Chapter 1 Flashcards
What are biological molecules?
Biological molecules are the basic molecules that ultimately make up all living organisms.
What bonds hold biological molecules together?
Ionic, Covalent, Disulphide, and Hydrogen
What is a hydrolysis reaction?
A reaction that breaks down molecules.
What is a condensation reaction?
A reaction that joins molecules.
What is the role of carbohydrates in living organisms?
Energy source (respiration) Energy store (starch in plants) Structure component (cellulose in plant cells)
Approximately how much of the cell do carbohydrates make up?
10% of the cell’s organic matter
What elements are carbohydrates made up of?
Carbon, Hydrogen, and Oxygen
What are the simplest carbohydrates called?
Monosaccharides.
What are monosaccharides?
The monomers of carbohydrates.
What are some properties of carbohydrates?
Soluble in water
Sweet tasting
Form crystals
How are monosaccharides grouped?
Based on the number of carbons they have.
3 carbons - trioses
5 carbons - pentoses
6 carbons - hexoses
What are the most common monosaccharides, and how do they occur? What structures do they form?
The most common monosaccharides are the hexoses.
These include glucose and fructose.
Pentose and hexose sugars occur as ring structures.
Glucose and fructose both have the formula of C6H12O6.
How can they both have the same formula yet be different sugars?
Glucose and fructose are structural isomers.
This means that the atoms are arranged differently
Show how the structures of glucose and fructose differ.
[Pictures on desktop]
What are the isomers of glucose?
Alpha and Beta glucose
How do the structures of alpha and beta glucose differ?
Beta glucose has the H on the bottom.
What is the role of glucose in biology?
Soluble in water.
Easily broken down.
Small molecule
How is a disacharide formed?
When two monosaccharides join together a disaccharide is formed.
Explain the formation of disaccharide
Two monosaccharides joined together by a condensation reaction, forming a covalent bond called a glycosidic bond.
How is the bond between maltose molecules formed and what is it called?
The glycosidic bond is between carbon atoms 1 and 4 and adjacent glucose units. This is called an alpha 1-4 glycosidic bond.
How are different disaccharides formed?
If the combination of monosaccharides is different or the link between adjacent carbon atoms is different.
Give examples of disaccharides.
Maltose - Two α glucose molecules.
Sucrose – α glucose and β fructose.
Lactose – α glucose and galactose.
What is needed for the formation of a disaccharide?
Two monosaccharides needed. Condensation reaction. Water released. Glycosidic bond formed. Glycosidic bond formed between adjacent carbons (1-4 glycosidic bond in maltose).
What is the difference between the formation of a monosaccharide and disaccharide?
Formed when different monosaccharides used.
Different carbon links.
Lactose (glucose and galactose).
Sucrose (glucose and fructose).
What are polysaccharides and how are they formed?
Polysaccharides are the polymers of carbohydrates.
Polysaccharides are formed when more than two disaccharides join together.
Give three examples of polysaccharides and explain how they differ.
Cellulose
Starch
Glycogen
Each have a unique structure and function due to the monosaccharides used and the glycosidic bonds formed.
STARCH
STARCH
What is starch?
Starch is a polysaccharide formed from condensation reactions between α glucose molecules.
What does starch consist of?
Amylose and Amylopectin.
What does amylose consist of?
Amylose consists of α glucose molecules attached in a 1-4 glycosidic bond.
Explain the structure of amylose.
Each chain is coiled in a helical structure.
The structure is held together by hydrogen bonds.
Explain the structure of amylopectin.
Amylopectin, like starch, has 1-4 glycosidic bonds.
However, amylopectin also has 1-6 glycosidic bonds.
This gives amylopectin a branched structure.
How does the structure of amylose contribute to its function?
The helical structure of amylose makes starch a very energy dense molecule.
Meaning many glucose molecules are packed into a small space.
Starch is also insoluble in water which makes it an excellent method of storing potential glucose molecule that could be used later in respiration.
How is food tested for starch?
Food containing starch is tested by iodine. The color of iodine changes from yellow to blue-black.
Method:
1-Place 2cm3 of the sample being tested into a test tube.
