exchange: topic 3 bio

What is amoeba

A unicellular organism

How does water and oxygen diffuse in a amoeba?

Directly across the cell through the membrane

What is amoeba

A unicellular organism

How does water and oxygen diffuse in a amoeba?

Directly across the cell through the membrane

How do food particles enter the amoeba?

Phagocytosis

How does CO2 leave the amoeba?

Diffusion

Is diffusion slow or quick in an amoeba?

Quick as diffusion distance is small

Do unicellular organisms have a small or large SA:VR?

Large

Name 4 features of exchange surfaces.

• thin

• Large SA

• Selectively permeable

• Maintenance of concentration gradient

What type of system do insects have for gas exchange?

Insects have a tracheal system

Describe the structure of tracheae.

They are supported by strengthening rings, made of chitin.

How does air enter the tracheae?

Through pores called spiracles.

Where would you find spiracles on an insect?

On each side of its abdomen

The spiracles have valves, what are they used for?

To reduce water loss.

Explain diffusion in the tracheal system of an insect.

• air passes into the tracheae which branches into smaller tubes

• The trachea finally end in the tissues which are respiring

• Oxygen diffuses into the tissues from the air in the tracheae

• Carbon dioxide diffuses into the air tracheae so that it can be expelled from the body

How do active insects speed up the movement of oxygen to their tissues (mass transport)?

They pump their abdomens in and out, using muscles. This helps fresh air to enter and leave the trachea so it can leave the body.

Explain why the ends of tracheoles are filled with water.

• anaerobic respiration produces soluble lactic acid which lowers the water potential of cells

• This causes water to move from the tracheoles into the cells by osmosis

• Decreasing volume of water in tracheoles and drawing air further into the tracheoles

• This increases the rate of diffusion as diffusion is through gas rather than liquid phase

What is the function of stomata in a plant cell?

Stomata open to allow gas exchange in plants and close to prevent water loss

What plant structure is the stomata surrounded by

2 guard cells

What is the effect on the stomata when guard cells are turgid?

Pores open to allow gas exchange

What is the effect on the stomata when guard cells are flaccid

Pores closed to reduce water loss

Explain the structure of the stomata

• unevenly thickened walls

• Cellulose microfibrils arranged as hoops around the guard cell

• As the guard cell becomes turgid it mainly increases increases in length

• Thin outer wall bends more easily

• Guard cells become ‘banana shaped’ and curve apart opening the stomata

Explain the mechanism of stomata opening

• ATP used to actively transport K+ into the guard cell

• Starch is converted into malata

• This lowers water potential in guard cell

• Water enters by osmosis down the water potential gradient

• Guard cell becomes turgid and stomata opens

What are xerophytes?

Plants which live in environments where there is little water e.g maram grass

What are halophytes?

Plants that live in areas where soil water is very salty

What is the alveoli?

Tiny air sacs art end of bronchioles lined with epithelium- site of gas exchange

What are the bronchioles?

Small muscular tubes- able to constrict to control air movement

What are bronchi?

Divisions of trachea- have cartilage, cilia and goblet cells which produce mucus to trap dirt particles

What is the trachea?

A large flexible airway supported by rings of cartilage, has cilia and goblet cells. Cilia waft trapped dirt upwards

What is the rib cage?

Protective bones, moved by intercostal muscles for ventilation

What are the intercostal muscles?

Internal and external muscles between ribs, used to move the ribs for ventilation

What is the diaphragm?

A muscular sheet separating abdomen and thorax and used for ventilation

What is the function of the c-shaped cartilage in the trachea?

To provide support to stop it from collapsing when air pressure falls

Why is the cartilage in the trachea c-shaped and not o-shaped?

To low food to be swallowed in the oesophagus and allows trachea to be semi-flexible

Why do bronchioles not have cartilage?

Bronchioles control air in and out of the alveoli by constricting/relaxing their muscles- rigid cartilage would stop this

What is ventilation?

The movement of the respiratory medium over the respiratory surface (breathing)

Why does ventilation maintain the concentration gradient?

