Cell Biology: Structure, Function, and Chemical Reactions

Cell Organization and Structure

Cells in Humans (Eukaryotic Cells)

Cell Membrane

The outermost membrane, a lipid bilayer, controls what enters and exits the cell. This structure is also used in vaccine production to hold mRNA.

Mitochondria (Mitochondrion)

The powerhouse of the cell, responsible for ATP (Adenosine triphosphate) production. The ATP production rate depends on the folds of cristae. Some cells, like liver cells, have multiple mitochondria. The mitochondrion contains a matrix, a thick liquid with a high concentration of enzymes that facilitate ATP production.

Lysosome

The cell's recycle bin.

Golgi Apparatus

Packages proteins for transport in and out of cells.

Rough Endoplasmic Reticulum

Creates proteins.

Smooth Endoplasmic Reticulum

Creates steroids.

Nucleus

The control center or brain of the cell, containing the majority of the cell's mass and performing many functions.

Cytoplasm

The entire region of the cell containing various organelles suspended in a semifluid medium called cytosol (saltwater and other organic material).

Cytoskeleton

Gives the cell its shape and consists of fine fibers.

Ribosomes

Produce proteins on the order of millions within a single cell.

Vesicles

Transport or carry materials within the cell.

DNA (Deoxyribonucleic Acid)

Packaged as chromatin, containing genes passed down from parents. Long DNA chains are tightly packed into structures called chromosomes (46 total per human). DNA is very resilient and long-lasting.

RNA

Requires oxygen and breaks down within days. It is involved in protein breakdown and the creation of urea, a highly toxic substance.

Cells in Plants

Cell Wall

Provides structural support to plant cells.

Chloroplast

The site of photosynthesis in plant cells.

Prokaryotic Cells (Bacteria)

Simple, unicellular organisms that perform all necessary functions independently. They are much older than eukaryotic cells.

Biochemical Reactions

Most biochemical reactions require energy input to start. Enzymes, catalysts made from proteins, speed up these reactions, such as food digestion, breaking down large molecules, or building larger, more complex substances. For example, carbohydrates are broken down into glucose. If glucose isn't used, it's converted into fat or lipids.

Activation Energy

Enzymes reduce the energy needed for reactions by holding substrates in position. The energy produced through enzyme-catalyzed reactions is the same as without enzymes, just achieved more efficiently.

Enzyme Naming

Enzymes are often named by adding a suffix to the substrate they act upon (e.g., glucose -> glucosase, sucrose -> sucrase, maltose -> maltase). Some exceptions exist, like lysozyme and pepsin.

Enzyme Function

Enzymes act as "locks" and substrates as "keys." The active site of the enzyme is where the catalytic reaction occurs. Enzymes are very specific and only work with certain substrates (lock and key mechanism). Heat and pH affect enzyme effectiveness. Body temperature (37°C) is optimal for human enzymes. Higher temperatures can destroy enzymes, while lower temperatures slow down reactions.

Carbohydrates

Disaccharides

Two simple subunits linked together (e.g., maltose, sucrose, lactose). Lactose intolerance is caused by a lack of lactase.

Polysaccharides

Complex carbohydrates requiring breakdown (e.g., cellulose, starch in rice).

Proteins

The general structure consists of an amino group and a carboxylic group. Eleven amino acids are synthesized in the body, while nine are obtained through nutrition.

Chemistry

The Mole

Avogadro's constant (6 * 10^23) represents the number of particles in one mole. For example, 3.01 * 10^23 particles is equal to 0.5 moles.

Mass

Atomic mass is equal to molar mass. For example, CO2 has a molar mass of 44g (1 mole).

Concentration

Measured in mol/liter for accurate solvent measurement.

Mole Ratio

The mole ratio of reactants and products can be observed from coefficients in a balanced chemical equation.

Diffusion

Spontaneous diffusion doesn't require extra energy and continues until equilibrium is reached (equal concentration in both regions). Factors increasing the rate of diffusion include higher temperature, larger surface area to volume ratio, smaller and lighter molecules, larger concentration gradient (difference in mol/m), and smaller distance between the two regions. Diffusion occurs from an area of higher concentration to an area of lower concentration.