BIO 1AO3 - T1 M1 and M2

What is a microbiome?

A population of microorganisms, or microbes, living in a particular environment.

Approximately how many microbial species may a healthy human host?

About 10,000 species.

Where is Streptococcus salivarius normally found?

In the upper respiratory tract and oral cavity.

Where is Staphylococcus haemolyticus normally found?

On the skin.

Where is Bacteroides thetaiotaomicron normally found?

In the intestine, where it is a predominant bacterium.

What are the four core classes of macromolecules presented in this module?

Nucleic acids, proteins, polysaccharides, and phospholipids.

How does the module define a cell?

A membrane-bound structure containing macromolecules.

What is a major function of the cell membrane?

It separates the cell's internal environment from the external environment.

Why is separating the internal and external environments important?

It allows the two environments to maintain different chemical compositions.

Why are phospholipids described as amphipathic?

They contain both a hydrophilic region and a hydrophobic region.

Which region of a phospholipid is hydrophilic?

The polar head group.

Which region of a phospholipid is hydrophobic?

The nonpolar hydrocarbon fatty-acid tails.

How do phospholipids arrange themselves in water?

The hydrophilic heads face the water while the hydrophobic tails cluster away from it.

Do phospholipid membrane structures require energy to assemble?

No. Phospholipids spontaneously form lipid aggregates in water.

How many carbons are typically found in a phospholipid fatty-acid chain?

Usually 16 or 18 carbons.

What type of carbon-carbon bonds occur in a saturated fatty-acid chain?

Only single bonds.

What type of bond makes a fatty-acid chain unsaturated?

One or more carbon-carbon double bonds.

Why do saturated and unsaturated fatty acids behave differently?

Their different bonds change the shape and behaviour of phospholipids and membranes.

How do phospholipids usually move within one layer of a membrane?

They move laterally, or side to side.

Why do phospholipids not easily flip from one bilayer layer to the other?

Flip-flop requires a large amount of energy because the polar head would pass through the hydrophobic interior.

Which four factors influence membrane fluidity?

Fatty-acid saturation, fatty-acid tail length, temperature, and cholesterol.

How do more unsaturated fatty acids affect membrane fluidity?

They increase membrane fluidity.

According to the module, how does more cholesterol affect membrane fluidity?

More cholesterol is associated with a less fluid membrane under the conditions shown.

What is the relationship between membrane fluidity and permeability?

A more fluid membrane generally has higher permeability, while a less fluid membrane has lower permeability.

What does selective permeability mean?

The membrane controls which substances enter and leave the cell or its organelles.

How can membrane proteins affect transport?

Proteins embedded in the bilayer can help substances cross the membrane.

What does the fluid mosaic model state?

Membranes contain proteins and carbohydrates embedded in a fluid phospholipid bilayer.

What is a concentration gradient?

A difference in a substance's concentration between two regions.

What does movement down a concentration gradient mean?

Movement from an area of higher concentration to an area of lower concentration.

What does movement against a concentration gradient mean?

Movement from an area of lower concentration to an area of higher concentration.

What is simple diffusion?

The movement of a solute directly through the lipid portion of the membrane from high to low concentration.

Does simple diffusion require cellular energy?

No.

What is facilitated diffusion?

The movement of a solute from high to low concentration with help from a membrane protein.

Does facilitated diffusion require cellular energy?

No.

What is osmosis?

The diffusion of water across a selectively permeable membrane.

In which direction does water move during osmosis?

From the less concentrated, hypotonic solution toward the more concentrated, hypertonic solution.

What are aquaporins?

Protein channels that are selectively permeable to water and allow water to cross membranes rapidly.

What is active transport?

The energy-requiring movement of substances against their concentration gradient.

What is the difference between primary and secondary active transport?

Primary active transport uses ATP directly, while secondary active transport uses ATP indirectly through an established gradient.

Why are active-transport pumps important for sodium and potassium?

They establish different sodium and potassium concentrations on opposite sides of the cell membrane.

What major events occurred during the Precambrian according to this module?

