Dr. Nourhan Issa Biology: Organization, Classification, Transport, and Biological Molecules

Comprehensive vocabulary flashcards covering Organization of the Organism, Characteristics and Classification, Movement In and Out of Cells, and Biological Molecules from Dr. Nourhan Issa's lecture notes.

Cell Membrane

A partially permeable barrier that surrounds the cell, controls the movement of substances in and out, and keeps cell contents contained.

Cytoplasm

A jelly-like region that acts as a site for most cellular chemical reactions and serves as a container for cell organelles.

Nucleus

The organelle that contains genetic information ($\text{DNA}$) and controls cell division and all vital cell activities.

Mitochondria

Small organelles visible under an electron microscope that carry out aerobic respiration to release energy for cellular metabolism.

Ribosomes

Very small organelles visible only with an electron microscope that carry out protein synthesis by assembling amino acids using instructions from $\text{DNA}$.

Chloroplast

An organelle containing the green pigment chlorophyll that absorbs sunlight for photosynthesis to synthesize glucose.

Vacuole (Plant Cell)

A large, permanent single compartment filled with cell sap that stores food and water and maintains cell turgor and shape.

Cell Wall

A rigid outer layer made of cellulose fibres in plants (or peptidoglycan in bacteria) that provides physical support and prevents bursting.

Carbohydrate Storage in Animals vs Plants

Animal cells store carbohydrates in the form of glycogen granules, whereas plant cells store carbohydrates as starch grains.

Root Hair Cell

A specialized plant cell featuring a long extension that provides a large surface area to absorb water by osmosis and mineral ions by active transport, with many mitochondria and a thin cell wall.

Palisade Cell

A specialized leaf cell packed with chloroplasts to trap light for photosynthesis, with a thin cell wall for $\text{CO}_2$ diffusion and an expanded vacuole that pushes chloroplasts toward the light.

Xylem Vessel

A long, hollow, dead plant tube with thick walls containing lignin and cellulose, lacking cross walls, specialized to transport water and minerals and support the plant stem.

Red Blood Cell

A biconcave disc lacking a nucleus and packed with haemoglobin, maximizing surface area and internal volume to transport oxygen from the lungs to tissues.

Ciliated Cell and Goblet Cell

Specialized respiratory tract cells where goblet cells secrete sticky mucus to trap dust and bacteria, and ciliated cells beat their cilia upwards to push mucus away from the lungs.

Tissue

A group of cells with similar structures working together to perform the same function.

Organ

A distinct structure made up of different tissues working together to perform a specific function.

Organ System

A group of organs with related functions working together to carry out a major body function.

Magnification Formula

The formula used to calculate image size, actual size, or magnification: $\text{Magnification} = \frac{\text{Image size}}{\text{Actual size}}$ ($M = \frac{I}{A}$).

Movement

An action by an organism or part of an organism causing a change of position or place.

Respiration

The chemical reactions in cells that break down food molecules and release energy for metabolism.

Sensitivity

The ability of an organism to detect changes in the internal or external environment and make responses.

Growth

A permanent increase in size and dry mass of an organism.

Dry Mass

The mass of an organism measured after it has been killed and dried so that all water is completely removed.

Reproduction

The biological processes that make more of the same kind of organism.

Excretion

The removal of the waste products of metabolism, toxic materials, and substances in excess of requirements from an organism.

Nutrition

The taking in of materials for energy, growth, and tissue development.

Binomial System

An internationally agreed scientific naming system where an organism's name contains two parts: the genus (capitalized) and the species (lowercase), written in italics.

Species

A group of living organisms capable of reproducing to produce fertile offspring.

DNA Classification (Barcoding)

A modern classification method comparing sequences of bases in $\text{DNA}$; organisms sharing a more recent common ancestor have base sequences that are more similar.

Five Kingdoms of Living Organisms

The system classifying all living organisms into Plantae, Animalia, Fungi, Protoctista, and Prokaryota based on cell type, body organization, and nutrition.

Ferns

Non-flowering plants possessing stems called rhizomes and leaves called fronds that reproduce via spores and do not produce flowers, fruits, or seeds.

Monocotyledons (Monocots)

Flowering plants characterized by seeds with one cotyledon, long narrow leaves with parallel veins, fibrous roots, and flower petals in multiples of $3$.

