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Biosciences > Molecules, Cells and Variation - 1.1 +1.2 > Flashcards

Molecules, Cells and Variation - 1.1 +1.2 Flashcards

1
Q

Maltose

A

Disaccharide made from glucose and glucose

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2
Q

Sucrose

A

Disaccharide made from glucose and fructose

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3
Q

Lactose

A

Disaccharide made from glucose and galactose

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4
Q

Hydrolysis of disaccharide

A

Boiling with acid

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5
Q

Benedict’s test for reducing sugars

A
  • Small amount of sample is placed in test tube with 2cm3 of Benedict’s solution.
  • This is heated in water bath for 5 mins.
  • Brick red/orange colour (produced by copper (I) oxide) is a +ve result.
  • If solution remains blue – no reducing sugar present.
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6
Q

Test for non-reducing sugars

A
  • Carry out Benedict’s test on sample to confirm -ve
  • Hydrolyse another sample by heating with dilute acid e.g. HCl or by using the enzyme sucrase at its optimum temperature.
  • When cooled, add dilute NaOH solution to neutralise the acid.
  • Add Benedict’s solution, heat in water bath for 5 mins.
  • +ve brick red colour indicates non-reducing sugar (sucrose) was originally present.
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7
Q

Polysaccharides

A
  • Polysaccharides differ in number and arrangement of glucose molecules they contain.
  • Function as storage or structural molecules, as they’re large and relatively insoluble in water.
  • They are non-reducing.
  • They are unsweet to taste.
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8
Q

Cellulose

A

Long-straight chains, which collectively form microfibrils, which together form macrofibrils.
In one layer, macrofibrils go the same direction, across layers they go different directions. Layers are interwoven causing rigidity. Fully permeable.

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9
Q

Starch

A

Storage molecule in plants. Stored in amyloplasts in the cytoplasm. Comprised of amylose and amylopectin.

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10
Q

Hydrolysis of starch

A

Hydrolysed by amylase to produce maltose

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11
Q

Why is starch suitable as a storage molecule?

A
  • Insoluble and osmotically inactive.
  • Molecule has helical shape forming compact store.
  • Contains large number of glucose molecules providing abundant supply of respiratory substrate.
  • Too large to cross cell membrane, remains in cell.
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12
Q

Glycogen

A

Storage molecule found in animals and fungi. Similar to starch but with is more branched so can be hydrolyzed more rapidly to release glucose for respiration.

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13
Q

Amyloplasts

A

Starch grains found in cytoplasm of plant cells. Contain the polysaccharide starch.

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14
Q

What properties of glycogen make it ideal for storage?

A

Insoluble and osmotically inactive

Stored in liver and muscle tissues

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15
Q

Difference in elements between lipids and carbohydrates.

A

Lipids possess more hydrogen and less oxygen.

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16
Q

Triglycerides

A

Type of lipid formed by joining 3 fatty acids to one glycerol molecule during a condensation reaction with the loss of three water molecules.

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17
Q

Hydrolysis of lipids

A
  • Heating with acid or alkali.

- Using the enzyme lipase at its optimum temperature and pH.

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18
Q

Bond between two monosaccharides

A

Glycosidic bond

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19
Q

Amylose

A

Long, unbranched chain of a-glucose. Angles of glycosidic bonds give a coiled sructure, like a cylinder. Makes it compact, so is good for storage.

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20
Q

Amylopectin

A

Long, branched chain of a-glucose. Side branches allow easy break down by enzymes as bonds are easily accessed. Allows fast release of glucose.

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21
Q

In cellulose, why is every other B-glucose molecule inverted?

A

β1-4 glycosidic bond joining the β glucose molecules together. Creates long, straight chain.

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22
Q

Why do microfibrils occur with cellulose?

A

Hydroxyl (OH) groups project from either side of glucose chains form hydrogen bonds with the hydroxyl (OH) groups of adjacent chains

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23
Q

How are macrofibrils positioned and what does this allow?

A

Macrofibrils in one layer are orientated in the same direction. In successive layers, they’re orientated in a different direction. They are interwoven and embedded in a matrix providing rigidity. Cellulose cell wall is usually fully permeable due to minute channels between the different layers of macrofibrils.

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24
Q

What allows amylopectin to branch?

A

a1-6 bonds glycosidic bonds

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25
Q

endopeptidases

A

Hydrolyse internal peptide bonds in proteins to produce smaller polypeptides.

