3.1.1 ~ Exchange surfaces

what does how easy of the exchange of substance depend on?

surface area to volume ratio

do smaller organisms have smaller or larger surface area to volume ratio?

a larger surface area to volume ratio

do larger organisms have a smaller of larger surface area to volume ratio?

a smaller surface area to volume ratio

what do organisms need to supply each of their cells with?

glucose and oxygen

what do organisms need to remove from their cells?

waste products

how can substances diffuse in single celled organisms?

substances can diffuse directly into or out of the cell across the cell surface membrane

why do single celled organisms have a fast diffusion rate?

because of the small distances substances have to travel

why is diffusion across the outer membrane slower for multicellular organisms?

• multicellular organisms have a higher metabolic rate than single celled organisms so use up more oxygen and glucose faster

• larger organisms have a low surface area to volume ratio

name the 4 feature of efficient gas exchange surface?

• thin- short diffusion distance

• large surface area- lots of substances can diffuse at once

• good blood supply- maintains a concentration gradient

• moist- gasses/ soluble substances can diffuse

name a key feature of root hair cells?

• a large surface area which helps increase the rate of absorption of water by osmosis and mineral ions by active transport from the soil

where are the alveoli the gas exchange surface?

they are the gas exchange surface in the lungs

what is each alveolus made from?

a single layer of thin flat cells providing a short diffusion distance

what are alveoli surrounded by?

a large capillary network giving each alveolus its own blood supply, the blood constantly takes oxygen away from the alveolus and brings more carbon dioxide

where are fish gills the gas exchange surface in?

fish

what are the exchange organs in mammals?

the lungs

explain the steps as you breath in?

• air enters the trachea

• the trachea splits into two bronchi

• one bronchus splits into each lung

• each bronchus branches off into smaller tubes called bronchioles

• the bronchioles end in small air sacs called alveoli where gases are exchanged

• the ribcage, intercostal muscles and diaphragm all work together to move air in and out

what 5 cells or or tissues in the gaseous exchange system made of?

• goblet cells

• cilia

• elastic fibres

• smooth muscle

• rings of cartilage

what do goblet cells secrete?

mucus which traps microorganisms and dust particles in the inhaled air stopping them from reaching the alveoli

what is the function of cilia?

• waft the mucus and trapped microbes upwards towards the throat so it is swallowed

• stomach acid then kills the microbes

where are elastic fibres and what is their function?

• in the walls of trachea, bronchi , bronchioles and alveoli

• when you breath in, the lungs inflate and the elastic fibres are stretched

• the fibres then recoil to help push the air out when exhaling

where is the smooth muscle and what is its function?

• located in the walls of the trachea, bronchi and bronchioles

• allows their diameter to be controlled

• during exercise less smooth muscle relaxes making the tubes wider so air can move in and out of lungs easier

where are the rings of cartilage located and what is their function?

• within the walls of the trachea and bronchi

• strong and flexible so prevent them from collapsing when you breath in and the pressure drops

what does ventilation consist of?

• inspiration and expiration

what are the steps in inspiration?

• the external intercostal muscles and diaphrgam contract

• this causes the ribcage to move upwards and outwards

• the diaphragm flattens increasing the volume of the thorax

• as the volume of the thorax increases the lung pressure decreases

• this cause air to flows into the lungs

what are the steps in expiration?

• the external intercostal muscles and diaphragm muscles relax

• the ribcage moves downwards and inwards

• this causes the diaphragm to curve

• the thorax volume decreases causing the air pressure to increase

• air is forced out of the lungs

is inspiration a passive or active process?

• an active process which requires energy

is expiration an active or passive process?

• a passive process which does not require energy

define tidal volume?

• the volume of air in each breath

define vital capacity?

• the maximum volume of air that can be breathed in or out

define breathing rate?

• the number of breaths taken per minute

define oxygen uptake?

• the rate at which an organism uses oxygen during respiration.

how does water enter fish?

water containing oxygen enters the fish through its mouth and passes out through its gills

what is each gill made of?

• thin branches called gill filaments/ primary lamellae

what do gill filaments/primary lamellae provide?

a big surface area for exchange of gases

what are gill filaments covered in?

• lots of tiny structures called gill plates/ secondary lamellae

what do gill plates/ secondary lamellae increase?

• surface area

what is each gill supported by?

• a gill arch

how can gill plates speed up diffusion?

• they have lots of blood capillaries and a thin surface layer of cells

what is the name of the system fish use for gas exchange?

• a counter current system

what takes place in the counter current system of fish?

• blood flows through the gill plates in one direction and water flows over in the other direction

what does the counter current system maintain a large concentration gradient between?

• water and blood

is the concentration of oxygen higher in the water or in the blood?

• always higher in the water so as much oxygen as possible diffuses from the water to the blood

what happens when the fish opens its mouth?

• the floor of the buccal cavity is lowered

• the volume of the buccal cavity increases

• pressure inside the cavity decreases

• water is then sucked into the cavity

what happens when the fish closes its mouth?

• the floor of the buccal cavity is raised

• the volume inside the cavity decreases

• pressure inside the cavity increases

• water is forced out the cavity across gill filaments

what is the name of the bony flap which covers each gill?

the operculum

how does an increase in pressure affect the operulum?

• it forces the operculum on each side to open allowing water to leave the gills

state the name of the air filled pipes which insects use for gas exchange?

• tracheae

how does air move into the tracheae?

• through pores on the insects surface called spiracles

how does oxygen travel to the cells?

down the concentration gradient

how does carbon dioxide from the cells travel?

• it moves down its own concentration gradient towards the spiracles to be released in the atmosphere

what do tracheae branch off into?

• smaller tracheoles which have thin permeable walls and go to individual cells

• also contain a fluid which oxygen dissolves in

• oxygen diffuses from this fluid into body cells

• carbon dioxide diffuses in the opposite direction

why do insects use rhythmic abdominal movements?

• to change the volume of their bodies and move air in and out of the spiracles

what do larger insects use to pump up their thoraxes whilst they are flying?

• wing movements