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A Levels > Biology Paper 1 > Flashcards

Biology Paper 1 Flashcards

1
Q

Test for reducing sugars

A

Benedict’s + heat in water bath
If sugar then orange brown solution

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2
Q

Test for non-reducing sugars

A
  • HCl + Boil
  • Neutralise with NaHCO3
  • Add Benedicts and heat in water bath
  • If sugar then orange brown solution
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3
Q

Test for starch

A

KI soln
Yellow to blue black

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4
Q

Test for lipids

A

Add ethanol THEN water and shake
Milky white emulsion

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5
Q

Test for proteins

A

Add NaOH
Add CuSO4 and mix
Blue to Purple if protein is present

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6
Q

How many H bonds between A & T

A

2

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7
Q

How many H bonds between C & G

A

3

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8
Q

Maltose is made of

A

α-glucose + α-glucose

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9
Q

Sucrose is made of

A

glucose + fructose

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10
Q

Lactose is made of

A

glucose + galactose

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11
Q

Describe starch

A
  • Made from α-glucose
  • Insoluble so doesn’t affect w.p.
  • Compact
  • Branched form has many ends so enzymes act rapidly so lots of glucose released

Can be both branched and unbranched + ONLY IN PLANTS

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12
Q

Describe glycogen

A
  • Insoluble so no effect on w.p.
  • Compact
  • Highly branched (more than starch) so has many ends which enzymes can act on so glucose released more rapidly (for respiration)

ONLY FOUND IN ANIMALS

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13
Q

Describe cellulose

A
  • Made of β-glucose
  • Straight unbranched chains
  • Chains run parallel so cross-linked by H bonds to add stregnth
  • Goruped to form microfibrils => fibres
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14
Q

Use of cellulose

A
  • Plant cell walls providing rigidity
  • Stops cell bursting during osmosis
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15
Q

Uses of lipids

A
  • Source of energy (respiration)
  • Waterproofing (waxy cuticle)
  • Insulation for heat
  • Insulation for electricity (myelin sheath)
  • Protection - around delicate organs such as kidneys
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16
Q

Formation of triglyceride

A

Glycerol + 3 fatty acids

LOSES 3 WATERS

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17
Q

Suitability of triglycerides

A
  • Low mass to energy ratio so good storage molecules
  • Large non-polar molecule so insoluble in water so no effect on w.p.
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18
Q

Define saturated

A

NO double bonds

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19
Q

Define mono-unsaturated

A

ONE double bond

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20
Q

Define poly-unsaturated

A

MORE THAN ONE double bond

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21
Q

Describe the structure of a phospholipid

A

Hydrophilic phosphate head with a hydrophobic fatty acid tail
2 fatty acids and one phosphate attached to a glycerol molecule

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22
Q

Describe the function of phospholipids

A
  • Polar molecule so in an aqueous environment forms a bilayer
  • Can form glycolipids in the cell-surface membrane (combine with carbohydrates)
  • Glycolipids used for cell recognition
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23
Q

Describe the structure of an amino acid

A

CH(NH2)(R)(COOH)

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24
Q

Where does the peptide bond form

A

Between -OH and -NH releasing a water molecule

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25
Q

Describe primary structure of proteins

A

A sequence of amino acids in a polypeptide chain

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26
Q

Describe secondary structure of proteins

A

H-Bonds between C=O and N-H groups forming a 3-D shape
Alpha helix or Beta pleated sheet

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27
Q

Describe tertiary structure of proteins

A

Secondary structure is twisted
* disulfide bridges
* ionic bonds
* H-bonds

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28
Q

Describe the quaternary structure of a protein

A

Multiple polypeptide chains combined often associated with prosthetic groups eg:haem

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29
Q

Describe a competitive inhibitor

A

Similar shape to substrate so can block active site of enzyme

can be countered by increasing conc. of substrate

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30
Q

Describe non-competetive inhibitor

A

Binds to allosteric site altering shape of active site so substrate cannot bind

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31
Q

Describe the structure of a nucleotide

A

Phosphate-Pentose-Base

either ribose or deoxyribose

32
Q

What bond forms between two nucleotides

A

Phosphodiester bond

33
Q

Differences between RNA and DNA

A

RNA - Uracil, Single standed, Ribose sugar, Usually shorter
DNA - Thymine, Double stranded, Deoxyribose sugar, longer

