Grade 11 Life Sciences Paper 1 Review (Human Systems, Respiration, Photosynthesis)

Comprehensive practice flashcards covering core Grade 11 Life Sciences terminology from provincial examinations, including human nutrition, gaseous exchange, cellular respiration, photosynthesis, and excretion.

Epiglottis

The cartilaginous flap-like structure that prevents the food bolus from entering the trachea during swallowing.

Tubular Secretion

The active process where metabolic waste products, toxins, and foreign substances (such as hormones, urea, and creatine) are moved from the peritubular capillaries into the renal tubule.

Excretory Pathway

The sequence of structures through which urine travels out of the body: Kidney $\rightarrow$ ureter $\rightarrow$ bladder $\rightarrow$ urethra.

Osmoregulation

The homeostatic process by which the body regulates and maintains the balance of water and solute (salt) concentrations in bodily fluids.

Ciliated Columnar Epithelium

Specialised epithelial tissue bearing microscopic hair-like cilia that lines the trachea and windpipe to trap dust, dirt, and pathogenic microbes.

Aldosterone

The steroid hormone secreted by the adrenal cortex that regulates the reabsorption of sodium ions ($\text{Na}^+$) by the renal tubules.

Pharynx

The region that connects the nasal cavity with the larynx and leads down into both the trachea and the oesophagus.

Secretion

The production and release of a functionally useful substance (such as digestive enzymes or saliva) from cells or specialised glands.

Chyme

The semi-liquid mass of partially digested food mixed with gastric juices produced by mechanical churning and chemical digestion in the stomach.

Distal Convoluted Tubule

The highly folded portion of the renal nephron located between the loop of Henle and the collecting tubule.

Osmosis

The passive movement of water molecules from a region of high water potential to a region of low water potential across a selectively permeable membrane without energy expenditure.

Renal Calyx

A cup-shaped structural chamber surrounding the renal papillae that collects and funnels urine into the renal pelvis.

Renal Capsule

The protective fibrous and adipose tissue layer enveloping the outer surface of the kidney to shield it from mechanical injury.

Renal Pelvis

The funnel-shaped central collecting structure of the kidney that gathers urine from all the calyces and channels it into the ureter.

Homeostasis

The ability of an organism to maintain a constant, stable internal physiological environment irrespective of fluctuations in the external environment.

Carotid Body Chemoreceptors

Specialised sensory receptors located within the walls of the carotid artery that detect elevated carbon dioxide ($\text{CO}_2$) levels and decreased pH in the arterial blood.

Chloroplast

A double-membraned plant organelle containing thylakoids stacked into grana and a fluid stroma, functioning as the site of photosynthesis.

Photolysis

The light-dependent splitting of water molecules ($\text{H}_2\text{O}$) into energised hydrogen ions and oxygen gas ($\text{O}_2$) during the light phase of photosynthesis.

Glycolysis

The initial, catabolic phase of cellular respiration occurring in the cytoplasm, where a six-carbon glucose molecule is broken down into two three-carbon pyruvic acid molecules, releasing 2 ATP.

Krebs Cycle

The cyclical, oxygen-dependent stage of aerobic respiration taking place in the mitochondrial matrix that breaks down pyruvate derivatives, yielding carbon dioxide, ATP, and high-energy hydrogen carried by NADH and $\text{FADH}_2$.

Lactic Acid Fermentation

An anaerobic pathway occurring in animal muscle tissue when oxygen is depleted, converting pyruvic acid into lactic acid and causing muscle fatigue and cramps.

Bartter Syndrome

A rare genetic kidney disorder characterised by impaired sodium ion reabsorption in the thick ascending limb of the loop of Henle despite the secretion of aldosterone.

Palisade Mesophyll

The elongated, chloroplast-dense parenchyma tissue situated directly beneath the upper epidermis of a leaf, serving as the primary site of photosynthesis.

Intercostal Muscles

Skeletal muscles positioned between the ribs that contract to elevate the rib cage upward and outward during inhalation.

Ureter

The muscular tubule that conveys urine via peristaltic contractions from the renal pelvis of the kidney to the urinary bladder.

