Topic 3

• Smaller organisms have a ........... surface area to volume ratio

  Higher
• How do single celled organisms exchange substances?

  Diffuse (simple diffusion) directly into or out of the cell across the cell surface membrane
• Give 2 reasons why in multicellular organisms, diffusion across outer membrane would be too slow?

  1. Some cells deep within body- big distance between them and outside

  2. Larger animals have low surface area to volume ratio- difficult to exchange enough substances to supply large volume
• What 2 things do most gas exchange surfaces have in common that increases the rate of diffusion?

  1. They have large surface area

  2. They're thin- short diffusion pathway
• Each gill is made of lots of thin plates called .....................which give a large surface area


  Gill filaments
• Gill filaments are covered in lots of tiny structures called............. which increase surface area

  Lamellae
• Explain the counter current system in fish?

  Blood flows through the lamellae in one direction and water flows over them in the other direction. Water with Hugh oxygen concentration flows over blood with low concentration maintaining a high concentration gradient over the whole length of the gill
• The main gas exchange surface in plants is the surface of the ............1......... cells in the leaf. Gases move in and out through special pores in the epidermis called ..........2........... the ........2........... can open to allow exchange of gases and close if the plant is losing too much water. ..............3............ control the opening and closing.

  1. Mesophyll. 2. Stomata. 3. Guard cells
• Insects have microscopic air filled pipes called .........1......... which they use for gas exchange. Air moves into these through pores on the surface called ..........2............ oxygen travels down the concentration gradient towards the cells. The ......1........... branch off into smaller .........3............. which have thin permeable walls and go to individual cells. Insects use rhythmic ..........4............. movements to move air in and out of .........2.......


  1. Tracheae 2. Spiracles. 3. Tracheoles. 4. Abdominal
• What has a tendency to make you lose water?

  Exchanging gases
• What do insects do/have to control water loss?

  Close their spiracles and they have waterproof waxy cuticle over body and tiny hairs around spiracles which reduce evaporation
• Explain How plants control water loss

  Stomata kept open for gaseous exchange- water enters guard cells making them turgid which opens the stomatal pore and if the plant gets dehydrated the guard cells lose water and become flaccid which closes the pore.
• What are xerophytes?


  Plants adapted for life in warm , dry or windy habitats where water loss is a problem.
• Give 5 examples of adaptions that xerophytes have to control water loss

  1. Stomata sink in pits to trap water vapour- reduces concentration gradient of water between the leaf and air - thus reducing evaporation of water from the leaf

  2. Layer of hairs on the epidermis to trap water vapour around the stomata

  3. Curled leaves with stomata inside, protecting them from the wind

  4, reduces number of stomata

  5. Thicker waxy waterproof cuticles on leaves and stems to reduce evaporation
• As you breath in, air enters the trachea this then splits into two bronchi - one leading to each lung. Each one then branches off into smaller tubes called bronchioles which have small air sacs called alveoli at the end. This is where gases are exchanged.
• Which three things work together to move air in and out of lungs?

  Rib cage, intercostal muscles, diaphragm
• Intercostal muscles are found between the ............... and have 3 layers: 2 you need to learn called ................ and .................. intercostal muscles.

  Ribs. Internal and external
• Ventilation consists of .......1.......... and ..........2........... and is controlled by movements of the ........3......... , ..........4......... intercostal muscles and .........5.........

  1. Inspiration 2. Expiration 3. Internal 4. External 5. Rib cage
• What do the external intercostal and diaphragm muscles do during inspiration?

  Contract
• During inspiration the external inter coastal and diaphragm muscles .........1.......... this causes the rib cage to move .........2....... and .........3......... and the diaphragm to .........4.........., increasing the volume of the thoracic cavity- as this increases the lung pressure ........5...... to below at,ospheric pressure so air flows from an area of high concentration to low.


  1. Contract. 2. Upwards. 3. Outwards. 4. Flatten 5. Decreases
• Inspiration is an ................... process

  Active (requires energy)
• During EXPIRATION, the external intercostal and diaphragm muscles ...........1........., the ribcage moves ..........2......... and .........3.......... and the diaphragm.........4........... upwards again. Volume of the thoracic cavity ............5.......... causing the air pressure to ........6......... to above atmospheric pressure.

  1. Relax. 2. Downwards. 3. Inwards. 4. Curves. 5. Decreases 6. Increase
• Normal expiration is a ................... process

  Passive ( doesn't require energy)
• During FORCED EXPIRATION the external intercostal muscles ........1......... and the internal intercostal muscles .........2........ pulling the ribcage further ........3......... and in. During this time the movement of two sets of intercostal muscles is said to be ............4..............

  1. Relax. 2. Contract. 3. Down 4. Antagonistic
• What are alveoli?

  Tiny air sacs in the lungs
• The wall of each alveolus is made from a single layer of thin flat cells called ...........1............ the walls of the capillaries are made from ...........2.............. ............ the walls of alveoli contain a protein called .......3........

  1. Alveolar epithelium 2. Capillary endothelium 3. Elastin
• What is the role of elastin in the walls of alveoli?

  It's elastic and helps the alveoli to return to their normal shape after inhaling and exhaling air.
• Air moves down the ........1........... , .........2........ and ..........3........ into the ...........4........ - happens down a pressure gradient

  1. Trachea. 2. Bronchi. 3. Bronchioles. 4. Alveoli
• Oxygen diffuses out of the alveoli , across the ..........1............... and the ............2............. and into the .............3.............. in the blood.

  1. Alveolar epithelium. 2. Capillary endothelium. 3. Haemoglobin
• What 3 features does alveoli have that speeds up diffusion?

  - thin exchange surface

  - large surface area

  - steep concentration gradient
• What is the pulmonary ventilation?

  The volume of air that is moved into the lungs in one minute
• What is the tidal volume of the lungs?

  Volume of air taken in in one breath ( usually about half a litre or 0.5dm3
• How to you calculate the pulmonary ventilation?

  Tidal volume x ventilation rate (breaths per minute)
• What is asthma?

  A condition caused by inflammation of the bronchioles. The inflammation irritates muscles aro7nd the airways causing them to narrow and constrict
• What is COPD?

  Chronic Obstructive Pulmonary Disease
• Explain what affect emphysema has on the lungs?

  Attacks elastic tissues in the alveoli destroying properties of elastin. This stops the alveoli from being able to expel air properly, reduces surface area and can break down the alveoli.

  -Immune cells secrete protease which results in destruction of elastic fibres and collagen: permanent enlargement and destruction of alveoli spaces
• Explain what affect pulmonary fibrosis has on lungs?

  scars are formed on the epithelium of the lungs which causes the epithelium to thicken which results in gases having to diffuse through larger distance. Scarring also reduces the elasticity of the alveoli.
• What causes pulmonary fibrosis?

  Can begin from injury to the lungs by smoking , infection or unknown event. Injury introduces antigen presenting cells - antigen collagen takes it to immune cells -immune response towards collagen
• What is tuberculosis?

  A bacterial disease spread mainly by coughing
• Describe latent tuberculosis

  Immune system cannot kill bacteria but builds a defensive wall around bacteria in areas called GRANULOMAS - small scars appear in lungs