Biological Molecules Flashcards
What is a monosaccharide?
A carbohydrate containing a single sugar molecule. Monosaccharides act as monmers for longer chain polysaccharides.
What is A disaccharide?
A carbohydrate containing 2 sugar molecules joined by a glycosidic bond during a condensation reaction.
What is a polysaccharide?
A carbohydrate made from multiple monosccharide monomers.
What are the 3 main monosaccharides?
Glucose
Fructose
Galactose
What are the 3 main disaccharides?
Maltose (2 Alpha glucose molecules)
Sucrose (1 Alpha glucose molecule and 1 fructose molecule)
Lactose (1 Alpha glucose molecule and 1 galactose molecule)
What are the 3 main polysaccharides?
Starch (Polymer of Alpha glucose)
Glycogen (Polymer of Alpha glucose)
Cellulose (Polymer of Beta glucose)
What is the test for reducing sugars (glucose, fructose, galactose, lactose and maltose)?
Benedicts test:
1. Crush or grind sample and mix strongly with water
2. Add Benedict’s reagent
3. Boil
4. A positive result is indicated by a clour change from blue to brick red (A semi-quantitative result gives a colour change from blue to green, yellow or brick red depending on concentration)
What is the test for non reducing sugars (sucrose)?
Following a negative result for reducing sugars:
1. Add hydrochloric acid
2. Boil
(This hydrolyses Sucrose into glucose and Fructose)
3.Add sodium hydrogen carbonate to neutralise
4.Repeat Benedict’s test. A positive result indicates the presence of reducing sugars in the original sample.
What is the structure of starch?
Starch is composed of 2 components - amylose and amylopectin (both polymers of alpha glucose):
Amylose - a long unbranched chain of alpha glucose that is tightly coiled allwing many glucose molecules to be stored in a small space
Amylopectin - a highly branched chain of alpha glucose. This provides a higher surface area allowing enzymes to quickly release sugars for respiration
What is the structure of glycogen?
Highly branched structure of alpha glucose allowing enzymes to quickly release sugars for respiration.
What is the structure of cellulose?
Long unbranched chain of beta glucose called microfibrils. As the hydroxyl groups on beta glucose molecules have different orientations, every second beta glucose molecule ust be inverted in order for a glycosidic bond to form. There are hydrogen bonds between microfibrils providing strength and rigidty to the cell wall.
What are the 2 main lipid molecules?
Triglycerides and Phospholipids
What is the structure of a triglyceride?
Consists of a glycerol molecule bonded to 3 fatty acid tails via ester bonds formed in a condensation reaction
What is the structure of a phospholipid?
Consists of a hydrophilic phosphate head bonded to a glycerol molecule via a phosphodiester bond. The Glycerol molecule is bonded to 2 fatty acid tails via ester bonds.
What is the difference betwenn saturated fatty acids and unsaturated fatty acids?
Saturated fats have no carbon - carbon double bond. This gives them a higher melting point and so are typically solid at room temperature. Unsaturated fats have at least 1 carbon - carbon double bond. This gives them a lower melting point and so are typically liquid at room temperature. The carbon - carbon double bond creates a kink in the structure which provides fluidity in the phospholipid bilayer of cell membranes.
Why do phospholipid molecules form a bilayer in cell membranes?
The hyrophilic phosphate heads are attracted to the aqueous solutions on either side of the membrane and thus face both outsied and inside the cell. The hydrophobic tails are repelled by the aqueous solution either side of the membrane and thus occur between the hydrophilic heads.
What are the 3 main nucleic acid?
DNA (Deoxyribose nucleic acid)
RNA (Ribonucelic acid)
ATP (Adenosine triphosphate)
What is the monomer of nucelic acids?
Nucleotides
What is the structure of a DNA nucleotide?
Consists of a phosphate head bonded to a deoxyribose molecule which is bonded to a nitrogen containing organic base ( either adenine, thymine, cytosine or guanine)
What is the structure of a RNA nucleotide?
Consists of a phosphate group bonded to a ribose molecule which is bonded to a nitrogen containing organic base ( adenine, uracil cytosine or guanine).
What is the structur of ATP?
Consists of an adenine base bonded to a ribose molecule bonded to 3 phosphate groups.
What is the structure of a DNA molecule?
Nucleotides running antiparallel with hydrogen bonds between complementary base pairs on opposite nucleotides. There are phosphodiester bonds between adjacent nucleotides on the same strand.
Describe the process of DNA replication?
- DNA helicase breaks hydrogen bonds between complemeentary base pairs on opposite nucleotides. This results in the DNA double helix unwiding, exposing the bases on either strand.
- Free nucelotides bind to the exposed bases on each strand of the unwound DNA molecule via hydrogen bonds
- DNA polymerase joins the nucelotides together with phosphodiester bonds to form 2 identical DNA molecules.
This process is described as semi conservative as each new DNA molecule contains one template strand and 1 replicated strand.
How did Meselsohn and Stahl prove that DNA replication was semi conservative?
DNA grown in Nitrogen 14 was less dense and thus when the DNA is centrifuged it forms a band close to the tops. DNA grown in Nitrogen 15 is more dense and thus forms a band close to a bottom. When bacteria grown in Nitrogen 15 was placed in Nitrogen 14 and grown for 1 generation, the DNA was centrifuged which formed a band in the middle proving the DNA molecules contained 1 strand of light DNA and 1 strand of heavy DNA.
