bio mid sem

prokaryotes

no nucleus or organelles

Eukaryotes

have a membrane-bound nucleus and organelles.

What are the major kingdoms/groups and which are prokaryotic vs eukaryotic?

Prokaryotic: Bacteria, Archaea. Eukaryotic: Protists, Fungi, Plants, Animals.

Gram-positive:

thick peptidoglycan wall, no outer membrane

Gram-negative:

thin peptidoglycan wall + outer membrane.

What structures distinguish plant cells?

cellulose cell wall, chloroplasts and large vacuole

animal cells

no cell wall or chloroplasts.

What are the main types of bacterial shapes?

Coccus = spherical; bacillus = rod; spirillum = spiral.

What are the main categories of microbial diversity based on temperature?

Psychrophiles = cold, mesophiles = moderate, thermophiles = hot.

What are the main categories based on pH?

Acidophiles = acidic, neutrophiles = near neutral, alkaliphiles = alkaline.

What are aerobic, anaerobic and facultative organisms?

Aerobic: require O₂. Anaerobic: grow without O₂. Facultative: can grow with or without O₂.

What are halophiles and extremophiles?

Halophiles: tolerate/grow in high salt. Extremophiles: adapted to extreme environmental conditions.

What is a virus and why isn't it considered living?

A non-living obligate parasite that requires a host cell's machinery to reproduce.

virus composition

DNA or RNA + protein capsid, sometimes an outer envelope. Many have an icosahedral structure.

What is a bacteriophage?

A virus that infects bacteria.

What are the five stages of the bacteriophage lytic cycle?

Adsorption → Penetration → Biosynthesis → Maturation → Release.

the lytic cycle

virus replicates and is released, destroying the host

lysogenic cycle

viral DNA integrates into host DNA and replicates with the host.

fungi

eukaryotes including yeasts and moulds

algae

photosynthetic eukaryotes with chloroplasts.

protozoa

unicellular, motile eukaryotes with no cell wall

What is binomial nomenclature?

Scientific naming using genus + species, e.g. Escherichia coli.

cytoplasm

hold organelles and metabolic reactions occur

What is the function of the mitochondrion?

Site of cellular respiration and oxidative phosphorylation, producing ATP.

What is the function of the cell membrane?

Forms the cell boundary and controls what enters and leaves the cell.

What is the function of the Golgi complex?

Modifies, sorts and packages proteins for transport/secretion.

rough ER

Protein synthesis and modification; has ribosomes attached.

nuclear membrane

Surrounds the nucleus and separates genetic material from the cytoplasm.

ribosomes

Protein synthesis.

What is the function of the smooth ER?

Primarily involved in lipid synthesis and other metabolic processes.

chloroplasts

Site of photosynthesis in plants and algae.

What is the function of lysosomes?

Contain digestive enzymes that break down cellular materials.

What is the function of the nucleolus?

Site where ribosomes are assembled.

vacuole

Storage, waste storage and osmotic regulation

What are the four major building blocks of cells?

Carbohydrates, lipids, proteins and nucleic acids.

What are the building blocks (monomers) of each major building blocks?

Carbohydrates → monosaccharides (sugars); proteins → amino acids; nucleic acids → nucleotides; lipids → fatty acids + glycerol.

functions of carbohydrates

sugars provide energy and starch/glycogen store energy. cellulose and chitin provide structural support.

What are mono-, di- and polysaccharides?

Monosaccharide: one sugar unit. Disaccharide: two sugar units joined by a glycosidic bond. Polysaccharide: many sugar units.

What are the key carbohydrate examples to know?

Glucose: major energy source. Sucrose: glucose + fructose. Lactose: glucose + galactose. Starch: plant energy storage. Glycogen: animal/fungal energy storage. Cellulose: plant structural material.

glycosidic bond

A bond that links monosaccharides together to form di- and polysaccharides, formed by condensation.

What are the main functions of proteins?

Structural, catalytic (enzymes), transport, regulatory and protective functions.

What are amino acids?

The monomers/building blocks of proteins. There are 20 common amino acids used to make proteins.

peptide bond

A covalent bond between amino acids, formed between the amino group of one and carboxyl group of another with removal of water.

four levels of protein structure

Primary: amino acid sequence. Secondary: α-helix/β-sheet. Tertiary: overall 3D shape of one polypeptide. Quaternary: association of multiple polypeptide chains.

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What is the difference between fibrous and globular proteins?

Fibrous: long, structural, generally insoluble (e.g. collagen). Globular: compact, functional, generally soluble (e.g. enzymes, haemoglobin).

What are lipids and their main characteristics?

Lipids are generally hydrophobic, meaning they are insoluble in water. They function in energy storage, membranes and signalling.

What are triglycerides/fats made from?

Glycerol + 3 fatty acids, joined by ester bonds.

