A-Level Biology: Gas Exchange, Heart, and Plant Transport Flashcards

What is the surface area to volume ratio of an organism?

It is the surface area of an organism divided by its volume; larger organisms have a smaller ratio.

why do the tips of fish gill filaments overlap

slows water flow increasing the time for gas exchange

how does lymph differ from blood

contains fatty acids

what would happen to blood flow if the right atrioventricular valve couldnt close

during ventricular systole,blood would enter right atrium from the right ventricle

what does the casparian strip do

block the apoplast pathway between the cortex and the medulla

to ensure the water and dissolved mineral ions have to pass into the cell cytoplasm through the plasma membrane

what effect would a hole in the septum,between the left and right atria,that lets blood pass through (ASD) have?

some oxygenated blood in the left atrium gets pumped back into the lungs

what would happen to the blood in the heart if the atrio-ventricular node was stimulated at the same times as the sino-atrial node?

atria and ventricle would contract at the same time

why does the plasma membrane contain transporter proteins

actively pump mineral ions from the cytoplasm of the cortex cells into the medulla and xylem

makes the water potential of the medulla and xylem more negative so that water moves from the cortex cells into the medulla and xylem by osmosis

once the water has entered the medulla,it cannot pass back into the cortex,as the apoplast pathway of the endodermal cells is blocked by the Casparian strip

importance of transpiration

transports useful mineral ions up the plant

maintains cell turgidity

supplies water for growth,cell elongation and photosynthesis

supplies water that,as it evaporates,can keep the plant cool on a hot day

lignin

impregnates xylem cell walls

kills cells

prevents vessel from collapsing

leaves gaps which form bordered pits,allowing water to leave one vessel and pass into the next vessel or leave the xylem and pass into the living parts of the plant

dicotyledonous

two seed leaves

xylem and phloem in vascular bundles

bundles may also contain collenchyma and sclerenchyma to give support and strength

endodermis

gets water into xylem vessels

inside has a layer of meristem called pericycle

conformational change

as o2 tension rises,the diffusion gradient into the haemoglobin molecule increases

eventually one o2 molecule enters the haemoglobin molecule and associates with one of the groups

this causes a slight change in the shape of the haemoglobin molecule

it allows more o2 moleules to enter the haemoglobin molecule and associate with the other haem groups relatively easily

this accounts for the steepness of the curve as the tension rises

why does mammalian haemoglobin produce an s-shaped curve?

well adapted to transporting o2 to the tissues of a mammal

o2 tension found in the lungs is sufficient to produce close to 100% saturation

the o2 tension in respiring body tissues is. sufficiently low to cause o2 to dissociate readily from the oxyhaemoglobin

why does the curve for fetal haemoglobin differ from the adult’s?

fetal curve is to the left

in the placenta,where o2 tension is low,fetal haemoglobin will absorb o2 from the surrounding fluid

this reduces the o2 tension even further

so o2 diffuses from the mother’s blood fluid into the placenta

this reduces the o2 tension within the mother’s blood making the maternal haemoglobin release more o2

haemoglobinic acid

hydrogen ions building up in rbc could cause contents to become very acidic

so they are taken out of the solution by associating with haemoglobin which acts as a buffer

atrial fibrillation

atria beating more frequently than ventricles

no clear P waves seen

endothelium

thin layer that is particularly smooth to reduce friction with the flowing blood

artery layers

inner layer (tunica intima) - thin layer of elastic tissue which allows the wall to stretch and recoil to help maintain bp

middle layer (tunica media) - thick layer of smooth muscle

outer layer (tunica adventita) - thick layer of collagen and elastic tissue which provides strength to withstand the high pressure and recoil to maintain the pressure

capillary walls

single layer of flattened endothelial cells

leaky walls which allow blood plasma and dissolved substances to leave the blood

venule walls

thin layers of muscle and elastic tissue outside the endothelium and a thin outer layer of collagen

hydrostatic pressure:blood plasma,tissue fluid, lymph

high,low,low

oncotic pressure:blood plasma,tissue fluid, lymph

more -ve,less -ve,less -ve

cells:blood plasma,tissue fluid, lymph

rbc neutrophils lymphocytes,some neutrophiles esp in infected areas,lymphocytes

proteins:blood plasma,tissue fluid, lymph

plasma proteins,few proteins,few proteins

erythrocyte

biconcave disc

no nucleus,Gogli body,rER,mitachondria

contains Hb(respiratory pigment)

7.5 micrometres diameter,2 micrometres thick

squeezes through blood vessels

large sa:v

neutrophil

granular cytoplasm

many lysosomes

multilobed nucleus

myogenic

self excitation

SAN

initiates contraction

pace maker

found in atrial wall just below entry point of vena cava

how is hydrostatic pressure generated in the heart

ventricular systole

why does the hydrostatic pressure of the blood drop as blood moves away from the heart?