Dicotyledons (Dicots)

Flowering plants characterized by seeds with two cotyledons, broad leaves with a branching network of veins, tap roots, and flower petals in multiples of $4$ or $5$.

Kingdom Fungi

Mostly multicellular eukaryotes (except unicellular yeast) with cell walls of chitin, lacking chlorophyll, feeding heterotrophically, and storing carbohydrates as glycogen.

Rhizoids

Feeding hyphae in bread mould that branch into food substrates to secrete extracellular digestive enzymes and absorb broken-down soluble nutrients.

Budding in Yeast

An asexual reproduction method where a small bud develops on the parent yeast cell, grows larger, and separates to form a new genetically identical cell.

Kingdom Prokaryota

Unicellular organisms such as bacteria lacking a nucleus and mitochondria, possessing circular loops of $\text{DNA}$, plasmids, and peptidoglycan cell walls.

Binary Fission

A rapid form of asexual reproduction in bacteria taking roughly $20\,\text{minutes}$ where a cell copies its $\text{DNA}$ and divides into two identical daughter cells.

Virus

A non-cellular obligate parasite containing only a strand of $\text{DNA}$ or $\text{RNA}$ inside a protein coat (capsid), capable of reproducing only inside a host cell.

Kingdom Protoctista

Eukaryotic, mostly unicellular organisms classified into plant-like autotrophs (e.g., Chlamydomonas) and animal-like heterotrophs (e.g., Paramecium).

Arthropods

Invertebrates with jointed limbs, a segmented body, and a tough, waterproof exoskeleton, divided into insects, arachnids, crustaceans, and myriapods.

Insects

Arthropods with $3$ body segments (head, thorax, abdomen), $3$ pairs of jointed legs, $1$ pair of antennae, compound eyes, and usually $2$ pairs of wings.

Arachnids

Arthropods with $2$ body parts (cephalothorax and abdomen), $4$ pairs of legs, no antennae, simple eyes, and book lungs/gills (e.g., spiders).

Crustaceans

Arthropods with $5$ or more pairs of legs, $2$ pairs of antennae, compound eyes, and a calcified exoskeleton, mostly aquatic and breathing via gills (e.g., crabs).

Myriapods

Arthropods with many body segments, $1$ pair of antennae, simple eyes, and either $1$ pair of legs per segment (centipedes) or $2$ pairs of legs per segment (millipedes).

Vertebrates

Animals with a backbone, divided into five classes: fish, amphibians, reptiles, birds, and mammals.

Dichotomous Key

A biological identification tool that splits organisms into groups step-by-step using paired contrasting questions, each yielding only two clear outcomes: yes or no.

Diffusion

The net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient due to random particle motion.

Factors Increasing Rate of Diffusion

Higher temperature (greater kinetic energy), steeper concentration gradient, larger surface area, and shorter diffusion distance.

Active Transport

The movement of molecules or ions from a region of lower concentration to higher concentration against a concentration gradient, using energy released by respiration and carrier proteins.

Protein Carrier Mechanism

Membrane proteins that bind specific molecules or ions, change shape using respiratory energy, and transport them from low to high concentration across the membrane.

Osmosis

The net movement of water molecules from a region of high water potential ($\text{HWP}$) to low water potential ($\text{LWP}$) through a partially permeable membrane.

Water Potential

A measure of the ability of water molecules to move freely; pure water has the highest water potential, and adding solutes lowers it.

Red Blood Cell in Hypotonic Solution

Water enters the cell down a water potential gradient by endosmosis, causing the red blood cell to swell and rupture.

Red Blood Cell in Hypertonic Solution

Water exits the cell down a water potential gradient by exosmosis, causing the cell to shrink and crenate.

Turgid Cell

A plant cell placed in a dilute solution where water enters by osmosis, causing the vacuole to expand and push cytoplasm firmly against the cell wall, generating high turgor pressure.

Flaccid Cell

A plant cell placed in a moderately concentrated solution where water leaves by exosmosis, causing the vacuole to shrink and the tissue to become soft and floppy.

Plasmolysis

A state in plant cells exposed to highly concentrated solutions where extreme water loss causes the cell membrane to pull completely away from the rigid cell wall.

Contractile Vacuole

An organelle in Amoeba that collects excess water entering continuously from freshwater surroundings and expels it outside to prevent the cell from bursting.

