3: Organisms exchange substances with their environment Flashcards

1
Q

Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake [2]

A
  1. Large(r) organisms have a small(er) surface area:volume (ratio); OR Small(er) organisms have a large(r) surface area:volume (ratio);
  2. Overcomes long diffusion pathway OR Faster rate of diffusion;
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2
Q

How does oxygen move through the insect? [4]

A
  1. Oxygen diffuses in through the spiracles;
  2. Spiracle closes;
  3. Oxygen diffuses through the trachea into the tracheoles;
  4. Oxygen delivered directly to the respiring tissues;
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3
Q

Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange. [3]

A
  1. Tracheoles have thin walls so short diffusion distance to cells;
  2. Highly branched / large number of tracheoles so short diffusion distance to cells;
  3. Highly branched / large number of tracheoles so large surface area (for gas exchange);
    4.Tracheae provide tubes full of air so fast rate of diffusion (into insect tissues);
  4. Fluid in the end of the tracheoles that moves out (into tissues) during exercise so faster diffusion through the air to the gas exchange surface;
    OR
    Fluid in the end of the tracheoles that moves out (into tissues) during exercise so larger surface area (for gas exchange);
  5. Body can be moved (by muscles) to move air so maintains diffusion / concentration gradient for oxygen / carbon dioxide;
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4
Q

Describe how the structure of the insect gas exchange system:
* provides cells with sufficient oxygen
* limits water loss.

Explain your answers. [6]

A
  1. Spiracles, tracheae, tracheoles;
  2. Spiracles allow diffusion (of oxygen)
    OR (Oxygen) diffusion through tracheae/tracheoles;
  3. Tracheoles are highly branched so large surface area (for exchange);
  4. Tracheole (walls) thin so short diffusion distance (to cells) OR Highly branched tracheoles so short diffusion distance (to cells) OR Tracheoles enter cells so short diffusion distance;
  5. Tracheole permeable to oxygen/air;
  6. Cuticle/chitin/exoskeleton (impermeable) so reduce water loss;
  7. Spiracles (can) close so no/less water loss OR Spiracles have valves so no/less water loss;
  8. Hairs around spiracles reduce water loss;
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5
Q

Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill. [3]

A
  1. Water and blood flow in opposite directions;
  2. Maintains diffusion/concentration gradient of oxygen OR Oxygen concentration always higher (in water);
  3. (Diffusion) along length of lamellae/filament/gill capillary;
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6
Q

A fish uses its gills to absorb oxygen from water.

Explain how the gills of a fish are adapted for efficient gas exchange. [6]

A

1 Large surface area provided by many lamellae over many gill filaments;
2 Increases diffusion/makes diffusion efficient;
3 Thin epithelium/distance between water and blood;
4 Water and blood flow in opposite directions/countercurrent;
5 (Point 4) maintains concentration gradient (along gill)/equilibrium not reached;
6 As water always next to blood with lower concentration of oxygen;
7 Circulation replaces blood saturated with oxygen;
8 Ventilation replaces water (as oxygen removed);

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7
Q

Describe the gross structure of the human gas exchange system and how we breathe in and out. [6]

A
  1. Named structures – trachea, bronchi, bronchioles, alveoli;
  2. Above structures named in correct order OR Above structures labelled in correct positions on a diagram;

**Breathing in **
3. Diaphragm (muscles) contract and diaphragm flattens;
4. External intercostal muscles contract and ribcage pulled up/out;
5. (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric pressure);

**Breathing out **
6. Diaphragm (muscles) relaxes and diaphragm moves up;
7. External intercostal muscles relax and ribcage moves down/in;
8. (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric pressure);

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8
Q

Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf. (4)

A
  1. (Carbon dioxide enters) via stomata;
  2. (Stomata opened by) guard cells;
  3. Diffuses through air spaces;
  4. Down diffusion gradient;
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9
Q

Explain why plants grown in soil with very little water grow only slowly. [2]

A
  1. Stomata close;
  2. Less carbon dioxide (uptake) for less photosynthesis/glucose production;
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10
Q

Describe the process of starch digestion. [5]

A

(salivary/pancreatic) Amylase;
Starch to Maltose;
Maltase;
Maltose to glucose;
Hydrolysis;
Glycosidic bonds;

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11
Q

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. [5]

