P1: Module 3: Exchange and Transport

Question 1

Suggest why the Titicaca water frog has evolved to have large skin folds

Answer 1

Increases Sa:Vol which Increases the rate of O2 absorption as O2 levels in lake are low

Question 2

When out of water the Titicaca frog is able to use its lungs to absorb O2. Their lungs contain gaseous exchange surfaces. Describe and explain 3 features of the lungs provides an efficient gas exchange surface

Answer 2

-Large SA; for maximum diffusion
-Aveolar wall is only 1 cell thick; provides a short diffusion distance
-Good blood supply; maintains a conc gradient

Question 3

What muscle in mammalian ventilation system contract to force air out of the lungs?

Answer 3

Internal intercoastal muscles

Question 4

Describe exhalation in a mammal

Answer 4

-Ribcage moves downwards and inwards
-External intercoastal muscles relax
-Diaphragm relaxes

Question 5

Sjogren’s syndrome is a rare condition that can reduce the production of mucus. Suggest how the upper respiratory tract of a person with Sjogren’s syndrome might be affected

Answer 5

More infections and coughing

Question 6

Why can expiration be a passive process?

Answer 6

It doesn’t use muscle contraction

Question 7

Some chemicals can act as allergens. If these allergens are inhaled they can cause breathing problems. Allergens cause the smooth muscle in the walls of the airways to contract.
Suggest the effects that this muscle contraction has on ventilation (2)

Answer 7

-As lumen diameter reduces; its harder to exhale and inhale

Question 8

Closed circulatory system

Answer 8

Blood stays in blood vessels

Question 9

Suggest two differences between closed circulatory system of sea bass and of a mammal

Answer 9

-Sea bass= single whilst mammal= double
-Sea bass goes through heart once whilst mammal goes through heart twice

Question 10

Outline why insects and other animals need well developed transport systems

Answer 10

Have high metabolic rate; so need large O2 supply; Has low SA:Vol; so diffusion would be too slow as distance is too far

Question 11

Explain why SA:Vol determines whether an organism needs a circ. system

Answer 11

Larger organisms have small SA:Vol; so rate of diffusion would be too slow as distance is too far; for sufficient uptake of O2

Question 12

Compare circ. systems of mammals and fish (6)

Answer 12

BOTH: -Closed systems (blood stays in blood vessels)
-Both have a heart
-Both carry O2 using hB
DIFF: -Fish= single circ (blood in heart once) whilst mammals=
double circ.
-Fish= one atrium and one ventricle so no septum whilst
mammals= have two atrias and two ventricles w/ a
septum
-Fish= blood pressure is lower to organs whilst
mammals= blood pressure is maintained at higher
pressures

Question 13

Describe how the structure of each blood vessel is adapted to its function

Answer 13

Artery:
-FUNC= carry blood away from heart under high
pressure
-STRUC= has thicker elastic layer enables them to
stretch and recoil and helps withstand the high
pressure; has collagen which provides support, maintains shape by limiting stretch.

Veins:
-FUNC= carry blood back to heart, under less pressure than arteries
-STRUC= thinner elastic layer and has valves to prevent backflow. Has more collagen than arteries to give structural support as they carry large volumes of blood

Capillaries:
-FUNC= allow substances to exchange between blood and surrounding cells
-STRUC= walls are one cell thick which allows a short diffusion distance, its only large enough to allow RBCs to travel through in single file this increases the contact of RBC to capillary wall

Question 14

Explain why oncotic pressure of blood depends only on conc of large plasma proteins (2)

Answer 14

Large plasma proteins cant pass through capillary wall but other solutes can; imbalance of large plasma proteins between blood and tissue fluid results in oncotic pressure

Question 15

VSD is a hole in the septum of the heart. Why would people w/ VSD get easily tired

Answer 15

Blood leaks from the left to right ventricle’s during ventricular systole; more oxygenated blood delivered to lungs ; deoxygenated blood passes into left ventricle during atrial systole; less oxygenated blood pumped around body so less O2 available for aerobic respiration

Question 16

Why does diastole follow systole in mammalian heart?

Answer 16

Cardiac muscle takes a short time to repolarise after being stimulated

Question 17

Outline why its important that fetal hB has a higher oxygen affinity than adult hB

Answer 17

Fetal recieves sufficient oxygen for respiration; maintains O2 conc gradient

Question 18

Suggest why reduced heart rate is sometimes seen in people who are very aerobically fit

Answer 18

Increased volume of ventricle
-Increased strength of muscle heart

Question 19

RBCs contain very high conc of enzyme carbonic anhydrase, a scientist planned to investigate the effect of pH on the activity of carbonic anhydrase.
State 2 factors that the scientist would need to control during this investigation (2)

Answer 19

-Temperature
-Enzyme conc

Question 20

Human blood is maintained at pH 7.4 by reactions that occur in RBs. Use your knowledge of these reactions to explain how a pH of 7.4 is maintained (3)

Answer 20

H+ reacts w/ hB to form haemoglobinic acid which lowers pH back to 7.4; H+ reacts w/ HCO3- to form H2CO3 which lowers pH back to 7.4; H2CO3 dissociates to form H+ and HCO3- which raises pH back to 7.4

Question 21

Explain why large multicellular plants need a transport system (3)

Answer 21

Small SA:Vol so diffusion would not fast enough as there’s long distance from external surface to cells

Question 22

Multicellular organisms eg plants have evolved internal transport systems. Explain the benefit of plants having internal transport systems

