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IGCSE Biology > 2. Structure And Functions In Living Organisms > Flashcards

2. Structure And Functions In Living Organisms Flashcards

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1
Q

Test for glucose

A

Benedict’s solution
- add Benedict’s solution to sample of food
- place in water bath 80 degrees for 5 mins
- blue —> brick red/yellow/green
- red has highest conc of sugar

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2
Q

Test for starch

A

Iodine test
- add a few drops of orange iodine solution to sample on spotting tile
- orange —> blue/black

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3
Q

Protein test

A

Biuret test
- add 2cm3 to food sample and shake
- add equal vol of dilute potassium hydroxide and shake
- add two drops of 1% copper sulfate solution
- blue —> pale purple

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4
Q

Test for lipids

A

Emulsion test
- add small vol of absolute ethanol and shake to dissolve any lipids in alcohol
- add equal vol of water
- cloudy white colour forms (emulsion forming)

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5
Q

Role of enzymes

A

Biological catalysts in metabolic reactions that speeds up the rate of reaction without being used up itself, provides pathway with a lower activation energy

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6
Q

Catalyst

A

Chemical which increases the rate of reaction without being used up itself in the reaction
- remain unchanged so they are free to catalyse more reactions

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7
Q

Lock and key theory for enzymes

A
  • substrate and enzyme collide
  • substrate binds to active site of enzyme
  • strains chemical bonds in substrate so the reaction occurs by an alternative pathway with a lower activation energy
  • forms products
  • products no longer fit onto active site or substrate so they release
  • enzyme is unchanged and is free to catalyse the next reaction
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8
Q

Factors that affect rate of enzymes:

A

Temperature, pH level, concentration of enzyme/substrate

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9
Q

Factors that affect rate of enzymes: temperature

A

As temperature increases the enzyme and substrate have more kinetic energy, they move faster and creates more successful collisions
After the optimum temperature enzymes denature as rate of reaction decreases, active site changes shape and substrate doesn’t fit

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10
Q

Factors that affect rate of enzymes: pH level

A
  • enzyme function can be affected as it disrupts the forces between different parts of the amino acid chain
  • changes active site shape so the protein denatures
  • no longer complementary to substrate
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11
Q

Factors that affect rate of enzymes: concentration

A

Increase in concentration of substrate or enzyme will speed up the reaction (adding more)
If enzyme becomes too saturated with too much substrate the rate with plateau
At a point it is no longer the limiting factor

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12
Q

Practical: investigate how enzyme activity can be affected by changes in temperature

A

C - temperature of water bath
O - vol of starch solution
R - repeat 3x so it’s reliable
M - measure time taken
M - for iodine to stop turning black (blue black from orange iodine)
S - concentration and volume of amylase
S - same concentration of substrate and enzyme

At 60 degrees no digestion/no colour change

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13
Q

Diffusion

A

Random movement of molecules from an area of higher concentration to an area of lower concentration across a partially permeable membrane
- allows organisms to gain nutrients in digestive system/gain oxygen in lungs/remove waste products in lungs/kidney

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14
Q

Practical: investigate how enzyme activity can be affected by changes in pH

A

C - ph of solution
O - same surface area of photocopier
R - repeat 10x for each pH
M - how long it takes for
M - photocopier to go colourless
S - volume and concentration of enzyme
S - temperature

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15
Q

Osmosis

A

Net movement of free water molecules from an area of high water potential to an area of low water potential across a partially permeable membrane

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16
Q

Active transport

A

Movement of molecules from an area of low concentration to an area of high concentration using ATP

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17
Q

Water potential

A

Measure of concentration of free water molecules in a solution

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18
Q

Partially permeable membrane

A

Allows only certain molecules through

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19
Q

Four main factors that affect the rate of diffusion/osmosis

A

Temperature, concentration gradient, distance, SA:VOL

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20
Q

Factors that affect the rate of diffusion/osmosis: temperature

A

At higher temperatures moleules have more kinetic energy and so move faster
Therefore diffusion occurs faster

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21
Q

Factors that affect the rate of diffusion/osmosis: concentration gradient

A

If there’s a very large difference in concentration, molecules with diffuses from the higher to lower concentration quickly

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22
Q

Factors that affect the rate of diffusion/osmosis: distance

A

Diffusion takes longer if molecules have to travel further (why cells are small as smaller volume reduces distance)

