General Biochemistry Flashcards Flashcards by Eilidh Breslin

What are prokaryotic cells

They comprise bacteria, they are relatively simple and have no true nucleus and no internal membrane bound organelles

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What are eukaryotic cells

Found in higher animals and plants
Large complex molecules

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What is the function of the plasma membrane

Semi permeable barrier between cytoplasm and external enviroment

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What is the function of the nucleus

Controls cell activity

DNA found here

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What is the role of the nucleolus

Ribosomes constructed here

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Where is the site of transcription

The nucleus

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What is the role of ribosomes

Main role id to facilitate protein translation

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What is the rough endoplasmic reticulum

Contains ribosomes
Protein modification and production

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What is the smooth endoplasmic reticulum

Predominant function is manufacturing of lipids
No ribosomes

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What role does the smooth ER play in the liver

Converts organic chemicals into safer water soluble products
In the liver can double the surface area

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Function of the golgi aparatus

further modifies proteins
stores proteins
packages proteins

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Function of vacuoles

Used as storage areas

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Function of vesicles

Function in transport

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Function of lysosomes

The breakdown of extracellular materials, large vesicles formed by the Golgi apparatus

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Function of mitochondria

Powerhouse of the cell
ATP formation

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What are the two membranes of the mitochondria

outer membrane - smooth and sieve like
inner membrane folded into CRISTAE - surfaces on which ATP is generated

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Function of the cytoplasm

Facilitates transport of material around the cell

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What is the cytoskeleton

In eukaryotic cells there are fibrous proteins in the cytoplasm known as the cytoskeleton
- maintain shape of cell
- anchors organelles

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What is a buffer

A solution which resists change in pH when acid or alkali is added to it

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What is the major buffer in saliva

Bicarbonate

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How do you calculate the pH from the hydrogen ion concentration of a solution

pH = -log10(H+)

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What is the pH of a solution with (H+) of 0.00001M

PH 5

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What are acids

A substance which in water tends to produce H+ ions

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What is a base

A substance which in water tends to combine with H+ ions

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What is the relationship between the strength of acid and Ka value

The stronger the acid the higher the Ka and the lower the pKa

What is Ka

The acid dissociation constant

What is pKa

A number that describes the acidity of a particular molecule

What is the Henderson-Hasselbalch Equation

pH = pKa+log10(B-)/(A)

How do you calculate pKa

pKa=-log10Ka

What are buffer solutions made of

Consist of a conjugate acid base pair of either a weak acid or weak base

What is the role of buffering in the body

Maintains body pH homeostasis

Why is buffering in the mouth important

Limits pH changes due to acid production by plaque bacteria

When is buffering most effective

When concentration of acid = concentration of conjugate base

When do buffers operate optimally

When half dissociated

Important buffers in saliva

Histatins Bicarbonate Phosphate

What acids are produced by oral bacteria

- lactic acid - formic acid - acetic acid - propionic acid - butyric acid

What is tooth erosion caused by

A direct result of acid in the diet on the teeth

What are the 3 different pKa values that bicarbonate acts as a buffer

PKa = 2.16, 7.21, 12.32

What are chelating agents

Chemical compounds that bound tightly to metal ions Could have an erosive effect on teeth Fruit juices contain chelating agents

What are some biological roles of proteins

- transport - storage - catalysts - motion

What is electronegativity

The power of an atom to attract electrons towards itself

Where are L isomers found

Proteins

Where are D isomers found

Bacterial cell walls

What is a primary structure of a protein

Amino acid sequence

What is secondary structure of a protein

Regions of amino acid chains that are stabilised by hydrogen bonds between chains

What is tertiary structure of a protein

3D arrangement of all atoms in polypeptide chains

What is quaternary structure of a protein

3D interaction of protein subunits in proteins with more than one polypeptide

What is an alpha helix

Secondary structure of protein Rod like Found in strong extensible proteins

Describe B pleated sheet

Zigzag chains Found in proteins where flexibility is needed

What protein has the triple helix structure

Collagen only Major component of connective tissue

What are fibrous proteins

Insoluble, metabolically unreactive Collagen, keratin, fibrin ect

What are globular proteins

Spherical Water soluble Myoglobin and actin are examples

What is the role of myoglobin

Oxygen storage in muscle

What is haemoglobbin composed of

2 alpha and 2 beta chains

Name some examples of messenger proteins

Insulin Glucagon Human growth hormone Just hormones in general

What are the monomers of polysaccharides

Monosaccharides

What are the functions of polysaccharides

Storage and structure Glycogen starch for example

What are the monomers of lipids

Fatty acids

What reactions of monosaccharides form disaccharides

Dehydration and hydrolysis

What are sterols

Lipids with some essential biological activity

What does caries involve

Acids that are produced by plaque bacteria

How does fluoride act to reduce tooth solubility

1) reduces enamel solubility at low pH 2) inhibits bacterial metabolism of carbohydrates 3) promotes enamel remineralisation by saliva

What inhibits solubilisation of enamel

An increase in calcium or phosphate concentration will shift the equilibrium to the left this inhibits solubilisation and inhibit remineralisation

What is a null hypothesis

States there is no significant difference between two variables in a hypothesis

What are enzymes

Enzymes are biological catalysts

How do enzymes act

Accelerate the time it takes to reach equilibrium

What is the role of amylase

Found in saliva, converts starch into sugars

What is the role of maltose

Breaks the sugar maltose into glucose

How do enzymes work

Lock and key model Induced fit model

What are enzymes usually

Proteins

What is the standard free energy change

The difference between energies of reactants and products

What does reaction rate depend on

Reaction rate depends on the activation energy

What is the activation energy

The energy input required to initiate a reaction

What is the effect of an enzyme on activation energy

Lowers activation energy

What factors can affect the rate of an enzyme reaction

- temperature - pH - enzyme/substrate concentration - inhibitors and activators - covalent modification

What is V max

Maximum reaction rate

What is Km

The substrate concentration at which half of the maximum velocity is achieved

What is an irreversible inhibitor

Damages enzymes beyond repair Generally cause covalent modifications of the enzyme

What is a reversible inhibitor

Full enzyme activity is regained when the inhibitor is removed

What is feedback inhibition

Control of metabolic pathways often occurs by feedback inhibition this is often done by the product of the pathway acting as an inhibitor on an earlier step in the pathway

What is the different between a competitive and non competitive inhibitor

Competitive - substrate and inhibitor compete for the same binding site Non competitive - bind to an allosteric site on the enzyme

What are allosteric enzymes

Possesses multiple subunits Contains a region in which small effector molecules can bind Positive modulators - increase affinity for active site Negative modulators - decrease affinity for activity site