So it can maximise the efficiency of diffusion

What is breathing caused by?

Movements of the intercostal muscles between ribs and diaphragm

What is inspiration?

Breathing in

What happens to the pressure in the lungs during inspiration?

The pulmonary pressure decreases

What is the pulmonary pressure?

Pressure in the lungs

What happens to the external intercostal muscles during inspiration?

They contract

What happens to the internal intercostal muscles during inspiration?

They relax

What happens to the rib cage during inspiration?

It moves upwards and outwards

What happens to the volume of the thorax during inspiration?

It increases

What happens to the diaphragm during inspiration?

Contracts and flattens

What is expiration?

Breathing out

What happens to the pulmonary pressure during expiration?

Increases

What happens to the internal intercostal muscles during expiration?

They contract

What happens to the external intercostal muscles during expiration?

They relax

What happens to the rib cage during expiration?

It moves downwards and inwards

What happens to the volume of the thorax during expiration?

It decreases

Why do alveoli need a large surface area for efficient exchange?

A larger surface increases the rate of diffusion

Why do alveoli have a thin barrier?

It reduces the diffusion distance to increase the rate of diffusion

What are the alveoli and capillaries made out of?

Epithelial cells (1 cell thick)

Why having a thin barrier in the alveoli a good adaption?(RBCs)

Red blood cells squeeze through capillaries making them closer to air in alveoli and slowing their movement, increasing the time for diffusion to take place

What protein structure does haemoglobin have?

Quaternary

Have many polypeptide chains does 1 haemoglobin contain?

2 alpha and 2 beta polypeptides

At what point does haemoglobin have to readily associate with oxygen to transport oxygen efficiently?

At the gas exchange surface

At what point does haemoglobin have to readily associate with oxygen to transport oxygen efficiently?

At respiring tissues

What does an oxygen dissociation curve show?

How saturated the haemoglobin is with oxygen at any given partial pressure

What is on the x-axis of an oxygen dissociation curve?

Partial pressure of oxygen (Kpa)

What is on the y-axis of an oxygen dissociation curve?

% saturation of haemoglobin

What shape is an oxygen dissociation curve?

S-shaped (sigmoid)

What happens at the start of an oxygen dissociation curve?

It is difficult for the first O2 molecule to bind due to the shape of Hb= gradient is shallow initially

What is happening in the middle of the oxygen dissociation curve?

The binding of the first oxygen molecules causes a change in shape of Hb which makes it easier for the second and third molecules to bind= a steeper gradient

What happens at the end of the oxygen dissociation curve?

The fourth oxygen molecule is difficult to bind because less available Hb sites to bind to =the gradient reduces and the graph flattens

What is the effect of carbon dioxide on haemoglobin?

It will have a deuces affinity for oxygen in the presence of CO2

Is CO2 lower or higher when respiring?

Higher

What happens when CO2 is dissolved in the blood?

CO2 lowers the pH so the blood will become more acidic

What happens to haemoglobin when the blood has a lower pH?

The Hb willl change in shape wich reduces the affinity for oxygen

What is the Bohr effect?

The effect of CO2 on the oxygen dissociation curve

What happens when haemoglobin has a higher affinity for oxygen?

They will bind will oxygen more easily but release it less easily

What happens when haemoglobin has a low affinity for oxygen?

They will bind with oxygen less easily but release it more easily

What are the golden rules of the oxygen dissociation curve?

• shift left = higher affinity for O2

• Shifts right = lower affinity for O2

Would an organism living in a low oxygen environment shift to the left or right of an oxygen dissociation curve?

Left (high affinity)

Would an organism with a high metabolic rate shift to the left or right of an oxygen dissociation curve?

Right

What substances are required for respiration?

• oxygen for respiration

• Carbon dioxide for photosynthesis

• Inorganic ions and water

• Organic nutrients for respiration and growth

What does water loss from the leaves of a plant cause?

Transpiration

Explain the transport system of plants

• water and inorganic ions are transported from the roots to other parts of plants in xylem tissue

• Organic nutrients for respirations are transported from sources to sinks in phloem tissue