What is the difference between saturated and unsaturated fatty acids?

Saturated: no C=C double bonds. Unsaturated: one or more C=C double bonds.

What is the structure and function of a phospholipid?

Has a polar/hydrophilic phosphate head and non-polar/hydrophobic fatty acid tails. They are major structural components of cell membranes.

nucleotide composition

A 5-carbon sugar + phosphate group + nitrogenous base.

What are DNA and RNA made of, and what is their main function?

They are polymers of nucleotides. DNA stores genetic information; RNA helps with gene expression and protein synthesis.

What are the key differences between DNA and RNA?

DNA: deoxyribose, thymine (T), usually double-stranded. RNA: ribose, uracil (U), usually single-stranded.

What are the three main types of RNA and their functions?

mRNA: carries genetic information to ribosome. tRNA: carries amino acids to ribosome. rRNA: major structural/component of ribosomes.

What is complementary base pairing in DNA?

A pairs with T; G pairs with C, held together by hydrogen bonds.

phosphodiester bond

A covalent bond linking nucleotides together in a DNA or RNA strand.

macronutrients

required in relatively large amounts (e.g. C, N, O, H, S, P, Mg, K).

Micronutrients

required in small/trace amounts (e.g. Fe, Zn, Mn).

What are enzymes?

Enzymes are proteins made of amino acids that act as biological catalysts, increasing reaction rates without being consumed.

How do enzymes increase reaction rates?

They lower the activation energy required for a reaction to occur. They do not change the overall energy change or equilibrium of the reaction.

What determines an enzyme's specificity and catalytic activity?

Its 3D structure, which is determined by its amino acid sequence.

What is an enzyme's active site?

The specific region of an enzyme where the substrate binds and catalysis occurs.

What are key characteristics of enzyme catalysis?

Enzymes are highly specific, have high catalytic power, operate under relatively mild conditions, and their activity is generally temperature- and pH-dependent.

How are enzymes commonly named?

Usually by adding –ase to the substrate (e.g. urease) or the reaction catalysed (e.g. alcohol dehydrogenase).

What are some examples of enzymes and their functions?

Peptidases: proteins → amino acids. Lipases: fats → glycerol + fatty acids. Amylases: starch → simple sugars. Catalase: H₂O₂ → H₂O + O₂.

Why is catalase important?

H₂O₂ is a potentially damaging oxidising agent produced during metabolism. Catalase rapidly decomposes it into less harmful H₂O and O₂.

What are cofactors and coenzymes?

non-protein molecules for activity. Cofactors: inorganic ions such as Zn²⁺ or Cu²⁺ coenzymes: small organic molecules.

What is the basic enzyme kinetic reaction scheme?

E + S ⇌ ES → E + P, where E = enzyme, S = substrate, ES = enzyme-substrate complex and P = product.

What is the Michaelis-Menten equation?

It describes the relationship between reaction velocity and substrate concentration for simple enzyme kinetics.

WVmax

The maximum reaction velocity when the enzyme is effectively saturated with substrate.

Km

The substrate concentration at Vmax/2

low vs high Km

lower Km: greater apparent between enzyme and substrate; higher Km: lower affinity

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What is enzyme activity?

A measure of the catalytic activity of an enzyme. One enzyme unit is the amount of enzyme producing a predetermined amount of catalytic activity under specified conditions.

What is specific activity?

enzyme activity / total protein, typically expressed as units per mg protein. It is useful for assessing enzyme purity/activity.

What are enzyme inhibitors?

Substances that bind to enzymes and reduce their activity. Many therapeutic drugs function as enzyme inhibitors.

What is the difference between reversible and irreversible inhibition?

Reversible inhibitors bind loosely and can be displaced. Irreversible inhibitors form stable interactions, often covalent, that permanently reduce enzyme activity.

What is competitive inhibition?

The inhibitor competes with substrate for the active site. Increasing substrate can overcome the inhibition. Vmax unchanged; apparent Km increases.

What is non-competitive inhibition?

The inhibitor binds at a site other than the active site and can bind to E or ES

uncompetitive inhibition

The inhibitor binds only to the ES complex, reducing both the apparent Vmax and Km.

What is substrate inhibition?

At high substrate concentrations, excess substrate can inhibit enzyme activity, causing the reaction rate to decrease.

How do competitive, non-competitive and uncompetitive inhibition affect Vmax and Km?

Competitive: Vmax unchanged, Km increases. Non-competitive: Vmax decrease, Km unchanged. Uncompetitive: Vmax decrease, Km decrease.

What causes irreversible enzyme inhibition?

modification/destruction of an essential amino acid in the enzyme. Heavy metals

Why are enzyme inhibitors important medically?

Drugs can be designed to mimic natural substrates and bind to enzyme active sites, allowing enzyme activity to be selectively inhibited.