Week 2: The Cell and Water

Cell Structure

Cell S___ is made up of individual components with specific functions essential for life processes.

Cell Structure

Components of Cell S__ include the cell wall, cell membrane, cytoplasm, nucleus, and cell organelles.

Cell Membrane

Cell M___ serves as the barrier for cell contents and is made of a double phospholipid layer.

Hydrophilic Heads

Hydrophi____ is the “water-loving” part of the phospholipid layer in the cell membrane.

Hydrophobic Tails

Hydropho__ is the “water-fearing” part of the phospholipid layer in the cell membrane.

Other Components of Cell Membrane

Other components_ Includes proteins, cholesterol, and glycoproteins.

Cell Wall

Cell W__ is a non-living component that covers the outermost layer of a cell.

Structure of Cell Wall

Structure of C___ is a rigid and stiff structure surrounding the cell membrane.

Function of Cell Wall

Function of C__ provides shape and support to the cell and protects it from mechanical shocks and injuries.

Presence of Cell Wall

Presence of C__ is found only in eukaryotic plants, fungi, and some prokaryotic organisms.

Cytoplasm

Cyt__ is a thick, clear, jelly-like substance inside the cell membrane.

Function of Cytoplasm

Function of Cy__ is that most of the cell’s chemical reactions take place in the cytoplasm.

Cytoplasm

Cell organelles such as the endoplasmic reticulum, vacuoles, mitochondria, and ribosomes are suspended in the cyt___.

Nucleus

Nucle___ contains the hereditary material of the cell, the DNA.

Function of Nucleus

Function of Nucl__ sends signals to the cell to grow, mature, divide, and die.

Nuclear Envelope

Nuclear En__ is a membrane surrounding the nucleus that separates the DNA from the rest of the cell.

Nucleolus

Nucleo__ is the site of ribosome synthesis; also involved in controlling cellular activities and reproduction.

Nuclear Membrane

Nuclear M__ protects the nucleus by forming a boundary between it and other cell organelles.

Chromosomes

Chromo___ play a key role in determining the sex of an individual; each human cell contains 23 pairs of chromosomes.

Endoplasmic Reticulum (ER)

Endo_ Reti transports substances throughout the cell; involved in carbohydrate metabolism, lipid and steroid synthesis, and protein production.

Golgi Bodies

Golgi____ is known as the cell’s “Post Office”; transport materials within the cell.

Ribosomes

Ribo__ is the protein synthesizers of the cell.

Mitochondria

Mitocho__ is called the “powerhouse of the cell” because they produce ATP, the cell’s energy currency.

Lysosomes

Lyso___ protect the cell by engulfing foreign bodies and aid in cell renewal; called the cell’s “suicide bags.”

Chloroplasts

Chloro__ is yhe main organelles of photosynthesis; contain the pigment chlorophyll.

Vacuoles

Vac___ store food, water, and other waste materials in the cell.

Prokaryotic Cells

Pro__ Cells are cells that lack internal cellular bodies (organelles). Examples: bacteria and archaea.

Eukaryotic Cells

Eu____ Cells are cells that contain organelles. Examples: protists, fungi, plants, and animals (everything except prokaryotes).

Hydrogen Bonds

Hydro_ B: Water molecules form hydrogen bonds due to polarity: oxygen has a partial negative charge and hydrogens partial positive charges.

Hydrogen Bonds

Hydro_ B: Each water molecule can form up to four bonds. These bonds are short-lived but collectively give water structure and unique properties.

Biological Importance of Hydrogen Bonds

Biological imporance of Hydro__ Bonds is that they stabilize large biomolecules (DNA, proteins), enable water’s solvent abilities, and are crucial for protein structure and properties.

Hydrogen Bonding

Hydro__ Bonding is a special dipole-dipole attraction important in the 3 major macromolecules; responsible for enzyme structure and water’s cohesiveness.

Extremely Cohesive Liquid

Hydrogen Bonding between water molecules makes water an extremely ___ liquid.

