Cell Biology and Molecular Basics

Flashcards covering key concepts in cell biology, macromolecules, water properties, cell membrane structure and function, osmosis, and nucleic acid basics and transcription.

Nucleus

Stores DNA (chromosomes) and acts as the cell's control center.

Ribosomes

Organelles responsible for making proteins. Free ribosomes produce proteins for the cytoplasm, while bound ribosomes (on rough ER) produce proteins for export, membranes, or other organelles.

Rough ER

Endoplasmic Reticulum studded with ribosomes, involved in making proteins destined for transport.

Smooth ER

Endoplasmic Reticulum involved in the synthesis of lipids.

Golgi Apparatus

Organelle that packages, modifies, and ships proteins.

Mitochondria

Organelles with a double membrane that produce ATP (energy) for the cell.

Chloroplasts

Organelles found in plant cells that perform photosynthesis to make sugars.

Lysosomes

Organelles responsible for breaking down and recycling cellular waste.

Vacuoles

Storage organelles, particularly a large central one in plant cells.

Plasma membrane

A selectively permeable barrier that controls what enters and exits the cell.

Cytoskeleton

A network of protein filaments that provides shape, support, and movement to the cell; it lacks a membrane.

Cilia/Flagella

Hair-like or whip-like appendages on the surface of some cells, used for movement.

Macromolecules (Order)

The order of DNA components from smallest to largest: Nucleotide → Double-stranded DNA → Chromosome.

Carbohydrates

One of the four main types of macromolecules, primarily used for energy.

Lipids

One of the four main types of macromolecules, including fats, oils, and steroids; involved in energy storage and membrane structure.

Proteins

One of the four main types of macromolecules, essential for structure, function, and regulation of the body's tissues and organs.

Nucleic acids

One of the four main types of macromolecules, including DNA and RNA, which carry genetic information.

Nonpolar bond

A type of chemical bond where electrons are shared equally between two atoms.

Polar bond

A type of chemical bond where electrons are shared unequally between two atoms due to differing electronegativity.

Electronegativity

A measure of how strongly an atom pulls on electrons in a chemical bond.

Water (H₂O)

A polar molecule capable of forming hydrogen bonds, essential for life.

Hydrophobic

Meaning 'water-fearing,' typically describes nonpolar molecules like O₂ and CH₄ that do not readily dissolve in water.

Hydrophilic

Meaning 'water-loving,' typically describes polar or charged molecules like H₂O, glucose, and NH₃ that readily dissolve in water.

Hydrogen bond

A weak attraction between the partial positive charge on a hydrogen atom in one polar molecule and the partial negative charge on an electronegative atom (like oxygen or nitrogen) in another polar molecule.

Phospholipid bilayer

The fundamental structure of the cell membrane, consisting of two layers of amphipathic phospholipids with polar heads facing outward and nonpolar tails facing inward.

Cell Membrane Function

Controls entry/exit of substances and provides compartmentalization within the cell.

Saturated fatty acids

Fatty acids that are solid at room temperature and lead to less fluid cell membranes when present in phospholipids.

Unsaturated fatty acids

Fatty acids that have one or more double bonds, leading to kinks in their tails and resulting in more fluid cell membranes.

Cholesterol (in cell membrane)

A lipid that stabilizes the cell membrane, making it less permeable when hot and more permeable when cold.

Membrane Permeability Ranking

The relative ease with which substances can pass through the plasma membrane, typically O₂ > CO₂ > H₂O > Glucose > Na⁺.

Osmosis

The net movement of water across a selectively permeable membrane toward a region of higher solute concentration.

Hypertonic solution

A solution with a higher concentration of solutes compared to another solution, causing water to move out of cells placed in it.

Hypotonic solution

A solution with a lower concentration of solutes compared to another solution, causing water to move into cells placed in it.

Isotonic solution

A solution with an equal concentration of solutes compared to another solution, resulting in no net movement of water.

Nucleotide

The basic building block of DNA and RNA, consisting of a nitrogenous base, a five-carbon sugar, and one or more phosphate groups.

DNA (Deoxyribonucleic Acid)

A nucleic acid containing deoxyribose sugar and bases Adenine (A), Thymine (T), Guanine (G), Cytosine (C).

RNA (Ribonucleic Acid)

A nucleic acid containing ribose sugar and bases Adenine (A), Uracil (U), Guanine (G), Cytosine (C).

Purines

Nitrogenous bases with a double-ring structure, including Adenine (A) and Guanine (G).

Pyrimidines

Nitrogenous bases with a single-ring structure, including Cytosine (C), Thymine (T), and Uracil (U).

DNA Base Pairing

Specific hydrogen bonding between bases: Adenine (A) pairs with Thymine (T) via 2 H bonds, and Guanine (G) pairs with Cytosine (C) via 3 H bonds (stronger).

DNA/RNA Directionality

Nucleic acids are synthesized and read in a 5' → 3' direction.

Transcription Initiation

The first stage of transcription where RNA polymerase binds to a promoter region (often containing a TATA box) with the help of transcription factors.

Transcription Elongation

The stage of transcription where RNA polymerase moves along the DNA template strand, synthesizing an RNA molecule in the 5' → 3' direction.

Transcription Termination

The stage of transcription where RNA synthesis ends, typically signaled by a poly(A) signal in eukaryotes.

5' Cap

A modified guanine nucleotide added to the 5' end of eukaryotic mRNA, important for stability and ribosome binding.

Splicing

The process in eukaryotic gene expression where introns (non-coding regions) are removed from pre-mRNA and exons (coding regions) are joined together.

Poly(A) tail

A string of adenine nucleotides added to the 3' end of eukaryotic mRNA, important for stability and exit from the nucleus.

Central Dogma

The fundamental concept in molecular biology that describes the flow of genetic information: DNA → RNA → Protein.