2-Add two drops of iodine solution and shake or stir.
3-The presence of starch is indicated by a blue-black coloration.
CELLULOSE
CELLULOSE
What is cellulose? Explain its structure.
Cellulose is a polymer of β glucose molecules.
Second β glucose molecule is rotated 180 degrees.
This results in the polymer consisting of long straight chains.
Give features of cellulose.
Cellulose is a structural carbohydrate and is only found in plants.
Because of the glucose monomers containing so many OH groups, lots of hydrogen bonds can be formed between them.
This makes cellulose very strong as it can withstand the hydrostatic pressures in a plant cell without bursting.
GLYCOGEN
GLYCOGEN
What is glycogen?
Often referred to as animal starch. Similar to starch, glycogen also consists of α glucose molecules.
Explain the structure of glycogen.
The structure of glycogen is similar to that of amylopectin in that it is a branched molecule and contains 1-4 and 1-6 glycosidic bonds. However, there are fewer 1-4 glycosidic bonds and more 1-6 glycosidic bonds, which makes is more branched than amylopectin.
How does the level of energy differ from glycogen and starch?
Glycogen is also less dense and more soluble in comparison to starch. However, it is still energy dense.
What do all amino acids have in common?
They all share the same basic structure (N-C-C Backbone)
How many different R groups are there?
20
Explain how a dipeptide is formed.
Two amino acids Condensation reaction Water released Bond between carboxyl group of one amino acid and amino group of another Peptide bond formed Dipeptide molecule produced
What do the functions and properties of a protein depend on?
Its structure.
What are the unique sequence of amino acids in a protein is referred to as?
Primary structure
What does the primary structure show?
The sequence of amino acids that make up a protein.
The first level of protein structure is referred to as the _______ ________. The primary structure is the simplest way of showing the ______ _______ found in a _______ molecule. Each amino acid is joined by forming a ________ bond between each amino acid. The structure and ________ of a protein depends on the _______ sequence of amino acids found in the primary structure.
The first level of protein structure is referred to as the primary structure. The primary structure is the simplest way of showing the amino acids found in a protein molecule. Each amino acid is joined by forming a peptide bond between each amino acid. The structure and function of a protein depends on the unique sequence of amino acids found in the primary structure.
How is tangling and breaking avoided in amino acid chains?
the chain is stabilised by hydrogen bonds between a =O in the amino group and N-H of another amino acid.
If alpha bonding occurs in chains how do they change in structure?
If this bonding occurs within one polypeptide chain, the chain coils into an alpha helix.
If beta bonding occurs between chains how do they change in structure?
If this bonding occurs between different, parallel polypeptide chains, the chains fold in beta pleated sheets.
Explain what is meant by the secondary structure
Alpha helix with one polypeptide chain. (1)
Coil structure (1)
Beta pleated between parallel polypeptide chains. (1)
Hydrogen bonds hold structure together. (1)
Explain what is meant by the tertiary structure
The tertiary structure is when these α coils or β pleats themselves coil or fold.
This 3-D shape is held together by a number of different bonds.
Hydrogen, Ionic bonds and Disulphide bonds.
The protein’s tertiary structure is vital to its function.
Where do hydrogen bonds form?
Whenever there are slightly +ve and –ve charged areas (either in a R group or between amine and carboxyl groups).
Weak hydrogen bonds will form.
Where do disulphide bonds occur?
Some amino acids (cysteine) contains sulphur.
Where two cysteine molecules are close to each other the two sulphur molecules form a covalent bond (disulphide bond).
Where do ionic bonds form?
Some R groups can carry a +ve or –ve charge.
If a +ve and –ve charge are found close to each other an ionic bond is formed.
Explain how hydrophobic and hydrophilic parts of the chain contribute to its shape.
Hydrophobic parts of a R group tend to dissociate with water.
Hydrophilic parts of a R group are often found on the edge of a polypeptide chain.
These interactions often cause the polypeptide chain to twist and change the shape.
Can be useful in biology to allow certain proteins move around in water.
How is the quaternary structure of a protein formed?
