Life Sciences: Comprehensive Biology Study Flashcards

Comprehensive review flashcards covering biological molecules, cellular organelles, plant and animal tissues, anatomy of plant organs, human skeletal structures, and mitotic cell division.

What is the primary difference between inorganic molecules and organic molecules?

Inorganic molecules are substances required by living organisms that do not contain both carbon and hydrogen (e.g., water), whereas organic molecules are substances that contain carbon, hydrogen, and oxygen (and sometimes other elements).

How are macro elements and micro elements distinguished?

Macro elements are mineral elements required by living organisms in large quantities, while micro elements are required in small quantities.

What are the biological functions and deficiency symptoms of sodium ($Na$)?

Functions include maintaining osmotic balance, osmoregulation, functioning of nerves and muscles, and secretion of $HCl$ in the stomach. Deficiency causes reduced plant growth, muscle cramps, and loss of body mass.

What are the biological functions and deficiency symptoms of potassium ($K$)?

Functions include facilitating photosynthesis, protein synthesis, activating enzymes, regulating blood pressure, nerve and muscle action, and cellular respiration. Deficiency leads to low resistance to drought, excessive water loss, diseases in plants, low $O_2$ levels, muscle cramps, and lung failure.

What are the functions and deficiency symptoms of calcium ($Ca$)?

Functions include maintaining cell walls and cell membrane permeability, formation of bone and teeth, and aiding blood clotting. Deficiency causes poor plant growth, rickets in children, and poor bone formation.

What are the functions and deficiency symptoms of phosphorus ($P$), iron ($Fe$), iodine ($I$), nitrogen ($N$), and magnesium ($Mg$)?

Phosphorus ($P$) forms cell membranes, nucleic acids, and $ATP$ (deficiency: brown spots/leaf fall; rickets, poor bone formation). Iron ($Fe$) forms haemoglobin and chlorophyll (deficiency: anaemia, chlorosis). Iodine ($I$) forms thyroxin (deficiency: goitre). Nitrogen ($N$) forms proteins, nucleic acids, and amino acids (deficiency: chlorosis, stunted growth, kwashiorkor). Magnesium ($Mg$) forms chlorophyll and bones/teeth and aids nerves/muscles (deficiency: chlorosis, muscle cramps).

What are the major physiological functions of water in living organisms?

Water makes up $70\text{--}95\%$ of cells and $60\text{--}75\%$ of the human body. It breaks down large organic compounds during digestion, acts as a medium for chemical reactions, transports food and mineral salts, dissolves metabolic waste for sweat and urine, acts as a lubricant, regulates body temperature, and protects organs and tissues.

What is eutrophication and what environmental condition triggers it?

Eutrophication is caused by the overuse of chemical fertilisers washing into rivers when it rains, leading to excessive growth of bacteria and a drastic decrease in dissolved oxygen ($O_2$) levels in the water.

What are the three main classes of carbohydrates and their basic structural characteristics?

1. Monosaccharides: Single sugars that are sweet and water-soluble (monomers). 2. Disaccharides: Double sugars formed from two monosaccharides that are sweet and water-soluble (polymers). 3. Polysaccharides: Long chains of many monosaccharides (polymers) that store energy and provide structural materials (e.g., cellulose, glycogen, starch).

What are the building blocks of lipids, and how do saturated and unsaturated fatty acids differ?

Lipids are composed of glycerol and fatty acids (releasing water upon condensation). Saturated fatty acids are solid at room temperature, derive from animal fats, and contribute to cholesterol and blocked blood vessels. Unsaturated fatty acids are liquid at room temperature, derive from plant oils, and do not form harmful cholesterol.

How do temperature extremes and pH changes affect proteins and enzymes?

High heat and pH changes cause proteins and enzymes to denature (permanently lose their three-dimensional structure and catalytic function). Cold temperatures render proteins and enzymes inactive (temporarily stop working without denaturing).

What is an enzyme, what is its optimum temperature in humans, and how does it function?

An enzyme is an organic catalyst made of protein that speeds up chemical reactions without being consumed. Its optimum temperature in the human body is $37^\circ\text{C}$. It functions via a lock-and-key mechanism where a specific substrate binds to the enzyme to form an enzyme-substrate complex.