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23
Q

Factors that affect the rate of diffusion/osmosis: SA:VOL

A

A larger surface area speeds up rate of diffusion as there’s more opportunités for molecules to move
SA:V is increased when structures are small

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24
Q

Isotonic solution in plant and animal cell

A

Animal - solution outside the cell as the SAME water potential as inside the cell
- no net movement

Flaccid in plant cells

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25
Q

Hypotonic solution in animal and plant cell

A

Animal cell - solution outside the cell has a HIGHER water potential then inside the cell
- net movement of water molecules INTO cell via osmosis

Turgid in plant cell - cytoplasm pushes against cell wall

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26
Q

Hypertonic solution in plant and animal cell

A

Animal - solution outside cell has LOWER water potential then inside the cell
- net movement of free water molecules OUT of the cell via osmosis

Plasmolyzed in plant cell - cytoplasm detached from cell wall

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27
Q

What happens to plasmolyzed plant cells

A

Plant will wilt because there’s not enough water to fill their cells and therefore the cytoplasm shrinks from cell wall

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28
Q

Practical: test how the concentration of a sucrose solution affects rate of osmosis

A

C - sucrose solution concentration
O - same type of potato
R - repeat 3x for each potato cut
M - change in mass of potato
M - with scale
S - same type of potato (same concentration of sucrose)
S - same length of potato ( same SA:VOL)

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29
Q

Practical: the effect of surface area to volume ratio on diffusion rate

A

C - SA:V of agar cubes
O - same agar jelly
R - repeat 3x for each agar cube to ensure reliability
M - length of agar colourless (diffusion occurring)
M - over 2 mins
S - same concentration and volume of solution
S - same temperature of room (can affect diffusion)

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30
Q

Other practicals on diffusion/osmosis: visking tube and onion cells

A

Visking tube - only allows small soluble molecules through so osmosis can occur, can change conc of sucrose solution or temp of water to investigate effect on osmosis (height liquid rises in a set time will increase if osmosis is faster

Onion cells
- soaked in pure water is turgid
- soaked in concentrated sugar/salt solution is plasmolyzed

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31
Q

3 cell structures in plants only

A

Vacuole, cell wall, chloroplasts

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32
Q

Nucleus

A
  • controls activity of the cell using DNA
  • contains chromosomes
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33
Q

Cell membrane

A

Boundary between cytoplasm and cell
- controls what substances enter and leave the cell
- selectively permeable
- inside wall

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34
Q

Cytoplasm

A

Jelly-like liquid where chemical reactions occur

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35
Q

Mitochondria

A
  • produces ATP used for respiration (aerobic)
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36
Q

Ribosomes

A

Site of proteinsynthesis

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37
Q

Chloroplasts

A

Absorb light energy used for photosynthesis

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38
Q

Cell wall

A

Made of cellulose
- gives the plant its shape, keeps it upright

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39
Q

Vacuole

A

Filled with cell sap
- stores dissolved sugars, mineral ions and other substances

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40
Q

Differences in animal and plant cell

A
  • Plant has a vacuole, cell wall and chloroplast
    Animal vacuole is small and temporary
    Plant vacuole is large and permanent
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41
Q

Pathway that food takes through alimentary canal

A

Mouth -> oesophagus -> stomach -> duodenum -> iluem -> colon -> rectum -> anus

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42
Q

Egestion

A

Removal of faeces (undigested food)

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43
Q

Excretion

A

Removal of metabolic waste (e.g. CO2/urea)

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44
Q

Ingestion

A

Taking food in through the mouth and swallowing

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45
Q

Digestion

A

Breaking down large insoluble molecules to smaller soluble molecules

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46
Q

Absorption

A

Movement of small soluble molecules (products of digestion) out of the gut and into the bloodstream by diffusion and active transport

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47
Q

Assimilation

A

Building larger biological molecules from the small soluble molecules in all cells

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48
Q

Alimentary canal: mouth

A

Mechanical digestion - food is crushed/torn/cut by teeth into smaller pieces (increases SA for enzymes and prevents discomfort when swallowing)
Chemical digestion - saliva released by salivary glands (contains salivary amylase, breaks down starch to maltose)
Food is formed into a bolus

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49
Q

Alimentary canal: oesophagus

A
  • bolus of food moves from mouth to stomach by muscular contractions called peristalsis
    Circular muscles contract behind bolus, moving it along
    Longitudinal muscles contract making the oesophagus wider
50
Q

