monohybrid inheritance

A characteristic controlled by one gene (CF and thalassaemia which effects haemoglobin production)


What is genetic testing used for

Used to identify abnormal alleles in genes


When does an embryo become a fetus

An embryo becomes a fetus at 10 weeks of pregnancy


What are the methods of genetic screening

Chronic villus sampling (CVS)
Non-invasive prenatal diagnosis (NIPD)
Pre-implantation genetic diagnosis (PGD)


How is amniocentesis carried out

• Inserting a needle into the amniotic fluid to collect fetal cells to be examined
• Is done 15-17 weeks into pregnancy with a 1% chance of a miscarriage


How is CVS (chronic villus sampling) carried out

• Small sample of placental tissue collected via the abdomen or vagina
• Done at 8-12 weeks
• 1-2% risk of a miscarriage


How is NIPD (non-invasive prenatal diagnosis) carried out

• Analyses the mother’s DNA fragments in the blood plasma
• 10-20% of the DNA fragments belong to the embryo called cell-free fetal DNA
• The DNA fragments are detectable at 4-5 weeks, but are only collected at 7-9 weeks
• The fragments can also be used for research or looking for other diseases


How is PGD (pre-implantation genetic diagnosis) carried out

• In vitro fertilisation (IVF) to create embryos ready for testing, and can later be implanted into the woman’s ovum
• Expensive
• Avoids need for an abortion
• 30% chance for success in women under 35


What are the key aspects of an ethical framework

• Should always tell the truth
• The questions --> what is right? what is wrong? And what should be done?
• Must always have an explanation as to why


What are the sections to ethical framework

Rights and duties
Maximising amount of good in the world
Making decisions for yourself
Leading a virtuous life


What does rights and duties cover in the ethical framework

• Human rights e.g the right to life and the right for fair trade
• Duties such as parenthood --> to look after your child
• Some of these come from religious faith or social conventions


What does maximising amount of good in the world cover in the ethical framework

• Telling the truth or a white lie
• Making people happy


What does making decisions for yourself cover in the ethical framework

• Informed consent for things such as operations
• Need to test someone’s actions against cost or gain of them doing something, to see if the gain is significantly higher than the cost (autonomy desirable)


What does leading a virtuous life cover in the ethical framework

• Treating people fairly
• Doing good moral and ethical things considered virtuous