FOR 10B- part TWO!

JUNE 2012

QUESTION 8

8 (a) (i)Explain the term osmosis [4]

 Definition from your notes :)

 

(ii)Explain the ways in which active transport is different from osmosis [4]

Definition also from your notes :)

(b)Explain how it is possible for oxygen in the lungs to diffuse rapidly into the blood.[2]

This one is in the textbook... I think I also gave this to u before....


MARK SCHEME
a) (i)(osmosis) ref. diffusion;of water ;

from high to low (water) molecular concentration or water potential / low to high solute

concentration.;Ref. to partially permeable membrane AW;

passive / no energy required ;e.g. of an application; [max. 4]

 

ANSWER: Osmosis is the movement of water molecules from a solution of higher water potential

to a solution of lower water potential. across a partially permeable membrane that does not

require energy   (4 marks)

 

(ii)(active transport) movement of ions / molecules / substances;

against a concentration gradient;needs living or cell membrane;energy required;

from respiration;e.g. of an application; [max. 4] 

 

ANSWER: Active transport is the movement of ions from a region of lower concentration to a region

of higher concentration with the use of energy. It can only occur in living cells. (4 marks)

(b)thin walls / one cell thick + alveoli / air sacs / capillaries;

haemoglobin + oxygen absorption;ref. relatively high concentration of oxygen in the lungs / oxygen regularly replenished / more oxygen in the air than in the blood;continuous movement of blood;

large surface area / alveoli have rich supply / surrounded by capillaries; [max. 2] 

 

ANSWER: The alveoli and capillaries have walls that are one-cell thick, and the alveoli are surrounded by capillaries.  (2 marks)

QUESTION 9

9 (a)Describe the removal of excretory products from the human body [8]

For this one just talk about how CO2, urea and excess water is removed. Just saying urea and CO2  products you already get two marks heehee

(b) Explain why the removal of faeces from the body is not regarded as excretion.[2]

 

This one I always mention to you, why poo poo is not excretory waste....

MARK SCHEME

9a) toxic / poisonous materials (R harmful);

waste products + metabolism AW;

(R refs. to salts)

urea;

liver / blood + kidneys;

urine;

urethra;

sweat;

skin / (epi)dermis;

carbon dioxide;

from cells / blood + alveoli;

exhaled / breathed out / expelled or removed from lungs AW;

 

ANSWER: Excretory products are removed from the body as they are toxic substances and waste products produced by metabolic activities. Urea is produced in the liver and sent to the kidneys to be excreted in the urine and also a small amount of urea is excreted by the skin through sweat. Carbon dioxide from the cells will diffuse into the capillaries, and then into the alveoli and is then breathed out.

(10 marks!!!)

9 b)undigested food;

cellulose / fibre / lignin / roughage;

not from metabolism AW; 

 

ANSWER: Faeces is made up of undigested food that has never been metabolised. (2 marks)