Bio exam 2

What are the 3 principles of cell theory?

1. All organisms are composed of one or more cells. 2. Cells are the basic living unit of structure and function. 3. All cells come from other cells.

What is magnification?

The increase in an object's image size.

What is resolution?

The ability of an instrument to show two nearby objects as separate.

What is contrast?

The difference that makes structures easier to see; cells are often stained to increase contrast.

What is a compound light microscope?

A microscope that uses visible light and glass lenses; can magnify up to about 1000×.

What is a stereomicroscope used for?

Looking at the outside of specimens; magnifies up to about 50×.

What does a scanning electron microscope (SEM) show?

Detailed external architecture and surfaces of specimens.

What does a transmission electron microscope (TEM) show?

Detailed internal cell structure.

What is the plasma membrane?

A boundary and gatekeeper surrounding the cell.

What is the cytoplasm?

The semifluid inside a cell made of water, salts, and dissolved organic molecules.

What is a lysosome?

A membrane-bound structure containing enzymes that digest food or damaged organelles.

What is the cytoskeleton?

A network of protein fibers that organizes cell structure and activities.

What are the 3 major cytoskeletal elements?

Actin filaments, intermediate filaments, and microtubules.

What are the functions of actin filaments?

Provide structure, form microvilli and pseudopods, and allow muscle contraction.

What are the functions of intermediate filaments?

Support the nuclear envelope, help form cell junctions, and strengthen structures like hair.

What are microtubules?

Hollow cylinders made of tubulin that help maintain cell shape and move organelles.

What do microtubules form during cell division?

The spindle apparatus.

What are cilia and flagella?

Hairlike projections that aid in cell movement.

How are cilia and flagella different?

Cilia are shorter and more numerous; flagella are longer and fewer.

What is the structure of cilia and flagella?

Membrane-bound cylinders with a 9+2 pattern of microtubules.

What is the endosymbiotic theory?

Mitochondria and chloroplasts came from prokaryotes that were engulfed by larger cells.

What were mitochondria originally?

Heterotrophic bacteria.

What were chloroplasts originally?

Cyanobacteria.

What evidence supports the endosymbiotic theory?

They have double membranes, circular DNA, bacterial-like ribosomes, and divide by splitting.

What is the fluid mosaic model?

The plasma membrane is a fluid structure made primarily of phospholipids with proteins embedded in it.

• proteins float inside or within the phospholipid bilayer

What does selectively permeable mean?

The membrane allows some substances through while restricting others.

What are the main components of the plasma membrane?

Phospholipids and proteins.

Why can't glucose freely cross the plasma membrane?

Glucose is a large polar molecule with hydroxyl groups.

What is a channel protein?

A membrane protein that allows certain molecules or ions through.

What are aquaporins?

Channel proteins specialized for transporting water.

What is a carrier protein?

A protein that binds a molecule or ion and changes shape to transport it across the membrane.

What is facilitated diffusion?

Movement of molecules down their concentration gradient using a carrier protein; no energy is required.

What is active transport?

Movement of molecules against their concentration gradient using energy and carrier proteins.

• when a substance moves from an area of low concentration to an area of high concentration while using energy

What energy is usually used for active transport?

ATP.

What is exocytosis?

Movement of materials out of the cell when a vesicle fuses with the plasma membrane.

What is endocytosis?

Movement of materials into the cell using membrane-bound vesicles.

What is phagocytosis?

Endocytosis of large particulate matter.

What is pinocytosis?

Endocytosis of liquids and small particles dissolved in liquid.

What is receptor-mediated endocytosis?

A type of pinocytosis involving receptors and a coated pit.

Which transport processes require no energy?

Diffusion and facilitated transport.

Which transport processes require energy?

Active transport, exocytosis, and endocytosis.

What happens when blood glucose rises?

Pancreatic beta cells release insulin.

What is insulin?

A hormone released by pancreatic beta cells that signals cells to take up glucose.

How does insulin affect muscle and liver cells?

Insulin binds to receptors and causes GLUT4-containing vesicles to merge with the cell membrane.

What is GLUT4?

A glucose transporter that allows glucose to enter cells by facilitated diffusion.

How does GLUT4 get into the cell membrane?

Insulin causes GLUT4-containing vesicles to fuse with the plasma membrane.

How does glucose enter cells after insulin signaling?

Through GLUT4 by facilitated diffusion.

What is signal transduction?

A process in which a signal causes a response inside a cell.