Cohesion

Cohe__ is the attraction between water molecules due to hydrogen bonding.

Cohesion

Cohe__ is responsible for water’s high surface tension and contributes to the movement of water in plants through capillary action, allowing it to travel from roots to leaves.

Attracted to each other

In Cohesion, water molecules are attracted to ___. (because of hydrogen bonding)

Adhesion

Adhe___ is the attraction between water molecules and other types of molecules or surfaces.

Adhesion

Adhe__ helps water “stick” to the walls of plant vessels, counteracting gravity and aiding in water transport.

Water

Wat__ has a high specific heat capacity, meaning it can absorb or release substantial heat with only a slight change in its own temperature.

Biological Importance of High Specific Heat

Biological Importance of High ___ heat is that it stabilizes temperature in organisms and environments, protecting cellular activities from rapid temperature changes.

Large amount of energy

Water requires a large amount of ___ to change from liquid to gas (evaporation).

Biological Importance of High Heat of Vaporization

Biological Importance of High__Vaporization is that it enables cooling mechanisms such as sweating and transpiration, helping regulate cellular and body temperature.

Remain liquid

Molecules with high energy evaporate, medium energy molecules are pulled back into the liquid, and low energy molecules remain___.

Water as a Solvent

Water as a sol___ readily dissolves other polar molecules and ionic compounds.

Hydrophilic Compounds

Hydrophi__ Compounds that dissolve easily in water.

Hydrophobic Interactions

Hydropho__ Nonpolar molecules do not dissolve in water and instead group together due to hydrophobic interactions.

Water

Wat__ as “Universal Solvent” dissolves more substances than any other liquid due to its polarity and hydrogen-bonding ability, allowing it to solvate ions and polar molecules.

Biological Importance of Universal Solvent

Biological Importance of univ_ s is that most cellular reactions occur in aqueous solutions. Water’s solvent property enables the transport and interaction of nutrients, waste, and biomolecules.

Hydrophobic Interactions

Hydropho__ Inte__ Non-polar molecules do not dissolve in water; instead, they aggregate together in aqueous environments.

Biological Importance of Hydrophobic Interactions

Biological Importance of HydrophoInte is that these interactions drive protein folding, cell membrane formation, and the creation of specialized cellular compartments.

Hydrophobic Molecules

Hydropho__ Mole__ is non-polar molecules, often with long carbon chains, that are poorly soluble in water and do not interact with it.

Examples of Nucleophiles

Examples of Nucleophi___ are oxygen, nitrogen, sulfur, carbon, and water (weak).

Nucleophiles in Condensation Reactions

Nucleophiles in Conde__ is important in condensation reactions, where hydrolysis is favored. In cells, these reactions occur only with hydrolases, usually require ATP, and exclude water to make reactions more favorable.

Nucleophilic Nature of Water

Nucleophilic Nature of Wat__ acts as a nucleophile (electron-pair donor) in hydrolysis, attacking electrophilic centers.

Biological Importance of Nucleophilic Water

Biological Importance of Nucleophilic Wat__ is that hydrolytic reactions are fundamental to metabolism, including digestion and energy production.

Ionization of Water

Ionization of Wa__ is a small fraction of water molecules dissociate into hydrogen ions (H⁺) and hydroxide ions (OH⁻): H₂O ⇌ H⁺ + OH⁻.

Biological Importance of Ionization

Biological Importance of Ioni__ is crucial for biochemical reactions, acid-base balance, and cellular signaling.

pH of Water

pH measures hydrogen ion concentration. Pure water is neutral with pH 7 at room temperature, where [H⁺] equals [OH⁻] equals 1×10⁻⁷ M.

Biological Importance of pH

Biological Importance of p_ is that cellular enzymes and processes are highly sensitive to pH; water’s natural pH and buffering capacity are vital for homeostasis.

pH Scale

pH equals –log [H⁺]. At equilibrium: pH equals –log(1.0 × 10⁻⁷)