biology sl

what is a covalent bond

a bond that forms when 2 atoms share a pair of electrons

explain the covalent bond in water

the 2 slightly positive hydrogen atoms bond with the slightly negative oxygen

what does it mean that water Is polar?

it has an unequal sharing of electrons

where do hydrogen bonds form in water ?

between the slightly negative oxygen of one water molecule , and the slightly positive hydrogen of another

what is cohesion

when water sticks to other water molecules due to hydrogen bonding

what is adhesion

when water sticks to other polar or charged molecules/surfaces

what are the solvent properties of water ?

water can dissolve ions, and can also dissolve other polar molecules like carbohydrates , which makes it a good medium for metabolic reactions, it can also transport nutrients and waste

what is specific heat capacity

the amount of heat needed for a substance to change temp, water has a high specific heat capacity which enables aquatic organisms to not suffer with rapid temp changes

what is thermal conductivity?

the ability of a substance to transfer heat, water has a low thermal conductivity

what is high latent heat of vaporisation ?

a substance requires a large amount of energy to change from a liquid to a gas without changing temperature, which is why sweat is seen to be a good coolant

what is surface tension?

when cohesive forces create a tight layer at the surface of the water

what does cohesion pair with ?

surface tension

what does surface tension help do?

allows light insects like the water strider to walk on water due to the intermolecular forces, as they distribute their body weight evenly, and their light weight doesn't break the tension

give an example of cohesion in plants ?

In the xylem , water evaporates from small holes In the leaves called the stomata, this is called transpiration, due to cohesion and hydrogen bonding, the water molecules are pulled up the plant as a continuous chain, and adhesion to the xylem wall helps maintain the column

what does adhesion pair with?

capillary action

what is capillary action ?

the ability of water to move through narrow spaces or tubes due to adhesion

what is buoyancy?

When water exerts and upward force on the object that is placed on it

what is viscosity ?

the resistance of a substance to flow, water has a high viscosity

what is the meaning of hydrophilic

attracted to water

what is the meaning of hydrophobic

not attracted to water

how does the ringed sea use waters properties ?

it floats easily in the water due to buoyancy , faces drag while swimming due to its streamlined body, has thick blubber to insulate and retain heat, lives in a thermally stable habitat to the high specific heat capacity of water

how does the black throated loon use waters properties ?

buoyancy helps it float on water, airs low viscosity makes flying easier, loses less body heat in air due to low thermal conductivity

what does DNA stand for?

deoxyribonucleic acid

what are the units of DNA?

nucleotides

what is the main role of DNA?

to store genetic information for inheritance

what does RNA stand for ?

Ribonucleic acid

what is the main role of RNA?

Helps In protein synthesis

do viruses use DNA or RNA?

RNA

why are viruses considered not living ?

because they are not made of cells, and cannot reproduce on their own

what is a nucleotide ?

the basic building blocks of DNA and RNA, millions of them join together to create the long strands

what are nucleotides composed of ?

A phosphate group, a pentose sugar ( ribose or deoxyribose) , and a nitrogenous base like adenine, thymine, etc

how many carbons does the pentose sugar contain and what its shape ?

5, a pentagon shape

what is the sugar phosphate backbone?

made of alternating phosphate and sugar units and holds the DNA or RNA strands together

how is the backbone formed ?

through covalent bonds between 5' phosphate group of one nucleotide ,and the 3' carbon of the sugar on the next nucleotide

what type of reaction is this process ?

A condensation reaction

what is the directionality of the strand?

runs from a 5' , to a 3' direction

what are the nitrogenous bases found in DNA?

Adenine, thymine, Guanine , cytosine

what are the nitrogenous bases found in RNA?

Adenine, uracil, guanine , cytosine

what is a codon ?

A triplet of bases that codes for an amino acid

what is the structure of DNA?

2 double helixes that are twisted around each other in an anti parallel way

why is it important for the strands to be anti parallel?

accurate base pairing, correct reading direction for enzyme function

which are weak hydrogen bonds or covalent bonds?

hydrogen bonds

what are the differences between dna and RNA?

dna is double stranded, RNA Is single stranded, rna contains uracil instead of thymine, rna is less stable , dna stores genetic code while rna is in charge of protein synthesis , the sugar of dna is deoxyribose, and for rna it is ribose

what is the meaning of the universal genetic code ?

universal means that all living organisms use the same codon, AUG codes for methionine in all life forms

what are the purines in dna?

adenine and guanine

what are the prymidines in dna?

cytosine and thymine

what do purines always pair with

prymidines

how many bonds are between adenine and thymine?

