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Year 12 - Biology > C2 - The Importance of Water > Flashcards

C2 - The Importance of Water Flashcards

1
Q

Why is water necessary?

A

All life forms depend on water.
Water is the major constituent of most organisms.

Two thirds of this water is found within cells and the rest is found in extra cellular bio fluids e.g. plasma in animals and phloem sap in plants.

Most biochemical reactions take place in water so without it there would be no life on planet Earth.

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2
Q

What is the structure of water?

A

Water is a polar molecule made up of an oxygen atom and two hydrogen atoms.
There’s a covalent bond between to O and H.

The water molecule is a bent molecule rather than linear (104.5°)

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3
Q

What is the charge of water?

A

Water has a slight charge so is called polar.

The oxygen atom has a slight negative charge and the hydrogen atoms have a slight positive charge.

Having opposite charges in two places makes it dipolar.

The water molecule is a bent molecule rather than linear and so the hydrogen atoms are on one side of the molecule and form a positive pole.
Meanwhile the oxygen atom is on the other forming the negative pole

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4
Q

What are hydrogen bonds?

Within water

A

Hydrogen bonds are the forces of attraction when water molecules are attracted to each other as the slight positive charges (of the H atoms) are attracted to the slight negative charges (of the oxygen atoms).

Hydrogen bonds are actually weak intermolecular forces rather than actual bonds.
Individually they are very weak but if there are a lot of hydrogen bonds in a given volume they are collectively quite strong

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5
Q

What is cohesion?

A

The attraction between two water molecules

The sticking of particles of the same substance

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6
Q

What is adhesion?

A

The attraction between water and another polar molecule

Sticking of particles of different substances

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7
Q

Why is water a good solvent?

A

What are molecules are attracted to other polar and charged particles which makes water a good solvent for substances with these properties.

The water molecules from a ‘shell’ around charged ions and other molecules that possess a slight charge on their surface

This prevents the ions and molecules from clumping together and so causes the ions to dissolve.
Nonpolar molecules cannot dissolve in water therefore cannot be transported in the plasma (instead they have to be combined with soluble molecules)

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8
Q

How is water being a solvent an important property?

A

It’s important:

For transporting substances around the body in the plasma such as glucose, insulin and lymph

In removing metabolic waste such as urea in urine

In allowing chemical reactions to take place within cells such as respiration and protein synthesis

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9
Q

Why does water have a high specific heat capacity?

A

There are many hydrogen bonds which restricts the movement of water molecules.

This increases the amount of energy needed to break the hydrogen bonds.

A large amount of energy is needed to make bodies of water change temperature and so water must lose a large amount of energy in order to cool down
(this means the temperature of water is relatively stable in comparison to air and land and so is an ideal habitat for aquatic organisms)

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10
Q

Why is water having a high specific heat capacity an important property?

A

It prevents our internal body temperature changing quickly as a result of changes in the environment

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11
Q

What is the latent heat of vaporisation?

A

The amount of heat needed to turn a substance to a gas.

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12
Q

Why does water have a high latent heat of vaporisation?

A

It’s molecules need a high amount of heat to enable a molecule to separate from other molecules in a liquid to become a vapour.

As it requires a large amount of heat to break the hydrogen bonds, this means that when water evaporates, it has a cooling effect.

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13
Q

Why is water having a high latent heat of vaporisation an important property?

A

It allows our bodies to lose heat through sweating

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14
Q

Why is water viscous?

A

Due to its cohesive and adhesive properties.

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15
Q

Why is the cohesion and adhesion of water an important property?

A

It allows water to be used as a lubricant in the form of pleural fluid (minimising friction between the lungs and rib cage) and mucus (e.g. To allow passage of faeces down the colon).

It’s critical to transport in xylem vessels in plants.

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15
Q

What is cytosol?

A

The liquid part of cytoplasm in an intact cell, excluding any part that is contained within organelles.

The less water in the cell, the slower the metabolic rate.

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16
Q

What are body/biofluids?

A

Liquids produced within the body.
Fluids secreted or excreted from the body e.g. Bile, semen, breast milk, amniotic fluid, cerebrospinal fluid.