A
  1. Micelles contain bile salts and fatty acids/monoglycerides;
  2. Make fatty acids/monoglycerides (more) soluble (in water) OR Bring/release/carry fatty acids/monoglycerides to cell/lining (of the iluem) OR Maintain high(er) concentration of fatty acids/monoglycerides to cell/lining (of the ileum);
  3. Fatty acids/monoglycerides absorbed by diffusion;
  4. Triglycerides (re)formed (in cells SER);
  5. Vesicles move to cell membrane;
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12
Q

Describe the role of micelles in the absorption of fats into the cells of the ileum. [5]

A
  1. Micelles include bile salts and fatty acids;
  2. Make the fatty acids (more) soluble in water;
  3. Bring/release/carry fatty acids to cell/lining (of the ileum);
  4. Maintain high(er) concentration of fatty acids to cell/lining (of the ileum);
  5. Fatty acids (absorbed) by diffusion;
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13
Q

Describe the role of enzymes in the digestion of proteins in a mammal. [4]

A
  1. (Reference to) hydrolysis of peptide bonds;
  2. Endopeptidase act in the middle of protein/polypeptide OR Endopeptidase produces short(er) polypeptides/ increase number of ends;
  3. Exopeptidases act at end of protein/polypeptide OR Exopeptidase produces dipeptides/amino acids;
  4. Dipeptidase acts on dipeptide/between two amino acids OR Dipeptidase produces (single) amino acids;
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14
Q

The action of endopeptidases and exopeptidases can increase the rate of protein digestion. Describe how. [2]

A
  1. Exopeptidases hydrolyse peptide bonds at the ends of a polypeptide/protein AND endopeptidases hydrolyse internal peptide bonds within a polypeptide/protein;
  2. More ‘ends’ OR More surface area;
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15
Q

Describe and explain two features you would expect to find in a cell specialised for absorption. [2]

A
  1. Folded membrane/microvilli so large surface area (for absorption);
    Accept ‘brush border’ for ‘microvilli’.
  2. Large number of co-transport/carrier/channel proteins so fast rate (of absorption) OR
    Large number of co-transport/carrier proteins for active transport OR
    Large number of co-transport/carrier/channel proteins for facilitated diffusion;
  3. Large number of mitochondria so make (more) ATP (by respiration) OR
    Large number of mitochondria for aerobic respiration OR
    Large number of mitochondria to release energy for active transport;
  4. Membrane-bound (digestive) enzymes so maintains concentration gradient (for fast absorption);
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16
Q

Describe the absorption of glucose (Cotransport) [3]

A
  1. Sodium ions actively transported from ileum cell in to the blood;
  2. Maintains / forms diffusion gradient for sodium to enter cells from gut (and with it, glucose);
  3. Glucose enters ileum cell by facilitated diffusion with sodium ions;
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17
Q

Describe the mechanism for the absorption of amino acids in the ileum [4]

A
  1. Facilitated diffusion of amino acid (into cell when higher concentration in lumen);
  2. Co-transport;
  3. Sodium ions actively transported from cell to blood/capillary/tissue fluid;
  4. Creating sodium ion concentration/diffusion gradient;
  5. Facilitated diffusion of amino acid into blood/capillary;
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18
Q

Explain how an arteriole can reduce the blood flow into capillaries. [2]

A
  1. Muscle layer contracts;
  2. Constricts/narrows arteriole/lumen;
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19
Q

Describe how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta. [6]

A
  1. Atrium has higher pressure than ventricle (due to filling / contraction);
  2. Atrioventricular valve opens;
  3. Ventricle has higher pressure than atrium (due to filling / contraction);
  4. Atrioventricular valve closes;
  5. Ventricle has higher pressure than aorta;
    Points 1, 3, 5, and 7 must be comparative: eg higher
  6. Semilunar valve opens;
    Marks 2, 4, 6, 8 given in the correct sequence can gain 4 marks
  7. Higher pressure in aorta than ventricle (as heart relaxes);
  8. Semilunar valve closes;
  9. (Muscle / atrial / ventricular) contraction causes increase in pressure;
20
Q

Describe how the movement of the diaphragm leads to air movement into the lungs [4]

A
  1. Diaphragm contracts and flattens.
  2. Volume of lungs increases.
  3. Pressure inside the lungs is lower than
    atmospheric pressure.
  4. Air moves into the lungs.
21
Q

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them. [4]

A
  • Many alveoli/ alveoli walls folded provide a large surface area;
  • Many capillaries provide a large surface area (So) fast diffusion;
    Alveoli or capillary walls/ epithelium/ lining are thin/ one cell thick / short distance between alveoli and blood;
  • Flattened/ squamous epithelium (So) short diffusion distance/ pathway / (So) fast diffusion;
  • Ventilation / circulation; So Maintains a diffusion / concentration gradient (So) fast diffusion;
22
Q

