Unit 3: FULL BIOCHEMISTRY - Leah Flashcards

What gives water its polarity?

• oxygen atom has a slightly negative charge and hydrogen has a slightly positive charge

Explain hydrogen bonds

A weak, intermolecular force where a (slightly) positive hydrogen is attracted to the (slightly) negative atom of another molecules

Define cohesion

Attraction between molecules of the same type (made up of the same atoms)

Why does water have surface tension?

• layer of water molecules at the surface of water does not have molecules of water above it

• meaning water has relatively strong cohesive force to the molecules immediately below and around them

What role does cohesion play in xylem water movement?

• When water evaporates from a leaf in a process called transpiration, the water that evaporates has cohesion to the water in a xylem tube that adjoins the exit point (stomata)

• creates a low pressure in this area called tension

• This tension pulls the other water molecules up the xylem tube

Define adhesion

Attraction between molecules of different types (made up of different atoms)

Explain two examples of adhesion

• When not being actively pulled up, water adheres to the xylem walls in plants

• Water adheres to the polar molecules making up the soil in small capillary-like channels

What types of substances can water dissolve easily?

Polar, ionic compounds (salt)

Describe hydrophilic substances

Polar, soluble in water

Examples of hydrophilic substances

• Cellulose

• glucose

• amino acids with polar side chains

• ionic compounds (salt)

Describe hydrophobic substances

Insoluble in water, non-polar

Examples of hydrophobic substances

• Lipids (fats and oils)

• fatty acids

• cholesterol

• waxes

• nitrogen gas

Physical properties of water

• Heat capacity

• buoyancy

• viscosity (resistance to flow, low)

• thermal conductivity

Describe solvation

• Solute particles become surrounded by solvent particles

• Solute particles are separated and pulled into solution

How does water dissolve a substance?

• The hydrogen bonds must break

• the water molecules surround the solute molecules and new hydrogen bonds form

• water molecules form hydration shells around the ions, preventing them to join together again

Explain the difference between hypertonic and hypotonic solutions

• Hypertonic - higher solute concentration outside the cell, causing water to leave the cell, making it shrink

• hypotonic - lower solute concentration outside the cell, causing water to enter the cell, making it swell or burst

What happens to an animal cell placed in a hypotonic solution?

Water enters the cell causing it to swell and potentially burst

What happens to an animal cell placed in a hypertonic solution?

Crenation- water exits the cell, causing it to shrink

List the six ways paramecium adapts to a hypotonic environment

1. Contractile vacuole maintains osmotic balance in Paramecium

2. Freshwater is hypotonic, causing water to flow in via osmosis

3. Vacuole collects excess water from the cytoplasm

4. It contracts and expels water through pores

5. Prevents swelling and bursting

6. Essential for osmoregulation and survival

Describe plant cells tonicity relative to their environment

• Most plant cells are hypertonic relative to their environment

• water tends to move into plant cells, resulting in high hydrostatic pressure

Explain tugor pressure

the pressure exerted against a cell wall to maintain plant shape

What happens to a plant cell placed in hypotonic solution?

Waters enters the cell causing it to become turgid, cell wall prevents bursting

What happens to a plant cell placed in hypertonic solution?

Plasmolysis- Water exits the cell, causing it to shrink

3 medical applications of isotonic solutions

• Eye drops

• contact lens solutions

• nasal irrigation

How many covalent bonds can a carbon atom form?

4

Name the four common functional groups

• Hydroxyl group

• amino group

• carboxyl group

• phosphate group

Why are monosaccharides soluble in water?

The presence of many polar hydroxyl groups

3 examples of monosaccharides and are they hextose or pentose?

• Glucose (hexose)

• Fructose (pentose)

• Galactose (hexose)

Describe the structures of monosaccharides when disolved in water?

Ring structures

What is the function of alpha glucose?

A product of photosynthesis, needed to make ATP during cellular respiration, monomer of starch and glycogen

Order of the hydroxyl groups in an alpha glucose ring

Down, down, up, down, up

What is the function of beta glucose?

Product of photosynthesis needed to make ATP during cellular respiration, monomer of cellulose

Order of the hydroxyl groups in a beta glucose ring?

