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A Level Biology > Topic 2 > Flashcards

Topic 2 Flashcards

(52 cards)

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1
Q

Features of Lungs - Gas exchange

A

Alveoli - Large SA:Vol ratio
Many capillaries - Steep concentration gradient
Constant ventilation - Steep concentration gradient
One-cell-thick walls - Low diffusion barriers

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2
Q

Properties of gas exchange surfaces

A

High surface area - High SA, Higher diffusion rate (NOT “faster” - More efficient)
Steep Conc. Gradient - Greater Conc. gradient, Faster diffusion
Gas exchange surface - Thicker gas exchange surface, Slower diffusion

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3
Q

Fick’s Law

A

Rate of diffusion is proportional to (Surface area x Difference in concentration) divided by Thickness of gas exchange surface

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4
Q

Cell Membrane Structure

A

Phospholipid bilayer - Hydrophilic phosphate head: pointing outwards - Hydrophobic lipid tails: pointing inwards

Fluid mosaic model - Contains proteins/cholesterol/glycoproteins/glycolipids - Channel proteins/Carrier proteins

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5
Q

Fluidity of Cell Membrane

A

More unsaturated lipid tails, More fluidity of membrane - Kinked lipid tails - Close packing prevented - More cholesterol, Less fluid

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6
Q

Evidence for fluid mosaic model

A

Phosphate heads darker than lipid tails - peripheral proteins easily dissociated - integral proteins not easily dissociated - Freeze-fracture studies - mouse/human membrane proteins intermixed

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7
Q

Osmosis

A

“NET” - “PASSIVE” - movement of WATER - partially permeable membrane - DOWN water potential gradient - until solution is “isotonic”

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8
Q

Diffusion:

A

“NET” - “PASSIVE” - No ATP - movement of molecules/ions - DOWN the conc. gradient - from high to low concentration

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9
Q

Facilitated Diffusion:

A

Net, “PASSIVE” movement of molecules/ions - through a membrane protein (Carrier/Channel protein) - DOWN the conc. Gradient - from high to low concentration

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10
Q

Active transport

A

Movement of molecules/ions - AGAINST the concentration gradient - Low to High conc. - Carrier protein needed - ATP hydrolysed for energy - to change shape of protein

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11
Q

Exocytosis

A

Bulk transport of substances - Out of cell - Secretory vesicle - Fuses with membrane

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12
Q

Endocytosis

A

Bulk transport of substances - Into cell - Vesicle formed from cell membrane

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13
Q

Channel Proteins:

A

Specific shape - Can be open/closed depending on presence/absence of a signal - signal can be hormonal - signal can be a change in voltage: “GATED channel”

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14
Q

Carrier Proteins:

A

Ion/Molecule binds to specific site on the protein - protein shape changes - ion/molecule crosses membrane

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15
Q

DNA Nucleotide
Description

A

Phosphate group - Deoxyribose sugar (5C)- Organic base (Adenine/Thymine/Cytosine/Guanine) - Linked by condensation reaction - Nucleotides join together by phosphodiester bonds

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16
Q

RNA Nucleotide

A

Ribose sugar (5C) - Phosphate group - Organic base (Adenine/URACIL/Cytosine/Guanine) - Linked by condensation reaction - Nucleotides join by phosphodiester bonds

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17
Q

DNA

A

Deoxyribonucleic acid - Double Helix - Sugar-phosphate backbone - Bases held together by H-Bonds - Double stranded - Polynucleotide strands are antiparallel

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18
Q

RNA

A

Ribonucleic acid - Single stranded - Can fold back on itself

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19
Q

Adenine - Thymine Bond

A

2 Hydrogen

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20
Q

Cytosine - Guanine Bond

A

3 Hydrogen

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21
Q

Transcription

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A

Inside nucleus - Helicase - DNA unzips - RNA nucleotides line up against antisense strand - complementary base pairing - phosphodiester bonds form - condensation reaction - RNA polymerase - mRNA detaches from DNA

22
Q

Translation

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A

mRNA attaches to ribosome - tRNA carries specific amino acid - anticodon-codon binding; complementary - condensation reaction between amino acids - peptide bonds form - tRNA released

23
Q

Triplet code - non-overlapping - degenerate

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A

Triplet-code: Each adjacent group of 3 bases codes for one amino acid

Non-Overlapping: Each triplet is discrete and adjacent

Degenerate: Several triplets can code for the same amino acid

24
Q

Gene Definition

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A

Sequence of bases - on DNA - codes for a sequence of amino acids - on a polypeptide