They can be placed into 2 groups:
Intracellular fluids
Extracellular fluids

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17
Q

What are intracellular fluids?

A

Fluid found within cells e.g. Cytosol

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18
Q

What are extracellular fluids?

A

Fluids found outside of cells e.g. Plasma and tissue fluid

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19
Q

What are the three main body fluids (in terms of volume)?

A

Blood plasma
Tissue fluid
Lymph

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20
Q

What is blood plasma?

A

Approx 55% of blood is (pal yellow) liquid (plasma). The remaining 45% is made up of cells
NO cells in plasma

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21
Q

What does plasma contain?

A

Plasma proteins (albumin, antibodies, clotting factors)

Absorbed nutrients (glucose, amino acids, fatty acids)

Excretory waste (urea, CO2)

Hormones (insulin, adrenaline)

Electrolytes (sodium and chlorine ions)

Heat

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22
Q

What is tissue fluid?

A

Fluid produced due to hydrostatic pressure which forces fluid out of the plasma and into the spaces between the cells.

The capillary walls are permeable to most components of the blood except most blood cells and large plasma proteins.

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23
Q

What’s hydrostatic pressure?

A

Pressure created by water within cells.

Tissue fluid forms as a result of HP due to the force created by the heart pumping blood from the left ventricle around the body in the arteries, arterioles and capillaries.
The pressure forces fluid out of the plasma carrying nutrients and oxygen.