more vessels whch have a larger cross section

reduced resistance to blood flow

arteries stretch

loss of fluid from capillaries

fats:blood plasma,tissue fluid, lymph

transported in lipoproteins,few fats,more fats esp near digestive system

what does the hydrostatic pressure of the blood do?

push fluid out into tissues

what does the hydrostatic pressure of tissue fluid do?

push fluid back into the capillaries

cotransport

proteins only allow the movement of the hydrogen ions into the cell if they are accopanied by sucrose molecules

source

any part of the plant that loads sucrose into the sieve tube

sink

anywhere that removes sucrose from the phloem sieve tubes

what does the oncotic pressure of blood do?

pull water back into the blood (-ve figure)

what does the oncotic pressure of tissue fluid do?

pull water into the tissue fluid

what does the net result of hydrostatic and oncotic pressure in blood and tissue fluid do?

pushes fluid out of capillary at the arterial end into the capillary at the venule end

ostia

pore which blood from the body enters the heart through

peristalsis

process by which heart pumps blood towards the head

disadvantages of open circulatory system

low bp

slow blood flow

circulation of blood may be affected by body movements or lack of

advantages of closed circulatory system

higher pressure so blood flows more quickly

more rapid delivery of o2 and nutrients

more rapid removal of co2 and other wastes

transport is independent of body movement

How does increased surface area aid in gas exchange?

Increased surface area, such as projections on root hair cells, facilitates more efficient diffusion.

What factors affect the rate of diffusion?

Diffusion distance, surface area, concentration gradient, and temperature.

Adaptations of large organisms to maximise diffusion

Increased surface area- e.g. projections on root hair cells

Steeper concentration gradient- e.g. ventilation, good blood supply and countercurrent flow mechanism

Shortened length of diffusion pathway- e.g. alveoli wall is one thin layer of squamous epithelial cells

Route that air takes during ventilation

trachea

bronchi

bronchioles

alveoli

ventilation

Inhaling and exhaling in humans

Controlled by diaphragm and antagonistic interaction of internal and external intercostal muscles

What is the role of the diaphragm during inspiration?

The diaphragm contracts and flattens, increasing lung volume and decreasing pressure.

Precautions that should be taken when using a spirometer

the subject should be healthy,free from asthma

the soda lime should be fresh and functioning\

there should be no leaks in the apparatus

the mouthpiece should be sterilised

the water chamber must not be overfilled (or water may enter the air tubes)

Inspiration

External intercostal muscles contract and internal relax

Pushing ribs up and out

Diaphragm contracts and flattens

Air pressure in the lungs drops below atmospheric pressure as lung volume increases

Air moves in down pressure gradient

What happens during expiration?

External intercostal muscles relax (and internal contract on forced expiration)

Pulling ribs down and in

Diaphragm relaxes and domes

Air pressure in lungs increases above atmospheric pressure as lung volume decreases

Air flows out down pressure gradient

Alveoli structure

Tiny air sacs located at the end of the bronchioles

The site of gas exchange

Highly abundant in each lung- 300 million in each human lung Surrounded by the capillary network

Squamous epithelium one cell thick

Why do large organisms need a specialised exchange surface?

They have a small surface area to volume ratio

Higher metabolic rate- demands efficient gas exchange

Specialised organs- e.g. lungs/gills designed for gas exchange

Vital capacity

The maximum volume of air an individual can inhale or exhale during a deep breath.

2.5-5 dm³

What is tidal volume?

The maximum volume of air an individual can inhale or exhale during a deep breath.

0.5dm³

Spirometer

An apparatus that measures the volume of air inspired and expired by the lungs

ventilation rate

Ventilation rate = tidal volume x breathing rate.

The volume of air inhaled per minute

What is the structure of fish gills?

Fish gills are stacks of gill filaments, each covered with gill lamellae at right angles.

How do fish gas exchange surfaces provides large

surface area?

Several gill arches

Many gill filaments covered in many gill lamellae are positioned at right angles

Creates a large surface area for efficient diffusion

What is countercurrent flow in fish gills?

It is the mechanism where water flows over gill lamellae in the opposite direction to blood flow,

Equilibrium is not reached

Steep diffusion gradient is maintained across entire length of gill lamellae

What adaptations do tracheoles in insects have for gas exchange?

Many tracheoles, which are highly branched and filled with fluid to enhance gas movement.

What is the significance of the alveoli structure?

Alveoli are tiny air sacs that provide a large surface area for gas exchange.

many for large sa:v

surfactant prevents collapse

elastic fibres stretch and recoil

thin walls

capillaries close to wall

ventilated

good blood supply to maintain conc. gradient

Why are the tracheole ends filled with fluid?

Adaptation to increase movement of gases

When insect flies and muscles respire anaerobically- lactate produced

Water potential of cells lowered, so water moves from tracheoles to cells by osmosis

Gases diffuse faster in air than liquid

How does the open circulatory system function?