Describe the pathway taken by an oxygen molecule from an alveolus to the blood [2]

A
  1. (Across) alveolar epithelium;
  2. Endothelium of capillary;
23
Q

Explain why death of alveolar epithelium cells reduces gas exchange in human lungs. [3]

A
  1. Reduced surface area;
  2. Increased distance for diffusion;
  3. Reduced rate of gas exchange;
24
Q

Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their functions. (6)

A

Elastic tissue
1 Elastic tissue stretches under pressure/when heart contracts;
2 Recoils/springs back;
3 Evens out pressure/flow;
**Muscle **
4 Muscle contracts;
5 Reduces diameter of lumen/vasoconstriction/constricts vessel;
6 Changes flow/pressure;
**Endothelium **
7 Endothelium smooth;
8 Reduces friction/blood clots/less resistance;

25
Q

The thickness of the aorta wall changes all the time during each cardiac cycle.

Explain why. (5)

A
  1. (Aorta wall) stretches;
  2. Because ventricle/heart contracts / systole / pressure increases;
  3. (Aorta wall) recoils;
  4. Because ventricle relaxes / heart relaxes /diastole / pressure falls;
  5. Maintains smooth flow / pressure;
26
Q

Suggest two ways the student could improve the quality of his scientific drawing [2]

A
  1. Only use single lines/do not use sketching (lines)/ensure lines are continuous/connected;
  2. Add labels/annotations/title;
  3. Add magnification/scale (bar);
  4. Draw all parts to same scale/relative size;
  5. Do not use shading/hatching;
27
Q

Describe two precautions the student should take when clearing away after the dissection. [2]

A
  1. Carry/wash sharp instruments/scalpel by holding handle OR Carry/wash sharp instruments by pointing away (from body)/down;
  2. Disinfect instruments/surfaces;
  3. Disinfect/sanitise hands OR Wash hands with soap (and water);
  4. Put organ/gloves/paper towels in a (separate) bag/bin/tray to dispose;
28
Q

State two safety precautions when using a scalpel.

A
  1. Cut onto a hard flat surface
  2. Cut away from the body
  3. Use a sharp blade
29
Q

Describe how tissue fluid is fo rmed and how it is returned to the circulatory system. (6)

A

**Formation **
1. High blood / hydrostatic pressure / pressure filtration;
2. Forces water / fluid out (of fenestrations/ capillary pores);
3. Large proteins remain in capillary;

Return
4. Lower water potential in capillary / blood;
5. Due to (plasma) proteins;
6. Water enters capillary / blood;
7. (By) osmosis;
8. (Correct reference to) lymph removes excess water;

30
Q

Heat from respiration helps mammals to maintain a constant body temperature.

Use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobins. (5)

A
  1. Smaller mammal has greater surface area to volume ratio;
  2. Smaller mammal/larger SA:Vol ratio more heat lost (per unit body mass);
  3. Smaller mammal/larger SA:Vol ratio has greater rate of respiration/metabolism;
  4. Oxygen required for respiration;
    (Haemoglobin) releases more oxygen / oxygen released more readily / haemoglobin has lower affinity;
31
Q

Explain a property of iron ions that enables these ions to carry out their role in red blood cells. [2]

A
  1. (Is) charged/polar OR (Is) part of haem(oglobin);
  2. (So) binds/associates/loads (with) oxygen OR (So) forms oxyhaemoglobin OR (So) transports oxygen;
32
Q

What is the equation for Cardiac Output?

A

CO = SV X HR

units = dm3 min-1

33
Q

How do you calculate the Heart rate?

A

60
_______________________________________
the time of one cardiac cycle in seconds

34
Q

Describe how haemoglobin normally loads oxygen in the lungs and unloads it in a tissue cell. [6]

A
  • Oxygen combines (reversibly) to produce oxyhaemoglobin;
  • each haemoglobin molecule/ one haemoglobin may transport 4 molecules of oxygen;
  • high partial pressure of oxygen / oxygen tension / concentration in lungs;
  • haemoglobin (almost) 95% / 100% saturated;
  • unloads at low oxygen tension(in tissues);
  • presence of carbon dioxide displaces curve further to right / increases oxygen dissociation;
  • allows more O2 to be unloaded;
  • increase temp/ acidity allows more O2 to be unloaded;
  • low pO2 / increase CO2 / increase term / increase acid occur in vicinity of respiring tissue;
35
Q

