Chapter 2 Water Flashcards
What is the structure of a water molecule?
Consists of 2 hydrogen atoms and one oxygen atom joined by shared electrons (covalent bonds)
Shared negative hydrogen electrons are pulled towards the oxygen atom, making the molecule polar.
What charge do the hydrogen and oxygen atoms acquire in a water molecule?
Slightly negatively charged oxygen (δ-) and slightly positively charged hydrogen (δ+)
This occurs due to the unequal sharing of electrons.
How do hydrogen bonds form between water molecules?
Slight negatively charged oxygen atoms attract slightly positively charged hydrogen atoms in adjacent water molecules
This is a result of dipoles formed by electronegativity.
How much weaker are hydrogen bonds compared to covalent bonds?
20 times weaker
Hydrogen bonds are technically weak intermolecular forces, not actual bonds.
What is the significance of water’s high specific heat capacity?
It helps keep aquatic habitats thermally stable and stabilizes internal body temperature as the environment changes
SHC = energy required to raise the temperature of 1g of water by 1°C.
What is the biological importance of water being transparent?
Allows light to pass through, which is important for the light-dependent stage of photosynthesis
This transparency facilitates the photosynthetic process in aquatic environments.
What is meant by the high heat of latent evaporation of water?
Energy required to break hydrogen bonds between water molecules to convert water from liquid to gaseous state
Important for thermoregulation in mammals, such as cooling by sweating.
Why is cohesion important in water molecules?
It allows the formation of long continuous columns of water in xylem vessels during transpiration
Cohesion is the attraction between dipoles of adjacent water molecules forming hydrogen bonds.
What role does water play as a universal solvent?
Carries polar molecules and ions, dissolving them for transportation and facilitating biochemical reactions
Important for transporting ions, proteins, and waste products in biological systems.
What happens to water when it freezes?
H2O molecules are held further apart, causing density to decrease and allowing ice to float
This insulates water beneath the ice and provides habitats for some organisms.
What is adhesion in the context of water?
Hydrogen bonding allows water to stick to surfaces like the lining of xylem vessel walls and cellulose in cell walls
This aids in the movement of water in plants and reduces friction in various biological fluids.
What is the definition of biofluids?
Liquids within the body, including those secreted or excreted by the body
Examples include bile, semen, breast milk, and cerebrospinal fluid.
What is the process of forming tissue fluid?
Hydrostatic pressure gradient forces plasma fluid out of capillaries through fenestrations
This is an example of ultrafiltration.
What is lymph and how is it formed?
Fluid that drains excess tissue fluid back into the blood circulatory system via lymph vessels
Lymph is similar to tissue fluid but contains more leucocytes.
What are the main components of serum?
Plasma with clotting factors removed, including electrolytes, antibodies, hormones, and soluble proteins
Serum is used in blood typing and diagnostic testing.
What is the primary function of plasma?
Transports dissolved substances and provides body cells with water
Plasma accounts for ~50-60% of total blood volume.
What are the functions of carbohydrates in biofluids?
Structural, cell markers, energy source, energy store, and macromolecule synthesis
Functions summarized as “SCEEM.”
What is a condensation reaction?
Joining of two monomers by the removal of H2O to form a new covalent bond
This process is essential for forming disaccharides.
What is the structure of glycogen?
A branched molecule formed from many α-glucose molecules via glycogenesis
It is compact and insoluble, allowing for efficient storage.
What is the role of serum albumin?
Regulates osmotic balance and pH buffering
It also aids in calcium transport.
What are the two main categories of biofluids?
Intracellular and extracellular
Intracellular includes cytosol; extracellular includes plasma and tissue fluid.
What is the primary characteristic of a polysaccharide?
Made of many monosaccharide molecules joined by glycosidic bonds
Polysaccharides are complex carbohydrates formed by the polymerization of monosaccharides.
What are the two polysaccharides that form starch?
- Amylose
- Amylopectin
Where is starch primarily located in plants?
Starch grains inside plant cells, seeds, and storage organs e.g. tubers
What is the role of starch in leaves during photosynthesis?
Acts as a temporary energy store when glucose is produced faster than it can be stored or moved
What type of bond joins glucose molecules in starch?
Glycosidic bonds
What are the common properties of amylose and amylopectin?
- Compact
- Hydrophilic but large, therefore insoluble
- Does not affect the water potential of the cell
What is the structure of amylose?
Linear structure
What is the structure of amylopectin?
Highly branched structure with α1-6 glycosidic bonds at branching points
How many glucose molecules can be found in a single amylose helix?
300 to 3000 glucose molecules
How many glucose molecules can be found in a single amylopectin molecule?
2000 to 200,000 glucose molecules
Which polysaccharide makes up approximately 30% of starch?
Amylose
Which polysaccharide makes up approximately 70% of starch?
Amylopectin
What is a reducing sugar?
Sugars that can donate an electron to another molecule
What is the qualitative test used to detect reducing sugars?
Benedict’s test
What happens in Benedict’s test when reducing sugar is present?
Cu2+ is reduced to Cu+
What is the color of the precipitate formed in Benedict’s test?
Copper oxide (CuO)
What is the first step in the method for testing for reducing sugars?
Add an equal volume of Benedict’s reagent and the solution to a boiling tube
What is the temperature and duration for heating the boiling tube in Benedict’s test?
