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Biology > Topic 3 - The Chemistry Of Life (SL) > Flashcards

Topic 3 - The Chemistry Of Life (SL) Flashcards

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0
Q

Describe cohesion as a property of water

A

Water molecule stick to each other because of the hydrogen bonds that form between them

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1
Q

PROPERTIES OF WATER

A 
Cohesion
Solvent properties
Heat capacity
Boiling point
Cooling effect of evaporation
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2
Q

Describe the solvent properties of water

A

Many substances dissolve in water because of its polarity
Inorganic particles with positive or negative charges dissolve, for example sodium ions
Organic substances with polar molecules dissolve, for example glucose
Enzymes also dissolve in water

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3
Q

Describe heat capacity as a thermal property of water

A

Water has a large heat capacity - large amounts of energy are needed to raise its temperature. The energy is needed to break some of the hydrogen bonds

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4
Q

Describe boiling point as a thermal property of water

A

High boiling point (100 degrees C) as to change it from a liquid to a gas all the hydrogen bonds have to be broken

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5
Q

Describe the cooling effect of evaporation as a thermal property of water

A

Water can evaporate at temperatures below boiling point

Hydrogen bonds have to be broken for this - the heat energy to break these bond is taken from the water, cooling it down

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6
Q

Cohesion of water - uses in living organisms

A

Strong pulling forces exam be exerted to suck columns of water up to the tops of the tallest trees in their transport systems - these rarely break.
Water is used as a transport medium in the xylem of plants

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7
Q

Solvent properties - uses in living organisms

A

Water is the medium for metabolic reactions

Water can be used as a transport medium (for instance blood in animals and sap in plants)

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8
Q

Heat capacity - uses in living organisms

A

Blood (mainly composed of water) can carry heat from warmer parts to cooler parts of body - used as a transport medium for heat

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9
Q

Boiling point - uses in living organisms

A

As a liquid, rather than a solid or gas, water can act as the medium for metabolic reactions

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10
Q

The cooling effect of evaporation - uses in living organisms

A

Evaporation from plant leaves and human skin has useful cooling effects.
Can be used as a coolant

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11
Q

What are the most common chemical elements of life?

A

Carbon
Hydrogen
Oxygen
Nitrogen

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12
Q

What are the three types of organic compound found in living organisms?

A

Carbohydrates, lipids and proteins

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13
Q

Role of sulphur (S) in plants, animals and prokaryotes

A

Needed to make 2 of the 20 amino acids that proteins contain

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14
Q

Role of calcium (Ca) in plants, animals and prokaryotes

A

Acts as a messenger, binding to proteins that regulate processes inside cells, including transcription

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15
Q

Role of phosphorus (P) in plants, animals and prokaryotes

A

Part of the phosphate groups in ATP and DNA molecules

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16
Q

Role of iron (Fe) in plants, animals and prokaryotes

A

Needed to make cytochromes - proteins used for electron transport during anaerobic cell respiration

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17
Q

Role of sodium (Na) in plants, animals and prokaryotes

A

Pumped into the cytoplasm to raise the solute concentration and cause water to enter by osmosis

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18
Q

What is a peptide linkage?

A

Two amino acids are joined together to form a dipeptide by a condensation reaction

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19
Q

What is a polypeptide?

A

A chain of many amino acids formed by condensation reactions

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20
Q

What are hydrolysis reactions?

A

The reverse of condensation reactions

Polypeptides + water ➡️ dipeptides or amino acids

Polysaccharides + water ➡️ disaccharides or monosaccharides

Glycerides + water ➡️ fatty acids + glycerol

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21
Q

Examples of monosaccharides

A

Glucose
Galactose
Fructose

22
Q

Use of monosaccharides in animals

A

Glucose - carried by the blood to transport energy to cells throughout the body

23
Q

Uses of monosaccharides in plants

A

Fructose - used to make fruits sweet tasting, attracting animals to disperse seeds in the fruit

24
Q

Examples of disaccharides

A

Maltose
Lactose
Sucrose

25
Q

Uses of disaccharides in animals

A

Lactose - the sugar in milk that provides energy to young mammals

26
Q

Uses of disaccharides in plants

A

Sucrose - carried by phloem to transport energy to cells throughout the plant

27
Q

Examples of polysaccharides

A

Starch
Glycogen
Cellulose

28
Q

Uses of polysaccharides in animals

A

Glycogen - used as a short term energy store in liver and muscles

29
Q

Uses of polysaccharides in plants

A

Cellulose used to make strong fibres that are used to construct the plant cell wall

30
Q

What are the functions of lipids?