Alimentary canal: stomach

A
  • food is churned around because of muscular contractions -> mechanical digestion
    Hydrochloric acid kills pathogens that enter
    -> creates optimum pH level (acidic) for pepsin enzyme that converts protein to dipeptides/peptides
51
Q

Alimentary canal: small intenstine

A

Digestion and absorption occur
Digestion happens in first section -> duodenum

52
Q

Alimentary canal: duodenum (bile)

A
  • final site of chemical digestion
  • food mixes with bile which emulsifies food (breaks large droplets into smaller droplets which increases SA for lipase to digest/breakdown fats)
  • neutralises stomach acid -> optimum temp for pH (enzymes in duodenum work best at pH 7-8)
53
Q

Alimentary canal: duodenum (enzyme)

A

Food mixes with enzymes:
Pancreatic amylase
Maltase
Lipase
Trypsin
Peptidase

54
Q

Enzymes in duodenum: pancreatic amylase

A

Pancreatic amylase converts starch —> maltose

55
Q

Enzymes in duodenum: maltase

A

Maltase converts maltose —> glucose

56
Q

Enzymes in duodenum: lipase

A

Lipase converts lipids —> glycerol and 3x fatty acids

57
Q

Enzymes in duodenum: trypsin

A

Trypsin converts protein —> dipeptides

58
Q

Enzymes in duodenum: peptidase

A

Peptidase converts dipeptides —> amino acids

59
Q

Alimentary canal: iluem

A

Absorption of digested food, small soluble molecules absorbed by diffusion
- some like glucose are absorbed via active transport
Contains finger-like projections called villi + microvilli

60
Q

How is the ileum adapted for its function

A

Microvilli+villi and folds - increase SA which creates more diffusion of digested food
Thin walls - short diffusion distance (one cell thick)
Good blood supply (capillary network) - maintains concentration gradient for diffusion
Has lacteal - absorbs lipids and maintains concentration

61
Q

Alimentary canal: large intenstine

A

Water removes undigested food -> forms faeces
Faeces is egested, stored in anus

62
Q

Digestion from starch to glucose

A

Starch -> maltose via amylase
maltose —> glucose via maltase

63
Q

Digestion of proteins

A

Protein -> amino acids via proteases

64
Q

Digestion of lipids

A

Lipids -> glycerol + fatty acids
Via lipases

65
Q

How temperature effects enzyme activity

A

->too low kinetic energy, few collisions as substrate and enzyme dont collide
->increase in temp increases kinetic energy which increases number of collisions, more enzyme subsrate complex formed, rate of reaction increases
->optimum pH, most number of ESC formed, rate is fastest
->enzyme denatured and active site changes shape

66
Q

Cell respiration

A

The process of breaking down food molecules to release ATP - series of chemical reactions

67
Q

Aerobic respiration

A

Uses oxygen to break down glucose and release energy and some ATP

68
Q

Aerobic respiration chemical and word equation

A

Glucose + oxygen —> carbon dioxide + water

C6H12O6 +6 O2 ——>6 CO2+ 6 H2O

69
Q

ATP provides..

A

..energy for cells

70
Q

Anaerobic respiration

A

Cells that respire without oxygen -> allows cells to obtain some energy when oxygen is limited
Glucose is not completely broken down - less ATP released

71
Q

Anaerobic respiration word equation in fungi and plants

A

Glucose —> ethanol + carbon dioxide

72
Q

Anaerobic respiration word equation in animals

A

Glucose —> lactic acid
If lactic acid builds up it can cause cramps

73
Q

Oxygen debt

A

Volume of oxygen needed to oxidise the lactic acid

74
Q

Differences in aerobic and anaerobic respiration

A

Aerobic - completely breaks down glucose, more energy released, uses oxygen
Anaerobic - partially breaks down glucose, less energy released, doesn’t use oxygen

75
Q

Practical: investigate carbon dioxide and heat from respiring seeds -> germinating peas experiment

A

C - change the content in the flask (germinating/dead seeds)
O - same size/species of seed
R - repeat 3x with both seeds
M - observe change in temperature on the thermometer
M - after 4 days
S - same number of seeds
S - same starting temperature of flasks

76
Q

Practical: investigate carbon dioxide and heat from respiring seeds -> hydrogen carbonate indicator

A

C - move lamp in different distances
O - same volume of hydrogen carbonate indicator
R - repeat 3 times
M - measure colour change in hydrogen carbonate indicator
M - after 3 hours
S - same amount of organism
S - same volume of hydrogen carbonate

