Movement Of Substances Flashcards
1
Q
Define diffusion
A
Movement of particles from an area of high concentration to an area of low concentration
2
Q
What does equilibrium mean?
A
Where particles will be equally distributed. Neither concentration is higher / lower than the other
3
Q
Four factors that affect rate of diffusion
A
Temperature
Distance
Concentration gradient
Surface area: volume
4
Q
How does temperature affect rate of diffusion?
A
molecules have more KE -> move faster
Diffusion occurs faster
5
Q
How does concentration gradient affect diffusion?
A
Large concentration gradient -> molecules will diffuse from high to low quicker
If concentration gradient is small -> diffusion will happen slower
6
Q
How does distance affect diffusion?
A
- Diffusion takes longer if molecules have to travel further
- therefore cells are small -> smaller volume reduces distance
7
Q
How does SA:V affect diffusion?
A
- Larger SA speeds up rate of diffusion -> there are more opportunities for molecules to move
- large SA compared to the distance molecules must travel
8
Q
Definition of osmosis
A
Net diffusion of free water molecules from an area of high water concentration to an area of low water concentration across a partially permeable membrane
9
Q
When are free water molecules not considered ‘free’
A
- When other molecules (eg. Sugar) dissolve into the water, the water molecules are attracted to them.
- this means there are less free water molecules in the substance
10
Q
What is a partially permeable membrane
A
- Membrane that only allows certain particles through
- particles can be selected by size
11
Q
Define water potential
A
- Measure of concentration of free water molecules in a solution
- pure water has a water potential of 0
12
Q
What happens to water potential in a solution as a solute is added?
A
- Water potential falls as there is a lower concentration of free water molecules.
- Solution with a high concentration of (eg. sucrose) have a low water potential.
13
Q
Why do plant cells and animal cells react differently when being placed in different concentrations?
A
Plant cells have a cell wall which allows the cell to withstand a large amount of pressure
14
Q
What is an isotonic solution?
A
- The solution outside the cell has the same water potential as inside the cel
- no net movement
15
Q
What is a hypotonic solution?
A
- The solution outside the cell has a higher water potential than inside the cell
- net movement of free water molecules into the cell
16
Q
What is a hypertonic solution?
A
- The solution outside the cell has a lower water potential than onside the cell
- net movement of free water molecules outside of the cell
17
Q
Animal cell in hypotonic solution
A
Lysed
18
Q
Animal cell in isotonic solution
A
Normal
19
Q
Animal cell in hypertonic solution
A
Shrivelled
20
Q
Plant cell in hypotonic solution
A
Turgid (normal)
21
Q
Plant cell in isotonic solution
A
Flaccid
22
Q
Plant cell in hypertonic solution
A
Plasmolyzed
- cytoplasm shrinks away from cell wall when there isn’t enough water to fill the cell
23
Q
Define active transport
A
Movement of molecules form an area of low concentration to an area of high concentration ( against/ up a concentration gradient) using ATP
24
Q
Does active transport go against / up or down a concentration gradient?
A
Against/ up
25
Does osmosis go against/ up or down a water potential gradient
Down
26
Does diffusion go against/ up or down concentration gradient
Down
27
What is a active transport used for
Transport substances against concentration gradient
28
What does an organism need in order to use active transport to transport substances?
Carrier proteins
- these use ATP to provide energy to move the substances across the membrane against the conc. gradient
29
What does the transport system in plants allow leaves to receive
Water - for photosynthesis
Mineral ions - to convert products of photosynthesis into useful substances
30
What does the xylem transport?
And where from -> to?
- Water and mineral ions
- roots -> leaves
31
What is the xylem made up of?
Cells that are:
-Thick walled
-dead
- hollow
- contain no cytoplasm
- arranged end to end to form tubes
32
What does the cell wall of the xylem contain + what does this do?