What is diabetes mellitus?

A condition involving high blood glucose levels over a long period.

What are common symptoms of diabetes in the notes?

Frequent urination, increased thirst, and increased hunger.

What is energy?

The capacity to cause change or perform work.

What is the first law of thermodynamics?

Energy cannot be created or destroyed; it can only be changed from one form to another.

What is the second law of thermodynamics?

Energy cannot change form without some energy becoming unusable, usually as heat.

What is entropy?

The relative amount of disorganization in a system.

Which has greater organization: glucose or CO₂ and H₂O?

Glucose is more organized.

What happens to total entropy during cell processes?

Every process increases the total entropy of the universe.

What is metabolism?

The sum of all chemical reactions in a cell.

What is catabolism?

The breaking down of molecules.

What is anabolism?

The building of molecules.

What is an exergonic reaction?

A reaction that releases energy; products have less free energy than reactants.

What is an endergonic reaction?

A reaction that requires an input of energy; products have more free energy than reactants.

What is ATP?

Adenosine triphosphate; the main energy molecule used by cells.

How is ATP formed?

ADP combines with a phosphate using energy.

What is the ATP cycle?

ATP releases energy when converted to ADP + phosphate, and energy is used to rebuild ATP.

What is a coupled reaction?

An exergonic reaction provides energy to drive an endergonic reaction.

What is a metabolic pathway?

A series of linked chemical reactions that are controlled and produce an end product.

What is an enzyme?

A protein catalyst that speeds up chemical reactions without being used up.

What is activation energy?

The energy that must be added to start a chemical reaction.

How do enzymes affect activation energy?

Enzymes lower activation energy, increasing the reaction rate.

What is an enzyme's active site?

The part of an enzyme that binds with its specific substrate.

What is a substrate?

The molecule that an enzyme binds to and acts upon.

How does substrate concentration affect enzyme activity?

More substrate causes more enzyme-substrate collisions until active sites become filled.

How does temperature affect enzyme activity?

Activity generally increases as temperature rises, but extreme temperatures can damage enzymes.

How does pH affect enzyme activity?

Each enzyme has an optimal pH; extreme pH can alter structure and denature the enzyme.

What is enzyme inhibition?

A process in which something decreases enzyme activity.

What is feedback inhibition?

A product binds to an enzyme and changes the active site's shape, slowing the pathway.

What is a cofactor?

A non-protein helper, often an inorganic ion such as copper, zinc, or iron.

What is a coenzyme?

An organic, non-protein cofactor; many coenzymes come from vitamins.

What is cellular respiration?

The release of energy from molecules such as glucose to synthesize ATP.

• Best associated with mitochondrion

What is the overall equation for cellular respiration?

Glucose + oxygen → carbon dioxide + water + ATP/energy.

What are the 4 phases of cellular respiration?

Glycolysis, preparatory reaction, citric acid cycle, and electron transport chain.

What are NAD+ and FAD?

Electron carriers that transport high-energy electrons.

What does NAD+ become when it carries electrons?

NADH.

What does FAD become when it carries electrons?

FADH₂.

Where does glycolysis occur?

In the cytoplasm.

Does glycolysis require oxygen?

No.

What happens during glycolysis?

One 6-carbon glucose is broken into two 3-carbon pyruvate molecules.

How many ATP are used during the energy-investment phase of glycolysis?

2 ATP.

What happens during the energy-harvesting phase of glycolysis?

NADH is produced and 4 ATP are formed.

What is the net ATP gain from glycolysis?

2 ATP.

What is substrate-level phosphorylation?

An enzyme transfers a phosphate directly to ADP to make ATP.

What is fermentation?

A process that allows ATP production to continue without oxygen by regenerating NAD+.

What happens during fermentation in animal cells?

Pyruvate accepts electrons and hydrogen ions to form lactate; NADH becomes NAD+.

What happens during fermentation in yeast?

Pyruvate is converted into ethanol.

Why is fermentation useful?

It regenerates NAD+ and provides a quick burst of energy when oxygen is low.

What are disadvantages of fermentation?

It produces much less ATP and lactate or ethanol can be toxic.

Where does the preparatory reaction occur?

In the mitochondria.

What happens during the preparatory reaction?

Pyruvate becomes acetyl-CoA, CO₂ is released, and NADH is produced.

How many times does the preparatory reaction occur per glucose?

Twice.

Where does the citric acid cycle occur?

In the mitochondrial matrix.