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[OBSELETE] Edexcel - A Level Bio > Topic 2 > Flashcards

Topic 2 Flashcards

1
Q

What are examples of gas exchange surfaces

A
  • Alveoli in mammals
  • Gills in fish
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2
Q

What are the properties of gas exchange surfaces?

A
  • Large surface are to volume ratio
  • Thin for a short diffusion pathway
  • Has a maintained steep concentration gradient
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3
Q

Why can’t mammals use diffusion and amiba can?

A

The rate of diffusion is lower in mammals because they have too high of a volume compared to surface are so diffusion is inefficient

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4
Q

What is Fick’s Law?

A
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5
Q

How is the mammalian lung’s structure adapted to its function?

A

Adaptation

  • Lots of Alveoli = Large Surface Area
  • One cell thick alveoli and capillary walls = thin diffusion distance
  • Continuous supply of blood from capillary = maintenance of steep concentration gradient
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6
Q

What is the role of cell membranes?

A
  • Defines cellular boundaries
  • Partially permeable
  • Regulates flow of information
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7
Q

What is the structure of phospholipids?

A
  • Hydrophilic phosphate head
  • Hydrophobic fatty acid tails
  • Connected to glycerol by ester bonds

The hydrophilic and the hydrophobic properties of the phospholipid means they are amphipathic

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8
Q

What structures do phospholipids make?

A
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9
Q

What does the fluid mosaic model explain?

A
  • Made in 1972
  • Explains cell to cell communication and interactions (glycolipids and glycoproteins)
  • Explains passive and active transport (Channel and carrier proteins)
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10
Q

Label this diagram

A

A - Glycolipids allow for cell to cell communication

B - Phospholipid bilayer

C - Cholesterol - Increases strength of bilayer and stabilises cell temperature

D - Channel Protein allows for passive transport in and out of cell

E - Glycoprotein used for cell to cell interactions

F - Carrier protein allowing for active transport using ATP

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11
Q

What is Osmosis?

A

Osmosis is the movement of water molecules from an area of low solute concentration to an area of high solute concentration through a partially permeable membrane

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12
Q

What does hypertonic and hypotonic mean?

A

In the cell membrane osmosis is in charge of the concentration of cell membrane isotonic.

  • Hypertonic ⇒ Too high of a concentration
  • Hypotonic ⇒ Too low of a concentration
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13
Q

What types of transport are passive or active transport?

A
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14
Q

Why do membranes need proteins to aid transport?

A

The amphipathic nature of the bilayer mean that transportation of dissolved substances needs to be aided with carrier proteins and channel proteins

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14
Q

Why do membranes need proteins to aid transport?

A

The amphipathic nature of the bilayer mean that transportation of dissolved substances needs to be aided with carrier proteins and channel proteins

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15
Q

What are the different types of diffusion across a cell membrane?

A
  • Facilitated diffusion
  • Active Transport
  • Exocytsis + Endocytosis
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16
Q

How does Facilitated diffusion work?

A

Facilitated diffusion

  • Uses channel proteins and carrier proteins (Opens and closes depending on hormone signals)
  • Passive transport (Down the concentration gradient)
    • Large molecule attaches to carrier protein
    • Protein changes shape
    • Releasing molecule to the other side
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17
Q

How does active transport work?

A
  • Uses ATP (Adenosine Tri-phosphate) and hydrolyses to release energy
  • Uses a carrier protein
  • Against conc gradient
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18
Q

How does exocytosis and endocytosis works?

A

Exocytosis and Endocytosis

  • Uses vesicles instead of proteins
  • Substances packaged in a vesicle
  • Travels to and fuses with membrane
  • Releasing the contents
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19
Q

What is Cystic Fibrosis?

A

General Information

  • Genetic disease
  • Caused by mutation of gene coding for CFTR protein
  • Effects opening and closing of ion channels
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20
Q

What does the CFTR channel do?

A

The CFTR and ENAC channel work together to regulate $Na^{+}$ and $Cl^{-}$ ions between Mucus and Tissue Fluid.

A person with CF would have little/non-functioning/no CFTR proteins meaning the ENAC channel is always open

Drawing water away from Mucus

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21
Q

What is the process of moving $Na^{+}$ and $Cl^{-}$ ions?

A
  1. Depending on what channel is open one of the two ions would move across membrane
  2. Creating an electrical gradient meaning the other ion moves across membrane
  3. Creating a conc gradient as there is more NaCl on one side of the membrane
  4. Osmosis would then mean water across the membrane

Pen = ENAC open (Excess water in mucus)

Highlighter = CFTR open (lack of water in mucus)

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22
Q

What happens when there is an excess or lack of water in mucus

A

Excess water in Mucus

  1. CFTR channel closed
  2. $Na^{+}$ moves to tissue fluid through ENAC
  3. $Cl^{-}$ moves to tissue fluid through basal membrane (electrical gradient)
  4. Water moves from mucus to tissue fluid through osmosis (conc gradient)

Lack of water in Mucus

  1. ENAC channel closed
  2. $Cl^{-}$ moves to mucus through CFTR channel
  3. $Na^{+}$ moves to to mucus through basal membrane (electrical gradient)
  4. Water moves from tissue fluid to mucus through osmosis (concentration gradient)
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23
Q

What are the effects of CF on the Resptory system?