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24
What does tissue fluid enable?
It allows capillaries to exchange substances with every cell in the body. Tissue fluid returns to the bloodstream via capillaries and the lymphatic system.
25
What's lymph?
A colourless fluid containing leucocytes that bathes the tissues and drains through the lymphatic system into the bloodstream. White blood cells and other substances that are continually exchanged with substances from the blood plasma. 1/10th of tissue fluid drains into lymphatic capillaries which drain into larger lymph vessels containing valves. It drains back into the bloodstream in the subclavian vein. It's important for our immune systems.
26
What moves lymph?
The contraction of skeletal muscles and hydrostatic pressure of the tissue fluid left in the capillaries.
27
What's urine?
A fluid stored in the bladder and discharged through the urethra. It is one of the body's chief means of eliminating excess water and salt, and also contains nitrogen compounds such as urea and other waste substances removed from the blood by the kidneys.
28
How is urine produced?
Metabolic reactions within the body produce waste products, some of which contain nitrogenous-high substances which are toxic and must be removed from the bloodstream. Soluble waste, excess water, ions and sugars are excreted mainly by the urinary system and perspiration. The urinary system consists of 2 kidneys with a ureter each that leads to the bladder and urethra. Urine is the end result of filtration and reabsorption of the substances in the blood stream. (And has high concentration of toxic substances and urea)
29
What is serum?
The blood plasma which has had it's clotting factors removed from it.
30
What does serum contain?
``` Electrolytes Antibodies Antigens Hormones Soluble proteins (which aren't involved in blood coagulation/clotting) ```
31
How's serum obtained?
By allowing whole blood to clot at room temp for 15-30. Clots and cells are removed by centrifuging it for 10 mins. The serum is immediately collected and stored at 2-8°C
32
What's serum used for?
Blood typing Diagnostic tests Testing for IgG
33
What biofluids are in plants?
``` Cytosol or cell sap (intra) Vacuole contents (intra) Contents of specialised cells e.g. Phloem and xylem (intra) Fluid in cell walls (intra) Fluid between cell walls (extra) ``` Xylem fluid is very dilute compared to phloem sap and cytoplasm. Unlike phloem sap, xylem fluid contains no sucrose otherwise they're similar. (Ions, molecules and auxins)
34
What are the charges of the hydrogen and oxygen within water?
The oxygen has a slight negative charge The hydrogen has a slight positive charge Oxygen has a greater affinity than hydrogen as it has more protons so has a greater positive charge overall. This charge makes water dipolar
35
What's the symbol for a slightly positive or negative dipole?
δ | The symbol δ indicates the partial charge of an individual atom.
36
What happens when a charged plastic rod is held alongside a stream of water?
The water bends towards or away from the rod based on their charges (attracted or repelled)
37
Why does water have so many properties?
Because of its ability to form hydrogen bonds.
38
Why is water a good solvent?
Water molecules form a layer around the ions and break the ionic substances apart. Non-polar molecules e.g. Lipids are insoluble because they do not attract the water molecules.
39
What is surface tension?
The tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area. Surface tension is the elastic tendency of a fluid surface which makes it acquire the least surface area possible. Surface tension allows insects (e.g. water striders), usually denser than water, to float and stride on a water surface. At liquid-air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion).
40
What enables surface tension within water?
The large number of hydrogen bonds
41
What's latent heat fusion?
How much heat must be lost for the substance to freeze.
42
Why does water have a high boiling point/S.H.C?
Because it has many hydrogen bonds which require a lot of energy to overcome.
43
Why are water molecules non linear and have an angle of 104.5° between the hydrogen atoms?
The electrons from the H are pulled in to the O atom due to the oxygen atom having a greater affinity for electrons than hydrogen.
44
What are the two groups of body fluids?
Intracellular fluids - found within cells e.g. Cytosol Extracellular fluids - found outside of cells e.g. Plasma, tissue fluid and lymph This also encompasses fluids which are secreted or excreted e.g. Bile, semen, breast milk, amniotic fluid and cerebrospinal fluid.
45
What's blood plasma? | What does it contain?
The pale yellow liquid which makes up 55% of the blood (the other 45% is made up of cells). It contains: - Dissolved foods/nutrients (glucose, amino acids, fatty acids) - Dissolved waste products (urea and CO2) - Plasma proteins (antibodies, clotting factors, albumin) - Hormones (insulin and adrenaline) - Electrolytes (chlorine and sodium ions) - Heat energy
46
What's hydrostatic pressure?
Pressure created by a fluid pushing against the sides of a vessel or inside of a cell. The force created by the heart pumping blood from the left ventricle around the body in the arteries, arterioles and capillaries.
47
What's tissue fluid?