What are the functions, deficiencies, and food sources of Vitamins A, D, and E?

Vitamin A maintains healthy skin, eyes, and membranes (deficiency: night blindness, xerophthalmia; sources: liver, milk, yellow/green vegetables). Vitamin D absorbs calcium for strong bones and teeth (deficiency: rickets, limited bone growth; sources: fish oil, egg yolk, butter, milk). Vitamin E acts as an antioxidant protecting unsaturated fatty acids and membranes (deficiency: excessive bleeding/haemorrhage, system damage; sources: plant oils, nuts, leafy vegetables).

What are the functions, deficiencies, and sources of Vitamins C and $B_1$?

Vitamin C maintains tissue and blood vessel health, absorbs iron, and heals wounds (deficiency: scurvy, slow-healing wounds, bleeding gums; sources: citrus fruits, tomatoes, leafy vegetables). Vitamin $B_1$ acts as a co-enzyme in cellular respiration and promotes appetite (deficiency: beri-beri, stunted growth, nerve and heart disorders; sources: whole grain cereals, nuts, meat, yeast, liver).

What is the sequence of the biological levels of organization?

Atom $\rightarrow$ Molecule (compounds) $\rightarrow$ Organelle $\rightarrow$ Cell $\rightarrow$ Tissue $\rightarrow$ Organ $\rightarrow$ System $\rightarrow$ Organism $\rightarrow$ Population $\rightarrow$ Species / Community $\rightarrow$ Ecosystem $\rightarrow$ Biome.

What are the primary characteristics and functions of meristematic, parenchyma, and collenchyma plant tissues?

Meristematic tissue consists of undifferentiated, small, thin-walled cells with large nuclei located at root and shoot tips that undergo mitosis for growth. Parenchyma consists of round cells with thin walls, large vacuoles, and intercellular spaces for storage. Collenchyma consists of cells with unevenly thickened cellulose walls that provide flexible strength and mechanical support in young stems and leaf veins.

What are the structural features and functions of sclerenchyma, xylem, and phloem tissues?

Sclerenchyma has evenly thickened lignin cell walls (fibres and stone cells) for rigid support. Xylem consists of dead, non-living vessels and tracheids with lignified walls to transport water and dissolved minerals while providing mechanical support. Phloem consists of living sieve tubes (lacking nuclei, perforated by sieve plates) and nucleated companion cells that transport manufactured food.

What are the four types of epithelial tissue in animals and where are they located?

1. Squamous Epithelium: Single layer of flat cells lining the mouth, oesophagus, and blood vessels. 2. Columnar Epithelium: Elongated, column-shaped cells lining the stomach and small intestine. 3. Ciliated Epithelium: Columnar cells with surface cilia lining air pipes (trachea) and nasal cavities. 4. Glandular Epithelium: Specialised secretory cells, including unicellular goblet cells (mucus) and multicellular glands (salivary, wax).

What is the microscopic structure of cartilage tissue?

Cartilage consists of a tough, flexible matrix composed of the protein chondrin containing fluid-filled spaces called lacunae, within which reside the cartilage cells called chondrocytes.

How do smooth muscle, cardiac muscle, and skeletal muscle differ structurally and functionally?

Smooth muscle: Spindle-shaped, unstriated, single oval nucleus, involuntary; controls slow peristalsis in internal organs. Cardiac muscle: Finely striated, branching fibres, central round nucleus, involuntary; exhibits automatism in the heart. Skeletal muscle: Cylindrical, multinucleated, striated with light and dark bands, enclosed in sarcolemma, voluntary; attached to bones for coordinated movement.

What is the functional difference between sensory (afferent) neurons and motor (efferent) neurons?

Sensory (afferent) neurons have one dendrite and one axon and transmit nerve impulses from sensory receptors to the central nervous system (CNS). Motor (efferent) neurons have many dendrites and one axon and transmit impulses from the CNS to effector organs (muscles and glands).

What are the structural differences between plant cells and animal cells?