Explain how oxygen in a red blood cell is made available for respiration in active tissues. [4]

A
  • CO2 (increased) respiration;
  • (increased) dissociation oxygen from haemoglobin;
  • Low partial pressure in tissues/plasma;
  • Oxygen diffuses from red blood cells to tissues;
36
Q

The oxygen dissociation curve of the foetus is to the left of that for its mother. Explain the advantage of this for the foetus. [3]

A
  • HbF hasHigher affinity / loads more oxygen;
  • At low/same/high partial pressure/pO2;
  • Oxygen moves from mother/to fetus;
37
Q

Explain how oxygen is loaded, transported and unloaded in the blood. (6)

A
  • Haemoglobin carries oxygen / has a high affinity for oxygen / oxyhaemoglobin;
  • In red blood cells;
  • Loading/uptake/association in lungs at high p.O2;
  • Unloads/ dissociates / releases to respiring cells/tissues at low p.O2;
  • Unloading linked to higher carbon dioxide (concentration);
38
Q

Binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.

Explain why.
[2]

A
  1. Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin; [conformational shift caused]
  2. Creates / leads to / uncovers second / another binding site OR Uncovers another iron / Fe / haem group to bind to;
39
Q

Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin. [2]

A
  1. Increases/more oxygen dissociation/unloading OR Deceases haemoglobin’s affinity for O2;
  2. (By) decreasing (blood) pH/increasing acidity;
40
Q

Explain how water enters xylem from the endodermis in the root and is then transported to the leaves. (6)

A

**(In the root) **
1. Casparian strip blocks apoplast pathway / only allows symplast pathway;
2. Active transport by endodermis;
3. (Of) ions/salts into xylem;
4. Lower water potential in xylem / water enters xylem by osmosis /down a water potential gradient;

**(Xylem to leaf) **
5. Evaporation / transpiration (from leaves);
6. (Creates) cohesion / tension / H-bonding between water molecules / negative pressure;
7. Adhesion / water molecules bind to xylem;
8. (Creates continuous) column of water

41
Q

Root pressure moves water through the xylem. Describe what causes root pressure. (4)

A
  1. Active transport by endodermis;
  2. ions/salts into xylem;
  3. Lowers water potential (in xylem);
  4. (Water enters) by osmosis;
42
Q

Name a factor that can affect transpiration

A

Light (intensity) / temperature / air movement / humidity;

43
Q

Give two precautions the students should have taken when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot. [2]

A
  1. Seal joints / ensure airtight / ensure watertight;
  2. Cut shoot under water;
  3. Cut shoot at a slant;
  4. Dry off leaves;
  5. Insert into apparatus under water;
  6. Ensure no air bubbles are present;
  7. Shut tap;
  8. Note where bubble is at start / move bubble to the start position;
44
Q

Describe the mass flow hypothesis for the mechanism of translocation in plants. [5]

A
  1. In source/leaf sucrose is actively transported into phloem;
  2. By companion cells;
  3. Lowers water potential of sieve cell/tube and water enters by osmosis;
  4. Increase in pressure causes mass movement (towards sink/root);
  5. Sugars used/converted in root for respiration for storage;
45
Q

Describe the transport of carbohydrate in plants. [5]

A
  1. Sucrose actively transported into phloem (cell); OR Sucrose is co-transported/moved with H+ into phloem (cell);
  2. (By) companion/transfer cells;
  3. Lowers water potential (in phloem) and water enters (from xylem) by osmosis;
  4. ((Produces) high(er) (hydrostatic) pressure; OR (Produces hydrostatic) pressure gradient;
  5. Mass flow to respiring cells OR Mass flow to storage tissue/organ;
  6. Unloaded/removed (from phloem) by active transport;
46
Q

Explain how the Atrio Ventricular valve maintains a unidirectional flow of blood. [2]

A
  1. Pressure in (left) atrium is higher than in ventricle causing valve to open;

OR (When) pressure above valve is higher than below valve it opens;

’2.Pressure in (left) ventricle is higher than in atrium causing valve to close;

OR (When) pressure in below valve is higher than above valve it closes;

47
Q

Explain the importance of the xylem being kept open as a continuous tube. [3]

A
  1. (Allows unbroken) continuous column of water OR (So) no barrier to (water) movement;

2.** Cohesion from H bonds** between (all) water (molecules)
OR Cohesion from (polar) attraction between (all) water (molecules);

  1. Evaporation/**transpiration creates tension **(in column)
    OR
    Water moves from xylem (into cells) creates tension
    OR
    (To) pull up water creates tension (in xylem);