2

how many bonds are between guanine and cytosine ?

3

how many covalent bonds can carbon form?

4

what is the structure of glucose?

6 carbon ring

what is the structure of a fatty acid

long, unbranched chain

what is the structure of glycogen

highly branched polysaccharide with rings

what is the structure of DNA bases?

can be single or double carbon rings

what is the structure of cholesterol?

steroid with 4 fused carbon rings

what are macromolecules?

large biological molecules made up of small sub units called monomers

how do monomers join?

through condensation reactions

explain how monomers join through condensation reactions?

One monomer loses a hydroxyl group (-OH), the other monomer loses a hydrogen (-H), the removed water molecule (H2O ) is released, a covalent bond forms between the 2 monomers

what bond makes polysaccharides?

glycosidic bond

what bond makes polypeptides ?

peptide bond

what bond makes nucleic acids?

phosphodiester bond

give an example of a condensation reaction used from monosaccharides ?

glucose + glucose= maltose + water

explain the condensation reaction of amino acids to make polypeptides ?

a peptide bond forms between the amino group and carboxyl group of the amino acid to create a polypeptide, a molecule of water is released

what is hydrolysis?

the chemical breakdown of polymers into monomers using water

what are hydrolysis reactions crucial for?

digesting food and nutrient absorption

what are monosaccharides?

the simplest carbohydrates

what are the 3 monosaccharides ?

glucose, fructose , galactose

what are the disaccharides?

lactose, maltose, sucrose

what are the polysaccharides?

starch, glycogen, cellulose

what are the 2 types of glucose and the difference between them?

Alpha glucose - OH on carbon 1 is below the ring plane

Beta Glucose - OH on carbon 1 is above the ring plane

Are polysaccharides soluble or insoluble in water ?

They are compact and insoluble in water

what are the 2 types of starch?

Amylose and Amylopectin

what are the differences between amylose and amylopectin?

Amylose is helical, and unbranched, 1-4 glycosidic bonds only, Amylopectin is highly branched, made of 1-4 and 1-6 glycosidic bonds, Amylose is mainly compact for storage

What glucose are amylose and amylopectin made of ?

Alpha glucose

what is the main role of starch ?

energy storage in plants

What is the role of cellulose?

Acts as a structural component in plant cell walls

what type of glucose is cellulose made of ?

Beta glucose

what is the structure of cellulose?

Straight , unbranched chains parallel to each other, stable and has hydrogen bonding between chains

Is cellulose soluble in water ?

No

what are glycoproteins?

Proteins with carbohydrates attached to them, they are typically embedded in the cell membrane

what are glycoproteins crucial for ?

immune defense, communication, recognition

are lipids hydrophobic or hydrophilic ?

hydrophobic

what are the 4 main types of lipids?

fats, oils, waxes, steroids

what are 2 types of steroids ?

Cholesterol, hormones

What are the roles of lipids?

long-term energy storage in animals, phospholipids on cell membranes from water repelling barriers that compartmentalise the cell, waxes create protective layers on leaves, and fur, steroids diffuse through membranes to regulate processes

what are triglycerides made of ?

One glycerol, and 3 fatty acids

what bonds link the faatty acid to the glycerol in condensation reactions ?

ester bond

How many water molecules are released in the reaction ?

3

what is the role of triglycerides ?

energy storage, insulation, protection

what are the components of phospholipids ?

1 glycerol, 2 fatty acids, 1 phosphate group

Where are phospholipids found ?

On cell membranes as bilayers

What is the structure of phospholipids in the cell membrane ?

The phosphate head is hydrophilic , the fatty acid tail is hydrophobic

Why are phospholipids said to be amphipathic ?

Because they have dual properties , both hydrophilic and hydrophobic

What are saturated fatty acids ?

Straight chains, solid, no carbon double bonds

What are monounsaturated fatty acids ?

semi-solid, 1 kink in the chain, 1 carbon double bond

what are polyunsaturated fatty acids?

fully liquid, multiple bends in the chain, 2 or more carbon double bonds

What are tryglycerides stored as in animals ?

Adipose tissue beneath the skin and around organs, provides insulation , protection of organs and long term energy storage

What are features of the phospholipid bilayer ?

membrane is fluid so proteins and lipids , semi permeable, self-healing

what is an example of a steroid ?

testosterone