Biology Exam 2

What kind of structure is the Cell Membrane?

Phospholipid Bilayer

Phospholipid Bilayer

Made of phospholipids with hydrophilic (water attracting) polar heads on the outside and hydrophobic (water repelling) non polar fatty acid tails on the inside. It also dictates which molecules can cross it to go in and out of the cell and which mechanisms it requires.

The Hydrophobic Core

an oily middle layer between the bilayer that stops water-loving, charged, or large molecules from drifting through freely

What passes through the Phospholipid Bilayer easily?

small, non polar molecules are the only substances that pass through easily and freely directly through the bilayer through simple diffusion without the help of membrane proteins

What are the molecules that are difficult to pass through the Phospholipid Bilayer?

Polar molecules, large molecules, and charged ions can pass through the membrane but not easily, it takes time and assistance from specialized membrane proteins to cross

Osmosis

the natural movement of water molecules through a thin barrier into an area with a higher amount of dissolved substances. It goes from High to Low in reference to the water movement (high amounts of water moves to the area with a low amount of water and high amount of solute)

What is the water movement in a Hypotonic solution?

Hypo (low or below) where the water flows from an area of low concentration of solutes (high amount of water) to an area of high solutes (low amount of water). This causes the cell to swell because water is entering the cell

What is the water movement in a Hypertonic solution?

Hyper (above) has a higher amount of solutes outside of the cell than the inside. The water naturally travels from an area of low concentration of solutes (inside the cell) to an area of high concentration of solutes (outside of the cell). This causes the cell to shrink because water is exiting the cell.

What is the water movement in a Isotonic solution?

there is no net movement of water, the water molecules move equally in and out of the cell across the membrane, resulting in no net movement of water

Why do Hypo, Hyper, and Isotonic solutions matter?

they matter because they control how water moves into and out of cells, which determines whether a cell stays healthy, shrinks, or bursts

Passive transport

Goes down the concentration gradient, is a part of diffusion, goes from high to low, does NOT use ATP (energy), solute independent, and is the only one in Osmosis

Facilitated transport

Goes down the concentration gradient, allows passage of other molecules, requires solute-specific transport proteins, and include aquaporins

Active transport

Goes against the concentration gradient, uses ATP (energy), and is the primary method for macromolecules (sugars, amino acids, and nucleotides)

Aquaporins

specialized membrane proteins that form tiny tunnels in cell membranes to let water molecules move in and out very quickly

Kinetic energy

the energy an object or molecule possesses due to its motion, which drives cellular processes, molecular transport, and organismal movement. Examples can be thermal energy and light.

Potential energy

stored energy that depends on the structure, arrangement, or position of matter, and it has the capacity to do cellular work. An example of this is a high concentration of ions sitting inside or outside of the cell. (potential energy has the potential to move but is not currently moving)

Flow of energy in Exergonic reaction

the energy flows outward from the reacting system into its surroundings (inside of the cell to the outside of the cell)

Flow of energy in Endergonic reaction

the energy moves inward from the surroundings into the system, meaning energy is absorbed and stored in the newly formed chemical bonds (outside of the cell to the inside of the cell)

How does ATP hydrolysis drives cellular work?

The breakdown of ATP is exergonic and that drives endergonic reactions. It drives cellular work by releasing stored energy and transferring a phosphate group to other molecules, making them active.

How do enzymes speed reactions?

Enzymes lower the activation energy which speeds up the reaction

How do inhibiters block or slow down enzymes?

they bind enzymes and prevent them from efficiently converting substrates into products

What are the two types of Enzyme Inhibition?

Reversible and Irreversible

Reversible Enzyme Inhibition

reversible inhibiters bind enzymes temporarily through non-covalent bonds and can be undone

Irreversible Enzyme Inhibition

irreversible inhibiters permanently modify or destroy enzyme activity, often by forming strong covalent bonds

Why does O₂ matter as the final electron acceptor?

it clears the electron transport chain, allowing cells to continuous produce energy

What is the difference between oxidation and reduction?

oxidation is the loss of electrons while reduction is the gain of electrons. These two processes always happen together in a chemical reaction.

How do electron carriers move energy from glucose to oxygen?

It moves energy from glucose to oxygen by Electron carriers. The electron carriers shuttle high-energy electrons from the breakdown of glucose to the electron transport chain, where the energy is used to make ATP before the electrons are handed off to oxygen.

Why is ATP a rechargeable currency?

it continuously cycles between high-energy charged state (ATP) and low-energy discharged state (ADP) by gaining or losing a phosphate group.

Aerobic respiration

produces a high yield of ATP using oxygen in the cytoplasm and mitochondria

Fermentation

produces a low yield of ATP without using oxygen entirely within the cytoplasm

What are the types of Fermentation?

Lactic Acid and Alcoholic Fermentation

Lactic Acid Fermentation

sugars are converted into lactic acid (or lactate and NAD+)

Alcoholic Fermentation

sugars are converted into alcohol (ethanol), carbon dioxide (CO₂), and NAD+

How do pigments absorb light and why do the wavelengths that they reflect determine what we see?

pigments appear colored because they absorb specific wavelengths of visible light and reflect or transmit the remaining wavelengths that reach our eyes

Why do light and CO₂ matter as inputs?

light and carbon (CO₂) are two of the most critical inputs for the life on Earth because they are the primary driving forces behind photosynthesis, the process plants algae, and some bacteria use to create food and energy

How do electron carriers move energy from light to sugar?

Electron carriers like NADP+ and NADPH move energy from light to sugar by absorbing high-energy electrons during the light reactions and delivering that chemical energy and reducing power to the Calvin Cycle to build glucose

What are the two stages of photosynthesis?

Light-Dependent Reactions and Light-Independent Reactions (Calvin Cycle)

Light Dependent Reaction

convert sunlight into chemical energy by producing ATP and NADPH while releasing oxygen

Light-Independent Reaction

use chemical energy from light-dependent reactions to turn carbon dioxide into sugar

Photosynthesis

The process by which green plants, algae, and some bacteria convert light energy from sun into chemical energy