A
  • Viscous mucus blocks airways
  • Cilia unable to dispose of mucus leading to trapped pathogens causing infection
  • Diffusion distance increased reducing diffusion efficiency
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24
What are the effects of CF on the digestive system?
- Pancreatic duct blocked with mucus blocking enzyme release - Lack of digestive enzymes means less breakdown of food - Less absorption of carbs lipids and proteins - Resulting in **Malabsorption Syndrome** meaning dietary supplements need to be taken with a higher caloric diet
25
What are the effects of CF on the reproductive system
- Cervix blocked by mucus making fertilisation hard - Sperm ducts blocked with mucus meaning sperm can’t leave body
26
What is a mononucleotide?
A single biological molecule made from: - A pentose sugar (Deoxyribose or Ribose) - A nitrogenous base (A,T or U,C,G) - A phosphate group *(Depends on DNA or RNA)*
26
What is a mononucleotide?
A single biological molecule made from: - A pentose sugar (Deoxyribose or Ribose) - A nitrogenous base (A,T or U,C,G) - A phosphate group *(Depends on DNA or RNA)*
27
What is a polynucleotide?
A polynucleotide is a: - Polymer of nucleotides - joined by phosphodiester bonds formed by condensation reactions - DNA has 2 polynucleotide strands - RNA has 1 polynucleotide strand
28
What is the structure of DNA?
- 2 antiparallel Polynucleotide strands joined together via hydrogen bonds in a double helix structure - With the equal amounts of thymine with adenosine and guanine and cytosine (due to complementary base pairings) - 3 Bonds between C and G - 2 Bonds between A and T
29
What is the process of protein synthesis?
Transcription 1. DNA Polymerase attaches to the non coding DNA and moves along to the coding region 2. DNA helicase then moves along breaking the hydrogen bonds, unwinding the double helix 3. Free floating RNA nucleotides pair with the exposed complementary base’s on the anti-sense strand 4. Temporary hydrogen bond hydrogen bonds form between the bases 5. RNA polymerase catalyses the condensation reaction forming phosphodiester bonds. 6. mRNA detaches from the antisense strand 7. mRNA leaves nucleus through a nuclear pore to the ribosome in the nucleus Translation 1. Ribosome attaches to the mRNA 2. tRNA anti-codon pairs to the complementary bases of the mRNA codon 3. Hydrogen bonds then form between tRNA and mRNA 4. tRNA 1’s amino acid would form a peptide bond by a condensation reaction to tRNA 2’s amino acid 5. Then the tRNA would be released from the mRNA 6. This repeats from the start codon to the stop codons
29
What is the process of protein synthesis?
Transcription 1. DNA Polymerase attaches to the non coding DNA and moves along to the coding region 2. DNA helicase then moves along breaking the hydrogen bonds, unwinding the double helix 3. Free floating RNA nucleotides pair with the exposed complementary base’s on the anti-sense strand 4. Temporary hydrogen bond hydrogen bonds form between the bases 5. RNA polymerase catalyses the condensation reaction forming phosphodiester bonds. 6. mRNA detaches from the antisense strand 7. mRNA leaves nucleus through a nuclear pore to the ribosome in the nucleus Translation 1. Ribosome attaches to the mRNA 2. tRNA anti-codon pairs to the complementary bases of the mRNA codon 3. Hydrogen bonds then form between tRNA and mRNA 4. tRNA 1’s amino acid would form a peptide bond by a condensation reaction to tRNA 2’s amino acid 5. Then the tRNA would be released from the mRNA 6. This repeats from the start codon to the stop codons
30
What is the nature of the genetic code?
Genetic code is: - Non-overlapping - Triplets read once - Degenerate - Multiple combinations of bases code for the same amino acid - Triplet Code - A group of 3 bases
31
What is a gene?
A gene is a sequence of bases in DNA which code for a protein resulting in a specific phenotype
32
What is an amino acid?
An **organic molecule** that acts as **monomers** for **building proteins**
33
What is the structure of an amino acid?
A **central carbon** attached to a **amine group**, **carboxylic group**, a **hydrogen** molecule and a **R group**
34
What is the primary stage of protein formation?
A **polypeptide chain of amino acids** held by **peptide bonds** (Formed in **condensation** reactions)
35
What is the secondary stage of protein formation
The **chain then folds** into either a **alpha helix** or a **beta pleated sheet** held together by **hydrogen bonds** (**4 residues down** in both structures)
36
What is the quaternary stage in protein folding?
tertiary structure ⇒ several tertiary polypeptide *Same bonds as tertiary*
37
What are globular proteins?
- 3D Spherical shape - for catalytic processes - Soluble - Due to hydrophilic side chain meaning easy transport *Amylase and haemoglobin are globular proteins*
38
What are fibrous proteins?
**Fibrous proteins** - Long polypeptide chains tightly coiled around - Lots of bonds (Hydrogen, Disulfide) - Found in supportive tissue *Collagen is a fibrous protein*
39