Effect of Seawater on Plants

High salt concentration in seawater creates a lower water potential outside than inside root hair cells, drawing water out by osmosis, resulting in plasmolysis, wilting, and death.

Glucose

A basic monosaccharide carbohydrate with chemical formula $C_6H_{12}O_6$ that serves as the primary energy source in cells, releasing roughly $17\,\text{kJ/g}$.

Condensation Reaction

A chemical reaction in which two simpler molecules join together to form a larger compound with the removal of a water molecule (e.g., glucose + glucose forming maltose).

Polysaccharides

Large carbohydrate polymers composed of many glucose units joined together; examples include plant storage starch, animal storage glycogen, and structural cellulose in plant cell walls.

Lipids (Fats and Oils)

Molecules composed of carbon, hydrogen, and oxygen (with an $\text{H}:\text{O}$ ratio greater than $2:1$), built from $1$ glycerol joined to $3$ fatty acids, releasing approximately $39\,\text{kJ/g}$.

Proteins

Polymers composed of carbon, hydrogen, oxygen, nitrogen (and sometimes sulfur or phosphorus) made from chains of $20$ different amino acids, used for growth, repair, enzymes, antibodies, and haemoglobin.

DNA (Deoxyribonucleic Acid)

A double-stranded nucleic acid molecule coiled into a double helix located in the cell nucleus, carrying genes that code for the sequence of amino acids in proteins.

Nucleotide

The repeating subunit of $\text{DNA}$, consisting of a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases: adenine ($\text{A}$), thymine ($\text{T}$), guanine ($\text{G}$), or cytosine ($\text{C}$).

Complementary Base Pairing

The specific pairing across opposite strands of $\text{DNA}$ where adenine pairs only with thymine ($\text{A}-\text{T}$) and guanine pairs only with cytosine ($\text{G}-\text{C}$).

Functions of Water in Living Organisms

Acts as a solvent for digestion, excretion (urine), and transport (plasma, $90\%$ water), acts as a medium for gas diffusion, cools the body through sweat evaporation, and serves as a reactant in photosynthesis.

Balanced Diet

A daily intake providing all required nutrients (carbohydrates, fats, proteins, vitamins, minerals, water, and fibre) in correct proportions according to individual age, sex, and activity level.

Vitamin C

A nutrient found in oranges, lemons, and raw vegetables that maintains skin and blood vessels and helps form collagen; deficiency leads to scurvy with bleeding gums and poor wound healing.

Vitamin D

A vitamin found in butter and egg yolks and produced by skin exposed to sunlight that promotes calcium absorption; deficiency causes rickets in children and osteomalacia in adults.

Calcium

A mineral ion from milk and cheese required for hardening bones and teeth and aiding blood clotting; deficiency results in weak bones, weak teeth, and poor clotting.

Iron

A mineral ion obtained from red meat, eggs, and spinach needed to synthesize haemoglobin for oxygen transport; deficiency causes anaemia, fatigue, paleness, and shortness of breath.

Dietary Fibre (Roughage)

Indigestible plant cellulose from bran and green leafy vegetables that adds bulk to feces and promotes peristalsis in the large intestine; deficiency leads to constipation and increased risk of colon cancer.

Iodine Test for Starch

A food test where yellow-brown iodine solution turns blue-black if starch is present, or remains yellow-brown if absent.

Benedict's Test for Reducing Sugars

A test where equal volumes of test solution and blue Benedict's reagent are heated in a water bath at approximately $80^\circ\text{C}$ for $2\,\text{minutes}$, changing from blue to green, yellow, orange, or brick-red precipitate.

Biuret Test for Proteins

A test where $2\,\text{cm}^3$ of protein solution is treated with $2\,\text{cm}^3$ of $\text{NaOH}$ followed by drops of $\text{CuSO}_4$, turning purple if protein is present or remaining blue if absent.

Ethanol Emulsion Test for Lipids

A procedure where fat or oil is dissolved in $2\,\text{cm}^3$ of pure ethanol and then mixed with water; a milky white emulsion confirms the presence of lipids.

DCPIP Test for Vitamin C

A chemical test where drops of blue $\text{DCPIP}$ reagent are added to a solution; if vitamin C is present, the dye is decolourized to colourless.