34
Q

Who discovered the structure of DNA

A

Watson and Crick

35
Q

Why is DNA stable

A
  • Phosphodiester backbone protects reactive bases
  • H-bonds link bases increasing stability
36
Q

Requirements for semi-conservative replication

A
  • ATCG nucleotides
  • Both strands of DNA act as a template
  • DNA Polymerase
  • DNA Helicase
  • Chemical energy (ATP)
37
Q

Describe semi-conservative replication

A
  • DNA Helicase breaks H-bonds
  • Double helix seperates and unwinds
  • Each strand acts as a template and free nucleotides bind
  • DNA polymerase joins nucleotides by forming phosphodiester bonds
38
Q

Describe the structure of ATP

A

Adenine + Ribose + 3 inorganic phosphates

39
Q

Where is ATP used?

A
  • Metabolic processes
  • Movement (muscle contraction)
  • Active transport
  • Activation of molecules (phosphorylation of other molecules)
40
Q

Importance of water to living organisms

A
  • High specific heat capacity - acts as a buffer against suddent temp changes
  • High latent heat of vapourisation - Effective for cooling (sweat)
  • Cohesion - Can be pulled up through a tube (xylem vessel)
  • Surface tension - Supports small organisms like pond skaters
  • Metabolism - Used in hydrolysis
  • Solvent - Dissolves lots of other substances
41
Q

Magnification = ?

A

Magnification = size of image/size of real object

42
Q

Light microscope

A
  • > 0.2um
  • Long wavelegnth of light
43
Q

Electron microscope

A
  • 0.1nm
  • Shorter wavelegnth
44
Q

Describe the process of cell fractionation

A
  • Blend cells
  • Filter debris
  • Cold, Isotonic, Buffer
  • Spin at increasing speeds
45
Q

Advantages of electron microscope

A

Short wavelegnth so high resolving power (0.1nm)
Electrons are negatively charged so can be focused with an electromagnet

46
Q

Describe TEM

A
  • Thin specimen
  • May destroy specemin
  • Image may contain artefacts
  • 2D image
  • 0.1nm

specimen must be dead

47
Q

Describe SEM

A
  • 3D image can be formed
  • 20nm
  • Non-colour
  • Can damage specimen

specimen must be dead

48
Q

Describe how you would calibrate an eyepiece graticule

A
  • Use a stage micrometer
  • Calculate legnth of division on graticule after lining up micrometer
49
Q

Describe the role of the RER

A

Large SA for synthesis of proteins and glycoproteins
Pathway for transport of materials

50
Q

Describe role of SER

A

Synthesises, stores and transports lipids and carbohydrates

51
Q

Describe the role of the Golgi

A

Made of cisternae

Transports, modifies and stores lipids/proteins
Forms vesicles for transport

52
Q

What are the 2 types of ribosomes

A

80S - Eukaryotic cells
70S - Prokaryotic cells

53
Q

Describe vaculoe

A

Fluid-filled sac bound by a tonoplast membrane. Has salts, sugars and amino acids dissolved inside.

54
Q

Purpose of vacuole

A
  • Temporary food store
  • Stregnth through turgidity
  • Pigments may colour petals to attract insects
55
Q

Describe phagocytosis

A
  • Chemical products of pathogen attract phagoctye
  • Phagocyte binds to chemicals on pathogen
  • Phagosome forms around the pathogen
  • Lysosome fuses with phagosome
  • Hydrolytic enzymes digest pathogen
56
Q

Describe the process of cell mediated immunity

A
  • Pathogens invade cells/are taken up by phagocytes
  • Antigens are presented on cell surface membrane
  • Receptors from T helper cell bind to antigens
  • This activates t-cell and it divides rapidly by mitosis
  • Cloned t cells develop into memory cells, stimulate b-cells to divide (and secrete antibodies) and activates cytotoxic t-cells
57
Q

Describe the process of humoural immunity

A
  • B-cell takes up antigens from pathogen and displays them on cell surface membrane
  • Helper T cells bind to antigens - activating the b cell
  • B cell divides by mitosis and produces plasma cells which secrete antibody
  • Antibody binds to antigens on pathogen and destroys them
  • Some B cells develop into memory cells
58
Q