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26
Q

exopeptidases

A

Remove single amino acids from the ends of the polypeptide chains, eventually producing dipeptides and amino acids

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27
Q

Secondary structure

A

Hydrogen bonds form between AA in chain. Cause alpha helix or beta pleated sheet

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28
Q

Tertiary structure

A

Further coiling/folding. Hydrogen, ionic and disulphide bonds form. Also hydrophobic interactions.

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29
Q

Disulphide bonds

A

Tertiary structure of proteins, occur between cysteine amino acids.

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30
Q

Quaternary structure

A

Relates to highly complex proteins consisting of more than one polypeptide chain and possibly the association of non-protein/prosthetic groups. Same bonds as 3rd.

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31
Q

Hydrogen bonding in proteins

A

Between C=O and N-H groups of backbone. Responsible for secondary structures. Can also occur in R groups.

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32
Q

Fibrous proteins

A

Have structural functions e.g. keratin-nails&collagen-bone. Insoluble, w/ simple tertiary and quaternary structure consisting of long parallel polypeptide chains. Often form fibres or sheets providing strength and flexibility.

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33
Q

Globular proteins

A

Consist of highly folded and coiled polypeptide chain. Produces compact, complex specific tertiary structure, which is soluble in water. Includes enzymes, antibodies, receptors and hormones.

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34
Q

Causes of denaturation

A

High temperatures above the optimum, breaking hydrogen bonds.
Changes in pH away from the optimum break hydrogen and ionic bonds.
Reducing agents can break disulfide bridges.
Heavy metal ions can bind to sites on the protein and bring about changes in shape.

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35
Q

Biuret test

A

Test for proteins
Add sample to test tube containing 2cm3 of biuret reagent.
A purple/lilac colour indicates protein is present.
If the solution remains blue, no protein is present.

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36
Q

Enzyme

A

Globular proteins, usually with a high molecular weight. Biological catalysts which regulate biological processes in living organisms. Tertiary structure of enzyme determines its specific function.

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37
Q

Amylase

A

Breaks down starch

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38
Q

Lipase

A

Hydrolyses ester bonds

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39
Q

Enzyme specificity

A

Feature of the unique tertiary structure of an enzyme.
Structure is held together by hydrogen bonds, ionic bonds and sometimes disulphide bridges.
This determines the shape and electrostatic charges of the active site

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40
Q

Induced fit hypothesis

A

Substrate interacts with active site and causes enzyme to change shape. This may put a strain on bonds of substrate making a reaction more likely e.g. hydrolysis.
Active site may also allow two molecules to come very close together, in a certain orientation, making a reaction more likely (e.g. a condensation reaction)

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41
Q

High temperatures and enzymes

A

There is a very high level of kinetic energy and the reaction proceeds at a very fast rate due to many collisions between enzyme and substrate. However, due to the very high kinetic energy, hydrogen bonds begin to break and the enzyme begins to denature. Therefore less or no substrate can bind at the altered active site. The reaction stops but there is still substrate left at the end.

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42
Q

How can the impact of a competitive inhibitor be reduced?

A

Addition of more substrate

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43
Q

End-product inhibition

A

When the end product of a metabolic pathway begins to accumulate, it may act as an inhibitor. Product starts to switch off its own production as it builds up. Process is self-regulatory. As the product is used up, its production is switched back on again. Called end-product inhibition, example of negative feedback.

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44
Q

Immobilised enzymes

A

Binding to, or trapping in, a solid support which can be recovered easily from the reaction mixture. Enzyme can be re-used, reducing cost of process.

45
Q

Advantages of immobilising enzymes

A

Cost
Restricts enzymes ability to change shape&denature
Allows continuous production

46
Q

Physical bonding methods of immobilising an enzyme

A
  • Adsorb onto insoluble matrix, such as collagen
  • Hold inside gel, such as silica gel (gel entrapment)
  • Hold within semi-permeable membrane e.g. polymer microspheres
  • Trap in a micro-capsule (microencapsulation) e.g. in alginate beads
47
Q

Chemical bonding example of immobilising enzyme

A

To the support medium e.g. using glutaraldehyde to bind the enzyme to cellulose fibres. Enzymes are covalently bonded, enzyme activity is high. Although preparation is difficult.

48
Q

How does an electron microscope work?

A

It uses a beam of electrons focused by electromagnets.

49
Q

How does a light microscope work?

A

Focuses light rays by lenses in light microscopy.

50
Q

Wavelength of electron microscope?

A

0.005nm

51
Q

Wavelength of light microscope?

A

500-700nm

52
Q

Maximum resolution of electron microscope?

A

0.05nm

53
Q

Maximum resolution of light microscope?

