Igcse Biology : Respiration and gas exchange

aerobic respiration

• requires oxygen

• produces 36 units of ATP

• completely breaks down glucose

• one used normally

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

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

anaerobic respiration in plants (fermentation)

glucose => ethanol + carbon dioxide

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

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

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

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

what is ATP used for

• cell division

• thermoregulation

• protein synthesis

• movement

• generating nerve impulses

• active transport

Respiration definition

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

intercoastal muscles

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

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

larynx

voice box

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.

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.

pleural cavity

contains the lungs

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.

inhalation

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

inhalation diaphragm and intercoastal muscles

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

exhalation

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

exhalation on intercoastal muscles and diaphragm

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

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

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

air that is inhaled concentrations of molecules

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

air that is exhaled concentrations of molecules

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

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

chemicals in cigarettes

• nicotine

• carbon monoxide

• tar

nicotine effects

• addictive

• narrows blood vessels thus increases blood pressure

• increases heart rate

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

tar effects

• carcinogen.

• cronic bronchitis

• emphysema

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

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

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