BIO exam 2

What are proteins?

Proteins are biological molecules made of one or more polypeptides folded into functional shapes.

What are the main functions of proteins?

Proteins can act as enzymes and provide defense, storage, transport, communication, movement, and structural support.

What is an amino acid?

The monomer of a protein or polypeptide.

What are the main parts of an amino acid?

An amino group, a carboxyl group, a central alpha carbon, a hydrogen atom, and an R group.

What determines the properties of an amino acid?

The chemical structure of its R group, or side chain.

What are the two ends of a polypeptide?

The N-terminus and the C-terminus.

What is primary protein structure?

The unique sequence of amino acids in a polypeptide.

What is secondary protein structure?

Local folding patterns, such as alpha helices and beta sheets, formed by hydrogen bonding between backbone atoms.

What is tertiary protein structure?

The three-dimensional shape of one polypeptide caused by interactions among its R groups.

What is quaternary protein structure?

The arrangement of two or more polypeptide chains into one functional protein.

What are motifs?

Common combinations of secondary structures found in many proteins.

What are protein domains?

Functional regions within a larger protein structure.

What do chaperone proteins do?

They help newly made proteins fold into their correct shapes.

What is denaturation?

The loss of a protein’s normal shape and function caused by changes in temperature, pH, or ionic concentration.

Why are lipids not considered true polymers?

Lipids are not made from repeating monomers in the same way as carbohydrates, proteins, and nucleic acids.

What does hydrophobic mean?

Hydrophobic means “water-fearing” and describes substances that do not mix well with water.

What are the major types of lipids?

Fats, phospholipids, and steroids.

What are triglycerides made of?

A triglyceride contains one glycerol molecule joined to three fatty acids.

What is the main function of fats?

Fats primarily store energy.

What is a saturated fatty acid?

A fatty acid with the maximum possible number of hydrogen atoms and no carbon-carbon double bonds.

What is an unsaturated fatty acid?

A fatty acid with one or more carbon-carbon double bonds and fewer hydrogen atoms than a saturated fatty acid.

How do saturated and unsaturated fats differ at room temperature?

Saturated fats are usually solid, while unsaturated fats are usually liquid.

What is a phospholipid?

A lipid made of glycerol, two fatty acid tails, and a phosphate-containing head group.

What does amphipathic mean?

Amphipathic molecules have both hydrophilic and hydrophobic regions.

How are phospholipids arranged in a bilayer?

Hydrophilic heads face the water, while hydrophobic tails point inward away from water.

What is a steroid?

A lipid with a carbon skeleton made of four fused rings.

What is one important example of a steroid?

Cholesterol is a steroid that is part of animal cell membranes and can serve as a precursor for other steroids.

What are the three statements of cell theory?

All organisms are made of one or more cells, cells are the basic units of life, and cells arise only from preexisting cells.

Why are cells usually small?

As a cell increases in size, its volume increases faster than its surface area, making diffusion less efficient.

What four structures are found in all cells?

A plasma membrane, cytoplasm, chromosomes, and ribosomes.

What is the function of the plasma membrane?

It acts as a selective barrier that controls what enters and leaves the cell.

What is cytoplasm?

Cytoplasm is the semifluid material inside a cell. The fluid portion is called cytosol.

What is the function of ribosomes?

Ribosomes synthesize proteins.

What is a prokaryotic cell?

A cell that lacks a membrane-bound nucleus and membrane-bound organelles.

What is a eukaryotic cell?

A cell with a membrane-bound nucleus and membrane-bound organelles.

Where is DNA located in a prokaryotic cell?

DNA is located in a region called the nucleoid.

What is the bacterial cell wall made of?

Bacterial cell walls are made of peptidoglycan.

What are some structures found in certain prokaryotes?

Pili, flagella, and capsules may be present in some prokaryotic cells.

What is the function of the nucleus?

The nucleus stores genetic information in chromosomes and controls many cell activities.

What is the function of the nucleolus?

The nucleolus produces ribosomal RNA and helps assemble ribosomes.

What is the endomembrane system?

A group of membranes and organelles that regulate protein transport and perform metabolic functions.

What is the function of rough endoplasmic reticulum?

Rough ER, which has ribosomes, synthesizes and modifies proteins for secretion or membranes.

What is the function of smooth endoplasmic reticulum?

Smooth ER synthesizes lipids, stores calcium ions, helps detoxify substances, and makes some carbohydrates.

What is the function of the Golgi apparatus?

The Golgi modifies, sorts, and packages proteins and lipids into transport vesicles.

What is the function of lysosomes?

Lysosomes contain hydrolytic enzymes that digest macromolecules and recycle damaged cell parts.

What is the function of peroxisomes?

Peroxisomes contain enzymes involved in fatty acid oxidation and produce hydrogen peroxide as a by-product.

What is the function of mitochondria?

Mitochondria carry out cellular respiration and produce ATP.

What is the function of chloroplasts?

Chloroplasts carry out photosynthesis in plants and algae.

What is the endosymbiont theory?

The theory that mitochondria and chloroplasts evolved from free-living prokaryotes that were engulfed by another cell.

What are the three main types of cytoskeletal fibers?

Microtubules, microfilaments, and intermediate filaments.

What are microtubules?

Microtubules are tubulin-based fibers that help maintain cell shape, move materials, and organize chromosomes.

What are microfilaments?

Microfilaments are actin-based fibers involved in cell shape, contraction, crawling, and cell division.