Indicator turns yellow in low light (less CO2)
Indicator turns red/purple in high light (more CO2)

77
Q

Gas exchange system is located

A

In the thorax (upper part of body)

78
Q

Trachea

A

Surrounded by c shape rings of cartilage to keep trachea open but make swallowing easier
Splits to form two bronchi

79
Q

Bronchi and bronchioles

A

Bronchi - tubes lead to lungs, also surrounded by cartilage rings
Bronchioles - bronchi divides/branches into smaller tubes called bronchioles which carry air deep into the thorax

80
Q

Aveoli

A

Site of gas exchange
- microscopic air sacs at the end of bronchioles

81
Q

Aveoli

A

Site of gas exchange
- microscopic air sacs at the end of bronchiole

82
Q

Pleural membrane

A

Lungs are surrounded in it to form a double layer between lungs and thorax
In between the membranes there’s a thin layer of pleural fluid
Forms a air tight seal and prevents the lungs from sticking to the thorax wall (as they inflate+deflate)

83
Q

Ribs

A

Protects organs in thorax

84
Q

Intercostal muscles

A

Intercostal muscles between ribs help to connect the bones and help air move in and out lungs

85
Q

Diaphragm

A

Separates organs or thorax and the abdomen
- domed sheet of muscle and fibrous tissue helps move air into and out lungs

86
Q

Ventilation

A

Process of moving air in and out the lungs (inhalation and exhalation)

87
Q

Inhalation (diaphragm and intercostal muscles)

A

Diaphragm contracts -> moves down and flattens
Intercostal muscles contact -> moves ribcage up and out

Volume of thorax increases and air pressure decreases
Air pressure is less than atmospheric pressure causing air to move into lungs

88
Q

Exhalation (diaphragm and intercostal muscles)

A

Diaphragm relaxes -> moves up and doming
Intercostal muscles relax -> moves rib cage down and in

Volume of thorax decreases and air pressure increases
Air pressure in the thorax is more than atmosphere is pressure, causing air to move out of lungs

89
Q

How are aveoli adapted for gas exchange

A

Large surface area -> lots of alveoli increases rate of diffusion
High concentration gradient -> surrounded by big capillary network which constantly carries deoxygenated blood and moves oxygenated blood away -> speeds up diffusion
Short distance -> walls of aveoli are only once cell thick and the cell is flattened, gases only need to move a small distance which speeds up diffusion

90
Q

Effects of smoking: carcinogens and chemicals

A

E.g. tar
Can alter DNA and increase risk of cancer

Chemicals in tobacco destroy cilia, reducing the number
Mucus production increases which cannot be moved out the airways quickly so it builds up and causes risk of infection and smokers cough
- bronchitis from build up of infected mucus in bronchitis

91
Q

Effects of smoking: carbon monoxide

A

Irreversibly binds to haemogoblin -> forms carboxyhaemogoblin
- reduces amount of oxygen transported by blood

92
Q

Effects of smoking: aveoli and what disease it causes

A

Smoke reaches aveoli which damages them
Aveoli walls break down and fuse together, forming larger irregular air spaces
- decreases surface area for gas exchange so less oxygen diffuses into blood
- emphysema

93
Q

Coronary heart disease

A

Fatty deposits form if you have lots of saturated fats in ur diet-> narrows lumen space of artery and reduces blood flow to heart muscle cells
Means that less oxygen is received in heart muscle cells -> aerobic respiration decreases and anaerobic respiration increases -> lactic acid build up -> heart attacks
Smoking increases blood pressure and increases the risk of fatty deposits forming

94
Q

Risk factors that make coronary heart disease more likely

A

Diet - eating saturated fats increases blood cholesterol and increases fatty deposits
High blood pressure - damages artery lining and increases risk of fatty deposits
Obesity - increases blood pressure and may be linked to poor diet
Lack of exercise - causes high blood pressure

95
Q

Arteries carry blood

A

Away from the heart at high pressure

96
Q

Veins carry blood

A

Into the heart at a low pressure

97
Q

Capillaries carry blood

A

Through all tissues and are site of exchange of materials by diffusion
- tiny vessels, many of them

98
Q

Artery structure

A
  • thick outer wall (Can transport blood at high pressure without bursting)
  • thick layer of elastic tissue (allows artery to stretch and recoil to keep blood flowing at high pressure)
  • thick layer of muscular tissue (Helps to control flow of blood by widening and narrowing)
99
Q