Plant cells have a rigid cellulose cell wall, brick-like shape, a large central vacuole, and plastids (chloroplasts, leucoplasts, chromoplasts), but lack lysosomes and store starch. Animal cells have no cell wall, a rounded shape, small temporary vacuoles, contain lysosomes, lack plastids, and store glycogen.

How does the fluid mosaic model describe the structure of the cell membrane?

The cell membrane consists of a double layer (bilayer) of phospholipids with interspersed protein molecules. Each phospholipid has a hydrophilic (water-attracted) outer head and two hydrophobic (water-repelling) inner tails that face inward toward each other. The proteins and lipids shift positions constantly, imparting fluid and mosaic qualities.

What functions are performed by the nucleus, mitochondria, endoplasmic reticulum, and Golgi body?

The nucleus controls all structural and hereditary functions via DNA chromatin networks. Mitochondria have a folded inner membrane and fluid matrix to release energy during cellular respiration. The endoplasmic reticulum forms a tubular transport network (rough ER has ribosomes for protein synthesis; smooth ER lacks ribosomes). The Golgi body processes, packages, and secretes cellular products.

What are the roles of chloroplasts, leucoplasts, and chromoplasts in plant cells?

Chloroplasts contain green chlorophyll and internal stroma to synthesize food via photosynthesis. Leucoplasts are unpigmented plastids that store starch and food. Chromoplasts contain various pigments that impart bright colors to flowers, fruits, and vegetables.

What contributions were made by Robert Hooke, Antonie van Leeuwenhoek, and Matthias Schleiden to microscopy?

In 1665, Robert Hooke studied cork cells and coined the biological term 'cell'. Antonie van Leeuwenhoek (1632–1723) constructed early single-lens microscopes magnifying up to $100\times$ and discovered bacteria and single-celled animals. In 1838, Matthias Schleiden was the first to establish that all plant structures are composed of cells.

How do tap root systems and adventitious root systems differ?

A tap root system develops directly from the radicle of the embryo, possessing a distinguishable primary root. An adventitious root system develops from any part of the plant other than the embryo radicle, having no distinguishable primary root.

What are the four successive external zones of a plant root from the tip upward?

1. Root cap (parenchyma tissue protecting the meristem). 2. Growing point (meristematic cells undergoing active division). 3. Region of elongation. 4. Region of root hairs / differentiation (where cells specialize into permanent tissues).

How are vascular bundles arranged internally in a dicotyledonous stem?

Vascular bundles are arranged in a ring; each bundle has xylem positioned toward the inside, phloem positioned toward the outside, a layer of meristematic vascular cambium between them, and a protective cap of sclerenchyma fibres on the outer boundary.

What structural adaptations allow xylem vessels and tracheids to transport water efficiently?

Both are elongated, hollow, non-living cells with absent or perforated cross walls to create unobstructed fluid tubes; their walls are reinforced with patterns of annular or spiral lignin to withstand pressure without collapsing, while unthickened portions permit lateral water movement.

What is secondary growth in stems and how do annual rings form?

Secondary growth is the thickening of the stem brought about by the division of vascular cambium between vascular bundles. The cambium produces secondary xylem toward the inside and secondary phloem toward the outside; every year, a new layer of secondary xylem forms an annual ring.

What are lenticels and what role do they play in woody stems?

Lenticels are porous openings formed in the cork layer of woody stems when the epidermis breaks open, replacing non-functional stomata to allow gaseous exchange.

What is the difference between transpiration and guttation?

Transpiration is the loss of water vapour from the aerial parts of a plant, primarily through the stomata of leaves. Guttation is the release of excess liquid water droplets through specialized openings called hydathodes located along leaf tips and margins.

Which physical forces drive the upward movement of water through xylem vessels in a plant stem?

The upward transport of water is driven by root pressure (osmotic push from the roots), capillary action (adhesion and cohesion in narrow tubes), and transpiration pull (the primary driving tension caused by evaporation of water from leaf mesophyll).

What are the advantages and disadvantages of an exoskeleton?

Advantages: Forms a protective outer barrier against predators and prevents internal desiccation/dehydration. Disadvantages: Cannot stretch, restricting continuous animal growth and requiring moulting; hard external plates reduce flexibility and movement at joints.

