Cellular Levels of Organization and Chemical Composition Lecture Notes

Flashcards covering the chemical levels of organization, organic vs inorganic substances, and cellular structures including organelles and the nucleus.

Water (inorganic)

The most abundant substance in cells, functioning as a medium for reactions, transporting chemicals like $O_2$, and maintaining body temperature at approximately 37^\rm{o}C.

Polar molecules

Molecules that exhibit unequal sharing of electrons ($e^-$), leading to a slight charge difference across the molecule.

Intracellular fluid (ICF)

The fluid located inside the cell, accounting for $2/3$ of total body fluids.

Extracellular fluid (ECF)

The fluid located outside the cell, accounting for $1/3$ of total body fluids and divided into interstitial fluid ($80\%$) and plasma ($20\%$).

Acids

Substances that dissociate in $H_2O$ releasing $H^+$ ions; a higher $[H^+]$ results in a lower pH.

Bases

Substances that bind to or buffer free $H^+$ ions in $H_2O$, such as hydroxyl ions ($OH^-$) or bicarbonate ($HCO_3^-$).

pH Scale

A measure of the concentration of free $H^+$ in solution, ranging from $0$ (acidic) to $14$ (basic/alkaline) with $7$ being neutral.

Blood pH

The physiological pH range for human blood, which is $7.35 - 7.45$.

Carbohydrates

Organic substances consisting of C, H, and O in the formula $(CH_2O)_n$, serving as energy sources and structural materials.

Monosaccharides

Simple sugars such as glucose ($C_6H_{12}O_6$), fructose, ribose, and deoxyribose that act as the basic building blocks of other carbohydrates.

Disaccharides

Carbohydrates formed by two monosaccharides covalently bonded together, such as sucrose ($\text{glucose} + \text{fructose}$), lactose, and maltose.

Polysaccharides

Complex carbohydrates made of many monosaccharides bonded together, such as glycogen in animals and starch in plants.

Lipids

Nonpolar, insoluble organic molecules consisting of C, H, and O that include fats, oils, and waxes.

Glycerides

The most common lipid in the body and diet, composed of a glycerol backbone and fatty acids (FAs).

Triglyceride

A neutral fat formed from one glycerol molecule and three fatty acid chains.

Phospholipids

Lipids composed of a polar, hydrophilic phosphate head group and two nonpolar, hydrophobic fatty acid tails.

Cholesterol

A lipid found in cell membranes used to synthesize steroids such as bile salts, vitamin D, and hormones like testosterone and estrogen.

Proteins

Organic substances consisting of C, H, O, N (and sometimes S) that function as structural materials, enzymes, antibodies, and transporters.

Amino acids

The basic building blocks of all proteins, consisting of an amino group, an acidic carboxyl group, and a variable R group.

Peptide bond

The specific chemical bond that joins amino acids together to form dipeptides, polypeptides, or proteins.

Nucleic Acids

Molecules consisting of C, H, O, N, and P, formed from building blocks called nucleotides.

Nucleotide

A building block of nucleic acids containing a phosphate group ($PO_4^-$), a monosaccharide (ribose or deoxyribose), and an organic base.

DNA (deoxyribonucleic acid)

A double-stranded helix containing deoxyribose and bases A, T, C, and G that serves as the template for RNA and handles cellular reproduction.

RNA (ribonucleic acid)

A single-stranded nucleic acid containing ribose and bases A, U, C, and G that functions in protein synthesis.

Adenosine Triphosphate (ATP)

A modified RNA nucleotide with three phosphate groups that stores energy in high-energy covalent bonds ($\sim$).

Cell

The basic structural and functional unit of the body, capable of performing all basic life functions.

Plasma Membrane

A boundary between the inside and outside of a cell composed of a phospholipid bilayer, cholesterol, proteins, and carbohydrates.

Integral proteins

Membrane proteins integrated within the membrane containing a hydrophobic region; some extend across the entire membrane as transmembrane proteins.

Peripheral proteins

Membrane proteins attached to either the inner or outer surface of integral proteins.

Microvilli

Small projections of the cell membrane that function to increase surface area, commonly found in the small intestine and kidney.

Fluid mosaic model

A description of the cell membrane where the 'fluid' represents moving phospholipids/proteins and 'mosaic' represents the dotted protein pattern on the surface.

Cytosol

The gel-like intracellular fluid containing water, ions, and suspended organic molecules.

Ribosomes

Non-membranous organelles composed of rRNA and proteins that serve as the sites for protein synthesis.

Centrosomes

Organizing centers for microtubules consisting of a pair of centrioles and pericentriolar matrix.

Cytoskeleton

A network of protein-based microfilaments, intermediate filaments, and microtubules that provide structural support and facilitate cell movement.

Mitochondria

Membranous organelles with a double membrane that are the site of ATP synthesis and contain their own DNA, RNA, and proteins.

Rough Endoplasmic Reticulum (RER)

A membranous network with attached ribosomes involved in the synthesis of secretory, lysosomal, and membrane proteins.

Smooth Endoplasmic Reticulum (SER)

A membranous network lacking ribosomes that synthesizes lipids and steroid hormones.

Golgi Apparatus

A stack of membrane discs that modifies, sorts, packages, and delivers proteins; often called the 'cellular post office'.

Lysosomes

Membranous organelles filled with digestive enzymes used to clean up bacteria, viruses, and worn-out organelles.

Nucleolus

A dense, non-membranous region of the nucleus where DNA, RNA, and proteins are used to assemble ribosomes.

Chromatin

The dispersed form of DNA uncoiled with histone proteins, found in the nucleus when the cell is not dividing.

Chromosomes

The condensed and individually visible form of DNA and histone proteins found in dividing cells.