The origins of life and photosynthesis, followed by the development of an oxygen-containing atmosphere.

Approximately how long ago did life and photosynthesis begin?

About 4 billion years ago.

What is a eukaryotic organism?

An organism whose cells contain a nucleus and many membrane-bound organelles.

What is a prokaryotic organism?

A unicellular organism that lacks a nucleus and has few or no organelles.

What evolutionary relationship exists between prokaryotes and eukaryotes?

They share a common ancestor.

What is an organelle?

A membrane-bound structure inside a cell.

In which eukaryotic cells are chloroplasts found?

Plant cells.

In which eukaryotic cells are mitochondria found?

Both plant and animal cells.

What is the main function of chloroplasts?

They perform photosynthesis and manufacture carbohydrates.

What is photosynthesis?

The process by which plants and other organisms convert light energy into chemical energy stored in carbohydrates.

Where is the chemical energy produced by photosynthesis stored?

In the chemical bonds of carbohydrate molecules.

What is the overall photosynthesis equation shown in the module?

6 CO2 + 12 H2O + light energy produces C6H12O6 + 6 H2O + 6 O2.

What is the main function of mitochondria?

They use cellular respiration to make usable energy in the form of ATP.

What is cellular respiration?

A process that releases energy stored in carbohydrate bonds and captures part of it in ATP.

Which organisms perform cellular respiration according to the module?

Plants and animals.

What similarity in appearance supports a bacterial origin for mitochondria?

Mitochondria look like bacterial cells.

What similarity in size supports a bacterial origin for mitochondria?

Mitochondria are approximately the same size as bacterial cells.

What type of genome do mitochondria possess?

Their own circular genome.

What protein-related ability do mitochondria possess?

They produce enzymes needed for protein synthesis.

What basic event does the endosymbiotic theory propose?

An early eukaryotic cell engulfed bacteria that remained inside and eventually became organelles.

What is endosymbiosis?

A relationship in which one organism lives inside another and both can benefit.

What does the endosymbiotic theory explain?

The evolutionary origin of mitochondria and chloroplasts from formerly free-living bacteria.

What living evidence does the endosymbiotic theory predict?

Eukaryotes should display examples of organisms acquiring and maintaining endosymbiotic partners.

How could phagocytosis contribute to the origin of plastids?

An early eukaryote could engulf a photosynthetic bacterium that remained inside the cell.

How do corals demonstrate symbiosis?

Corals are animals that live in close association with microbes.

How does the sea-slug example demonstrate endosymbiosis?

The sea slug consumes photosynthetic algae and retains their chloroplasts.

What must happen to a temporary endosymbiotic relationship during organelle evolution?

It must become permanent and heritable.

What molecular evidence supports the endosymbiotic theory?

Bacteria, mitochondria, and chloroplasts share related proteins and genes.

What is cellular compartmentalization?

The division of a cell into distinct membrane-bound regions with specialized functions.

How do organelle membranes support compartmentalization?

They create separate internal environments where particular cellular processes can occur.

What distinguishes one cellular compartment from another?

Each compartment can contain a unique set of enzymes and produce or hold different products.

How can organelles increase a cell's metabolic capacity?

Their membranes increase the surface area available for membrane-based metabolic reactions.

What is a monosaccharide?

A single sugar unit that can serve as a building block for larger carbohydrates.

How are monosaccharides joined to form disaccharides?

They polymerize through glycosidic linkages.

How do plants and animals store carbohydrates for energy?

They store them as polysaccharides.

What important products of glucose processing help make ATP?

Electron carriers.

How does the electron transport chain contribute to ATP production?

It establishes a proton gradient that drives ATP synthesis in mitochondria.

Can molecules other than carbohydrates be used as cellular fuel?

Yes. Proteins and fats can also be processed as fuel.

What type of reaction is ATP hydrolysis?

An exergonic reaction that releases energy for cellular processes.

What is the endomembrane system?

A group of eukaryotic organelles that performs most lipid and protein synthesis, including the endoplasmic reticulum, Golgi apparatus, and lysosomes.