What are enzymes?
- Enzymes are **3D globular proteins** - Which are **biological catalysts** - which catalyse by **lowering activation energies** for certain reactions
40
Where can enzymes be found?
- Enzymes can be **intercellular** like the enzymes found in lysosomes - They can be **extracellular** like thrombin which catalyses the conversion of fibrinogen to fibrin
41
What is an enzyme substrate complex?
- Where a **substrate binds** to the **active site** of the enzymes - Where the **active site changes shape slightly** to fit the substrate *This is known as **induced fit***
42
What is the first stage of DNA replication?
Stage 1 - Preparation - DNA Helicase - Breaks hydrogen bonds between bases - Unwinding double helix - Forming two template strands
43
What is the second stage of DNA replication?
Stage 2 - Alignment - Complementary free floating nucleotides are attracted to their complementary base - This is possible due to the exposed complementary base pairings
44
What is the third stage of DNA replication
Step 3 - Formation - DNA polymerase catalyses Condensation Reactions - This binds the each new strand to a template strand - Through new hydrogen bonds
45
What is the final stage of DNA replication?
Step 4 - Detachment - The two new DNA molecules contain 1 template strand and 1 replicated strand - This completes **semi-conservative replication**
46
What is the definition of a gene?
A section of DNA that codes for a protein
47
What is the deinition of an allele?
One or two more DNA sequences occur at a particular gene locus.
48
What is the definition of a genotype?
A genotype is the genetic constitution of an organism
49
What is the definition of a genotype?
The expression of this genetic constitution and its interaction with the environment
50
What is the definition of recessive?
Where two of the same alleles are required to express the genotype
51
What is the definition of dominant?
Where only one of the alleles is required to express the genotype
52
What is the definition of incomplete dominance?
A gene interaction in which both alleles of a gene are partially expressed resulting in an intermediate or different phenotype
53
What is the definition of homozygotes?
The presence of two identical alleles at a particular gene locus
54
What is the definition of heterozygote?
The presence of two non-identical alleles at a particular gene locus
55
What is a pedigree?
56
What is monohybrid inheritance?
The inheritance of characteristics controlled by a single gene
57
What is an inherited recessive disorder?
A disorder caused by a faulty allele is only expressed when two recessive alleles are inherited.
58
What are frameshift mutations?
Mutations Like Frameshift Mutations **insert or delete** one or two nucleotides from a gene This results in the following: - Changes in triplet/codons in the mRNA and DNA - A new start and stop codon - Where different incorrect codons would code for shorter and other sequences of amino acids
59
What are the different types of gene mutations?
- Substitution - Deletion - Insertion
59
What are the different types of gene mutations?
- Substitution - Deletion - Insertion
60
How does CF affect gas exchange?
Gas Exchange - CF increases mucus in the airways - Increasing diffusion distance - Meaning the gas exchange rate decreases
61
How does CF affect gas exchange?
Digestion - Increased mucus leads to pancreatic / bile ducts being blocked - Meaning that the digestive enzymes cannot be released - Meaning that any food taken in would not be digested and absorbed as effectively
62
How does CF affect reproduction?
Reproduction Male - Mucus blocks sperm ducts/sperm ducts are missing - Meaning little to no sperm is released during ejaculation Female - The increased mucus in the cervix - Makes it harder for sperm to enter and fertilise the egg
63
What is genetic testing?
- It can be performed on any DNA sample - Then tested to see if the DNA contains the gene for a genetic disease
64
What can genetic screening be used for?
- To confirm a diagnosis for newborns and adults - To identify carriers to assess the probability of an offspring having the disease - To test embryos during IVF
65
What is amniocentesis?
Amniocentesis - Method of invasive fetal testing - Needle insertion into the amniotic fluid - Collecting fetal cells from the placenta of the fetus - Carried around 15-17 weeks + 1% risk of miscarriage
66
What is chronic villus sampling (CVS)?
Chronic Villus Sampling - Method of invasive fetal testing - Placental tissue removed through the wall of the abdomen or vagina - CVS can be carried earlier in pregnancy (8-12 weeks) + 1-2% miscarriage
67
How does non-invasive prenatal diagnosis (NIP)?
Non-Invasive Prenatal Diagnosis - Analysis of DNA fragments in the mother's blood plasma - cffDNA becomes detectable at 4-5 weeks

[OBSELETE] Edexcel - A Level Bio (9 decks)

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