Extracellular fluid which bathes the cells of most tissues, arriving via blood capillaries and being removed via the lymphatic vessels. It's formed as a result of hydrostatic pressure acting at the arterioles end of capillaries. The pressure forces fluid out of the plasma into spaces between cells. The capillary walls are permeable to most common components of the blood except most blood cells and large plasma proteins.
48
What does the formation of tissue fluid enable?
It enables capillaries to exchange substances with every cell in the body. Tissue fluid returns to the bloodstream via the capillaries and lymphatic system.
49
What's lymph?
Lymph is a clear-to-white fluid made of: White blood cells, especially lymphocytes, the cells that attack bacteria in the blood. A tenth of tissue fluid drains into lymphatic capillaries which drains into larger lymph vessels that contain semilunar valves. Once within lymph vessels, the fluid is called lymph. It drains back into the bloodstream in the subclavian veins.
50
What moves lymph?
The contraction of skeletal muscles and the hydrostatic pressure of tissue fluid leaving the capillaries.
51
What's urine?
A waste product from metabolic reactions which is toxic and high in nitrogenous content therefore has to be removed from the bloodstream (urea). The urinary system consists of two kidneys each with a ureter leading to the bladder and a urethra. Urine, the end result of the processes of filtration and reabsorption, typically contains a high concentration of urea and toxic substances.
52
What's serum?
Blood plasma which has had it's clotting factors removed. It contains electrolytes, antibodies, antigens, hormones and other soluble proteins that aren't involved in the coagulation (clotting) of the blood. It's used for blood typing and diagnostic tests.
53
What biofluids are in plants?
They include intracellular fluids e.g. Cytosol or cell sap, the vacuole contents, and the contents of specialised cells e.g. Phloem sleeve tube elements and xylem vessels. Xylem fluid is very dilute compared to phloem sap and cell cytoplasm. Unlike phloem sap, the contents of the xylem do not contain sucrose but otherwise the composition is similar and consists of ions and some organic molecules including auxins.
54
What are carbohydrates?
A group of substances used as an energy source, energy storage and for structural materials in organisms.
55
What's the general formula for a carbohydrate?
Cx(H2O)y E.g. C6H12O6 (glucose)
56
What are the 3 main types of carbohydrate?
Monosaccharides - simple sugars with the general formula (CH2O)n where n is 3-7 Disaccharides - double sugars formed from two monosaccharides Polysaccharides - large molecules formed from many monosaccharides
57
What are monosaccharides?
Simple sugars made by photosynthesis and are an energy source for respiration. They taste sweet, can form crystals and dissolve in water. They always contain a C=O (carbonyl group) and at least 2 OH (hydroxyl group)
58
What's a pentose or hexose?
The type of sugar relating to the structure based on the number of carbon atoms Pentose has 5 Hexose has 6
59
What are the disaccharides maltose, lactose and sucrose made from?
Maltose: a-glucose + a-glucose Lactose: a-glucose + galactose Sucrose: a-glucose + fructose
60
What's a glycosidic bond?
A covalent bond formed between two monosaccharides.
61
What's a condensation reaction?
The reaction to join two monosaccharides. When 2 monosaccharides are joined together a molecule of water is removed during the reaction and the two molecules are joined together to give a single molecule (disaccharide) joined by a covalent (glycosidic) bond. (The opposite is known as a hydrolysis reaction where water is added to break the glycosidic bond)
62
Why are condensation and hydrolysis reactions vital? | What are pathways?
They're significant to the formation and breakdown of compounds in cellular metabolism. (The sum of all the biochemical reactions in the cell is collectively referred to as cellular metabolism. It includes all the reactions involved in synthesising and breaking down macromolecules, and goes involved in generating small precursor molecules e.g. Amino acids for cellular requirements.) Pathways are the sequence of biochemical reactions which take place in metabolism
63
How do you remember the position of the OH and H atoms on alpha and beta carbohydrates.
ABBA Alpha Below Beta Above
64
What are disaccharides?
'Double sugars' They're more suitable for transport and storage than monosaccharides. The disaccharide sucrose is the form in which carbohydrates are transported in the phloem tubes of plants. It's also a storage carbohydrate in many plants e.g. Sugar cane.
65
What's lactose?
A disaccharide found in milk formed from the condensation of a-glucose and galactose, resulting in a b-glycosidic bond. Milk is rich in lactose and is a vital energy source. Our intestinal villi secrete the enzyme lactase (b-D-galactosidase) to digest (hydrolyse) it. This enzyme splits the lactose molecule into its two monosaccharides, glucose and galactose which can be absorbed.
66
What are polysaccharides?
Polymers formed from many repeated condensation reactions joining many monosaccharides (monomers). These long chains are held by glycosidic bonds and can be branched or un branched. They're large and ideal for storage.