Pleural Membrane

A continuous double-layered protective serous membrane surrounding the lungs that secretes lubricating fluid to reduce friction during respiratory movements.

Islets of Langerhans

Clusters of endocrine cells scattered throughout the pancreas responsible for synthesising and secreting the hormones insulin and glucagon.

Larynx

The cartilaginous organ located at the top of the trachea containing the vocal cords that vibrate to produce sound.

Diaphragmatic Hernia

A pathological condition resulting from a tear or perforation in the diaphragm that allows abdominal organs to herniate into the thoracic cavity, impeding lung expansion.

Podocytes

Specialised epithelial cells forming the visceral inner layer of Bowman's capsule with foot-like pedicels that wrap around glomerular capillaries to form filtration slits.

Glomerular Ultrafiltration

The non-selective filtration of blood under high hydrostatic pressure across the fenestrated glomerular capillaries and podocyte slits into the lumen of Bowman's capsule.

Afferent vs. Efferent Arterioles

The afferent arteriole entering the glomerulus has a wider lumen than the exiting efferent arteriole, generating high capillary pressure essential for ultrafiltration.

Alcoholic Fermentation

An anaerobic respiratory process occurring in plant cells and yeast in which pyruvic acid is decarboxylated and reduced into ethanol and carbon dioxide.

Deamination

The biochemical process in the liver wherein the amino groups ($-\text{NH}_2$) of excess amino acids are removed and converted into toxic ammonia, which is then transformed into urea.

Peristalsis

Involuntary, wave-like alternating contractions and relaxations of circular and longitudinal smooth muscles that propel food contents through the alimentary canal.

Lipase

The digestive enzyme responsible for hydrolysing emulsified dietary lipids into fatty acids and glycerol molecules.

Lacteal

A central lymphatic capillary located within the core of each intestinal villus that absorbs processed fatty acids and glycerol.

Diabetes Mellitus

A metabolic endocrine disorder resulting from an absolute deficiency or ineffectiveness of insulin, characterised by chronic hyperglycaemia and glycosuria (glucose in urine).

Crohn's Disease

A chronic inflammatory bowel disease causing atrophy and flattening of the intestinal villi, severely compromising nutrient absorption and leading to malnutrition.

Bicarbonate Ions ($\text{HCO}_3^-$)

The predominant chemical form in which carbon dioxide is transported through the bloodstream within the plasma.

Oxyhaemoglobin

The bright red complex formed when oxygen reversibly binds to the haem group of haemoglobin inside erythrocytes for systemic transport.

Clear Limewater

A chemical indicator solution consisting of dilute calcium hydroxide that turns milky or cloudy upon bubbling with carbon dioxide gas.

Iodine Solution

A chemical reagent used to detect the presence of starch in plant tissues, exhibiting a positive colorimetric change from yellow-brown to blue-black.

Medulla Oblongata

The lower portion of the brainstem containing vital reflex centres that regulate the rhythm, depth, and rate of breathing as well as heart rate in response to arterial carbon dioxide changes.

Antidiuretic Hormone (ADH)

A peptide hormone produced by the hypothalamus and released by the posterior pituitary that increases water permeability of the distal convoluted tubules and collecting ducts.

Glucagon

A peptide hormone secreted by the alpha cells of the pancreatic islets that raises blood glucose levels by stimulating the breakdown of glycogen into glucose in the liver.

Hepatic Portal Vein

The blood vessel that transports deoxygenated, nutrient-rich blood directly from the capillary networks of the gastrointestinal tract to the liver.

Emulsification

The physical breakdown of large dietary fat globules into smaller lipid droplets by bile salts, greatly increasing the surface area for lipase action.

Bell Jar Lung Model

An experimental apparatus representing thoracic breathing mechanics, where a glass Y-tube models the trachea and bronchi, balloons model the lungs, and a flexible rubber sheet models the diaphragm.

Respirometer

A closed experimental apparatus equipped with potassium/sodium hydroxide and a U-tube manometer used to measure the rate of oxygen consumption in respiring living organisms.