What are the structural features of the human skull, and what is the adult dental formula?

The skull is composed of immovable cranial and facial bones joined by sutures. The spinal cord exits the skull via the foramen magnum, bounded by two smooth occipital condyles that articulate with the atlas vertebra. An adult has $32$ teeth with the dental formula $2:1:2:3$ (incisors, canines, premolars, molars).

What are the four structural regions of the human vertebral column?

The vertebral column consists of $33$ vertebrae grouped into cervical vertebrae, thoracic vertebrae, lumbar vertebrae, and sacral vertebrae, separated by shock-absorbing cartilaginous discs.

How are the 12 pairs of ribs classified in the human rib cage?

The first $7$ pairs attach directly to the sternum and are called true ribs. The next $5$ pairs are false ribs (the first $3$ pairs connect to the cartilage of the rib above before reaching the sternum, while the last $2$ pairs are floating ribs with no anterior attachment).

What bones make up the human pectoral girdle and pelvic girdle?

The pectoral girdle consists of two scapulae and two clavicles (attaching to the scapula and sternum). The pelvic girdle consists of two hip bones joined anteriorly at the pubic symphysis and posteriorly to the sacrum; each hip bone consists of three fused bones (ilium, ischium, and pubis) containing the acetabulum socket.

What is the structural anatomy of a typical long bone (such as the femur)?

A long bone consists of expanded ends called heads (composed of spongy bone containing red marrow and covered by articular cartilage) and an intervening shaft (composed of dense compact bone covered by periosteum, enclosing a marrow cavity lined by endosteum).

What is haemopoiesis and where does it occur?

Haemopoiesis is the biological production of blood cells from stem cells residing inside the bone marrow of the breastbone (sternum), skull, hips, ribs, and spine.

How do tendons and ligaments differ in structure, elasticity, and skeletal function?

Tendons connect muscle to bone and are made of white, non-elastic collagenous fibres that do not stretch. Ligaments connect bone to bone across joints and are composed of yellow, elastic fibres that stretch to allow controlled movement.

What are the three functional classes of joints in the human body?

1. Fixed or immovable joints (e.g., sutures of the skull). 2. Slightly movable joints (e.g., gliding joints between carpal or tarsal bones). 3. Freely movable or synovial joints (e.g., ball-and-socket joints of the shoulder/hip, hinge joints of the elbow/knee).

What causes rickets, osteoporosis, rheumatoid arthritis, osteoarthritis, and gout?

Rickets/osteomalacia: Lack of Vitamin D leading to soft, deformed bones. Osteoporosis: Calcium deficiency resulting in brittle, fragile bones. Rheumatoid arthritis: Autoimmune inflammation of the synovial membrane. Osteoarthritis: Progressive wear and deterioration of articular cartilage. Gout: Accumulation of excess uric acid crystals in the joints.

What occurs during Interphase, Prophase, and Metaphase of mitosis?

During Interphase, the cell replicates its DNA in the chromatin network. In Prophase, chromatin condenses into visible chromosomes (each with two sister chromatids), the centrosomes separate toward opposite poles, spindle fibres form, and the nuclear membrane disappears. In Metaphase, chromosomes line up along the equator and attach to spindle fibres via centromeres.

What occurs during Anaphase and Telophase of mitosis?

During Anaphase, centromeres divide and contracting spindle fibres pull sister chromatids apart toward opposite poles. During Telophase, single-stranded chromosomes arrive at opposite poles, new nuclear membranes assemble around each set, and two identical daughter nuclei are formed.

How does cytokinesis differ between plant cells and animal cells?

In animal cells, the cell membrane invaginates or pinches inward along the middle until the cytoplasm is cleaved into two separate cells. In plant cells, a rigid cell plate/new cell wall forms directly across the center to partition the cytoplasm into two daughter cells.

What are the primary biological functions of the six vegetative and reproductive plant organs?

Roots anchor the plant and absorb water/minerals; stems provide structural support and transport water/assimilates; leaves conduct photosynthesis, gaseous exchange, and transpiration; flowers perform sexual reproduction; fruits enclose seeds and aid dispersal; and seeds protect the plant embryo and provide stored food for germination.