67
What's glycogen?
A storage polysaccharide found in animal cells, fungal cells and many prokaryotic cells (NOT plant cells). It's a highly branched molecule (has many terminal end points) meaning a large number of single glucose molecules can be hydrolysed at any moment. During prolonged exercise, blood glucose levels fall so glycogen is quickly hydrolysed to glucose to raise glucose levels back up again.
68
What's starch?
A polysaccharide made in plant cells. It's made through the joining together of a-glucose molecules by condensation reactions.
69
What are the two forms of starch?
Amylose and amylopectin Both are hydrophilic but are too large to be soluble in water, making them useful as energy storage compounds. Starch is used to store glucose and as a temporary energy store in leaves when glucose is being made faster by photosynthesis than it can be used or moved.
70
What does alpha glucose + alpha glucose produce?
Maltose
71
What does alpha glucose + galactose produce?
Lactose
72
What does alpha glucose + fructose produce?
Sucrose
73
What is a hydrolysis reaction?
When water is added to break the glycosidic bond between disaccharides. The opposite of condensation reactions
74
What's the difference between alpha and beta glucose?
Alpha glucose has a OH molecule below the carbon (1) atom
75
What are reducing sugars?
Sugars e.g. lactose and maltose, which are able to reduce other molecules (e.g. Cu2+ to Cu+) This can be tested with Benedict's reagent
76
What is the test for a reducing sugar? How is it carried out? What are the results and why?
Benedict's test 1) Add equal volumes of Benedict's reagent and the solution to be tested for the presence of reducing sugars. 2) Heat in a boiling water bath for 5-10 mins 3) Observe the colour of the precipitate formed to estimate the quantity of reducing sugar present. The reagent contains copper (II) ions. The reducing sugar reduces the Cu2+ ions to Cu+ which forms a brick red copper (I) oxide precipitate. The colour of the solution changes from green to brick red according to the amount of sugar present. (this is a semi-quantitative test which can be made more quantitative by filtering and weighing the mass of precipitate produced.)
77
What is the Benedict's test for and what is the outcome?
A test for reducing sugars The Benedict's reagent contains copper (II) ions. The reducing sugar reduces the Cu2+ ions to Cu+ which forms a brick red copper (I) oxide precipitate. The colour of the solution changes from green to brick red according to the amount of sugar present. (this is a semi-quantitative test which can be made more quantitative by filtering and weighing the mass of precipitate produced.)
78
How is the test for a non-reducing sugar carried out?
1) Hydrolyse the sugar with an equal volume of dilute HCl in gently boiling water for 5 mins. 2) Slowly add NaHCO3 to neutralise the acid and test with pH paper to ensure it is neutral 3) Re-test the solution with Benedict's reagent in a boiling water bath for 5 mins. If a non-reducing sugar is present, it will now turn Benedict's solution yellow-brick red
79
Why is it essential to neutralise the acid before adding Benedict's solution when testing for a non-reducing sugar? (using sodium hydrogen carbonate)
Benedict's solution is an alkaline so it won't react if the solution has a low pH / is acidic
80
What is a biosensor?
An analytical device used to detect the presence of a chemical by combining a biological component. If the substance binds, a colour change or electrical change is produced.
81
How does a clinistrip work?
They (clinistix and diastix) detect if glucose is present They contain the enzyme 'glucose oxidase' which is attached to a pad at the end of the strip. If glucose is present, it will be oxidised to gluconic acid and hydrogen peroxide. The enzyme 'peroxidase' is also present on the pad which breaks down the hydrogen peroxide into oxygen and water. The oxygen then oxidises a colour dye on the pad. The intensity of the colour change indicates the amount of glucose present.
82
How do glucometers work?
They have the enzyme 'glucose hydrogenase' which converts glucose in the blood to gluconolactone and produces a small current detected by an electrode
83
Why is it important to measure glucose levels?
Many people who live with diabetes don’t feel any particular symptoms, unless they are experiencing hyperglycemia (glucose level is too high) or hypoglycemia (glucose level is too low). Hyperglycemia can cause significant damage to some organs, which then leads to complications of diabetes. These include: cardiac or vascular event, such as myocardial infarction (heart attack) or stroke; kidney problems that may require dialysis; eye problems, which may lead to loss of vision (blindness); sexual issues, such as erectile dysfunction; problems with circulation and scarring, which can lead to amputation. To avoid the complications of diabetes, you must control your blood glucose very well to minimize the risk of hyperglycemia. This will allow you to prevent the complications of diabetes.
84
What is a colorimeter?
A device which shines a beam of light through a solution and measures the absorbance or transmission of particular wavelengths of light. A photoelectric cell detects the light that has passed through the solution
85