When more than one polypeptide chain is joined together
Example proteins that have a quaternary structure and how are they held together?
Insulin and haemoglobin with hydrogen, disulphide and ionic bonds
What do globular proteins consist of? Give examples.
Globular proteins consist of polypeptide chains that fold up into a spherical shape.
Antibodies, Enzymes, Haemoglobin, Some hormones.
Are globular proteins soluble or insoluble in water?
Soluble
What does haemoglobin consist of?
4 polypeptide chains with two alpha chains and two beta chains.
Consist of many different amino acids. (approx. 140).
The four chains are held together to form a unique tertiary and quaternary structure.
What is the function of haemoglobin?
To carry O2 from the lungs to respiring cells.
Where does the oxygen bind to in the haemoglobin?
The haem group which contains iron ions.
What are the structures found in proteins that are not amino acids?
Prosthetic groups which are only found in globular proteins.
What do fibrous proteins consist of?
Long polypeptide chains which run parallel to one another.
What is the function of fibrous proteins?
Structural
List properties of fibrous proteins that make them good for tendons
Insoluble.
Rigid.
High tensile strength.
Properties of collagen
three polypeptide chains wound together.
Each of the three chains are coiled themselves.
Forming a triple helix.
Collagen is very strong because covalent bonds (called cross links) are formed between each chain.
These cross links occur staggered along the polypeptide chains.
This results in a collagen fibril.
Many fibrils form collagen fibre.
Structural properties of collagen
The triple helix is held together by covalent bonds.
Every third amino acid in collagen is glycerine (the smallest amino acid).
This allows the chains to pack together.
The side chains of other amino acids are hydrophobic.
This means collagen is insoluble in water.
LIPIDS
LIPIDS
How much of the cell do lipids make up? and what do they contain?
About 5% of the organic matter of the cell. They contain carbon, hydrogen, and oxygen. (less oxygen than carbohydrates).
What are lipids referred to when they are solid and when they are liquid?
Solid - lipid
Liquid - oil
What is the solubility of lipids?
They are insoluble in water.
Why are lipids needed in the body?
Energy source. (broken down to release energy in respiration)
Energy storage. (stored in adipose tissue usually under the skin)
Cell membranes
Insulation (Found surrounding nerve cells)
Protection (waxy cuticle in a leaf containing a layer of lipids)
Some hormones (steroids) are lipids.
What are the three types of lipid?
Triglycerides,phospholipids, and cholesterol.
What is the main function of triglycerides?
Energy storage. Energy can be released from the breaking down of the hydrocarbon tails in the fatty acids. They are found in the fats and oils.
What are triglycerides made up of?
One glycerol and three fatty acids. The glycerol molecule remains the same, however the fatty acids can vary slightly.
What makes a fatty acid unsaturated? Give a property of unsaturated fats.
Introducing c=c bonds makes a fatty acid unsaturated. This will push the fatty acids away from each other and makes them more fluid.
Unsaturated fats tend to be fluid while animal fats contain c-c and are solid.
Why are triglycerides hydrophobic?
Because they are insoluble in water, they cannot from hydrogen bonds with water molecules since the charges are evenly distributed throughout the structure. They are stored in adipose tissue.
What does the respiration of lipids require?
The hydrolysis of the ester bonds holding the fatty acids and glycerol together. They are then broken down completely to produce carbon dioxide and water. This process releases lots of energy.
Describe the structure of phospholipids.
2 fatty acids attached to the glycerol. The third hydroxyl group of the glycerol is covalently hydrophilic while the fatty acid group is hydrophobic.
What makes phospholipids good in cell membranes?
The water solubility of the phosphate group.
What is cholesterol?
A type of lipid that doesnt contain glycerol and fatty acids. It is a small molecule with a 4 ring carbon structure, mainly found in cell membranes.
Where in the cell membrane is the cholesterol found?
In between phospholipids, which helps with maintaining the strength and stability of the cell membrane.
How does temperature affect the function of cholesterol?
Low temperatures - prevents crystallization
High temperatures - prevents excessive fatty acid mobility which could affect the permeability of the membrane