What are intermediate filaments?

Intermediate filaments are stable fibers that support cell shape, anchor organelles, and form the nuclear lamina.

What do motor proteins do?

Motor proteins move materials along cytoskeletal fibers. Examples include kinesin, dynein, and myosin.

Which cytoskeletal elements help cells move?

Actin filaments and microtubules are the main cytoskeletal elements involved in cell movement.

What is the structure of eukaryotic cilia and flagella?

They usually have a $9 + 2$ arrangement, with nine pairs of microtubules surrounding two central microtubules.

How do cilia and flagella differ?

Cilia are shorter and more numerous, while flagella are usually longer and fewer.

What is the function of a plant cell wall?

The cell wall protects plant cells, maintains their shape, and prevents excessive water uptake.

What is the plant cell wall made of?

It is made primarily of cellulose fibers embedded in other polysaccharides and proteins.

What is the extracellular matrix?

The extracellular matrix is a network of glycoproteins and other materials surrounding animal cells.

What are examples of extracellular matrix components?

Collagen, proteoglycans, fibronectin, and integrins are important ECM components.

What are cell junctions?

Cell junctions connect neighboring cells or connect cells to the extracellular matrix.

What are adhesive junctions?

Adhesive junctions mechanically attach neighboring cells or their cytoskeletons to the extracellular matrix.

What are tight junctions?

Tight junctions connect adjacent plasma membranes and prevent leakage between cells.

What are gap junctions?

Gap junctions allow chemical or electrical signals to pass directly between neighboring animal cells.

What are plasmodesmata?

Plasmodesmata are openings in plant cell walls that connect the cytoplasm of neighboring cells.

What is the fluid mosaic model?

The fluid mosaic model describes a flexible phospholipid bilayer containing proteins that move within or along the membrane.

What are the four components of cellular membranes?

A phospholipid bilayer, transmembrane proteins, an interior protein network, and cell-surface markers.

What are the three components of a phospholipid?

Glycerol, a phosphate group, and two fatty acids.

Why do phospholipids form bilayers?

Their hydrophilic heads interact with water, while their hydrophobic tails move away from water and face one another.

What factors affect membrane fluidity?

Temperature, lipid composition, and the amount of saturated and unsaturated fatty acids affect membrane fluidity.

How do saturated and unsaturated fatty acids affect fluidity?

Saturated fatty acids pack tightly and make membranes less fluid. Unsaturated fatty acids have bends that prevent tight packing and increase fluidity.

What are peripheral proteins?

Peripheral proteins attach to the surface of the membrane but do not penetrate its hydrophobic interior.

What are integral proteins?

Integral proteins penetrate or are embedded in the hydrophobic interior of the membrane.

What are transmembrane domains?

Transmembrane domains are hydrophobic regions of proteins that span the lipid bilayer.

How are membrane pores formed?

A transmembrane protein can form a pore when its interior is polar, allowing water and small polar molecules to pass through.

What is passive transport?

Passive transport is the movement of substances across a membrane without using cellular energy.

What is diffusion?

Diffusion is the net movement of molecules from an area of high concentration to an area of low concentration.

Which molecules cross the membrane most easily by simple diffusion?

Small nonpolar molecules cross the hydrophobic interior of the membrane most easily.

What is facilitated diffusion?

Facilitated diffusion moves substances from high to low concentration through membrane proteins without using ATP.

What is a channel protein?

A channel protein forms a hydrophilic passageway through the membrane for specific molecules or ions.

What is a carrier protein?

A carrier protein binds a specific molecule and changes shape to move it across the membrane.

What is osmosis?

Osmosis is the net movement of water across a selectively permeable membrane toward the solution with the higher solute concentration.

What are aquaporins?

Aquaporins are membrane channels that facilitate the movement of water.

What is a hypertonic solution?

A hypertonic solution has a higher solute concentration outside the cell, causing water to leave the cell.

What is a hypotonic solution?

A hypotonic solution has a lower solute concentration outside the cell, causing water to enter the cell.

What is an isotonic solution?

An isotonic solution has the same solute concentration as the cell, so there is no net movement of water.

What is osmotic pressure?

Osmotic pressure is the force needed to stop the movement of water caused by osmosis.

What is active transport?

Active transport uses energy to move substances against their concentration gradients, from low concentration to high concentration.

What types of carrier proteins are used in active transport?

Uniporters move one substance, symporters move two substances in the same direction, and antiporters move two substances in opposite directions.

What does the sodium-potassium pump do?

The sodium-potassium pump uses ATP to move three sodium ions out of the cell and two potassium ions into the cell.

What is coupled transport?

Coupled transport uses energy released from the movement of one substance to drive the active transport of another substance.

What is endocytosis?

Endocytosis is the movement of substances into a cell through the formation of a vesicle.

What is phagocytosis?

Phagocytosis is the uptake of large particles or other cells.

What is pinocytosis?

Pinocytosis is the uptake of extracellular fluid and dissolved substances.

What is receptor-mediated endocytosis?

Receptor-mediated endocytosis takes in specific molecules after they bind to receptors on the cell surface.

What is exocytosis?

Exocytosis is the movement of substances out of a cell when a vesicle fuses with the plasma membrane.

What is a ligand?

A ligand is a signaling molecule that binds to a specific receptor.

What is a receptor?

A receptor is a protein that recognizes and binds a particular ligand.

What is signal transduction?

Signal transduction is the series of events inside a cell that occurs after a ligand binds to a receptor.