Unit 1 Biology: Cells, Cell Cycle, Transport & Multicellular Organisms

Vocabulary practice flashcards covering cell types, organelles, membrane transport, tonicity, surface area-to-volume dynamics, mitosis stages, and stem cell potency.

Prokaryotes

Simple, small cells ($0.1\text{--}5\,\mu\text{m}$) lacking a true nucleus and membrane-bound organelles, with circular DNA located in the nucleoid region (e.g., Bacteria and Archaea).

Eukaryotes

Complex, larger cells ($10\text{--}100\,\mu\text{m}$) containing a membrane-bound nucleus with linear DNA and membrane-bound organelles (e.g., Animals, Plants, Fungi, and Protists).

Tissue

A group of similar specialized cells working together to perform a specific function (e.g., Cardiac muscle tissue).

Organ

A structure made of two or more different tissue types working together to carry out specific bodily tasks (e.g., Heart, Lungs).

Organ System

A group of interconnected organs collaborating to perform major body functions (e.g., Cardiovascular or Respiratory system).

Organism

An individual living entity composed of integrated organ systems (e.g., Human).

Nucleus

A large double-membrane sphere with nuclear pores and a dark central nucleolus that stores linear DNA and controls cell activities, gene expression, and cell division.

Mitochondria

Bean- or oval-shaped organelles with a smooth outer membrane and heavily folded inner membrane (cristae); acts as the site of aerobic cellular respiration to convert glucose into usable energy (ATP).

Ribosomes

Non-membrane-bound tiny structures composed of two subunits (large and small) that serve as the site of protein synthesis by translating mRNA into polypeptide chains.

Rough Endoplasmic Reticulum (Rough ER)

Interconnected, flattened membrane sacs continuous with the outer nuclear membrane and studded with ribosomes; folds, modifies, and transports newly synthesized proteins.

Smooth Endoplasmic Reticulum (Smooth ER)

A tubular network of membranes in the cytoplasm lacking ribosomes; synthesizes lipids/steroids and detoxifies drugs and metabolic poisons.

Golgi Apparatus

A stack of flattened, curved membrane sacs (cisternae) with pinching vesicles that modifies, sorts, and packages proteins and lipids into vesicles for transport or secretion.

Lysosomes

Small, single-membrane spherical sacs containing digestive enzymes to break down waste, pathogens, and worn-out organelles.

Chloroplasts

Oval double-membrane organelles containing stacks of green discs (thylakoids/grana); site of photosynthesis, converting light energy into chemical energy (glucose).

Vacuole

A single-membrane fluid-filled sac that stores water, ions, and nutrients, while maintaining turgor pressure in plant cells.

Cell Wall

A thick, rigid external layer outside the plasma membrane (made of cellulose in plants) that provides structural support, protection, and prevents cell bursting (lysis).

Phospholipid Bilayer

A double layer of phospholipids with hydrophilic phosphate heads directed outward toward intracellular/extracellular fluid and hydrophobic fatty acid tails directed inward.

Cholesterol (Membrane Component)

Lipid molecules wedged between hydrophobic fatty acid tails that stabilize membrane fluidity, preventing rigidity in the cold and excessive fluidity in the heat.

Glycoproteins and Glycolipids

Carbohydrate chains attached to membrane proteins or lipids on the outer cell surface that act as identification tags for cell recognition and immune response.

Passive Transport

Movement of substances with or down a concentration gradient ($\text{High} \rightarrow \text{Low}$) without the expenditure of cellular energy ($\text{ATP}$), utilizing the kinetic energy of particles.

Active Transport

Movement of substances against or up a concentration gradient ($\text{Low} \rightarrow \text{High}$) requiring cellular energy ($\text{ATP}$) and transport proteins or membrane vesicles.

Simple Diffusion

Net movement of solute molecules (e.g., $O_2$, $CO_2$) directly through the phospholipid bilayer from high to low solute concentration until equilibrium is reached.

