Biological molecules Flashcards
What are the functions of water?
- Water is a reactant in lots of important chemical reactions, including hydrolysis reactions.
- Water is a solvent, and most biological reactions take place in solution so water is really essential.
- Water also transports substances. Because it is a liquid and a solvent it can easily transport lots of materials like glucose and oxygen around plants and animal cells.
- Water helps with temperature control as it has a high specific heat capacity and a high latent heat of evaporation.
- Water is a habitat due to its qualities of temperature regulation- meaning lots of organisms can survive and reproduce in it.
What is the structure of a water molecule?
A molecule of water is made up of two hydrogen atoms and an oxygen atom, held together by a shared pair of electrons/covalent bonds.
Why are water molecules dipolar?
Because the shared pair of electrons are pulled closer to the oxygen atom- due to a greater positive attraction- the oxygen atom becomes slightly negative and therefore the hydrogen atom becomes slightly positive. This slight charge on either atom makes it a polar molecule.
How do hydrogen bonds in water work?
The slightly negatively charged oxygen atoms attract the slightly positively charged hydrogen atoms of other water molecules.
This attraction is called hydrogen bonding and it gives water some of its useful properties.
How do hydrogen bonds give water a high specific heat capacity?
Specific heat capacity is the temperature required to raise 1 gram of a substance by 1 degree C. The hydrogen bonds between the water molecules can absorb a lot of energy. So water has a high heat capacity as it takes a lot of energy to heat up.
This means that water doesn’t experience rapid temperature changes making it a stable environment/habitat for organisms to live in.
How do hydrogen bonds give water a high latent heat of evaporation?
It takes a lot of heat energy to break the many hydrogen bonds in water so water has a high latent heat of evaporation as it takes a lot of energy to evaporate. This is useful in living organisms for cooling things- like sweat taking lots of heat away when it evaporates and thus cools us down.
How does water’s polarity make it very cohesive?
Cohesion is the attraction between molecules of the same type, water molecules are very cohesive because they are polar.
This helps water to flow, making it great for transporting substances. It also helps water to be transported up plant stems in the transpiration stream.
How does water’s polarity help to make it a good solvent?
A lot of important substances in biological reactions are ionic, meaning they are made up of one positive atom/molecule and a negative atom/molecule. Because the water is polar, the slightly positive end will be attracted to the negatively charged ions, and the negative end to the positively charged ions. This means the ions will be surrounded by water molecules/they’ll dissolve.
This is useful as ions can be dissolved in the water in the blood and then carried around the body.
Why is the fact that water’s less dense when it’s solid useful?
As temperature drops water cools down and turns from a liquid to a solid. Water molecules are held further apart in ice than in liquid water because each water molecule forms four hydrogen bonds with other water molecules- making a lattice shape. This makes ice less dense than water, which is why it floats.
This is useful in living organisms because in cold temperatures ice forms an insulating layer on top of the water and the water underneath doesn’t freeze and remains at a nice temperature and fish can still move around.
What are Carbohydrates?
Carbohydrates are polymers, polymers are molecules made up of many different smaller molecules called monomers bonded together. The monomers that make-up carbohydrates are called monosaccharides.
What kind of monosaccharide is glucose?
Glucose is a hexose sugar as it contains six carbon atoms.
What are the two structures of glucose?
There are two forms of glucose; alpha and beta glucose. They both form ring structures.
How is glucose’s structure related to its function?
It’s the main energy source in plants and animals so, its structure makes it soluble so it can be easily transported. Its chemical bonds also contain lots of energy.
What is ribose’s structure and function?
Ribose is a monosaccharide with five carbon atoms, meaning it is a pentose sugar. Its structure is: CH2OH-CH-CHOH-CHOH-CHOH-O- (back to CH)
It is the sugar component of RNA nucleotides
What are the bonds that monosaccharides form when bonded together?
A glycosidic bond (1,4 in glucose)
What is a condensation reaction (in polymerization)?
A hydrogen atom on one monosaccharide bonds to a hydroxyl group on the other, releasing a molecule of water.