A

200nm

54
Q

Advantages of electron microscope

A
  • High maximum useful magnification (over a million)

- Electrons have shorter wavelength than light and thus greater resolution

55
Q

Resolution

A

The ability to distinguish between two close objects

56
Q

Disadvantages of electron microscope

A
  • Vacuum is required, so no living specimens.
  • Complicated preparation and staining techniques which can produce artefacts
  • Expensive, and expert training is required to use.
57
Q

Transmission electron microscope process

A
  • Beam of electrons transmitted through specimen.
  • Specimen must be thin
  • Stained using electron dense substances such as heavy metal salts
  • These deflect electrons in beam, the pattern the remaining electrons produce whilst passing through is converted to an image.
58
Q

Limitations of TEM

A
  • Very thin sections of the specimen must be used
  • Doesn’t show 3D arrangement of cellular components.
  • Specimen gradually deteriorates in electron beam.
59
Q

Advantages of TEM

A
  • Higher resolution than SEM

- Can see internal structures even of molecular size e.g. proteins and nucleic acids

60
Q

Scanning electron microscope process

A
  • Specimen is coated with thin film of heavy metal (e.g.gold)
  • Electron beam scanned to and fro across specimen
  • Reflected electrons from surface are collected and produce an image on screen.
61
Q

Advantages of SEM

A
  • Surfaces of structures are shown
  • Gives a three-dimensional effect
  • Much thicker sections can be examined than TEM
62
Q

Limitations of SEM

A
  • Lower resolution than TEM

- Only the surface of an object can be viewed.

63
Q

Consistent structures present in prokaryotes

A
  • Cell wall (murien/peptidoglycan)
  • Cell membrane
  • Circular genomic DNA (attached to mesosome)
  • Ribosomes
  • Food reserve granule (lipid or glycogen)
  • Cytoplasm
64
Q

Differential Centrifugation

A
  • Centrifugation separates structures of different densities.
  • Differential centrifugation involves centrifuging at different speeds (forces) and can be used to separate and isolate the different organelles in a cell.
65
Q

Hypotonic

A

Extracellular fluid has lower osmolarity than fluid inside cell, so net flow of water goes into cell.

66
Q

Hypertonic

A

Extracellular fluid has a higher osmolarity than the cell’s cytoplasm, so water moves out of cell to region of higher solute concentration.

67
Q

Plasmolysis

A

Contraction of protoplast of plant cell due to water loss

68
Q

Centrioles

A
  • Produce spindle fibres that seperate chromosomes during mitosis/meiosis.
  • Small hollow cylinders containing microtubules.
69
Q

Importance of cristae

A
  • Provide large surface area for stalked particles they possess
  • These contain enzymes used for ATP production by the electron carrier system (oxidative phosphorylation)
70
Q

Importance of matrix

A
  • Contains enzymes of Kreb’s cycle (aerobic respiration)
  • Contains mitochondrial DNA and ribosomes.
  • DNA contains information for organelle replication
  • Ribosomes required for protein synthesis
71
Q

What do ribosomes consist of?

A

Two subunits, one small, one large.

Made of protein and ribosomal RNA.

72
Q

What does the rough endoplasmic reticulum consist of?

A
  • Has ribosomes on surface that produce secretory proteins that are transported through the cisternae.
  • Proteins are sent to the Golgi body for packaging.
73
Q

Smooth endoplasmic reticulum

A

Involved in production and transport of lipids.

74
Q

Location of ribosomes

A

Present in the cytoplasm singly, in a chain (polysomes) or attached to the RER

75
Q

Golgi body

A

Acts as an internal processing and transport system.

  • Produces glycoproteins
  • Packages and secretes proteins
  • Forms lysosomes and cell walls.
  • Lipid biosynthesis.
76
Q

Lysosomes

A

Spherical w/ single membrane. Contains hydrolytic enzymes

77
Q

Enzymes found in lysosomes

A

Proteases, nucleases and lipases.
Have to be kept apart from the rest of the cell.
Enzymes contained were synthesised on RER and transported to Golgi apparatus.

78
Q

Functions of lysosomes

A

Digestion of material taken in by endocytosis
Autophagy
Release of enzymes outside the cell

79
Q

Autophagy

A

Process by which unwanted structures within cell are engulfed and digested within lysosomes.
First enclosed by single membrane, from SER. This structure fuses w/ lysosome to form ‘autophagic vacuole’ wherethe unwanted material is digested. Part of normal turnover of cytoplasmic organelles, old ones replaced by new ones.