Up, down, up, down, up

Describe the two polymers making up starch

• Amylose, unbranched, 1-4 linkage

• Amylopectin, branched, 1-4 and 1-6 linkages

Alpha and beta glucose have the same chemical formula but different arrangements of atoms, what is this term?

Isomers

What is the function of ribose?

makes up the RNA polymer

Order of the hydroxyl groups in ribose?

Up, down, down, up

What is the function of deoxyribose?

makes the DNA polymer

What is the difference between ribose and deoxyribose?

Deoxyribose doesn't have a hydroxyl group on the second carbon, but instead two hydrogens

Describe the outcome condensation reaction

Two products are formed, one is larger than either of two reactant and the other is water

Describe the outcome of a hydrolysis reaction

Water is always a reactant and two products are formed that are smaller than the other reactant

What is anabolism?

The synthesis of larger molecules from smaller ones (condensation)

What is catabolism?

The breaking down of larger molecules into smaller ones (hydrolysis)

Where does the energy required for anabolic reactions come from?

Catabolic reactions

What types of bonds link monosaccharides together?

Glycosidic bonds

3 examples of polysaccharides

Starch, glycogen and cellulose

Describe the structure of starch

Made up of alpha glucose molecules, polymers amylose (1-4) or amylopectin (1-4 and 1-6)

What is the function of starch?

Storage form of carbohydrates in plants

How is glucose from food absorbed for use in cellular respiration?

Salivary enzyme called amylase breaks down starch into smaller units (glucose), which is then absorbed

Describe the structure of glycogen

Made up of a-glucose monomers, highly branched with 1-4 and 1-6 linkage at the branch points

What is the function of glycogen?

Storage form of carbohydrates in humans and other vertebrates

Explain how blood sugar is regulated in the human body

When blood sugar increases glucose is stored as glycogen in liver/muscle cells (signalled by insulin), when blood sugar decreases glycogen is digested to release glucose into the blood again

Describe the structure of cellulose

Cellulose is made up of B-glucose monomers linked by 1-4 glycosidic bonds, unbranched, packed tightly as long extended chains adjacent to one another (hydrogen bonds in between), every glucose monomer is upside down compared to its neighbors

What is the function of cellulose in plant cells?

Mostly what the cell wall is made of, provides structural support to the cell

Function of cellulose as fibre?

Cellulose can't be broken down by human digestive enzymes, so fibre moves through the digestive tract undigested and maintains its health

Why can herbivores such as cows, buffalos and horses digest cellulose?

Bacteria in the rumen secret the enzyme cellulase, which can break down cellulose into glucose

How is a triglyceride formed? How many water molecules are released?

One molecule of glycerol bonds with 3 fatty acids in a condensation reaction forming an ester bond and 3 water molecules

How is a phospholipid formed?

Same as triglycerides, but only 2 fatty acids are joined via an ester bond while the third c-atom has a hydrophilic phosphate group, 3 water released

Why are lipids important for energy storage?

1. Lipids store more energy per gram than carbs 2. stores as triglycerides in adipose tissue, taking up less space 3. metabolised slowly and insoluble in water

Describe the structure of a fatty acid

Long hydrocarbon chain, methyl group (CH3) on the left end, carboxyl group on the right (COOH)

Describe a saturated fatty acid

Mostly single bonds between C-atoms, solid at room temp, often from animal sources

Describe an unsaturated fatty acid

Have one or more double bonds between C-atoms, liquid at room temp (oils), often from plant sources

Why are unsaturated fatty acids liquid at room temperature?

Double bonds mean that the hydrogen atoms attached to the carbons are positioned on the same side, causing a kink in the chain and preventing tight packing of molecules

What are the differences between cis-unsaturated and trans-unsaturated fatty acids

Cis-unsaturated: naturally occuring, hydrogen atoms are on the same side of the C=C bond, kink in the chain

Trans-unsaturated: result of human food processing, hydrogen atoms are on the opposite side, causes a straighter chain

How do unsaturated fats become trans-unsaturated fats?

