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IGCSE Biology > Topic 2 > Flashcards

Topic 2 Flashcards

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1
Q

What are the 3 main biological molecules?

A
  • Carbohydrates
  • Lipids
  • Proteins
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2
Q

What are carbohydrates made up of?

A

Molecule made from carbon, hydrogen and oxygen.

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3
Q

What is the function of carbohydrates?

A

Carbohydrates provide energy (plants use glucose for cellulose cell walls and starch to store energy. Glycogen is stored as energy in the liver for animals)

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4
Q

What are the tests for carbohydrates?

A
  • Benedicts Solution (blue -> red, reverse rainbow simple chains of glucose)
  • Iodine test (orange/brown -> blue/black for starch)
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5
Q

What are lipids made of?

A

Molecule made from carbon, hydrogen and oxygen, plus 3 fatty acids joined tot a glycerol molecule.

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6
Q

What is the function of lipids?

A

Energy-dense molecules. Fat stored under skin is adipose tissue (insulates). Used to produce cell membranes and hormones. Plants store oil in seeds.

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7
Q

What is the test for lipids?

A

Ethanol emulsion test (positive result = milky white emulsion)

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8
Q

What is a solid fat?

A

Saturated fats

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9
Q

What is a lipid fat?

A

Oils (unsaturated)

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10
Q

What is a protein made of?

A

Molecule made from carbon, hydrogen, oxygen and nitrogen (sometimes sulfur). Made from long chains of amino acids.

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11
Q

What is the function of proteins?

A

Proteins are used to make new proteins or enzymes. They are used for growth and cell repair of cells. They are used to make antibodies.

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12
Q

What is the test for proteins?

A

Biuret test (blue -> purple)

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13
Q

Enzymes:

A

Made of proteins (folded amino acid chains). Biological catalysts that speed up the rate of a chemical reaction without being used/altered.

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14
Q

What determines the shape of the active site?

A

The folding of amino acid chains.

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15
Q

What would happen without enzymes?

A

Living cells would have reactions that are necessary for the key life processes, take too long, therefore resulting in death.

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16
Q

What is the induced fit model?

A

When the substrate is not complimentary to the shape of the active site, but is very close to the complimentary sites shape. It is still capable of binding to the enzyme and inducing the active site to change.

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17
Q

What binds to the active site?

A

Substrates.

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18
Q

What is the structure called when the enzyme is attached to substrates?

A

Substrate-enzyme complex.

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19
Q

Factors affecting enzymes:

A
  • Temperature (higher eK = more chance of binding)
  • pH level (active site shape is influenced by pH)
20
Q

What is photosynthesis?

A

The process by which plants synthesise carbohydrates from raw materials using energy from light.

21
Q

Word equation for photosynthesis:

A

water + carbon dioxide -> glucose + oxygen (in the presence of light and chlorophyll.

22
Q

Balanced equation for photosynthesis:

A

6CO2 + 6H2O - > C6H12O6 + 6O2

23
Q

What is chlorophyll?

A

The green pigment (protein) found in chloroplasts and catalyses the reaction. Chlorophyll transfers energy from light into energy in chemicals, for synthesis of carbohydrates.

24
Q

5 uses of carbohydrates in plants:

A
  1. Stored in plants as starch
  2. Used for respiration
  3. Cellulose for cell walls
  4. Glucose-> sucrose to be transported through phloem vessels
  5. Nectar, for pollinators
25
Q

Why is glucose converted to sucrose in plants?

A

Glucose is highly reactive, may result in immediate reactions, and it is not energy efficient.

26
Q

2 symptoms of magnesium deficient plants:

A
  1. Magnesium needed to produce chlorophyll
  2. Magnesium deficient plants turn yellow (chlorosis) near/between veins
    VEINS DO NOT TURN YELLOW
27
Q

4 symptoms of nitrate deficient plants:

A
  1. Stunted growth
  2. Tips of leaves turn yellow
  3. Old leaves dry out
  4. Nitrates needed for ALL proteins
28
Q

What is hydrocarbonate indicator used for?

A

Used to monitor the net release of CO2 in plants. red = normal, purple = less CO2, Yellow = more CO2

29
Q

What does light do in photosynthesis?

A

Provides the energy that is used in chlorophyll to produce/convert into chemical energy

30
Q

What is a limiting factor?

A

Something that is in short supply that restricts a process.

31
Q

What are the 3 factors plants rely on?

A
  1. Light intensity
  2. Carbon dioxide concentration
  3. Temperature
32
Q

What is the effect of temperature on a plant?

A
  • denatures enzymes
  • too much transpiration
  • too little heat reduces enzyme reaction rate
33
Q

What are 5 leaf adaptations for the structure?

A
  1. Large surface area
  2. Very thin - aids diffusion
  3. Alternating arrangement - more exposure to light
    4.Top = shiny, more chlorophyll. Bottom = stomata
  4. Sometimes has fenestrations (gaps) to stop ripping in high winds
34
Q

What do the guard cells do?

A

Open/close stomata

35
Q

What is the stomata?

A

Tiny holes, allowing gaseous exchange.

36
Q

What does the waxy cuticle do?

A

Stops water loss, allowing light to pass through, protecting the leaf surface.

37
Q

What does the epidermal cells do?

A

Protection, but thin to let light in

38
Q

5 features of the palisade mesophyll section of a leaf:

A
  1. Many chloroplasts
  2. Packed tightly together
  3. Large surface area
  4. Vacuole pushes chloroplasts to edges of cell
  5. Thin cell walls aid gaseous exchange
39
Q

What is the palisade mesophyll sections optimised for?

A

Optimized for light exposure

40
Q

What is spongey mesophyll optimised for?

A

Optimized for gaseous exchange

41
Q

4 features of the spongey mesophyll section:

A
  1. Irregular shaped
  2. Fewer chloroplasts
  3. Smaller than palisade cells
  4. Spaced out with air pockets
42
Q

What does the xylem do?

A

Carries water and mineral ions up the plant.

43
Q

What does the phloem do?

A

Carries nutrients around the plant (sucrose)

44
Q

What is a balanced diet?

A

A dietary course that contains the correct amounts of each group of nutrients.

45
Q
A

IGCSE Biology (10 decks)

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