Describe the structure of an antibody

A

Y shape protein
Has a variable region and a constant region

58
Q

Describe the structure of an antibody

A

Y shape protein
Has a variable region and a constant region

59
Q

How does HIV replicate

A
  • HIV protein capsid fuses with cell surface membrane of T-helper cell
  • RNA and enzymes enter cell and reverse transcriptase converts RNA into DNA
  • DNA is inserted into cell’s DNA
  • HIV DNA creates mRNA which contains the instructions of the viral proteins
  • Using the cell’s ribosomes HIV particles are made
  • HIV particles break away from T-cell and infect more cells
60
Q

Describe the method for an ELISA test

A
  • Apply the sample to a surface in which antigens will attach to.
  • Wash surface to remove unattached antigens
  • Add antibody specific to the antigen
  • Wash surface to remove XS antibody
  • Add a second antibody (with an enzyme attached) which binds to first antibody and wash
  • Add colourless substrate which when reacts with enzyme turns into coloured product
61
Q

Explain how antibiotics work

A

By preventing bacteria making normal cell walls. The weakened cell walls cannot withstand the pressure causing osmotic lysis

62
Q

Why do antibiotics not work on viral diseases

A

Viruses lack their own metabloic pathways so they use host cells. Antibiotics cannot reach the host cells.

Viruses also have a protein coat so there are no sites where antibiotics can work

63
Q

Explain how insects are adapted for gas exchange

A
  • Oxygen is used up at tracheole ends so O2 diffuses down gradient (opposite for CO2)
  • Contraction of muscles squeezes trachea enabline mass movement of respiratory gases
  • Ends of tracheoles are filled with water - lactate from anaerobic respiration causes wp to lower so water leaves tracheoles and draws air into them. Final diffusion pathway is in a gas phase so faster.
64
Q

Explain the structure of gills

A

Gills are made up of gill filaments which are made up of gill lamellae which increase the SA of the gills.

65
Q

Explain countercurrent flow

A

Conc gradient is maintained as blood flows the opposite way that the water flows.
This means that 80% of O2 avaliable is absorbed

66
Q

How is a plant adapted for gas exchange

A
  • Stomata so short diffusion pathway
  • Lost of air spaces in mesophyll so gases can come in contact with mesophyll spaces
  • Large SA of mesophyll spaces for rapid diffusion
67
Q

Describe the structure of a leaf

A

Waxy Cuticle
Upper epidermis
Palisade cells
Mesophyll cells
Lower epidermis

68
Q

Plant adaptations to control water loss

A

Thick cuticle - Waterproof barrier
Rolling up of leaves - No water potential gradient
Hairy leaves - Traps moist air to reduce water potential gradient
Stomata in grooves - Trap moist air for water potential gradient
Reduced SA to volume ratio - Slower rate of diffusion

69
Q

Structure of human gas-exchange system

A

Trachea to bronchi to bronchioles to alveoli

70
Q

Describe inspiration

A

External intercostal muscles contract and internal relax.
Volume of thorax increases
Diaphragm muscles contract and flatten increasing thoracic cavity volume
Decreases pressure in the lungs so air is forced into the lungs

71
Q

Describe expiration

A

Internal intercostal muscles contract and external relax.
Volume of thorax decreases
Diaphragm muscles relax and is pushed up decreasing thoracic cavity volume
Increases pressure in the lungs so air is forced out of the lungs

72
Q

Why is diffusion in the alveoli rapid

A
  • RBC are slowed down through the capillaries
  • Distance between air and rbc is reduced as rbc are flattened against capillaty walls
  • Large SA
  • Thin walls of capillaries and alveoli so short diffusion pathway
73
Q

Order of digestive system

A

Mouth - Oesophagus - Stomach - Ileum - Large intestines - Rectum

74
Q

Describe carbohydrate digestion

A
  • Salivary amylase hydrolyses starch to maltose
  • Stomach acid denatures amylase and stops further hydrolysis
  • Pancreatic amylase continues further digestion of starch
  • Epithelial lining contains maltase (in membrane) which forms alpha-glucose
75
Q

Describe lipid digestion

A

Lipids are split up into micelles by bile salts wihch increases SA so lipase action increases
Lipids are digested into fatty acids and mono glycerides

76
Q

Describe protein digestion

A
  • Endopeptidases hydrolyse peptide bonds in the central region of a protein
  • Exopeptidases hydrolyse bonds on terminal amino acids releasing dipeptides and amino acids
  • Dipeptidases are membrane bound - break bond between two amino acids

A Levels (3 decks)

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