Answer 22

SA:Vol small; transport system ensures nutrents/ water reaches all tissues

Question 23

NaCl dissociates into Na+ and Cl-. Explain how casparian strip prevents these ions from reaching the xylem of the plant by apoplast pathway

Answer 23

Phospholipid bilayer repels charged particles; forces water to pass through plasma membrane

Question 24

Soluble mineral ions are present in soil. Explain why water molecules can form H bonds with the nitrate (NO3-) ions

Answer 24

Water is a polar molecule; NO3- is negative; H bonds between H on water and O on nitrate formed

Question 25

State one similarity and two diff between structure of xylem and phloem

Answer 25

-SIMI: both made up of cells joined end to end
-DIFF: -x= lignified p= not lignified only contains cellulose
-x= no companion cells p= companion cells

Question 26

Mosses are small plants. Suggest why they don’t need roots or xylem to survive

Answer 26

Large SA:Vol; distance water/ ions need to travel is short so they dont need roots or xylem

Question 27

State the function of pits in xylem tissue

Answer 27

Lateral movement of water

Question 28

Explain one practical precaution that should be taken when using a potometer

Answer 28

Dont allow air to enter cut shoot underwater at an angle to prevent airlock/ ensures a continuous column of water

Question 29

A student selected diff tomato plant leaves and sealed a plastic bag over each w/ a paper clip, he did the same for watermelon leaves. The plastic bags were left for 6 hours then they used a syringe to collect any water inside, identify 2 problems and solutions

Answer 29

-Water accumulating in bag which decreases transpiration; solution; record for shorter time eg less than 6 hours
-Ppaer clip seal isnt completely airtight so water vapour may escape; soltion= use sticky tape or elastic band

Question 30

Describe how a potometer can be used to calculate more accurate value of transpiration

Answer 30

Ensure the leaves are dry, making it airtight, cutting shoot underwater at an angle; measure distance of air bubble travels per interval calculate vol of water uptake maintain constant conditions

Question 31

Name and describe 2 pathways water takes to reach xylem at base of stem

Answer 31

-Symplast= plasmodesmata
-Apoplast= cell wall

Question 32

Adhesion

Answer 32

Attraction of water molecules to impermeable walls of xylem tissue

Question 33

Theres 2 Q:
Sucrose is carried in phloem sap from source to sink
1) Explain why starch isn’t transported in the sap
2) Suggest why sucrose is more suitable transport than glucose

Answer 33

1)Starch isnt soluble in water
2)Sucrose is less likely to be used in respiration

Question 34

Explain how mass flow of phloem sap occurs in plants with a vascular system

Answer 34

Assimilates enter sieve tube in phloem at sources which lowers water pot. of sieve tube; water enters sieve tube by osmosis and increases hydrostatic pressure; assimilates leave sieve tube at sink and increases water pot inside sieve tube; water leaves which lowers hydro pressure; assimilates move from high to low hydrostatic pressure

Question 35

Explain with an example how some parts of plant can act as both a source and sink

Answer 35

Certain parts can store and release carbohydrates when needed; eg root which can act as sink or source at diff times of year

Question 36

Explain the process of loading sucrose into phloem and its movement in the phloem

Answer 36

Sucrose pumped into companion cell; by active transport; H+ is a co transport of sucrose; Sucrose diffuses into phloem sieve tube; water enters sieve tube element from companion cell; water enters sieve tube element from xylem; increased pressure forces flow of sap down phloem; through pores in sieve plates

Question 37

Define the term magnification.

Answer 37

How many times bigger a microscope image is compared to the original specimen.

Question 38

Define the term resolution

Answer 38

The shortest distance between two objects that are still seen as separate objects.

Question 39

Describe how to prepare slide to be used with a light microscope

Answer 39

Cut the specimen very thinly

Use forceps to put it in the middle of the glass slide.

Pipette two drops of water onto the specimen.

Add a stain, if necessary.

Place a cover slip on top

Being careful not to create any air bubbles

Question 40

Function of Nucleus, Nucleolus, Nuclear envelope

Answer 40

Nucleus Controls the cell’s activities Contains the DNA / chromosomes

Nucleolus Produces ribosomes

Nuclear envelope Double membrane around the nucleus Has pores that allow mRNA to leave the nucleus

Question 41

Function of Rough ER, Smooth ER, Golgi apparatus

Answer 41

Rough ER Processes and folds proteins

Smooth ER Synthesises and processes lipids

Golgi apparatus Processes and packages proteins into vesicles

Question 42

Function of Plasma membrane, Centrioles, Cell Wall, Flagella, Cilia, Vesicle

Answer 42

Plasma membrane Controls the movement of substances into and out of the cell Has receptor molecules used in cell signalling

Centrioles Pull the chromosomes / chromatids to opposite poles during cell division

Cell Wall Supports the plant cell

Flagella Allow movement of the cell

Cilia Cilia move to move substances along the cell surface

Vesicle Transports substances in and out of the cell

Question 43

Explain why some organisms need specialised exchange surfaces. (3)

Answer 43

They have a small surface area to volume ratio

High metabolic rate

Some cells are too deep in the body for rate of diffusion alone to supply the cells

Question 44

It is more difficult for moths and bumblebees to maintain their body temperature than for
mammals and birds to maintain their body temperature.
Explain why.

Answer 44

(insects are smaller and) have a , large(r) / AW , surface
area to volume ratio 
(insects have) greater rate of heat loss 
mammals and birds have , more effective / thicker ,
insulation