Vein structure

A
  • fairly thin outer wall (blood flows at lower pressure so thick walls not needed)
  • think layer of muscle and elastic tissue (wall can contract to keep blood flowing)
  • semilunar valves (prevents blood flowing backwards)
100
Q

Capillary structure

A

Wall is one cell thick (short distance for diffusion of substances from blood to tissues)

101
Q

Practical: affect of exercise on breathing

A

C - amount of exercise
O - same age/gender/size/general fitness of students
R - repeat 3x with different amounts of exercise
M - measure change in breathing rate
M - immediately after exercise
S - same type of exercise
S - same temperature of environment

102
Q

Practical: affect of exercise on breathing

A

C - amount of exercise
O - same age/gender/size/general fitness of students
R - repeat 3x with different amounts of exercise
M - measure change in breathing rate
M - immediately after exercise
S - same type of exercise
S - same temperature of environment

103
Q

Transpiration

A

The evaporation of water from the surface of a plant

104
Q

4 environmental factors that affect rate of transpiration

A

Humidity, wind speed, temperature and light intensity

105
Q

Environmental factors that affect rate of transpiration: temperature

A

Water will evaporate quicker from leaves as water molecules have more kinetic energy -> transpiration will therefore increase as temp increases

106
Q

Environmental factors that affect rate of transpiration: humidity

A

In humid air there’s lots of water vapour -> smaller concentration gradient so transpiration slows down
Transpiration therefore increases if humidity decreases

107
Q

Environmental factors that affect rate of transpiration: wind speed

A

In moving air, water vapour will be blown away from leaf which speed sup transpiration
Transpiration therefore increases as wind speed increase

108
Q

Environmental factors that affect rate of transpiration: light intensity

A

In daylight stomata of leaf opens to supply CO2 for photosynthesis
Allows more water to diffuse out of leaves and into atmosphere

109
Q

Practical: role of environmental factors affecting rate of transpiration in leafy shoot
E.g. light

A

C - change intensity of light
O - plants of same species
R - repeat for each light intensity
M - measure distance travelled by bubble in potometer
M - in 30 mins
S - control the temperature/wind speed/humidity of environment

Black bag so there’s no photosynthesis -> stomata closes -> decrease in rate of transpiration

110
Q

Practical: role of environmental factors affecting rate of transpiration in leafy shoot
E.g. wind/temp

A

Wind -> use fan, blows away water droplets and increases rate of transpiration as it creates a concentration gradient
Temperature -> use hairdryer, more evaporation, more kinetic energy with movement of water droplets, increases rate of transpiration

111
Q

Rate of transpiration equation

A

Rate of transpiration = distance moved by air bubble (M) / time (min)

112
Q

Why does breathing rate increasing during excerise

A

As a response to increased concentration of carbon dioxide in the blood -> excrete carbon dioxide more rapidly -> supplies more oxygen to muscles -> more aerobic respiration

113
Q

Chemical element in carbohydrate

A

Made of carbon, hydrogen, oxygen
(CHO)

114
Q

Chemical element in lipids (fats)

A

Made of carbon, hydrogen, oxygen
(CHO)

115
Q

Chemical element in proteins

A

Made of carbon, hydrogen, oxygen and nitrogen
(CHON)

116
Q

Carbohydrates are broken down in

A

a chemical reaction (respiration) to release energy in the form ATP

117
Q

Structure of carbohydrate as large molecules made from smaller units

A

Simple sugars —> glucose and fructose
Two sugar molecule —> Glucose + fructose = sucrose
Complex carbohydrates —> starch (used to store glucose in plants) and glycogen (used to store glucose in animals ans fungi), less soluble and have less effect on water movement in and out of cells

118
Q

Structure of lipids as large molecules made from smaller units + function

A

Made of 3 fatty acids joined to glycerol molecule
Functions: energy storage, thermal insulation, electrical insulation, buoyancy

119
Q

Structure of proteins as large molecules made from smaller units + function

A

Made of many amino acids joined together
Functions: structural molecules like collagen and keratin, hormones, combating disease - antibodies, transport of haemogoblin

120
Q

Levels of organisation in organisms and examples

A

Organelles, cells, tissues, organs and systems + organisms
Mitochondria, plant cell, muscle, heart, cardiovascular system, human

IGCSE Biology (5 decks)

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