ANAPHY CHAP 3: Cell Structures and Functions

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Matter

Anything that occupies space and has mass; it is made of particles called atoms.

Mass

The amount of matter in an object, with the $kg$ (kilogram) as the international unit.

Weight

The gravitational force acting on an object of a given mass.

Elements (Body Composition)

Four elements ($C$, $H$, $O$, $N$) that make up $96\%$ of body weight.

Atom

The smallest particle of an element that has the same chemical characteristics of that element.

Electrical Charge

The tendency of particles to attract each other; opposite charges attract while same charges repulse.

Subatomic Particles

The components of an atom: Neutrons (no charge), Protons (positive charge), and Electrons (negative charge).

Nucleus (Atomic)

The center of an atom containing Protons and Neutrons; its mass is calculated as $P+N$.

Mass Number

The sum of Protons and Neutrons ($P+N$) in an atom.

Atomic Number

The number of Protons in each atom.

Isotopes

Atoms of the same element with the same number of Protons and Electrons but a different number of Neutrons.

Chemical Bonding

The bonding of two or more chemical atoms, molecules, or ions to give rise to a chemical compound.

Valence Shell

The outer shell of an atom which does not contain electrons until the inner shells reach their maximum.

Octet Rule

The principle that atoms combine to reach $8$ electrons in their middle shells; the most inner shell has a maximum of $2$ electrons.

Ionic Bond

A chemical bond formed by transferring electrons between atoms.

Covalent Bond

A chemical bond formed by sharing electrons between atoms; also known as a molecular bond.

Electronegativity

The ability of an atom's nucleus to pull electrons towards it; strong electronegativity involves $6-7$ electrons, while weak involves $1-2$.

Ion

A charged particle with an unequal number of protons and electrons.

Electrolytes

Substances with the capacity to conduct electrical currents; main body fluid examples include $Na^+$, $Cl^-$, $Mg^{2+}$, $Ca^{2+}$, and $K^+$.

Reactants

Substances that enter into a chemical reaction.

Products

Substances that result from a chemical reaction.

Synthesis Reaction (Anabolism)

A reaction where reactants combine to form a larger, more complex product, such as the conversion of $ADP$ to $ATP$.

Decomposition Reaction (Catabolism)

A reaction where reactants are broken down into smaller, less complex products, such as the conversion of $ATP$ to $ADP$.

Exchange Reaction

A combination of decomposition and synthesis reactions.

Reversible Reaction

A reaction where a forward reaction converts reactants to products and a backward reaction converts products back to reactants.

Potential Energy

Stored energy.

Kinetic Energy

Energy caused by movement.

Catalyst

A substance that increases the rate of a chemical reaction without being changed or depleted.

Enzymes

Protein catalysts that usually end in the suffix "-ase".

Amylase

An enzyme made by the pancreas and salivary glands that helps the body break down carbohydrates.

Lipase

An enzyme that breaks down lipids (fats) to be absorbed at the intestine.

Acid

A proton donor with a greater concentration of $H^+$ than $OH^-$.

Base

A proton acceptor with fewer $H^+$ than $OH^-$; also known as alkaline.

Normal Blood pH

The range of $7.35-7.45$.

Acidosis

A condition where blood pH is below $7.35$, leading to a depressed nervous system, disorientation, and coma.

Alkalosis

A condition where blood pH is above $7.45$, causing the nervous system to be overexcitable, nervous, and prone to convulsions.

Buffers

Chemicals that maintain body homeostasis by resisting changes in pH; human blood uses a buffer of carbonic acid ($H_2CO_3$) and bicarbonate anion ($HCO_3^-$).

Inorganic Molecule

A molecule that does not contain Carbon, such as $Oxygen$, $Carbon Dioxide$, and $Water$.

Organic Molecule

A molecule that contains Carbon; exceptions include $CO_2$ and $CO$.

Hydrophilic

Molecules that are attracted to water.

Hydrophobic

Molecules that lack attraction to water or "hate" water.

Carbohydrates

Organic molecules ($C, H, O$) used for energy and structured as monosaccharides, disaccharides, or polysaccharides.

Glycogen

The main storage form of glucose in animals, acting as a ready supply for $ATP$ production.

Lipids

Water-insoluble molecules composed of $C, H, O$; classes include fats, phospholipids, eicosanoids, and steroids.

Amino Acid

The building block of protein.

Adenosine Triphosphate (ATP)

The important molecule for storing and providing energy in cells.

DNA Nitrogenous Bases

Adenine ($A$), Thymine ($T$), Cytosine ($C$), and Guanine ($G$), where $A=T$ and $C=G$.

RNA Nitrogenous Bases

Adenine ($A$), Uracil ($U$), Cytosine ($C$), and Guanine ($G$), where $U=A$.

Plasma Membrane

The outermost component of a cell, made of a phospholipid bilayer, that regulates the passage of substances.

Simple Diffusion

The movement of solutes from a higher to lower concentration gradient without using $ATP$.

Osmosis

The movement of fluid across a semi-permeable membrane from low osmotic pressure to high osmotic pressure.

Hypertonic

A solution with a high concentration of solute that causes cells to shrink.

Hypotonic

A solution with a low concentration of solute that causes cells to swell or burst.

Active Transport

The movement of molecules from low to high concentration gradient using $ATP$, such as the $Na-K$ pump.

Phagocytosis

A form of endocytosis known as "cell-eating" where solid particles are ingested.

Pinocytosis

A form of endocytosis known as "cell-drinking" involving liquid particles.

Nucleolus

The site within the nucleus for $RNA$ synthesis and ribosomal subunit assembly.

Rough Endoplasmic Reticulum (RER)

An organelle containing ribosomes that serves as a major site for protein synthesis.

Smooth Endoplasmic Reticulum (SER)

An organelle without ribosomes that is the site of steroid synthesis, lipogenesis, and detoxification.

Golgi Apparatus

A series of membrane sacs that package, modify, and distribute proteins and lipids produced by the ER.

Lysosome

A vesicle containing hydrolytic enzymes (lysozymes) responsible for apoptosis.

Mitochondria

The powerhouse of the cell and major site of $ATP$ production, containing folds called cristae.

Cytoskeleton

Structures that support the cytoplasm and organelles, consisting of microtubules, microfilaments, and intermediate filaments.

Microvilli

Cell projections that increase surface area to enhance absorption, commonly seen in the stomach and intestines.

Codon

A three-nucleotide sequence in $mRNA$.

Interphase

The longest non-dividing phase of cell division, consisting of $G_1$, $S$ (DNA replication), and $G_2$ phases.

Mitosis

The division of somatic cells into two identical diploid daughter cells, following the steps of Prophase, Metaphase, Anaphase, and Telophase.

Cytokinesis

The final stage of mitosis where the cytoplasm divides into two.

Karyolysis

The dissolution of the nucleus during apoptosis.

Pyknosis

The shrinking of the nucleus and condensation of chromatin during apoptosis.

Karyorrhexis

The fragmentation of the nucleus and disintegration of chromatin during apoptosis.