Enzyme Regulation & Cell Membrane Transport: Key Concepts for Biology

What is competitive inhibition in enzyme regulation?

A type of enzyme inhibition where a molecule competes with the substrate for the enzyme's active site, blocking the substrate from binding.

How can the effects of competitive inhibition be reduced?

By increasing substrate concentration, which increases the chance of substrate binding instead of the inhibitor.

What occurs during non-competitive inhibition?

An inhibitor binds to the allosteric site, changing the enzyme's shape and preventing effective substrate conversion, regardless of substrate concentration.

What is the role of the allosteric site in enzyme regulation?

It is a site on the enzyme separate from the active site where regulatory molecules can bind, altering the enzyme's shape and activity.

What is allosteric activation?

When activators bind to the allosteric site, increasing enzyme activity by changing the enzyme's shape to enhance active site function.

What is feedback inhibition?

A regulatory mechanism where the end product of a metabolic pathway binds to the allosteric site of the first enzyme, slowing or stopping the pathway.

How does feedback inhibition help maintain homeostasis?

It prevents the build-up of excess product, ensuring balance within the cell's metabolic processes.

What are cofactors in enzyme activity?

Inorganic ions, often metal ions like magnesium or calcium, that bind to enzymes and are essential for their function.

What are coenzymes?

Organic molecules that bind to enzymes, acting as carriers for chemical groups or electrons, often derived from vitamins.

Give an example of a coenzyme.

NAD⁺ and FAD, which are involved in cellular respiration.

What is the smallest unit of life capable of performing all functions necessary for survival?

The cell.

What is the significance of microscopy in studying cells?

Modern microscopes allow detailed examination of cell components.

What happens during irreversible inhibition?

An inhibitor binds covalently to an enzyme, permanently inactivating it.

What is precursor activation in allosteric regulation?

When a precursor molecule builds up and binds to the allosteric site of another enzyme, activating it and starting a new reaction pathway.

What is the effect of drug inhibitors on enzyme activity?

They are most effective when highly specific and potent, reducing side effects and toxicity.

How do natural enzyme inhibitors function in organisms?

They can act as poisons to protect the organism or assist in capturing prey.

What is the role of magnesium in enzyme function?

It acts as a cofactor for certain enzymes, essential for energy production.

What is the difference between cofactors and coenzymes?

Cofactors are inorganic helpers (usually metals), while coenzymes are organic helpers (often vitamin-based).

What is the significance of enzyme inhibitors in metabolism?

They regulate pathways and conserve energy by controlling enzyme activity.

What is the relationship between enzyme shape and function?

The shape of an enzyme determines its ability to bind substrates and catalyze reactions effectively.

What is contained within a membrane-bound nucleus?

DNA

What is the structure of the cell membrane?

A phospholipid bilayer with embedded proteins

What fills the interior of a eukaryotic cell?

Cytoplasm

What are chromosomes made of?

DNA and an equal mass of protein

When are chromosomes visible?

Only during cell division

What is chromatin?

The unfolded state of chromosomes in non-dividing cells

What fills the nucleus and is surrounded by the nuclear membrane?

Nucleoplasm

What is the function of the nucleolus?

Involved in ribosome production

What are nuclear pores responsible for?

Allowing water and small particles to move freely, and RNA exits through them

What are the two types of Endoplasmic Reticulum (ER)?

Rough ER (RER) and Smooth ER (SER)

What is the function of Rough Endoplasmic Reticulum (RER)?

Synthesizes proteins for export or membrane formation

What does Smooth Endoplasmic Reticulum (SER) synthesize?

Lipids and lipid-containing molecules

What does the Golgi apparatus do?

Sorts, packages, and distributes lipids and manufactures macromolecules

What do lysosomes contain and what is their function?

Digestive enzymes that break down old cell parts and destroy bacteria

What are peroxisomes and their functions?

Small organelles that manufacture cholesterol and bile acids, and break down toxic substances

What are vesicles and their functions?

Small membrane-bound sacs that transport substances between organelles and store materials temporarily

What is the main function of vacuoles in plant cells?