90°C for 5-10 minutes
What is the difference between qualitative, semi-quantitative, and quantitative tests?
- Qualitative: presence or absence
- Semi-quantitative: relative quantity
- Quantitative: absolute quantity
What is the filtration method used for in Benedict’s test?
To make the test more quantitative by measuring the mass of the precipitate
What are some common errors in the filtration method?
- Not removing all precipitate
- Loss of precipitate due to air currents
- Loss through filter paper pores
What improvements can be made to increase accuracy in the filtration method?
- Use finer graded filter paper
- Avoid spills
- Wash test tube and filter multiple times
- Dry to constant mass
- Take repeat readings
What principle does a colorimeter operate on?
Measures absorbance or transmission of light through a solution
What is the purpose of zeroing the colorimeter?
To ensure it reads 0% absorbance and 100% transmission
What is the difference between absorbance and percentage transmission?
- Absorbance: light absorbed by the solution
- % Transmission: light passing through the solution
What is a biosensor?
An analytical device using a biological molecule to detect a specific chemical molecule
What are the main components of a biosensor?
- Molecular recognition (bioreceptor)
- Transduction
- Amplifier
- Display (processor)
What is the normal range for blood glucose levels?
3.89 to 5.83 mmol dm-3
What is the function of glucose oxidase in Clinistix?
Catalyzes the reaction between glucose and oxygen
What color change indicates abnormal glucose levels in Clinistix?
Dark ‘pink’ or dark ‘brown’ color
How do glucometers detect glucose in blood?
By measuring the electrical current generated from the reaction of glucose with glucose dehydrogenase
What are the advantages of using biosensors?
- Specificity
- Quantitative results
- Small sample required
- Rapid results
What are some disadvantages of color change biosensors?
- Subjective color comparison
- Semi-quantitative readings
- Single-use plastic waste
What are some advantages of chemical change biosensors?
- Absolute values
- No subjective interpretation
- Can be used with smartphone apps
What is the method for testing for non-reducing sugars?
Hydrolyze with hydrochloric acid, neutralize, then test for reducing sugars
What is the role of hydrochloric acid in testing for non-reducing sugars?
Hydrolyzes glycosidic bonds in disaccharides
What should be done after adding hydrochloric acid in the non-reducing sugar test?
Neutralize with sodium hydrogen carbonate before testing with Benedict’s reagent
What is the effect of HCl on disaccharides like sucrose?
HCl hydrolyses the glycosidic bond within disaccharides, resulting in glucose and fructose.
What is the purpose of adding sodium hydrogen carbonate to the boiling tube?
To neutralise the acid since Benedict’s reagent is alkaline (~pH 10) and no reaction will occur at low pH.
How is pH determined in the solution after adding sodium hydrogen carbonate?
By testing the contents with pH paper until it shows pH 7.
What indicates the presence of a non-reducing sugar in the Benedict’s test?
A positive result after pre-treatment with HCl and sodium hydrogen carbonate.
What color indicates a negative reaction in a starch test using potassium iodide?
Yellow-brown.
What color complex forms when iodine interacts with amylose?
Blue-black complex.
What is proteinuria?
An abnormally high level of protein in the urine.
What can the presence of different proteins in urine indicate?
Specific disorders.
What does the presence of albumin in urine indicate?
Albuminuria.
What are potential reasons for proteins appearing in urine even with healthy kidneys?
- Small proteins filtered out in the glomerulus * Proteins produced by cells lining the genitourinary tract.
What is the method for the qualitative test for proteins?
Add sodium hydroxide and copper (II) sulfate, then observe for color change.
What color indicates the presence of peptide bonds in the Biuret test?
Lilac solution.
What is the chemical basis for the Biuret test?
Reaction between N atoms in peptide bonds and Cu2+ ions in alkaline solution.
What are Clinistrips used for?
To detect the presence of proteins in urine via colorimetric tests.
How does urine pH affect the accuracy of protein test strips?
Alkaline conditions can lead to false negatives or positives.
Define osmosis.
Movement of water molecules from higher water potential to lower water potential through a partially permeable membrane.
What is the water potential of pure water at standard conditions?
0 kPa.
What happens to water potential as solute is added?
It becomes negative.
What are the three types of solutions based on water potential?
- Hypertonic * Isotonic * Hypotonic.
What happens to an erythrocyte in a hypertonic solution?
Water moves out, causing the cell to crenate.
What is incipient plasmolysis in plant cells?
State where the protoplast is not applying pressure on the cell wall.
What is turgor pressure?
Pressure exerted by the protoplast against the cell wall in plant cells.
What is the relationship between water potential (Ψ), solute potential (Ψs), and pressure potential (Ψp)?
Ψ = Ψs + Ψp.
What is the method for determining the water potential of plant cells?
Prepare sucrose solutions, weigh potato cylinders, and measure mass change after immersion.
What does a large error bar indicate in data interpretation?
Less reliable data set with greater spread from the mean.
What is the main limitation when using different potatoes for experiments?
Variations in age and type of potatoes.
What is a potential error when weighing potato cylinders?
Not blotting properly, leading to inaccurate mass readings.
What is the significance of the point where the trend line crosses the x-axis in a water potential experiment?
Indicates the concentration of sucrose solution with the same water potential as the potato tissue.
