Biology 160

Describe endergonic and exergonic reactions

*Endergonic reactions* are non spontaneous and require a certain amount of activation energy to occur (usually more than the overall energy of the exergonic reaction). *Exergonic reactions* are spontaneous and only require a small amount of energy to trigger the reaction and release free energy.

Describe endocytosis and exocytosis as a means of moving materials across the membrane.

*Endocytosis* - a type of active transport that moves particles, such as large molecules, parts of cells, and even whole cells, into a cell. *Exocytosis* - its purpose is to expel material from the cell into the extracellular fluid.

Discuss the concepts of free energy and activation energy

*Free energy* only takes a very small amount to have it react. It also reacts spontaneously. *Activation energy* requires energy in order to harvest and release the energy in the compound bonds.

Define facilitated diffusion and describe the role of channels or pores in facilitated diffusion.

*Materials diffuse across the plasma membrane with the help of membrane proteins.* A concentration gradient exists that would allow these materials to diffuse into the cell without expending cellular energy. However, these materials are ions are polar molecules that are repelled by the hydrophobic parts of the cell membrane. Facilitated transport proteins shield these materials from the repulsive force of the membrane, allowing them to diffuse into the cell. *Channels* are specific for the substance that is being transported. Channel proteins have hydrophilic domains exposed to the intracellular and extracellular fluids; they additionally have a hydrophilic channel through their core that provides a hydrated opening through the membrane layers (Figure). Passage through the channel allows polar compounds to avoid the nonpolar central layer of the plasma membrane that would otherwise slow or prevent their entry into the cell. *Aquaporins* are channel proteins that allow water to pass through the membrane at a very high rate.

List the basic tenets of cell theory.

1) All living organisms are composed of one or more cells. 2) The cell is the basic unit of Life. 3) New cells arise from pre-existing cells.

Explain why fluidity is an essential property of biological membranes.

1) Allows membrane proteins to diffuse rapidly 2) It permits membrane lipids and proteins to diffuse from sites where they are inserted into the bilayer after their synthesis to other regions of the cell. 3) It allows membranes to fuse with one another and mix their molecules. 4) it ensures that membrane molecules are distributed evenly between daughter cells when a cell divides. *(Book Answer)*: The fluid characteristic of the cell membrane allows greater flexibility to the cell than it would if the membrane were rigid. It also allows the motion of membrane components, required for some types of membrane transport.

Identify the components of cellular membranes and discuss the function(s) of each.

1) Nuclear Envelope - outermost layer of nucleus made of two layers of phospholipid membrane. The nuclear envelope is punctuated with pores that control the passage of ions, molecules, and RNA between the nucleoplasm and cytoplasm. 2) Lysosomes - Destroy pathogens 3) Vesicles - Pathways for molecules to move between parts of the cell 4) ER - SER does synthesis of carbohydrates, lipids, and steroid hormones. RER modifies proteins structurally, also makes phospholipids for cell membrane. 5) Golgi Apparatus -Receive lipids & proteins from vesicle connected to ER, sort and package them, then distribute them out through vesicles. 6) Plasma Membrane - Regulate what comes in and out of the cell

Discuss the functions of the plasma membrane.

1) Phospholipid - Main fabric of the membrane 2) Cholesterol - Attached between phospholipids and between the two phospholipid layers. 3) Integral proteins (for example, integrins) - Embedded within the phospholipid layer(s). May or may not penetrate through both layers. 4) Peripheral proteins - On the inner or outer surface of the phospholipid bilayer; not embedded within the phospholipids. 5) Carbohydrates (components of glycoproteins and glycolipids) - Generally attached to proteins on the outside membrane layer.

Compare and contrast the main characteristics of prokaryotic and eukaryotic cells.

1) Prokaryotic Cells lack a nucleus; DNA found in its nucleoid. 2) Prokaryotic sometimes have a Fimbriae, a Capsule, a Flagella or a Pili. - Fimbriae are used by bacteria to attach to a host cell. - The capsule enables the cell to attach to - surfaces in its environment. - Flagella are used for locomotion. - Pili are used to exchange genetic material during a type of reproduction called conjugation. 3) Prokaryotic are significantly smaller than Eukaryotic meaning molecules diffuse quicker with less distance to travel. 4) Prokaryotic are predominantly single celled organisms. 5) Eukaryotic cells are larger and can house organelles that split up cell processes meaning more complex molecules can be created.

List the functions of membrane proteins.

1) Transport. MOVEMENT OF CHEMICALS INTO OR AROUND CELL. 2) Enzymatic activity. A protein built into the membrane with active site exposed. 3) Signal Transduction. 4) Cell-cell recognition. 5) Intercellular Joining. 6) Attachment to the cytoskeleton & extracellular matrix (ECM)

Describe the main components of the eukaryotic cell and their functions.

1) a membrane-bound nucleus; 2) numerous membrane-bound organelles such as the endoplasmic reticulum, Golgi apparatus, chloroplasts, mitochondria, and others; and 3) several, rod-shaped chromosomes.

Describe the functions of cellular structures possessed by all cells.

1) a plasma membrane, an outer covering that separates the cell's interior from its surrounding environment; 2) cytoplasm, consisting of a jelly-like cytosol within the cell in which other cellular components are found; 3) DNA, the genetic material of the cell; and 4) ribosomes, which synthesize proteins.

Explain the first and second laws of thermodynamics

1. Energy cannot be created or destroyed 2. Entropy always increases

Explain the role of ATP as the cellular energy currency

ATP is made in the cell as a necessary source of energy for the cell to use. It is very useful because of the quick release of energy when chemically reacting ATP into ADP and breaking the chemical bond.

