G) gas exchange, H) plant transport

what is diffusion

the movement of molecules from an area of high concentration to an area of low concentration​

gas exchange during respiration

• Process requires the uptake of oxygen and release of carbon dioxide

• The oxygen diffuses down the concentration gradient from a high concentration (outside the leaf) to a low concentration (inside the leaf) the cells use oxygen in respiration so the concentration is always low inside respiring cells.​

• The carbon dioxide diffuses down the concentration gradient from a high concentration (inside the leaf) to a low concentration (outside the leaf)​

gas exchange during photosynthesis

• requires uptake of carbon dioxide and release of oxygen​

• carbon dioxide diffuses down the concentration gradient from a region of high concentration (outside the leaf) to a region of low concentration (inside the leaf)

• Oxygen diffuses down the concentration gradient from an area of high concentration (inside the leaf) to a low concentration (outside the leaf)​

how is the structure of leaf adapted for gas exchange

• The leaf has thin walls which gives a short diffusion distance​

• They are flat providing a large surface area to volume ratio​

• They have many stomata which allows movement of gases in and out of the air spaces inside the leaf to maintain a steep concentration gradient​

• Air spaces allow gas movement around the mesophyll cells​

• Many stomata in lower epidermis open in sunlight to allow gas movement in and out of the leaf​

• Close contact between the cells and air spaces allows efficent gas exchange for photosynthesis and respiration.​

cactus adaptations to their desert climate

• Thick, waxy cuticle to reduce water loss and reflect heat​

• Large, fleshy stems to store water​

• Spines instead of leaves to reduce water loss and protect themselves from grazing animals​

• Shallow, widespread roots to catch as much rainfall as possible when it comes

• Some cacti species have very deep roots to find water underground​

stomata role in gas exchange

• spaces found between two guard cells

• found in the lower epidermis of the leaf

• The guard cells = responsible for the opening and closing of the stomatal pore which controls gas exchange and water loss​

• Stomas open when water moves (by osmosis) into the guard cells and causes them to become turgid

• this allows gases to diffuse in and out the leaf and the stomata tend to be open when there's plenty of water and sunlight​

• Stomatas close when guard cells lose water (by osmosis) so they become flaccid

  this then prevents any diffusion in and out of the leaf and the stomata close due to low water or low sunlight

what is hydrogen-carbonate indicator

indicator of carbon dioxide concentration in a solution​

what color would indicator be if carbon dioxide levels were high

yellow

what color would indicator be if carbon dioxide levels were atmospheric

red

what color would indicator be if carbon dioxide levels were low

purple

method for investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator​

1. Measure out 20cm3 of hydrogen carbonate indicator into 4 boiling tubes​

2. Put some cotton wool into each boiling tube​ Label the boiling tubes A, B, C, D​

3. Tube A - put in no leaf (it's a control tube)​

4. Tube B - place a leaf in tube and leave in light​

5. Tube C - place a leaf in tube and wrap in aluminium foil so to block out light​

6. Tube D - place a leaf in tube and wrap in a gauze to allow partial light.

7. Put a bung on all 4 tubes​ Leave in light for some time​

tube A result

the control tube should remain an orange/red color to show that carbon dioxide is at atmospheric levels - there has been no net movement​

tube B result

the tube was placed in light with a leaf which is photosynthesizing and respiring

• because the plant would be photosynthesizing more than respiring the hydrogen carbonate indicator will turn purple as there is less carbon dioxide than atmospheric levels​

tube C result

the leaf was wrapped with aluminium foil so could not have access to sunlight

• no light means that the leaf could not photosynthesizing but only respiring meaning carbon dioxide would be being produces

• The indicator will turn yellow as the carbon dioxide levels have gone beyond normal atmospheric levels.​

tube D result

this leaf only had partial light so the rate of photosynthesis and respiration were equal meaning there was no net change in carbon dioxide levels so indicator will remain orange/red​

what is the thorax

part of the body between the neck and the abdomen​

ribs and intercostal muscles during inhalation

the intercostal muscles contracts and move the ribs upwards and outwards

this increases the volume of the lungs which reduces the pressure inside the lungs

so, the air moves in to equalise it​

ribs and intercostal muscles during exhalation

the intercostal muscles relax and move downwards and inwards which reduces the volume of the lungs and forces air outward

The ribs move down and inwards​

diaphragm during inhalation

diaphragm muslces contracts and move downwards​

diaphragm during exhalation

diaphragm muscles relax and move upwards​

bronchi role

distribute the air throughout the lungs​

they carry the air to and from the lungs

Bronchioles role

found at the end of the bronchi​

they carry air to the alveoli​

Alveoli role

tiny air sacks where gas exchange occurs

they are at the end of the bronchioles

This Is where oxygen moves into the blood and carbon dioxide moves out

Alveoli adaptations

A huge combined surface area​

Moist, thin walls to maximise diffusion​

Millions of capilaries behind the walls​

Tar in cigarettes affect on cilia

destroy the cilia which carries away the dust and microbes trapped in mucus

therefore causes a buildup of mucus which can cause bronchitis

this also causes a smoker's cough to try remove mucus

tar in cigarettes affect on alveoli

destroy alveoli walls and causes them to merge which decreases the surface to volume ratio for gas exchange

This causes insufficent gas exchange and will increase the risk of Emphysema - shortness of breath​

nicotine in cigarette affect

causes blood vessels to narrow, placing a strain on circulatory system and resulting in the increase in blood pressure

The narrowing of blood vessels can cause the increasing risk of coronary heart disease as there is a buildup fat globules.​

carbon monoxide affect (smoking)

Carbon monoxide from smoking will bind irreversibaly to haemaglobin, reducing the capacity of oxygen transport by red blood cells and also increases the risk of Ephysema.​

effect of exercise on breathing

Exercise causes the frequency of breathing to increase in order to provide more oxygen for respiration and to pay off any oxygen debt.​

After exercise breathing rate continuous to be the same increased rate as more oxygen is needed to break down the lactic acid produces.​

unicellular organism transport

They have a larger surface area in relation to their volume, hence having a large surface area to volume ratio​

With this large surface area to volume ratio, they have an efficient rate of diffusion which allows them to solely rely on diffusion.​

multicellular organism transport

they have a small surface area in relation to their volume, and hence have a small surface area to volume ratio​

With a small surface area to volume ratio, Multicellular organisms therefore have inefficient rate of diffusion, preventing cell to rely on diffusion to transport necessary substances in and out of the cell

phloem role

The phloem moves food substances that the plant has produced by photosynthesis to where they are needed for processes

Transport in the phloem is both up and down the stem the phloem is made up of cells called sieve tubes and companion cells​

sieve tube phloem

Specialized for transport and has no nuclei

Each sieve tube has a perforated end so its cytoplasm connects one cell to the next​

companion cell phloem

Transport of substances requires energy

One or more companion cells attached to each sieve tubes provides the energy

A sieve tube would be completely dependent on its companion cell​

xylem

xylem transports water and minerals from the roots up the plant stem and into the leaves​

Most of the cells making up the xylem are specialised cells called vessels

root hair cell

A root hair cell is a specialized root cell of a plant that absorb water and mineral ions from the soil for plant growth

The water moves into the root hair cell by osmosis as there is a strong concentration of water in the soil and a low concentration of water inside the root hair cell

Root hair cell adaptations

large surface area to volume ratio which increases the rate of water absorption

effect on transpiration - light intensity

as light intensity increases the rate of transpiration increases

this is because it stimulates more stoma to open