Biological Molecules Flashcards
What are functions of water in living organisms?
- Reactant in chemical reactions e.g.hydrolysis
- Water is a solvent
- Transports substances, due to it being a liquid and solvent it can easily transport substances
- Helps control tempertaure because it has a high specific heat capacity and a high latent heat of evaporation
- Aid digestion (components of stomach acid + saliva)
- In skin to make it pliable
- Lubricant to help swallow
- Help cushion joints
- Less dense as a solid than liquid
What is high specific heat capacity?
The energy neede to raise the temperature of 1gram of a substance by 1 degree C
Why does water have a high specific heat capacity?
Because of its hydrogen bonds. The hydrogen bonds between water molecules can absorb a lot of energy so it takes a lot of energy to heat it up.
Why is having a high specific heat capacity useful?
Because it means water doesn’t experience rapid tempurature changes, making it a good habitat as it means the temperature is more stable.
Describe high latent heat of evaporation?
-It takes a lot of energy (heat) to break the hydrogen bonds, so water has high latent heat of evaporation because a lot of energy is used up when water evaporates.
How is high latent heat of evaporation useful?
It means that water is great for cooling things.
When mammals sweat, the sweat evaporates and cools the skin.
How does waters polarity make it useful?
It makes it cohesive. Water molecules are very cohesive because they are polar.
Why are water molecules polar?
Because they have slightly negatively charged oxygen atoms and slightly positivly charged hydrogen atoms.
Why is water being cohesive useful?
- It helps it to flow
- Makes it good for transpoting substances
- Helps water to be transported up xylem vessels in the transpiration stream
How does waters polarity make it useful?
Makes it a good solvent.
How does waters polarity help it dissolves biological substances effectivly?
- A lot of biological substances are ionic meaning that they are made from one positivly charged atom or molecule and one negativly charged.
- Due to water being polar, the positive end of the water molecule will be attracted to the negative ion and visa versa
- This means that the ion can be completely surrounded by water molecules (dissolved)
How does waters density help make it useful?
Water is less dense at solid than liquid because each water molecule make 4 hydrogen bonds to other water molecules making it a lattice shape.
-Ice floats, meaning it can form an insulating layer at the top of water to maintain the habitat below e.g. top of pond freezes over but bottom doesn’t so creatures don’t freeze
When is water most dense?
At 4 degrees C
Where do the hydrogen bonds occur in water?
H+ and O-
What is a polysaccaride?
A chain on monosaccarides, often a carbohydrate.
Describe the structure of glucose
-A hexose monosaccaride ( monosaccaride with six carbon atoms)
What are the two forms of glucose?
- Alpha and beta glucose
What is the structure of both glucose?
A ring structure
Explain the difference in structure between alpha and beta glucose
- Alpha glucose has the hydrogen on carbon 6 above the plain of the ring
- Beta glucose has the hydrogen on carbon 6 below the plain of the ring
How does glucose’s structure make it good for its function?
- It functions as the main energy source in animals and plants.
- Its structure makes it soluable so it can be easily transported and its chemical bonds contain a lot of energy, broken down=provide a lot of energy
Describe the structure of ribose
A pentose monosaccaride
What are the 3 elements that all carbohydrates are made up of?
Carbon, Hydrogen, Oxygen
For every carbon atom, generally how many H and O atoms are there?
2 hydrogen and 1 oxygen
What bond joind monosaccarides together
Glycosidic bond
Condensation reaction
Reaction where 2 molecules are joined together with the removal of water
Hydrolysis reaction
Reaction that occurs when a molecule is split into 2 smaller molecules with the addition of water. The water molecule reacts with the glycosidic bond to break it
Describe a condensation reaction involving amino acids
A H from the amino group joins a OH from the carboxyl group. A peptide bond forms. Water is lost
Structure of starch
-A mixture of 2 polysaccarides of alpha glucose- amylose and amylopectin
Function of starch
- Used in plant cells as an energy source.
- Plants store excess glucose as starch, and when a plant needs more glucose for energy it breaks down the starch to release glucose.
Describe the structure of amylose
- A long, unbranched chain of alpha glucose
- Angles of the glycosidic bonds give it a coiled structure
- This makes it compact which means its good for storage as it fits into a small space
- 1-4 glycosidic bond
- Insoluable in water
Describe the structure of amylopectin
- A long, branched chain of alpha glucose
- Its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily so glucose can be released quickly
Describe the function of glycogen
- Main energe storage material in animals
- Animals store excess glucose as glycogen, a polysaccaride of alpha glucose.
Describe the structure of glycogen
-Has many side branches coming off it, a 1-4 glycosidic bond for the straight chains and a 1-6 glycosidic bond for the branches.
What makes glycogen good for storage?
Its a very compact molecule
Describe the structure of cellulose
- Long, unbranched chain of beta glucose
- Straight chained molecules because of the way beta glucose bonds
What bond holds the cellulose chain together?