Why is it important to choose the correct filter on a colorimeter?
A filter that produces light that will be absorbed by the solution should be used - A blue solution appears blue because it transmits blue light but absorbs red or orange.
86
How is the presence of starch detected?
By using iodine - KI reagent If there's no starch, the reagent remains yellow/brown however, in the presence of starch, it turns blue/black. Amylose reacts to form a deep blue-black whereas amylopectin produces a red-purple colour. This is due to how iodine molecules can easily fit into the hole in the middle of the amylose helix and this produces the blue-black colour. (qualitative test)
87
Why is it necessary to test (urine) for the presence of proteins?
It's presence can be an indication of kidney disease (proteinuria is urine with abnormally high levels of protein) Levels of kidney damage are identified by levels and types of proteinuria. This can cause heart and blood vessel disease. Small proteins however are filtered through the kidney's glomerulus.
88
What is the chemical test for proteins? | What are the results?
The biuret test 1) Add equal volumes of the sample to be tested and NaOH. 2) Add a few drops of copper sulfate solution and mix. 3) If the solution turns purple, protein is present. This is because the reagent has NaOH and copper (II) sulfate. In the alkaline conditions, the peptide bonds (from the protein) form a complex with the Cu(II) ions, making the solution purple.
89
How do urine test strips work?
The strip has a pad containing tetrabromophenol blue which changes from yellow to dark blue if proteins are present.
90
What is osmosis?
The passage of water molecules from an area of high water potential to an area of low water potential (ψ in kPa) across a partially permeable membrane. Water molecules posses kinetic energy and more until a dynamic equilibrium is established
91
what are the key points of water potential? | 5
- At STP (25 degrees C and 100kPa) pure water has a water potential of 0 - Adding solutes to water decreases its water potential as the solute molecules reduce the number of collisions the water molecules make with the membrane so there is reduced pressure on the membrane hence a lower water potential - Water potential of a solution is always below 0 - The greater the amount of solute, the more negative the water becomes - Always goes down the concentration gradient
92
How does osmosis occur within animal cells e.g. erythrocytes?
They have many solutes dissolved within them and are very flexible and thin so cannot withstand high pressure. When placed in pure water, water will therefore move into the cell cytoplasm. This exerts higher pressure on the cell which ruptures the cell membrane, known as lysis (bursting) (erythrocytes go through haemolysis but other cells experience cytolysis) When placed into a solution of concentrated solute, water will still move but this time it will move out of the cell which reduces pressure on the membrane, causing it to shrink and shrivel - it becomes crenated
93
What 3 structures are affected by osmosis in plants?
The central vacuole (contains salts, sugars and acids in solution) The protoplast (cell membrane, cytoplasm and tonoplast that surrounds the vacuole The cell wall (made of cellulose)
94
How does osmosis affect plant cells?
When placed in pure water, water enters the cell and the volume of the central vacuole and cytoplasm increase causing the protoplast to exert pressure on the wall however the cellulose wall is strong, won't burst and can prevent further entry of water molecules. (known as being turgid) When placed in a solution of concentrated solutes, water leaves the cell, volume and pressure decrease and the protoplast no longer presses against the wall (plasmolysis) until it comes away from the cell wall (plasmolysed)
95
What is the state of an animal and plant cell in higher, equal and lower water potential?
Animal cell: Lysis (swells and burts) No Change Crenated (shrivelled) Plant cell: Turgid (swells) Incipient plasmolysis (less pressure on cell wall) Plasmolyses (shinks & protoplast comes away from the cell wall)
96
Describe the structure of a triglyceride molecule:
It consists of 3 fatty acid molecules and a glycerol molecule bonded by an ester bond (between the glycerol and fatty acid).
97
State three roles of lipids in living organisms:
``` Insulation Protection Energy release and storage Membranes (phospholipid) Hormones Buoyancy Waterproofing ```
98
What is the difference between lipids in animals and plants?
Animal fats are mainly saturated, solid at room room temperature and the fatty acids have fewer/no double bonds.
99
Suggest two medical conditions associated with increased blood cholesterol levels:
Type 2 diabetes Coronary heart disease / heart attack / angina Stroke Atheroma
100
What is the test for a reducing and non reducing sugar?
Reducing: Benedict's reagent (copper sulphate and sodium hydroxide) which is added and heated and solid Cu2+ precipitate produced. Non-reducing: acid (HCl) is added then neutralised then heated and Benedict's reagent is added.
101
Describe the routes that water molecules take through the cell surface membrane:
It moves through the phospholipid belayer via protein channels.

Year 12 - Biology (15 decks)

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