Carbohydrates, Lipids, Proteins and Enzymes Flashcards
Which elements do carbohydrates contain?
Carbon, oxygen and hydrogen
What are monosaccarides?
A single sugar monomer that are soluble
What is a disaccharide?
Two monosaccharides covalently linked together by condensation reaction that are soluble
What is a polysaccharide?
Many monosaccharides covalently linked that is insoluble in water
What is a glyosidic bond?
Covalent bond between two sugar molecules
What does a condensation reaction do?
A hydrolysis reaction?
Condensation- link monosaccharides together
Hydrolysis- Breaks di- and polysaccharides down. Catalysed by specific enzymes
Give examples of monosaccharides
Glucose, fructose, galactose, ribose and deoxyribose
What are hexoses and what are pentoses?
Hexoses- six C atoms - glucose
Pentoses- five C atoms - ribose
Draw a- D- glucose
Draw beta- d- ribose
What are the similarities between glucose and ribose?
- All atoms in the ring are C except for one O
- There is one side chain
- All the C atoms except for the one with the attached side chain have one OH and H group
Which form do living organisms use?
D-forms (right handed)
Where is ribose found?
found in RNA and ATP
Draw b- D- glucose
Give examples of disaccharides
Lactose, maltose and sucrose
Give examples of equations of formation of disaccharides
glucose+glucose= maltose+ h2o
]glucose+ galactose = lactose+ H20
glucose+ fructose= sucrose+ H20
What are examples of polysaccharides?
Starch, cellulose and glycogen
What are the bonds that link glucose subunits?
Glycosidic bonds between C1 of one glucose and the C6 of another glucose
What happens in more branched molecules of glucose?
Glucose molecules can be loaded and unloaded more rapidly because there are more sites for glucose to attached or detached.
Describe cellulose (general)
Component of plant cell wall
Polymer of b-D-glucose
unbranched
Describe the orientation of glucose units in cellulose
Glucose units alternate so polymer is straight.
Cellulose molecules are aligned in parallel and are linked by hydrogen bonds forming bundles called cellulose microfibrils.
What are cellulose microfibrils?
They have high tensile strength and are the basis of plant cell walls and prevent cell bursting.
What is starch?
Store of glucose in plants bc it is insoluble in water. It allows large amounts of glucose to be stored without causing osmotic problems. It is energy store in seeds and storage organs
Describe the structure of starch
Polymer of a-D-glucose
Same orientation of glucose units so polymer is helical
Does not have a fixed size
Exists in two forms- amylose and amylopectin
Describe amylose and amylopectin
Amylose- 1,4 glycosidic bonds, is unbranched and has a helical shape
Amylopectin has some 1,6 glycosidic bonds in addition to 1,4 bonds, is branched and has a more globular shape.
What is glycogen?
Store of glucose in animals. Stored in liver and muscles. It is insoluble in water, large amounts can be stored without causing osmotic problems.
Describe glycogen in relation to its structure
Polymer of a-D- glucose
same orientation of glucose units so polymer is helical
has 1,4 and 1,6 glycosidic bonds so it is branched. It has more 1,6 glycosidic bonds than amylopectin so it is more branched and compact
Does not have a fixed size
What elements do lipids contain?
Carbon
Hydrogen
Oxygen
Describe the characteristics in lipids
Mostly/entirely hydrophobic
Insoluble in water
Diverse group
What are the three main types of lipids?
Triglycerides
Phospholipids
Steroids
What is the structure of a fatty acid and what is the general formula?
CH3(CH2)nCOOH
What is the range of the length of the fatty acid chain?
14-20 carbon atoms
What is the difference in saturated or unsaturated fatty acids?
Saturated fatty acids- all C atoms in the chain are linked to each other by single covalent bonds
Unsaturated fatty acids- there are one or more double bonds between C atoms. They are monosaturated if they have one double bond. They are polysaturated if they have more than one double bond
What can unsaturated fatty acids be?
Cis or trans
What is the structure of cis unsaturated fatty acids?