- Lignin
- waterproof
33
Examples of ions that the xylem transports + why
Nitrate ions - make amino acids and proteins
Magnesium ions - make chlorophyll
34
What does the phloem transport
Where from -> to
-sucrose and amino acids
- leaves (where they are made) -> growing points (eg. tips of the shoot and flowers) or storage areas (roots/bulbs)
35
What is the phloem made of
- Living cells
- arranged end to end to form tubes
36
What is the cell walls in phloem made of
Cellulose
37
What is the sugar made photosynthesis converted to in phloem
Sucrose
38
What does moving sucrose and amino acids around require + what is this called
- Requires Energy
- called translocation
39
What is the main site of water absorption in plants
Root hairs take in water through the soil
40
How are root hairs adapted for absorbing water
- thin walled ( short diffusion distance)
- hair like extensions ( increase SA or the root epidermis)
41
Function of a root hair cell
Absorb water and minerals from soil
42
How do mineral ions enter root hair cells
Active transport
-water conc. is lower than root hair cell’s conc. so ions move in
43
How does water enter root hair cells
Osmosis
- soil water has higher conc. of water molecules so water will move in
44
Define transpiration
Evaporation of water from the surface of a plant
45
Functions of the transpiration stream
- carry mineral ions to the leaves for synthesis of amino acids and chlorophyll
- keep turgor pressure high in leaf cells (holding leaves up)
- evaporation cools in leaves
- supplies water for photosynthesis
46
How does water pass out of the leaves
- leave cells out the mesophyll
- evaporates through air spaces between spongy mesophyll
- diffuse out stomata as water vapour
47
Why does water leave the xylem to replace water lost?
Osmosis
- cells have a lower conc. of water molecules
- water moves into them from surronding mesophyll cells
- water leaves xylem to replace water lost from nearby cells
48
What is the loss of water vapour form the leaves called
Transpiration
49
What is transpiration stream
Water pulled up xylem in the stem and roots in a continuous flow
50
Environmental conditions that affect rate of transpiration
- temperature
- humidity
- wind speed
- light intensity
- water supply
51
How does temperature affect rate of transpiration
- hotter day, water will evaporate quickly from leaves
- water molecules have more KE
- Transpiration increases = temp increases
52
How does humidity affect rate of transpiration
- very humid air contains lots of water vapour
-> smaller conc. gradient -> transpiration slows
- dry air - diffusion of water vapour from leaf to atmosphere will be fast
- transpiration increases = humidity decreases
53
How does wind speed affect rate of transpiration
- moving air, water vapour is blown away from leaf as fast as it diffuses out
-> speed up transpiration
- still air = transpiration slows down
- transpiration increases = wind speed increases
54
How does light intensity affect rate of transpiration
- in daylight - stomata are open to supply CO2 for photosynthesis
- allows more water to diffuse out of the leaves into the atmosphere
- Light intensity increases = transpiration increases
55
How does water supply affect rate of transpiration
- lack of water = plant is losing water faster than it is being taken up by roots
- plant will start to wilt
- before this, guard cells become flaccid + stomata start to close
-> reducing transpiration and delaying wilting
- water supply decreases = transpiration increases
56
What are stomata
Holes in ( normally bottom) surface of leaf
57
Where are guard cells ands what do they do
- Either side of the stomata
- control opening and closing of stomata
- each guard cell has a thickened, inflexible inner cell wall ( on stomatal side)
58
When the stomata is opened and close what are the guard cells
Open - swollen
Closed - shrunken
59
How does the guard cells open the stomata
- in light = photosynthesise
- conc. of sugars increases + water potential decreases in guard cells.