80
Q

Stroma

A

Fluid in chloroplasts.
Site of light-independent reaction
Contains enzymes, sugars and amyloplasts.

81
Q

Chloroplasts

A

Site of photosynthesis.
Flattened biconvex discs, surrounded by envelope made of two membranes.
Envelope encloses membrane system of thylakoids, which form stacks of grana.
These provide large surface area for chlorophyll for the light-dependent reactions of photosynthesis.
Membrane system is surrounded by the stroma

82
Q

Tissue

A

Aggregations of similar cells that perform a specific physiological function

83
Q

Organ

A

Structure consisting of different tissues, which has a specific physiological function

84
Q

System

A

Several organs combined

85
Q

How are palisade mesophyll cells adapted for photosynthesis?

A

Possess numerous chloroplasts.
Have relatively thin cell walls.
Are cylindrical.
There are with few air spaces in between.

86
Q

What is an advantage of having thin cell walls in plant cells?

A

Allow carbon dioxide to diffuse in at a faster rate.

87
Q

What is an advantage of palisade mesophyll cells being cylindrical?

A

Have a relatively large surface area increasing the rate of gaseous diffusion.

88
Q

What is an advantage of palisade mesophyll cells having few air spaces between one another?

A

Allows maximum light absorption.

89
Q

Epithelial tissues

A

Line inside/outside or organs and have a range of functions.

Can be categorized into 3 types: squamous, cuboidal and columnar.

90
Q

Columnar tissues

A

Found in small intestine and proximal convoluted tubule of the kidney. Cylindrical in shape and specifically adapted for absorption of small molecules, mainly by active processes. Have microvilli+mitochondria.

91
Q

Process of cloning plants in vitro

A

A few cells are taken from the plant and are placed in a suitable nutrient medium. Growth factors e.g. IAA are applied to stimulate the totipotent cells to differentiate into shoots and roots.

92
Q

Other than rapid production of a multiple clones of a particular plant, what else is cloning plants in vitro used for?

A
  • Produce clones of plants w/ desirable traits .
  • To quickly produce mature plants.
  • Regeneration of plants from GM cells
93
Q

Difference between totipotent and pluripotent stem cells?

A

Totipotent stem cells can produce extra embryonic tissue

94
Q

Three primary germ layers pluripotent cells can differentiate into

A

ectoderm - outside layer
endoderm - innermost layer
mesoderm - middle layer

95
Q

Uses of stem cells

A
  • research into chemical signals that cause cells to differentiate to specific cells
  • carry out drug tests on differentiated cells formed from stem cells, reducing the amount of drug testing on animals.
96
Q

Features increasing membrane permeability of plasma membranes

A

Unsaturated fatty acids
Abundance of channel/carrier proteins
Large areas of phospholipid

97
Q

Features decreasing membrane permeability of plasma membrane

A

Saturated fatty acids
Cholesterol
Lack of bilayer
Lack of proteins

98
Q

Role of receptor proteins on surface

A

Bind to hormones due to specific tertiary structure and trigger a cellular response

99
Q

Diffusion

A

The net movement of molecules down a concentration gradient from an area of high concentration to an area of low concentration until the molecules are equally distributed.

100
Q

Rate of diffusion

A

SAxCG/DD

101
Q

Facilitated diffusion

A

The transport of polar molecules (e.g.glucose, amino acids) and charged species(e.g.ions) across membranes.

102
Q

Carrier proteins

A

Span bilayer and change shape in presence of specific complementary molecule.
Can be specific to single molecules or groups of similar molecules.

103
Q

Channel proteins

A

Retain shape and transport ions.
Charge of channel causes specificity.
Pore size also determines passage of ions.

104
Q

Active transport

A

Movement of molecules/ions through a partially permeable membrane by carrier proteins against a concentration gradient.

105
Q

Factors affecting respiration rate and thus active transport

A

Temperature.
Volume of oxygen.
Metabolic and respiratory inhibitor

106
Q

Osmosis

A

Net movement of water molecules from a dilute solution to a more concentrated solution across a selectively permeable membrane.

107
Q

Pinocytosis

A

Material taken up is in liquid form. Vesicles formed are v small, in which case the process is known as micropinocytosis and the vesicles as micropinocytotic vesicles.

108
Q

Endocytosis and exocytosis

A

Active processes involving the bulk transport of materials through membranes, either into cells (endocytosis) or out of cells (exocytosis)

109
Q

Cisternae

A

Flattened membrane sacs which make up the golgi body and the ER, where they form an internal cell transport system.

Biosciences (24 decks)

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