Igcse Biology : Respiration and gas exchange

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1

aerobic respiration

  • requires oxygen

  • produces 36 units of ATP

  • completely breaks down glucose

  • one used normally

  • glucose + oxygen => Water + carbon dioxide + 36 ATP

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2

anaerobic respiration in animals

  • doesn't require oxygen

  • produces 2 units of ATP

  • partially breaks down glucose

  • creates oxygen "debt" that has to be repaid ( thus heavy breathing after exercise )

  • glucose => lactic acid + 2 ATP

  • C6H12C6 => 2C3H6O3

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3

anaerobic respiration in plants (fermentation)

glucose => ethanol + carbon dioxide

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4

Adaptation of leaf for gas exchange

  • Thin: short diffusion pathway

  • Flat: large surface area to volume ratio

  • Spongy mesophyll layer: spaces for the gases

  • Stomata on lower epidermis: allow for movement in and out of the leaf

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5

stomata: what is it ?

a hole in the leaf, held by two guard cells. It is called the "stomatal spore".

  • controls gas exchange and water loss

  • when guard cells are turgid, they swell up and the stomata is open

  • when guard cells are flaccid, the stomata gets closed

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6

why can't anaerobic respiration be maintained for long periods of time

  • lactic acid might cause cells to become acidic

  • causes muscles to contract

  • and enzymes can get denatured at low ph, thus chemical reactions are slowed down

  • not enough energy is produced to keep the body moving

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7

why is lactic acid bad

  • lactic acid is, surprise, acid.

  • the acidic environment eventually denatures the proteins in inside the cells, and thus is harmfull in large quantitites.

  • after some time, oxygen will be used to turn the lactic acid into water and CO2

  • the amount of oxygen needed to turn all the lactic acid into water and CO2 is reffered to as oxygen dept

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8

what is ATP used for

  • cell division

  • thermoregulation

  • protein synthesis

  • movement

  • generating nerve impulses

  • active transport

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9

Respiration definition

Respiration is a chemical reaction in which living cells release energy from glucose (food) by producing ATP.

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10

intercoastal muscles

muscles between the ribs which control their movement causing inhalation and exhalation

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11

trachea

  • long tube of cartilages connecting the mouth and nose to the lungs.

  • it is lined with goblet and epitheal cells, which trap particles from the air

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12

larynx

voice box

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13

Diaphragm

  • a dome-shaped, muscular partition separating the thorax from the abdomen in mammals.

  • It plays a major role in breathing, as its contraction increases the volume of the thorax and so inflates the lungs.

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bronchus (pl. bronchi)

  • one of two branches from the trachea that conducts air into the lungs, where it divides and subdivides.

  • The branchings resemble a tree; therefore, they are referred to as a bronchial tree.

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15

pleural cavity

contains the lungs

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16

what are the passages down the lungs lined with ?

  • goblet and epitheal cells.

  • there is mucus which traps particles, pathogens like bacteria or viruses, and dust and prevents them from getting into the lungs and damaging the cells there.

  • the epitheal cell's cillia push up the mucus so that the trapped things are brought up.

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17

inhalation

breathing in: muscles contract, pressure drops so that air enter and fills lungs.

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18

inhalation diaphragm and intercoastal muscles

diaphragm contracts and flattens, pulls lungs down. intercoastal muscles contract, pulling lungs up and out.

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19

exhalation

breathing out: muscles relax, pressure increases so air is forced out lungs.

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20

exhalation on intercoastal muscles and diaphragm

intercoastal muscles relax, ribs down and in. diaphragm relaxes and goes in dome shape

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21

what happens during exhalation ? (5)

  • The diaphragm relaxes it moves upwards back into its domed shape

  • The external set of intercostal muscles relax so the ribs drop down and in

  • This decreases the volume of the chest cavity (thorax)

  • Leading to an increase in air pressure inside the lungs relative to outside the body

  • Air is forced out

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22

what happens during inhalation ? (5)

  • The diaphragm contracts and flattens

  • The external set of intercostal muscles contract to pull the ribs up and out:

  • This increases the volume of the chest cavity (thorax)

  • Leading to a decrease in air pressure inside the lungs relative to outside the body

  • Air is drawn in

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23

air that is inhaled concentrations of molecules

78% of nitrogen, 0.04% CO2, 21% oxygen

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24

air that is exhaled concentrations of molecules

78% of nitrogen, 4% CO2, 16% oxygen

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25

Alveoli adaptations for gas exchange

  • small for greater surface are/ shape for large surface area

  • thin, one cell thick walls to facilitate diffusion

  • close to blood capillaries, can quickly bind to haemoglobin

  • layer of moisture inside, so gases can disolve and diffuse more quickly

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26

chemicals in cigarettes

  • nicotine

  • carbon monoxide

  • tar

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27

nicotine effects

  • addictive

  • narrows blood vessels thus increases blood pressure

  • increases heart rate

  • these things cause blood clots, which cause heart disease and stroke

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28

tar effects

  • carcinogen.

  • cronic bronchitis

  • emphysema

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29

cronic bronchitis

  • cillia in trachea are destroyed because of tar

  • tar on the trachea stimulates goblet cells to produce more mucus than needed.

  • cillia do not move mucus up anymore, causing cronic inflammation and smoker's cough

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30

emphysema

  • product of frequent infections, scar tissue is formed

  • alveoli are less elastic than before, and thus burst

  • resulting in less surface area for diffusion

  • results in individual being breathless

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31

Carbon monoxide effects on body

bonds permanently to haemoglobin, so it cannot carry oxygen anymore. breathing/heart rate needs to be increased, which can cause heart disease

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32
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