A

Energy storage
Heat insulation
Buoyancy

31
Q

What are the advantages of lipids in energy storage?

A

Contain more energy per gram than carbohydrates so stores of lipids are lighter than stores of carbohydrate that contain the same amount of energy

Insoluble in water so do not cause problems with osmosis in cells

32
Q

What are the advantages of carbohydrates?

A

More easily digested than lipids so the energy stored by them can be released more rapidly
More soluble in water so are easier to transport to and from the store

33
Q

What makes up a nucleotide?

A

Phosphate
Sugar (e.g. deoxyribose)
Base (A, T, C, G)

34
Q

What is complementary base pairing?

A

A only bonds with T

C only bonds with G

35
Q

Number of strands in a molecule of DNA and RNA

A

DNA - two strands forming a double helix

RNA - One strand only

36
Q

Type of sugar in DNA and RNA nucleotides

A

DNA - Deoxyribose

RNA - Ribose

37
Q

Types of bases in DNA and RNA

A

DNA - A, T, C, G

RNA - A, U, C, G

38
Q

What are enzymes?

A

Enzymes are biological catalysts. They are globular proteins which act as catalysts of chemical reactions

39
Q

What is denaturation?

A

Denaturation is changing the structure of an enzyme (or other protein) so that it can no longer carry out its function

40
Q

What is an active site?

A

An active site is a region on the surface of an enzyme to which substrates bind and which catalyses a chemical reaction involving the substrates

41
Q

Stages in enzyme catalysis

A
  1. A substrate collides with the active site and binds to it
  2. The substrate fits the active site - other molecules may not fit so will not bind
  3. The active site catalyses a chemical reaction. The substrates are turned into products
  4. The products detach from the active site, leaving it free for more substrate to bind
42
Q

Factors affecting enzyme activity

A

Temperature, substrate concentration, pH

43
Q

Effect of temperature on enzyme activity

A

As pH increases or decreases from the optimum, enzyme activity is reduced. This is because the shape of the active site is altered. Most enzymes are denatured by very high or very low pH, so the enzyme no longer catalyses the reaction

44
Q

Effect of temperature on enzyme activity

A

Enzyme activity increases as temperature increases - collisions between enzymes and substrates occur more frequently
At high temperatures enzymes are denatured - heat causes vibrations inside enzymes which break bonds needed to maintain the structure

45
Q

Effect of substrate concentration on enzyme activity

A

Low substrate concentrations - enzyme activity increases steeply as substrate concentration increases - random collisions occur more frequently
High substrate concentrations - most active sites are occupied so there is little effect

46
Q

What is cell respiration?

A

Controlled release of energy, in the form on ATP, from organic compounds in cells

47
Q

Describe production of oxygen as a method of measuring rates of photosynthesis

A

Aquatic plants release bubbles of oxygen when they carry out photosynthesis. If these bubbles are collected, their volume can be measured

48
Q

Describe uptake of carbon dioxide as a method of measuring rate of photosynthesis

A

If CO2 is absorbed from water, the pH of the water rises. This can be monitored with pH indicators or with pH meters

49
Q

Describe increases in biomass as a method of measuring rate of photosynthesis

A

If batches of plants are harvested at a series of times and the biomass of the plants is determined, the rate of increase in biomass gives an indirect measure of the rate of photosynthesis in plants

50
Q

Effect of light intensity on photosynthesis

A

At low to medium light intensities, the rate is directly proportional to light intensity
At high light intensities, the rate reaches a plateau

51
Q

Effect of CO2 concentration on photosynthesis

A

No photosynthesis at very low concentrations
At low to fairly high CO2 concentrations the rate is positively correlated with CO2 concentration
At very high CO2 concentrations the rate reaches a plateau

52
Q

Effect on temperature on photosynthesis

A

As temperature increases the rate increases more and more steeply
Above the optimum temperature the rate falls steeply

Biology (5 decks)

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