Life Science Mid-Term FLASHCARDS

Phospholipid bilayer

Structural component of cell membranes, consisting of a double layer of phospholipids, with hydrophilic heads facing outward and hydrophobic tails facing inward.

Active transport

Movement of substances across a cell membrane using energy, typically against a concentration gradient.

Passive transport

Movement of substances across a cell membrane without the use of energy, usually along a concentration gradient.

Osmosis

The diffusion of water across a selectively permeable membrane.

Hypertonic solution

A solution with a higher concentration of solutes compared to another solution, leading to cell shrinkage when placed in it.

Hypotonic solution

A solution with a lower concentration of solutes compared to another solution, causing cells to swell when placed in it.

Isotonic solution

A solution with an equal concentration of solutes compared to another solution, causing no net movement of water into or out of cells.

Facilitated diffusion

Process by which substances are transported across cell membranes by means of protein channels without using energy.

Mole

Unit of measurement in chemistry that represents 6.02 x 10^23 particles (atoms, molecules, ions), also known as Avogadro's number.

Concentration

The amount of solute present in a certain volume of solvent, often expressed in units like g/L or mol/L.

Molar mass

The mass of one mole of a substance, typically expressed in grams per mole (g/mol).

Δ% change

Percentage change formula calculated as (final - initial) / initial x 100.

Channel proteins

Proteins that create a pathway for molecules to pass through the plasma membrane, often facilitating selective transport.

Glycoproteins

Proteins with carbohydrate groups attached, involved in cell recognition and signaling.

Cholesterol in cell membrane

A lipid that stabilizes membrane structure and fluidity, crucial for maintaining proper cell function.

Diffusion

The movement of particles from an area of higher concentration to an area of lower concentration until equilibrium is reached.

Cell Membrane Function

Regulates substance passage, maintains integrity, and aids cell communication, composed of a phospholipid bilayer, proteins, and cholesterol.

Phospholipid Bilayer Structure

A double layer of phospholipids with hydrophilic (polar) heads facing external aqueous environments and hydrophobic (nonpolar) tails facing inward.

Role of Cholesterol in Cell Membrane

Helps maintain membrane fluidity and stability by preventing it from becoming too rigid or too fluid at varying temperatures.

Role of Channel Proteins

Form hydrophilic pores in the membrane, allowing specific ions or molecules to pass through via passive transport.

Role of Glycoproteins

Act as cell recognition markers and adhesion sites on the external surface of the cell membrane.

Hydrophilic Region

A 'water-loving' part of a molecule that readily interacts with water, typically due to its polar nature (e.g., phospholipid heads).

Hydrophobic Region

A 'water-fearing' part of a molecule that repels water, typically due to its nonpolar nature (e.g., phospholipid tails).

Energy in Passive Transport

Does not require cellular metabolic energy (ATP), as substances move spontaneously down their concentration gradient.

Energy in Active Transport

Requires cellular metabolic energy (e.g., ATP) to move substances against their concentration gradient.

Concentration Gradient

The difference in concentration of a substance across a space; particles tend to move from areas of high concentration to low.

Effect of Hypertonic Solution on Animal Cell

Water leaves the cell, causing it to crenate (shrink and shrivel) due to osmosis.

Effect of Hypotonic Solution on Animal Cell

Water enters the cell, causing it to swell and potentially lyse (burst) due to osmosis.

Effect of Isotonic Solution on Animal Cell

No net movement of water; the cell maintains its normal shape and volume, achieving equilibrium.

Effect of Hypertonic Solution on Plant Cell

Water leaves the central vacuole and cytoplasm, causing the plasma membrane to pull away from the cell wall (plasmolysis).

Effect of Hypotonic Solution on Plant Cell

Water enters the central vacuole and cytoplasm, pushing the plasma membrane against the cell wall, making the cell turgid (firm).

Logol's Test for Starch

A positive test (presence of starch) results in a color change from yellow-brown to blue-black.

Benedict's Test for Glucose

A positive test for reducing sugars (like glucose) requires heating and results in a color change from blue to green, yellow, orange, or brick-red.

Reason for Facilitated Diffusion

Used for large or polar substances that cannot pass directly through the lipid bilayer, requiring assistance from transport proteins without energy.

Definition of a Mole (mol)

An amount of substance containing 6.02 imes 10^{23} particles (Avogadro's number), used to quantify atoms, ions, or molecules.

Avogadro's Number

The number of constituent particles (atoms, molecules, or ions) in one mole of a substance, which is approximately 6.02 imes 10^{23}.

Molar Mass Calculation

Determined by summing the average atomic masses of all atoms in a molecule as found on the periodic table; units are g/mol.

Unit g/L (g/dm^{3})

Grams per liter, a unit of concentration indicating the mass of solute in grams dissolved per liter of solution.

Unit mol/L (mol/dm^{3})

Moles per liter (Molarity), a unit of concentration indicating the number of moles of solute dissolved per liter of solution.

Concentration Definition

A measure of the amount of solute dissolved in a given amount of solvent or solution, representing the solute-to-solvent ratio.

Converting Moles to Particles

Multiply the number of moles by Avogadro's number (6.02 imes 10^{23}) particles/mol.

Converting Particles to Moles

Divide the number of particles by Avogadro's number (6.02 imes 10^{23}) particles/mol.

Converting Moles to Mass

Multiply the number of moles by the molar mass (g/mol) of the substance.

Converting Mass to Moles

Divide the mass (g) of the substance by its molar mass (g/mol).

GUESS Method

A systematic problem-solving approach: Given, Unknown, Equation, Substitute, Solve.

Potato Osmosis Lab Aim

To determine the precise concentration of a salt (NaCl) solution that is isotonic with potato cells by observing mass changes.

Percent Change Equation

Calculated as ((final - initial) / initial) imes 100.

Meaning of Negative Percent Change

Indicates a decrease in the measured quantity from the initial value.

Meaning of Positive Percent Change

Indicates an increase in the measured quantity from the initial value.

Saline Solution Challenge

A practical exercise involving calculations and measurements to prepare a solution of specific concentration (e.g., 0.1 mol/L NaCl).

Aqueous Solution

A solution in which water is the solvent.