When unsaturated fats are exposed to heat during hydrogenation, the double bonds in the fatty acids break and hydrogen atoms are added. However, the heat also promotes the rearrangement of some cis double bonds into trans configurations, resulting in trans fats.

What is adipose tissue composed of?

Cells that store fat in the form of triglycerides

What are the two functions of adipose tissue?

1. Storing long-term energy 2. Heat insulation

Describe the properties of waxes

Strongly hydrophobic, highly saturated, long hydrocarbon chains and solid at room temp

What is common amongst all steroids?

A backbone of four carbon rings

What differentiates steroids?

Different functional groups attached to the rings

Why do steroids dissolve easily in the interior of phospholipid bilayers?

Steroids consist of hydrocarbon rings and are therefore hydrophobic and non-polar

What are the benefits of having short-term energy from carbohydrates?

Maintains blood sugar levels, requires less oxygen so efficient for high-intensity activity, fast ATP production which the brain relies on, recovery from oxygen debt, cellular respiration

What are the benefits of long-term energy from lipids?

More energy per gram, sustained energy supply for times of food scarcity, long-duration activities, insoluble in water

What are the monomers of proteins?

Amino acids

What is a polypeptide chain?

A linear chain of amino acids linked by peptide bonds

What is the key difference between a protein and a polypeptide chain

Polypeptide- a simple chain of amino acids, may or may not be functional

Protein- a fully folded and functional molecules, composed of one or more polypeptides

Describe a primary protein structure

Linear sequence of amino acids in a polypeptide chain

Describe a secondary protein structure

Local folding patterns such as alpha-helices and beta-sheets, which are stabalised by hydrogen bonds

Describe a tertiary protein structure

The overall 3D shape of a single polypeptide, formed by interactions between side chains

Describe a quaternary protein structure

The arrangement of multiple polypeptide subunits into a functional protein complex

What are the four classifications of amino acids?

Nonpolar/hydrophobic, polar/hydrophilic, basic/positive and acidic/negative

What are the four groups attached to a central carbon atom making up an amino acid?

R group, hydrogen atom, amino group and carboxylic acid group

Explain how dipeptides are formed?

The -OH from the carboxyl group combines with the -H from the amino group, condensation reaction, water released

What are essential amino acids and how many are there?

They cannot be synthesised from the human body and must be obtained through the diet, there are 9

What are conditional amino acids?

They are usually non-essential (can be synthesised from the human body) but can become essential under conditions such as illness or stress

An example of a conditional essential amino acid

Arginine, cysteine, glutamine and tyrosine

What determines the structure of an amino acid?

The base sequence of the gene that codes for the polypeptide

What is the function of hemoglobin?

Transports oxygen in the blood by binding to oxygen in red blood cells.

What is the function of keratin?

Provides structural support and strength to hair, nails, and skin.

What is the function of rhodopsin?

A light-sensitive protein in the retina that helps detect low-light conditions for vision

What is the function of collagen?

Provides structural support and elasticity in connective tissues like skin, tendons, and cartilage.

What is the function of digestive enzymes?

Break down food into smaller molecules for absorption and energy use

What is the function of insulin?

Regulates blood sugar levels by facilitating glucose uptake into cells.

What is the function of immunoglobulin?

Recognises and neutralises pathogens to protect the immune system

Give an example of a fibrous and globular protein

Keratin and Haemoglobin

Define denaturation

A structural change of a protein that results in the loss of its biological properties

Explain how heat causes denaturation

Heat causes an increase in kinetic energy which breaks the weak hydrogen bonds within the molecules, the polypeptides unfold and the shape is lost

Explain denaturation in a fried egg

Added heat leads to breakage of hydrogen bonds and cross-linkage between sulfur-containing R groups of amino acids in the polypeptides (disulfide bridges)

Explain how changes in pH cause denaturation

Changes in pH change the attractions between the groups in the side chains (R groups), which are important more maintaining the shape. pH disrupts hydrogen bonds and ionic bonds.

What is the role of glycoproteins in cell-cell recognition?

Glycoproteins act as cell surface markers that help in cell-cell recognition, immune response, and communication by allowing cells to identify and interact with each other. Cells recognised as non-self will trigger an immune response.