What elements are all carbohydrates made up of?
Carbon, Hydrogen, and Oxygen. The ratio is usually CnH2nOn
What is a hydrolysis reaction (in polymerization)?
A molecule of water reacts with the glycosidic bond, breaking it apart.
How are disaccharides formed?
Disaccharides are formed when two monosaccharides join together,
maltose = glucose (A) + glucose (A)
sucrose = glucose (A) + fructose
lactose = glucose (A or B) + galactose
How are polysaccharides formed?
A polysaccharide is formed when more than two monosaccharides join together. For example, lots of glucose (A) join together to form amylose
What is the structure of starch?
- Starch is a mixture of two polysaccharides of alpha-glucose (amylose and amylopectin)
What is the function of starch?
- Plants store excess glucose as starch and use it as a store it can break down to get glucose when it is needed (because glucose is soluble and starch is not, it doesn’t mess with the water potential of the cell and cause osmosis.)
What is the structure and function of amylose?
Amylose is a long branch chain of alpha-glucose. The angles of the glycosidic bond give it a coiled structure. This makes it compact, so it’s really good for storage because you can fit more into a smaller space.
What is the structure and function of amylopectin?
It’s a long, branched chain of alpha glucose. Its side branches allow the enzymes to break down the molecule to get at the glycosidic bonds easily. This means that the glucose can be released quickly.
What is the structure of glycogen?
Glycogen is a polysaccharide of alpha glucose and its structure is very similar to amylopectin. However, it has more side branches coming off of it. Lots of branches mean that stored glucose can be released quickly, which is important for energy release in animals. It is also very compact, which means it is good for storage
What is the function of glycogen?
Animal cells get energy from glucose too. But animals choose to store excess glucose as glycogen- as it is insoluble.
What is the structure of cellulose?
Cellulose is made up of long unbranching chains of beta glucose. When beta-glucose molecules form they form straight-chain molecules. The cellulose chains are linked together by hydrogen bonds to form strong fibers called microfibrils.
What is the function of cellulose?
Cellulose provides structural support for cells (i.e. in plant cell walls)
What are triglycerides?
Triglycerides are macromolecules (complex molecules with a large molecular mass), as with all lipids they contain Carbon, Hydrogen, and Oxygen. They are composed of one molecule of glycerol with three fatty acid tails attached to them.
What is the structure of a triglyceride?
They are composed of one molecule of glycerol with three fatty acid tails attached to them. The fatty acid molecules have long tails made of hydrocarbons. The tails are hydrophobic, which means lipids are insoluble in water. All fatty acids have the same basic structure, but the hydrocarbon tail varies.
How are triglycerides and ester bonds related?
Triglycerides are synthesized by the formation of an ester bond between each fatty acid and the glycerol molecule. The ester bonds are formed by a condensation reaction. This is called esterification. Hydrolysis can reverse the ester bonds- breaking down the triglyceride using water.
What are the differences between saturated and unsaturated fatty acids?
Saturated fatty acids don’t have any double bonds between carbon atoms. Unsaturated fatty acids have at least one double bond between carbon atoms. Mono-unsaturated means one and poly-unsaturated means more than one.
(having a double bond causes the chain to kink- the more you have, the less straight the chain)
How are phospholipids similar to triglycerides?
Phospholipids are macromolecules. They’re pretty similar to triglycerides except one of the fatty acid molecules is replaced by a phosphate group. The phosphate group is hydrophilic while the fatty acid tails are hydrophobic.
How is the structure of Triglycerides related to their function?
They are used mainly as storage molecules in animals and plants, but some bacteria use them to store energy and carbon.
- The long hydrocarbon chains of the fatty acids contain lots of chemical energy which is released when they’re broken down. Because of this lipids contain twice as much energy/g as carbohydrates.
- They’re insoluble so they don’t cause water to enter the cell via osmosis. They bundle together as insoluble droplets due to the hydrophobic tails bundling together using their glycerol heads to shield themselves.