In an open circulatory system, the transport medium does not stay in vessels at all times.

The transport medium is usually pumped directly to the open body cavity

There are very few transport vessels

Closed circulatory system

The transport medium remains inside of the vessels

Single closed circulatory system

The blood only passes through the heart once per cycle of the body e.g. fish

Double closed circulatory system

The blood passes through the heart twice per cycle of the body e.g. most mammals

residual volume

air that remains in the lungs even after forced expiration

this air remains in the airways and alveoli

1.5dm³

spirometer when person breathes

as a person breathes from the spirometer,oxygen is absorbed by the blood and replaced by co2

the co2 is absorbed by the soda lime in the spirometer so that the volume of air in the chamber decreases

the volume of co2 released and absorbed by the soda lime equals the volume of o2 absorbed by the blood

measuring the gradient of the decrease in volume enables the rate of o2 uptake to be measured

increased o2 uptake will result from:

increased breathing rate

deeper breaths

What is the role of the intercostal muscles during ventilation?

They work antagonistically to control the movement of the ribs during inhalation and exhalation.

What is the effect of a steeper concentration gradient on gas exchange?

A steeper concentration gradient increases the rate of diffusion, enhancing gas exchange efficiency.

Why is the alveoli wall thin?

The alveoli wall is one thin layer of squamous epithelial cells to shorten the diffusion pathway.

What happens to air pressure in the lungs during inhalation?

Air pressure in the lungs drops below atmospheric pressure as lung volume increases.

What is the function of the gill arches in fish?

Gill arches support the gill filaments and help maintain their structure for efficient gas exchange.

How does lactate production in insects affect gas exchange?

Lactate production during anaerobic respiration lowers water potential in cells, promoting gas movement from tracheoles.

What is the primary function of the respiratory system in large organisms?

To facilitate efficient gas exchange due to their higher metabolic demands.

What type of circulatory system do fish have?

Single closed circulatory system

What happens in the single circulatory system of fish?

blood pressure drops as blood passes through the tiny capillaries of gills

blood has a low pressure as it flows towards the body and will not flow very quickly

rate at which oxygen and nutrients are delivered to respiring tissues and co2 and urea are removed is limited

Why do fish have a single circulatory system?

not as metabolically active as mammals

do not need to maintain body temp

need less energy

this supplies sufficient o2 and nutrients for their need

What happens in the double circulatory system of mammals?

blood pressure must not be too high in the pulmonary circulation,otherwise it may damage the delicate capillaries in the lungs

the heart can increase the pressure of the blood after it has passed through the lungs,so the blood is under high pressure as it flows to the body and flows more quickly

the systematic circulation can carry blood at a higher pressure than the pulmonary circulation

Why do mammals have a double circulatory system?

active

maintain body temp

What type of circulatory system do most mammals have?

Double closed circulatory system

route of blood in fish

heart to gills to body to heart

route of blood in mammals

heart to body to heart to lungs to heart

What is the role of tissue fluid?

Enables delivery of useful molecules to cells and removal of waste

What components are found in tissue fluid?

Water, glucose, amino acids, fatty acids, ions, and oxygen

Tissue fluid formation

At the arteriole end of a capillary, the smaller diameter results in high hydrostatic pressure

Small molecules forced out (ultrafiltration)

Red blood cells/plasma proteins too big to fit through capillary pores so remain

What is the structure and function of capillaries?

Capillaries have a narrow diameter (1 red blood cell wide) to slow blood flow and have small pores for liquid/small molecules to be forced out.

Red blood cells squashed against walls shortens diffusion pathway

What are arterioles and their function?

Arterioles branch off from arteries and have the thickest muscular layer to restrict blood flow.

Arteriole structure compared to artery

Thinner elastic layer and outer layer than arteries as pressure is lower

What is the structure of arteries?

Arteries have a thick muscular layer, thick elastic layer, and thick outer layer,small lumen and no valves

capillary endothelium

Flat (squamous) cells

One cell thick

Contains small pores/fenestrations for small molecules to pass through (e.g. glucose, oxygen)

What is unique about the capillary endothelium?

It has a small lumen and no valves, allowing small molecules to pass through.

Different type of blood vessels

Arteries Arterioles Capillaries Venules Veins

What happens to the hydrostatic pressure in capillaries towards the venule end?

There is a lower hydrostatic pressure due to a loss of liquid and a higher oncotic pressure.

Reabsorption of tissue fluid

Large molecules remaining in capillary lower its water potential

Towards venule end there is a lower hydrostatic pressure due to a loss of liquid and a higher oncotic pressure

Water is reabsorbed back into capillaries by osmosis

Role of the lymph in tissue fluid

reabsorption

Not all liquid will be reabsorbed by osmosis as equilibrium will be reached

Excess tissue fluid is absorbed into the lymphatic system to form lymph and drains back into the bloodstream and deposited near the heart