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A Level Biology > Topic 2 > Flashcards

Topic 2 Flashcards

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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

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

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

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

A

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

25
Q

Structure of Amino Acid

A

Central carbon bonded to…
- carboxylic acid group - Amine group - R-group (Varies) - Hydrogen

26
Q

Formation of polypeptide chain

A

Amino acids - joined by condensation reactions - peptide bonds - into polypeptide chain (primary structure)

27
Q

How 3D shape of polypeptide controls solubility

A

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
Q

Globular proteins

A

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
Q

Fibrous proteins

A

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
Q

Catabolic reactions

A

“Breaking down” - Substrate molecule broken down into smaller product molecules

31
Q

Anabolic reactions

A

“Building up” - Substrate molecules form a larger product molecule

32
Q

Lock and Key Theory

A

Enzyme has SPECIFIC active site - fits complementary substrate molecule(s) - Enzyme-substrate complex - bonds broken/formed - product(s) released

33
Q

Induced Fit Theory

A

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
Q

DNA Replication

A

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
Q

Evidence for semi-conservative replication

A

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
Q

Types of Mutation

A

Frame-shift
Deletion
Substitution
Insertion

37
Q

Point Mutations

A

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
Q

Cause of CF

A

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
Q

Effects of the CFTR mutations

A

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
Q

Gene definition

A

Sequence of bases - on DNA - codes for amino acid sequence in polypeptide

41
Q

Allele definition

A

Alternative form of a gene - found at the same locus - on DNA

42
Q

Effect of CF on Gas Exchange

A

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
Q

Effect of CF on Digestion

A

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
Q

Effect of CF on Reproduction

A

Males: Vas deferens blocked/absent - fewer/no sperm reach egg - reduced fertility

Females: mucus plug develops in the cervix - reduced fertility

45
Q

Ways to test for CF in embryo

A

Chorionic villus sampling
Amniocentesis
Non-invasive prenatal diagnosis
Pre-implantation genetic testing

46
Q

Amniocentesis process

A

Invasive - Needle inserted into amniotic fluid - fetal cells collected - between 15-17 weeks - 1% miscarriage risk

47
Q

Chorionic villus sampling process

A

Invasive - small sample of placental tissue removed - through abdomen wall/vagina - between 8-12 weeks - 2% miscarriage risk

48
Q

Non-invasive prenatal diagnosis

A

“Cell free fetal DNA” fragments in mothers blood analyzed - 7-9 weeks - different tests require different concentrations of cffDNA

49
Q

Pre-implantation genetic testing process (Only IVF)

A

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
Q

Issues with testing for CF

A

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
Q

CORE PRACTICAL 3:
Investigate membrane structure, including the effect of alcohol concentration or temperature on membrane permeability.

A

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
Q

CPAC 4 Investigate the effect of enzyme and substrate concentrations on the initial rates of reactions.

A

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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