General Chemistry of Cells

The statement that animal and plant cells do not share a common nucleus is incorrect because both types of cells have a nucleus, which houses their genetic material.

The statement that living organisms are not governed by the laws of chemistry and physics is false. All matter, living or nonliving, is subject to the same fundamental laws of nature.

The statement that genes are likely made of proteins is incorrect. DNA, though composed of only four nucleotide monomers, carries genetic information and is key to protein synthesis.

The statement that sunlight is the only source of energy in the biosphere is false because some organisms, like deep-sea organisms, rely on energy from chemical reactions rather than sunlight.

The statement that the resolution of cellular structures below 200 nm is impossible due to the wavelength of light is false. Techniques like electron microscopy can overcome the light diffraction limit by using beams of electrons.

Fluorescence microscopy can be used to visualize and identify specific cells and structures due to the ability of fluorescent dyes to specifically bind to certain molecules.

It is possible to separate and characterize individual DNA molecules based on size and other properties through techniques like gel electrophoresis, which relies on different DNA fragment migration rates.

The use of different fluorescent dyes to visualize proteins A and B in C. elegans embryos suggests the use of fluorescence microscopy. The overlay of images suggests potential protein interaction, but further investigation is needed to confirm.

The energy of electromagnetic radiation is inversely proportional to its wavelength. This means shorter wavelengths have higher energy.

Compounds with only single bonds absorb energy in the ultraviolet (UV) region of the electromagnetic spectrum.

Compounds with double or triple bonds absorb energy in the visible and infrared regions of the electromagnetic spectrum.

The long hydrocarbon tails of phospholipids create a non-aqueous environment within biological membranes.

Biological membranes act as permeability barriers, controlling the movement of substances into and out of cells.

Biological compounds often contain carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.

The wavelengths of electromagnetic radiation are measured in nanometers (nm).

Ethylene gas is used commercially to accelerate fruit ripening.

Molecules with both hydrophobic and hydrophilic regions, like phospholipids in cell membranes.

Hydrophobic molecules, like hydrocarbons, lack polar regions and don't interact with water molecules.

Hydrophilic molecules, like those with polar groups (OH, SH, C=O, CHO), interact readily with water due to hydrogen bonding.

Sterols, like cholesterol in animal cells, are a type of lipid that helps maintain membrane fluidity.

The structure of a membrane phospholipid, like phosphatidylethanolamine, demonstrates its amphipathic nature with a hydrophilic head and hydrophobic tails.

Amines are protonated at normal cell pH, becoming positively charged and acting like sodium ions in membranes.

Charged organic molecules are typically soluble in water because they interact with water molecules through electrostatic interactions.

The tendency of a liquid's surface to resist being broken, due to the strong cohesive forces between its molecules.

The amount of heat energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius. It's high for water.

A type of bond formed between a hydrogen atom covalently linked to a highly electronegative atom (like oxygen) and an electron pair of a neighboring molecule.

The uneven distribution of electrons in a molecule, resulting in a partial positive charge on one end and a partial negative charge on the other.

The ability of water to move upward through the vascular tissues of plants, driven by the cohesive forces between water molecules.

The movement of molecules from an area of high concentration to an area of low concentration.

The process by which cells take in substances from their surroundings, by engulfing them in membrane-bound vesicles.

The process by which cells release substances from their interior to the outside, by enclosing them in membrane-bound vesicles.

Cells maintain a specific internal environment by controlling what enters and exits. This selective permeability is essential for life, enabling cells to obtain nutrients, eliminate waste, and maintain their structure and function.

Molecules with smaller sizes (below 100 molecular weight) can easily pass through cell membranes regardless of polarity, including water.

Water, despite being polar, readily crosses cell membranes due to its small size, allowing cells to regulate water content.

Large, uncharged polar molecules like glucose have a harder time crossing cell membranes compared to smaller molecules.

Membranes act like barriers, controlling which molecules can enter or leave a cell. This is essential for maintaining the internal environment needed for cellular function.

Phospholipids, building blocks of cell membranes, have polar heads (charged) and non-polar tails (uncharged). This duality creates a barrier that controls how molecules pass.

The hydrophobic (water-repelling) tails of phospholipids within the membrane create a non-aqueous environment, making it difficult for polar molecules to pass through.

Charged and polar molecules have a hard time penetrating cell membranes because the membrane interior is non-polar. They require special transport mechanisms to cross.

The movement of substances across a membrane is regulated by its structure. Specifically, the hydrophobic interior of the lipid bilayer restricts the passage of charged molecules like ions. This is because the ions are surrounded by a sphere of hydration, making it difficult for them to interact with the hydrophobic tails of the membrane.

The lipid bilayer is more permeable to water than to small, charged ions like sodium (Na+) and potassium (K+). This is because the hydrophobic environment inside the membrane makes it energetically unfavorable for charged ions to pass through.

Membranes are crucial for regulating the flow of molecules in and out of cells. They act as selective barriers, allowing some substances to pass through while restricting others.

Transport proteins are embedded within the cell membrane and facilitate the movement of specific molecules across the membrane. They act as channels or carriers, enabling the passage of substances that would otherwise be unable to cross.

The amphipathic nature of phospholipids is crucial for the formation of the lipid bilayer. The hydrophilic heads face the aqueous environment on either side of the membrane, while the hydrophobic tails form a barrier in the interior.

Membranes are highly selective barriers, controlling the movement of substances in and out of cells. This is essential for maintaining cellular homeostasis and ensuring proper function.

The hydrophobic interior of the lipid bilayer creates a non-aqueous environment that is unfavorable for charged or polar molecules to cross. This property helps the membrane regulate the passage of various substances.

Cells have evolved specialized transport proteins to facilitate the movement of essential molecules across the membrane. These proteins are essential for maintaining cell function and survival.