25
Structure of Amino Acid
Central carbon bonded to… - carboxylic acid group - Amine group - R-group (Varies) - Hydrogen
26
Formation of polypeptide chain
Amino acids - joined by condensation reactions - peptide bonds - into polypeptide chain (primary structure)
27
How 3D shape of polypeptide controls solubility
Primary structure dictates final 3D shape - Polypeptide can fold into a-helix or b-pleated sheet - interactions between R-groups influence folding - H-bonds/Disuphide bridges/Ionic interactions - Hold polypeptide chain in 3D shape Polar R-groups on outside - Soluble Non-Polar R-groups on outside - Insoluble
28
Globular proteins
Structure: tertiary/quartenary structure - hydrophilic R-groups facing outwards - spherical Properties: Soluble, enzymes/hormones etc. Structure + Function: Enzymes are globular - 3D shape allows formation of enzyme/substrate complexes 3D shape - allows protein binding - e.g. Haemoglobin/Myoglobin
29
Fibrous proteins
Structure: little/no tertiary structure - hydrophobic R-groups facing outwards - large - repeated amino acid sequences Properties: Insoluble, structural Structure + Function: Long chains - can cross-link for strength - structural molecules e.g. keratin/collagen Insoluble - structural molecules - not broken down/absorbed etc.
30
Catabolic reactions
“Breaking down” - Substrate molecule broken down into smaller product molecules
31
Anabolic reactions
“Building up” - Substrate molecules form a larger product molecule
32
Lock and Key Theory
Enzyme has SPECIFIC active site - fits complementary substrate molecule(s) - Enzyme-substrate complex - bonds broken/formed - product(s) released
33
Induced Fit Theory
Flexible active site - substrate enters A.site - Enzyme changes shape slightly to better fit substrate - Enzyme-substrate complex - Bonds broken/formed - Product(s) released
34
DNA Replication
Semi-conservative - DNA unzips - Helicase catalyses - mononucleotides line up against both strands - comp. base pairing - phosphodiester bonds - condensation reactions - DNA polymerase catalyses - H-bonds form between bases
35
Evidence for semi-conservative replication
Bacteria grown in culture media - containing heavy nitrogen (15N) or light nitrogen (14N) - DNA extracted/centrifuged - Gen 1 had a band of DNA halfway between 15N and 14N - One DNA strand contains 15N and one strand contains 14N In CONSERVATIVE model: - Further generations have a band at 15N In SEMI-CONSERVATIVE model: - Further generations have bands between 14N and 15N
36
Types of Mutation
Frame-shift Deletion Substitution Insertion
37
Point Mutations
Silent: Doesn’t change protein sequence - degenerate nature - same amino acid coded for by multiple codons Nonsense: Results in coding for a stop codon - rather than amino acid - shortened protein - function impeded/non-functional Missense: Results in a different amino acid - some missense mutations have no effect
38
Cause of CF
CF is caused by mutations in CFTR gene - can lead to CFTR proteins that are absent/have reduced or no function - 100s of mutation identified in CF
39
Effects of the CFTR mutations
In some cases ATP can’t bind to & open ion channels - or channel is open but chloride ion transport is reduced Less chloride transport into mucus - less sodium ion movement into mucus down E.C gradient - less water movement into mucus - sticky mucus
40
Gene definition
Sequence of bases - on DNA - codes for amino acid sequence in polypeptide
41
Allele definition
Alternative form of a gene - found at the same locus - on DNA
42
Effect of CF on Gas Exchange
Chloride ions not moved into mucus - Water does not move out of cells - sticky mucus - Not cleared by cilia/coughing Sticky mucus decreases gas exchange - decreases surface area of lungs by blocking alveoli - less diffusion of gases - diffusion barrier is thicker - slower diffusion of gases Frequent lung infections - dirt and pathogens get trapped and cannot be cleared
43
Effect of CF on Digestion
Chloride ions not moved into mucus - Water does not move out of cells - sticky mucus Sticky mucus blocks pancreatic duct - digestive enzyme release impaired - lower rate of digestion - enzymes trapped damage pancreas - cause cysts of hard, fibrosed tissue (hence cystic fibrosis) - could cause a form of diabetes CF patients have higher daily energy requirement - might need to take digestive enzyme supplements
44
Effect of CF on Reproduction
Males: Vas deferens blocked/absent - fewer/no sperm reach egg - reduced fertility Females: mucus plug develops in the cervix - reduced fertility
45
Ways to test for CF in embryo
Chorionic villus sampling Amniocentesis Non-invasive prenatal diagnosis Pre-implantation genetic testing
46
Amniocentesis process
Invasive - Needle inserted into amniotic fluid - fetal cells collected - between 15-17 weeks - 1% miscarriage risk
47
Chorionic villus sampling process
Invasive - small sample of placental tissue removed - through abdomen wall/vagina - between 8-12 weeks - 2% miscarriage risk
48
Non-invasive prenatal diagnosis
“Cell free fetal DNA” fragments in mothers blood analyzed - 7-9 weeks - different tests require different concentrations of cffDNA
49
Pre-implantation genetic testing process (Only IVF)
Family history of serious genetic condition - IVF embryo - when embryo has 8 cells, one is removed and tested - DNA analysed Pros and Cons of IVF: IVF avoids need for possible abortion Expensive, stressful and low success rate
50
Issues with testing for CF
Might go against beliefs of family - false positive might lead to abortion of healthy fetus - false negative might lead to a family not being ready to raise a genetically abnormal kid - carries a miscarriage risk
51
CORE PRACTICAL 3: Investigate membrane structure, including the effect of alcohol concentration or temperature on membrane permeability.
plant of 5 different “variants” (e.g. age) - same mass/surface area - Heat plant samples to different temp/add different concentrations of ethanol - colorimeter to measure permeability
52
CPAC 4 Investigate the effect of enzyme and substrate concentrations on the initial rates of reactions.
at least 5 concentrations of substrate/enzyme - same volume - Method of measuring dependent variable (e.g. time for color change - if indicator is used, ABSORBANCE)

A Level Biology (4 decks)

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