The H atoms are bonded to C atoms on the same side of a double bond. The molecule bends where there is a double bond. Thus they are loosely packed. The melting point is lower as they are less good at packing together so they are liquid at RT- oils.
What is the benefit of cis unsaturated fatty acids in the membrane?
Phospholipids with this increase membrane fluidity because the kinks make the fatty acids less good at packing and lower the mp.
What is the structure of trans unsaturated fatty acids?
The H atoms are bonded to C atoms on opposite sides of a double bond. Trans fatty acids do not have a bend but are straight molecules. Thus they are tightly packed and have a higher melting point and exist as a solid. They are produced artificially.
Describe triglycerides
Consist of three fatty acids and one glycerol
Each fatty acid is linked to glycerol through ester bond by a condensation reaction
Can be fats or oils
Used as energy stores, heat insulators and shock absorbers
Draw a triglyceride
Describe a phospholipid
Consist of one glycerol, two fatty acids and one phosphate group
Amphipathic
Structural component of membranes
Describe steroids
Structure with four fused rings
Ex- cholesterol, testosterone, oestrogen, progesterone
Function as hormones and cholesterol is a structural component of animal membrane
State the negative correlations found for CHD.
Populations that have diets rich in cis-monosaturated fatty acids have a negative correlation of CHD.
Possible explanations- large amounts of such fats, genetic, other aspects of their diet
State the positive correlation found in CHD
Positive correlation between large amounts of trans-fat consumed and rate of CHD. There is evidence that there is a causal link between consumption of trans-fats and CHD.
Compare and contrast carbohydrates and lipids as energy stores in humans
- Lipids and carbohydrates are both used for energy storage in humans.
- Lipids are stored as
fat/triglycerides and carbohydrates as glycogen - Lipids are long-term energy stores, while carbohydrates are short-term energy stores
- The amount of energy released in cell respiration per gram of lipid is double the amount released per gram of carbohydrates.
- Carbohydrates are mobilized/taken out of storage more rapidly than lipids making their energy more quickly available
- Carbohydrates are easier to transport than lipids making their energy more accessible. This is because small carbohydrates, e.g. glucose, are soluble in water and can be transported
in the plasma, whereas lipids/fatty acids are insoluble - Lipids can be used only in aerobic cell respiration, while glucose can be used in both aerobic and anaerobic respiration
- Glycogen is stored in liver and muscle, whereas lipids are stored in adipose tissue, which is
located beneath the skin and around some organs, e.g. the kidneys. Adipose tissue under the skin also functions as a heat insulator
What is Body Mass Index?
Used to assess whether a person’s body mass is at a healthy level
What is the formula for BMI?
Mass in kilograms/ (height in meters)2
Units are kg m-2
What does exergonic mean?
If the reactants have more energy than the products
What does endergonic mean?
If the reactants have less energy than the products
What are catalysts?
Substances that speed up chemical reactions without being changed themselves
What are enzymes?
Globular proteins that act as biological catalysts: they speed up reactions in cells by reducing the activation energy without being changed themselves
Where does the substrate bind?
Active site
What must a substrate have in order to take part in a reaction?
It has to gain energy to reach the transition state in which it is more likely to react- this is the activation energy.
What does the activation energy do?
Used to weaken the bonds within a substrate. Enzymes increase the rate of reaction by reducing the activation energy but the net change of the reaction is NOT changed
Describe the lock and key model
Enzymes are specific for their substrate- enzyme- substrate specificity
Enzyme- substrate specificity is due to the active site being specific for a substrate. The enzyme’s active site and the substrate have complementary shapes that fit together. They also have chemical properties that match each other .
The substrate and enzyme only bind to each other if there is a successful collision.
Substrates are converted into products while they are bound to the active site, the products are then released and the active site is free to catalyse another reaction.
Describe the induced fit model
As the substrate approaches, there is a conformational change of the enzyme and its active site so that the shape of the active site becomes complementary to that of the substrate improves its fit for the substrate
Binding to the active site results in weakening of the bonds within the substrate
The reaction occurs and substrate is converted into product. Products dissociate and the enzyme returns to its original conformation.
This is why enzymes exhibit broad specificity