- water moves into guard cells (osmosis)
- become turgid + banana shaped
= opens stomata
60
How does the guard cells close the stomata
- in dark = no photosynthesis
- sugar conc. decreases = water potential increases
- water moves out of guard cells
- become flaccid
= stomata close
61
Why are sugars needed in plants
Respiration or growth
62
What is the sieve tube
- living
-thin layer of cytoplasm at edge of cell
- filled with sap
Sap = concentrated solution of sucrose + amino acids
- sap flows through sieve plates and through phloem
63
Does sieve tube have a nucleus
No
Controlled and supported by neighbouring companion cells
64
What do companion cells do
- have lots of mitochondria
- actively transport sucrose into phloem
65
How does water move into the sieve tube
- There is a low water potential in seive tube due to high conc. of sucrose in phloem
- water moves in ( osmosis )
- creates high pressure
66
What is a photometer used for
Device used to estimate transpiration rates
67
Potential Errors in measuring rate of transpiration experiment
- set up potometer underwater - prevent air bubbles from blocking xylem
- grease joint with lots of petroleum jelly - prevents water loss and air entry
- tap needs to be closed and full of water - prevent bubbles
68
How does a Visking tube work
Only allows small soluble molecules to pass through ( eg. Glucose and water)
- osmosis can occur
69
examples of experiments to investigate factors affecting rate of diffusion and osmosis
- Agar cubes -> SA:VR and rate of diffusion
- potato chips in different conc. sucrose/ salt solutions -> osmosis
- visking tube -> osmosis
70
How does potato chips placed in different conc. of sucrose/ salt solution affect rate of osmosis
- if solution has a higher water potential than potato - water will move into potato chip and mass will increase
- if solution has lower water potential than potato - water will move out of potato chip and mass will decrease
71
What are amino acids broken down into in the liver
Ammonium and carbohydrates
72
How are amino acids filtered into the liver
Through the hepatic artery and hepatic portal vein ( along with rest of blood)
73
Why is ammonium converted into urea
Ammonia is very toxic
Urea is less toxic
74
How are useful amino acids and urea released back into the body the blood stream (from liver) ?
Through the hepatic vein
75
What do nephrons do
Filter the blood
76
Why are amino acids broken down in the liver
They cant be stored
77
What does the kidney do
- Filters the blood
- removes any excess materials + passes them to bladder to be excreted
78
What is the cortex on a diagram
The outside part of the kidney
79
What is the medulla on a diagram
The triangular shaped blotches between the cortex and pelvis
80
What is the pelvis on a diagram
The innermost part of the kidney
81
Difference between afferent and efferent arteriole
Afferent - entrance to glomuereus
Efferent - exit to glomereus
Efferent diameter is smaller than afferent
82
What does a small exit out of the glomereus (via efferent arteriole) cause
Build up of pressure in the capillaries forming glomerules
83
What does the pressure in the golmerulus cause ?
What is the end product called?
- Small molecules eg. Urea, glucose, amino acids, salts out of capillaries and into bowman’s capsule
- glomerular filtrate
84
Why dont larger molecules move into bowman’s capsule in ultrafiltration?
They are to big to fit across capillary walls
Therefore stay in blood
85
What controls whether molecules can pass into bowman’s capsule in ultrafiltration?
Basement membrane
86
What are the stages in the kidney?
Ultrafiltration
Selective reabsorption
Water reabsorption
87
How are the cells lining the pct specialised for movement of molecules?
Folded membrane - increase surface area
Many mitochondria - Provide ATP for active transport
88
Where does the glomerular filtrate travel after the bowman capsule
PCT
89
What do the specialised cells in the walls of the PCT do?
Move useful materials back into blood stream by diffusion and active transport
90
What is reabsorbed in the PCT (selective reabsorption)
All glucose
All amino acids
Some salts
80% of water
91
What is involved in water reabsorption
Loop of Henley and collecting duct
92
What does the loop of henle do?
Concentrates urine
- by transporting salt back into blood by active transport
- causing the water to diffuse into blood by osmosis
93
What does the collecting duct do
Osmoregulation - Responds to hormone called ADH to vary how much water is reabsorbed
94
Where does the blood travel in the kidney
Glomerulus
Bowman’s capsule
PCT
Loop of Henle
Distal convoluted tubule
Collecting tubule
95
How is the Upper epidermis specialised for photosynthesis
Transparent
Allowing light to penetrate to the mesophyll
96
How are leaves specialised for photosynthesis
Large surface area
Thin
To maximise absorption of sunlight by photosynthesising cells.
Increases no. Of stomata - CO2 can diffuses quicker
97
How are the palisade cells specialised for photosynthesis
Long, thin, tightly packed
Lots of chloroplasts - maximises absorption of sunlight energy
Main site of photosynthesis
98
How are the stomata specialised for photosynthesis
Allow gases to diffuse into air spaces of the leaf - short diffusion distance for CO2
99
How is the xylem specialised for photosynthesis
Transports water (absorbed in roots) into leaves -short diffusion distance for water into photosynthesising cells