Store water, ions, sugars, and regulate turgor pressure

What is the role of chloroplasts in plant cells?

Carry out photosynthesis and convert light energy into chemical energy

What is the function of mitochondria?

Break down energy-rich molecules and convert stored energy into usable energy (ATP)

What is the composition of the cell wall in plants?

Cellulose and pectin

What is the cytoskeleton?

An internal network of protein fibers that provides structural support and facilitates intracellular transport

What are cilia and flagella?

Appendages that assist in cell movement or moving substances along the cell surface

What is the Fluid Mosaic Model?

A description of the cell membrane as a semi-fluid phospholipid bilayer with a mosaic of proteins

Why is membrane fluidity important?

It is crucial for normal cell function

What is the importance of membrane fluidity?

Proper fluidity is crucial for normal cell function; it affects the permeability and functionality of the membrane.

How does temperature affect membrane fluidity?

At high temperatures, the bilayer becomes too fluid and porous; at low temperatures, it solidifies, forming a barrier.

What role do double bonds in fatty acid tails play in membrane fluidity?

Double bonds introduce kinks that prevent phospholipids from packing tightly, increasing fluidity.

How does the length of fatty acid tails affect membrane fluidity?

Longer fatty acid tails lead to stronger intermolecular attractions, resulting in less fluidity.

What is the effect of cholesterol on membrane fluidity at room temperature?

Cholesterol reduces fluidity at room temperature.

What is the role of cholesterol at low temperatures?

Cholesterol prevents solidification, stabilizing the membrane.

What are the two types of proteins found in the cell membrane?

Peripheral proteins (attached to the surface) and integral proteins (embedded within the membrane).

What are the functions of integral proteins in the cell membrane?

They transport substances across the membrane, catalyze chemical reactions, and facilitate cell-to-cell recognition.

What are glycolipids and glycoproteins?

Glycolipids are lipids with carbohydrate chains attached, while glycoproteins are proteins with carbohydrate chains. Both aid in cell recognition and communication.

How do glycolipids and glycoproteins contribute to cell identity?

They serve as receptor sites and help identify the cell with unique shapes that allow specific molecules to bind.

What is diffusion in the context of cell membranes?

Diffusion is the net movement of ions or molecules from an area of higher concentration to an area of lower concentration.

What is passive transport?

Passive transport allows substances to move across the cell membrane without energy, following their concentration gradient.

What is osmosis?

Osmosis is the movement of water across a semi-permeable membrane from an area of low solute concentration to high solute concentration.

What are isotonic, hypertonic, and hypotonic solutions?

Isotonic solutions have equal concentrations, hypertonic solutions have higher solute concentration outside the cell (causing water to leave), and hypotonic solutions have lower solute concentration outside the cell (causing water to enter).

What is facilitated diffusion?

Facilitated diffusion is the process where larger or charged molecules cross the membrane with the help of transport proteins, still following the concentration gradient.

What are the two types of transport proteins involved in facilitated diffusion?

Channel proteins (allow specific ions/molecules through quickly) and carrier proteins (bind to specific molecules and release them on the other side).

What is active transport?

Active transport moves solutes against their concentration gradient (low to high) and requires energy in the form of ATP.

What is the sodium-potassium pump?

A carrier protein that uses ATP to pump sodium out of the cell and potassium into the cell, maintaining low sodium and high potassium inside.

What is secondary active transport?

Secondary active transport uses the electrochemical gradient created by primary active transport to move other molecules or ions.

What is endocytosis?

Endocytosis is the process of moving materials into the cell, which can occur through phagocytosis, pinocytosis, or receptor-mediated endocytosis.

What is exocytosis?

Exocytosis is the process where large molecules or waste leave the cell using vesicles that fuse with the cell membrane.

What is the function of vesicles in membrane-assisted transport?

Vesicles transport large macromolecules in or out of the cell, requiring energy.

What is the role of clathrin in receptor-mediated endocytosis?

Clathrin forms a cage around the vesicle, aiding in the transport of specific molecules into the cell.