Osmosis

Net movement of free water molecules across a selectively permeable membrane from a region of low solute concentration (high free water) to high solute concentration (low free water).

Endocytosis

Active bulk transport where the plasma membrane invaginates around extracellular substances and pinches off inside the cytoplasm to create an intracellular vesicle.

Exocytosis

Active bulk transport where an internal membrane-bound vesicle merges with the plasma membrane to discharge its contents outside the cell.

Phagocytosis

A form of endocytosis commonly referred to as 'cell eating,' in which large solid particles are engulfed by the cell.

Pinocytosis

A form of endocytosis commonly referred to as 'cell drinking,' in which extracellular fluids are brought into the cell.

Hypotonic Solution

An external solution with a lower solute concentration (higher free water) than the inside of the cell, causing net water movement into the cell.

Isotonic Solution

An external solution with solute and free water concentrations equal to the cell's interior, leading to no net movement of water.

Hypertonic Solution

An external solution with a higher solute concentration (lower free water) than the inside of the cell, leading to net water movement out of the cell.

Lysis

The swelling and bursting of an animal cell placed in a hypotonic solution caused by water intake and the lack of a protective cell wall.

Turgid

The swollen, firm state of a plant cell in a hypotonic solution; considered the ideal state because the rigid cell wall prevents bursting.

Flaccid

The limp state of a plant cell placed in an isotonic solution due to an absence of net water pressure.

Plasmolyzed

The state of a plant cell in a hypertonic solution wherein water loss causes the cytoplasm to shrink and the plasma membrane to pull away from the cell wall.

Surface Area to Volume (SA:V) Ratio

The mathematical relationship ($\text{SA} \div V$) between outer boundary area ($\text{SA} = 6 \times s^2$) and internal capacity ($V = s^3$) that limits cell size, decreasing sharply as a cell expands.

Chromatin

Loose, uncoiled, thread-like DNA wrapped around histone proteins present during Interphase, allowing genetic material to be read and copied.

Sister Chromatids

Two identical copies of a duplicated chromosome produced during the $S$ phase of Interphase, held together at the centromere.

Centromere

The constricted central region of a duplicated chromosome that joins two identical sister chromatids and serves as the attachment point for spindle fibers.

Interphase

The stage of the cell cycle consisting of $G_1$, $S$, and $G_2$ phases during which the cell grows, replicates its DNA, and synthesizes organelles/proteins prior to division.

Prophase (Mitosis)

The first phase of mitosis where chromatin condenses into visible X-shaped chromosomes, the nuclear envelope dissolves, and the mitotic spindle starts assembling.

Metaphase (Mitosis)

The stage of mitosis where spindle fibers attach to centromeres and align X-shaped chromosomes along the cell equator (metaphase plate).

Anaphase (Mitosis)

The stage of mitosis where centromeres divide and shortening spindle fibers pull sister chromatids apart to opposite poles of the cell.

Telophase (Mitosis)

The final stage of mitosis where separated chromosomes arrive at opposite poles, uncoil into chromatin, two new nuclear envelopes reform, and the spindle disassembles.

Cytokinesis

The physical division of the cytoplasm separating the parent cell into two genetically identical diploid ($2n$) daughter cells via a cleavage furrow in animal cells or a cell plate in plant cells.

Differentiation

The developmental process by which unspecialized stem cells switch specific genes on or off to acquire specialized structures and functions.

Totipotent

Stem cells possessing the potential to differentiate into any cell type, including extra-embryonic tissues such as the placenta (e.g., Zygote).

Pluripotent

Stem cells that can develop into nearly any body cell from all three germ layers, but cannot form placenta tissues (e.g., Embryonic stem cells).

Multipotent

Stem cells capable of giving rise to a limited range of specialized cells within a specific tissue family (e.g., Bone marrow blood stem cells).

Unipotent

Stem cells that produce only one specific cell type while maintaining the ability to self-renew (e.g., Muscle satellite cells).