Biology Quiz 3

What are the three components of cell theory?

1. All living organisms are composed of cells.
2. Cells are the fundamental units of life.
3. All cells come from preexisting cells.

What experiment disproved spontaneous generation?

Pasteur’s experiment — sterilized flasks only grew cells when exposed to air.

What is the cell’s surface area?

Everything covering the outside of the cell (the plasma membrane).

What is the cell’s volume?

Everything inside the cell, including cytoplasm and organelles.

Are surface area and volume directly or inversely related?

Directly — as surface area increases, volume increases too.

Why are cells not extremely large?

Larger cells have greater energy needs and waste, but limited surface area for exchange — SA is a limiting factor for cell size.

What is the smallest size visible by the human eye?

About 200 μm.

Which microscope has better resolution — light or electron?

Electron microscope.

Which microscope can visualize living cells?

Light microscope.

Why do cells need a membrane?

To separate the internal and external environments and allow selective passage of molecules.

What biological molecule enables cell-to-cell adhesion?

Proteins on the cell membrane.

Where would you not expect to find cytoplasm in a eukaryotic cell?

In the nucleus.

What is the cytosol and how is it different from cytoplasm?

Cytosol is the fluid portion of the cytoplasm that’s not inside organelles.

What features are found in eukaryotes but not in prokaryotes?

Membrane-bound organelles and a nucleus.

What is the nucleoid?

The region in prokaryotes where DNA is located (not membrane-bound).

What are the characteristics of bacterial cell walls?

Rigid, contain peptidoglycan, not a major barrier like the membrane.

What is the function of pili and flagella?

Pili help in adherence; flagella help in movement.

Are firmicutes more related to hyperthermophilic bacteria or hadobacteria?

Hyperthermophilic bacteria.

Between spirochetes and chlamydias, which is more closely related to bacteria?

Spirochetes.

Where is a thick layer of peptidoglycan found?

In Gram-positive cell walls.

Why do Gram-positive bacteria retain violet stain?

The thick peptidoglycan traps the crystal violet dye.

Why do Gram-negative bacteria turn pink?

Their thin peptidoglycan layer can’t retain violet dye and takes up safranin.

What are two important functions of prokaryotes?

Nitrogen fixation and forming microbiomes (e.g., gut microbiome).

What does the endosymbiosis theory explain?

How eukaryotes evolved from prokaryotes that were engulfed and formed mutualistic relationships.

What does the nuclear envelope consist of?

Two lipid bilayers with nuclear pores.

Why do proteins need an NLS (nuclear localization signal)?

To enter the nucleus, since only small molecules can diffuse freely.

What is the function of mitochondria?

Cellular respiration — producing energy from food.

What does the nucleus do?

Stores DNA, chromatin, and proteins.

What is the cytoskeleton?

A network of microtubules, filaments, and microfilaments that maintain cell shape and movement.

What do peroxisomes do?

Break down fatty acids and detoxify hydrogen peroxide.

What is the function of the Golgi apparatus?

Modify, sort, and package proteins.

What does the smooth ER do?

Synthesizes lipids and hormones and detoxifies compounds.

What does the rough ER do?

Synthesizes and modifies proteins with ribosomes attached.

What is the role of the cell membrane?

Regulates movement of substances into and out of the cell.

What is the nucleolus responsible for?

Ribosome formation.

What do centrioles do?

Help organize cell division.

What is the function of the cell wall?

Provides structural integrity.

What do chloroplasts do?

Produce ATP through photosynthesis.

What is the function of plasmodesmata?

Channels that allow transport and signaling across cell walls.

What does the vacuole do?

Stores water and manages waste.

What do chromoplasts produce?

Carotenoid pigments.

What do amyloplasts store?

Polysaccharides (starch).

What is the endomembrane system?

A system for protein and lipid synthesis, transport, and recycling between ER and lysosome.

What are key protein modifications?

Proteolysis and glycosylation.

What direction does the Golgi move in cisternal maturation?

From cis to trans.

What are the 5 key steps of protein packaging?

1. Tagging
2. Sorting
3. Vesicle budding
4. Interaction with receptors
5. Delivery to lysosomes

How do secondary lysosomes form?

When phagosomes fuse with primary lysosomes.

What monomers form microfilaments?

Actin monomers.

Which end of a microfilament grows?

The positive end.

What are intermediate filaments made of?

Fibrous subunits that stabilize cell structure.

What subunits form microtubules?

Alpha and beta tubulin dimers.

Which cytoskeleton structure does kinesin move along?

Microtubules.

Which fatty acid tails increase membrane permeability?

Short, unsaturated tails (due to double bonds increasing fluidity).

How do peripheral proteins differ from integral proteins?

Peripheral bind to the surface; integral are embedded in the bilayer.

Would leucine be on the ends of a transmembrane protein?

No, ends are hydrophilic, and leucine is hydrophobic.

What is homotypic vs heterotypic binding?

Homotypic: same molecule binds; heterotypic: different molecules bind.

What are cell junctions?

Specialized structures that connect cells.

What do tight junctions do?

Prevent movement of materials through epithelial cells.

What is the function of desmosomes?

Hold cells together while allowing materials to pass through.

What do gap junctions do?

Allow communication between cells.

What does integrin do?

Connects the extracellular matrix to actin filaments inside the cell.