- Many hydrogen bonds link the chains together
- Form strong fibres called microfibrils
What do microfibrils do?
Provide structural support for cells e.g. in plant cell walls
Function of cellulose
A major component of cell walls
3 types of lipids
Triglycerides, phospholipids, cholestral
Describe the structure of a tryglyceride
-A molecule of glycerol with 3 fatty acids bonded to it
Describe the structure of a fatty acid
- Long hydrocarbon tails which are hydrophobic
- The tails make lipids insoluable
- All fatty acids have the same basic structure but the hydrocarbon tail varies
What bonds hold tryglycerides together?
Ester bonds
Describe how tryglcerides are synthesised
- Ester bond forms between the glycerol molecule and each fatty acid
- Each ester bond is formed by a condensation reaction
How is each ester bond broken back down?
Hydrolysis reaction
Name the process in which tryglycerides are synthesised
Esterification
Name the two kinds of fatty acids
Saturated and unsaturated
Describe a saturated fatty acids structure
Don’t have any double bonds between their carbon atoms
Describe an unsaturated fatty acid structure
Have at least one double bond between their carbon atoms
What are tryglycerides many used as in plants and animals?
Energy storage molecules
Why are tryglycerides good for storage?
- The long hydrocarbon tails of fatty acids contain lots of chemical energy = a lot of energy is released when they’re broken down
- They’re insoluable, so they don’t cause water to enter cells by osmosis, which would make them swell
How do tryglycerides arrange themselves in a cell?
Bundle together as insoluable droplets because the fatty acid tails are hydrophobic and so face inwards while the glycerol heads face outwards sheilding them from water
What are phospholipids used for in cells?
- Found in cell mambranes in eukaryotes and prokaryotes making up the phospholipid bilayer
- Contol what enters and leaves the cell
How does phospholipid’s structure help their function?
- Phospholipid heads are hydrophilic and tails are hydrophobic so they form a double layer with heads facing out
- The centre of the bilayer is hydrophobic so water soluable substance can’t pass through it- acts as a barrier
Structure of cholesteral and function
- Has a hydrocarbon ring structure attached to a hydrocarbon tail
- Ring structure has a polar hydroxyl (OH) group attached
- in eukaryotic cells, they help strengthen the cell membrane by interacting with the phospholipid bilayer
How cholesterals structure helps it function
- Has a small size and flattened shape, allowing the cholesteral to fit in between the phospholipid molecules in the membrane
- Bind to the hydrophobic tails of the phospholipids causing them to pack more closely together making the membrane less fluid and more rigid
Define protein
- A polymer made of long chains of amino acids
- Also known as polypeptides
Dipeptide
-Formed when two amino acids join together
What is the general structure of all amino acids?
-A carboxyl group (-COOH) and an amino group (-NH2) attach to a carbon atom
What is the difference between amino acids?
-The R (variable) group
What is in the R group of glycine?
-One hydrogen atom
What are the chemical elements that all amino acids contain?
- Carbon, Oxygen, Hydrogen and Nitrogen
- Some contain sulfur
What bond joins amino acids together?
-Peptide bonds
What type of reaction occurs to make a polypeptide?
-A condensation reaction
What is a condensation reaction?
- A reaction where one molecule of water is released.
- The -OH from the carboxyl group is removed from one amino acid and the -H from the amino group is removed from the other
Hydrolysis reaction
-Adding a water molecule to break a peptide bond
What are the four levels of protein structure?
- Primary structure
- Secondary structure
- Tertiary structure
- Quaternary structure
Primary structure of a protein
-The sequence of amino acids in a polypeptide chain
Secondary structure of a protein
- The bond that alter the shape of a polypeptide chain
- Hydrogen bonds form between nearby amino acids in the chain to coil to make an alpha pleated sheet or fold to make a beta pleated sheet
Tertiary structure of a protein
- The coiled or folded chain of amino acids is often further coiled or folded.
- More bonds form between parts of the polypeptide chain.
- For proteins made of a single polypeptide chain this is the final 3D structure
Quaternary structure of a protein
-The way several polypeptide chains that make a protein are held together by bonds/assembled
An example of a quaternary protein
-Haemoglobin, made of 4 polypeptide chains bonded together
Bonds in primary structure
-Peptide bonds
Bonds in secondary structure
-Hydrogen bonds
Bonds in tertiary and quaternary structure
- Ionic bonds
- Disulfide bridges
- Hyrdophobic and hydrophilic interactions
- Hydrogen bonds
Describe ionic bonds
-Attractions between negativly-charged R groups and positivly-charged R groups on different parts of a molecule
Describe disulfide bridges
-Whenever two molecules of the amino acid cytenine come close together, the sulfur atom in one cytenine bond to the sulfur atom in the other cytenine, forming a disulfide bond
Hydrogen bonds
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