Know what oxidation and reduction are

An *Oxidation* reaction strips the electron form an atom in a compound. A *Reduction* reaction gives this electron to another compound. The shift of an electron from one compound to another removes some potential energy from the first compound (the oxidized compound) and increases the potential energy of the second compound (the reduced compound).

Discuss enzyme regulation by various factors

Enzyme action must be regulated so that in a given cell at a given time, the desired reactions are being catalyzed and the undesired reactions are not. Enzymes are regulated by cellular conditions, such as temperature and pH. They are also regulated through their location within a cell, sometimes being compartmentalized so that they can only catalyze reactions under certain circumstances. Inhibition and activation of enzymes via other molecules are other important ways that enzymes are regulated. Inhibitors can act competitively, noncompetitively, or allosterically; noncompetitive inhibitors are usually allosteric. Activators can also enhance the function of enzymes allosterically. The most common method by which cells regulate the enzymes in metabolic pathways is through feedback inhibition. During feedback inhibition, the products of a metabolic pathway serve as inhibitors (usually allosteric) of one or more of the enzymes (usually the first committed enzyme of the pathway) involved in the pathway that produces them.

Describe the role of enzymes in metabolic pathways

Enzymes are able to speed up the process of chemical reactions by attaching to a molecule and decreasing the needed activation energy.

Identify the inputs (reactants) and outputs (products) for cellular respiration for each stage: Glycolysis Transition step Kreb's Cycle Electron Transport Chain

Glycolysis: Glucose (Reactant)/2 pyruvates, 4 ATP (2 Net ATP), 2 NADH molecules (Products) Transition Step: Pyruvate (Reactant)/acetyl CoA, Oxygen joins with C to make 2 CO2, 2 NADH (Products) Kreb's Cycle: acetyl CoA+oxaloacetate (Reactants)/4 CO2, 2 ATP, 6 NADH, 2 FADH2 Electron Transport Chain: NADH and FADH2 (Reactants)/ 6 H2O, 34 ATP

Discuss the concept of entropy

High entropy means high disorganization and low energy. While on the contrary, Low entropy means low disorganization and high energy.

Describe two properties of phospholipid membranes.

Hydrophilic ends pointing outwards and Hydrophobic ends pointing inwards towards each other.

Know how ADP becomes ATP

In the cytoplasm or mitochondra, with energy derived from glucose catabolism, a third phosphate is added to Adenine *di*-phosphate (ADP) to create Adenine *tri*-phosphate (ATP). When one of these phosphates is removed from ATP this is an exergonic reaction that releases free energy.

Explain the difference between kinetic and potential energy

Kinetic energy is a type of energy associated with objects or particles in motion Potential energy is a type of energy that has the potential to do work; stored energy

Predict whether molecules and ions will pass easily through biological membranes based on their size, polarity, and formal charge.

Lipid-soluble material with a low molecular weight can easily slip through the hydrophobic lipid core of the membrane. Substances such as the fat-soluble vitamins A, D, E, and K readily pass through the plasma membranes in the digestive tract and other tissues. Fat-soluble drugs and hormones also gain easy entry into cells and are readily transported into the body's tissues and organs. Molecules of oxygen and carbon dioxide have no charge and so pass through membranes by simple diffusion. nonpolar or lipid-soluble materials pass through plasma membranes more easily than polar materials, allowing a faster rate of diffusion. While some polar molecules connect easily with the outside of a cell, they cannot readily pass through the lipid core of the plasma membrane. Additionally, while small ions could easily slip through the spaces in the mosaic of the membrane, their charge prevents them from doing so. Ions such as sodium, potassium, calcium, and chloride must have special means of penetrating plasma membranes. Simple sugars and amino acids also need help with transport across plasma membranes, achieved by various transmembrane proteins (channels).

Define diffusion.

Movement of particles from an area of high concentration to an area of low concentration until the concentration is equal across a space.

Describe how energy is released through hydrolysis of ATP

The bond is broken, turning it into ADP and releasing the potential energy stored within the bond.

Explain how enzymes function as molecular catalysts

They decrease the minimum amount of activation energy needed to begin the chemical reaction.

Know what coupled reactions are

This is where the energy created by one exergonic reaction provides the activation energy necessary to start an endergonic reaction. The most common form of this is with ATP and glycolysis in the cells.

Discuss how chemical reactions play a role in energy transfer

chemical reactions, such as catabolic ones which involve the breaking down of complex molecules to simpler molecules, releases potential energy contained within the complex molecules.

Identify and discuss cellular responses to hypertonic, hypotonic, and isotonic solutions.

hypotonic - In a hypotonic situation, the extracellular fluid has lower osmolarity than the fluid inside the cell, and water enters the cell. It also means that the extracellular fluid has a higher concentration of water in the solution than does the cell. In this situation, water will follow its concentration gradient and enter the cell. hypertonic - a hypertonic solution, the prefix hyper- refers to the extracellular fluid having a higher osmolarity than the cell's cytoplasm; therefore, the fluid contains less water than the cell does. Because the cell has a relatively higher concentration of water, water will leave the cell. isotonic - In an isotonic solution, the extracellular fluid has the same osmolarity as the cell. If the osmolarity of the cell matches that of the extracellular fluid, there will be no net movement of water into or out of the cell, although water will still move in and out.

Define osmosis.

the diffusion of water through a selectively permeable membrane (high to low) *water will move from the side of the membrane with lower osmolarity (and more water) to the side with higher osmolarity (and less water).* Osmolarity describes the total solute concentration of the solution. A solution with low osmolarity has a greater number of water molecules relative to the number of solute particles; a solution with high osmolarity has fewer water molecules with respect to solute particles.