Structure and functions in living organisms - IGCSE Flashcards
Cell
The basic building block of all living organisms
Organelle
A specialised strcture found inside a cell
Organs
Aggregations of tissues performing specific functions
Organ systems
Groups of organs that work together to form organisms
Tissue
A group of cells with a similar structure and function
Cell differentiation
The process by which a cell becomes specialised to its function
Cell wall
An outer, strctural layer that surrounds some cells
In plant cells, it’s made of cellulose. In fungi it’s made of chitin
Chloroplast
An organelle which is the site of photosynthesis
Cytoplasm
A jelly-like substance that contains all the organelles of the cell, dissolved nutrients and salts
Mitochondria
An organelle which is the site of respiration
Nucleus
An organelle found in most eukaryotic cells that contains the genetic material of the cell and controls its activities
Ribosomes
Orgamelles that are the site of protein synthesis
Stem cell
An undifferentiated cell that can divide to produce many specialised cells of the same tyoe
Vacuole
An organelle found in plant cells that stores cell sap and supports the cell
Active site
Part of the enzyme that is complementary to the shape of the substrate
The shape of the active site may change if the enzyme is exposed to high temperatues or extremes of pH
Amino acids
Small molecules from which proteins are assembled
Enzymes
Biological catalysts that increase the rate of reactions in living organisms
Glycogen
A large carbohydrate made from many glucose molecules joined together
It serves as an energy store in animals
Lipids
A group of large molecules that are made from long fatty acid chains and glycerol
Lipids include fats and oils
Protein
Large molecules made up of amino acids
Starch
A large carbohydrate molecule made up of many glucose molecules
It contains the elements carbon, oxygen and hydrogen.
It’s an energy storage molecule in plants
Concentration gradient
The difference in concentration between two areas
Osmosis
The diffusion of water molecules from a more dilute solution to a more concentrated solution across a partially permeable membrane
Surface area to volume ratio
The size of the object compared with the amount of area that contacts the environment
Amylase
An enzyme produced in salivary glands and pancreas that breakd down starch into maltose
Maltase
An enzyme produced in the pancreas that breaks down lipids into fatty acids and gycerol
Protease
An enzyme produced in the stomach and pancreas that breaks down proteins into amino acids
Bile
A green, watery fluid made in the liver and stored in the gallbladded that is used to neutralise stomach acid in the duodenum and emulsify fats
Oesophagus
A muscular tube that takes food from the mouth to the stomach
Peristalsis
The squeezing movement of muscles that pushes the bolus of food along the digestive tract
Pancreas
An organ that produces digestive enzymes and releases them into the small intestine
Duodenum
The first section of the small intestine where digestive enzymes and bile are added to the ingested food
Ileum
The second section of the small intestine where the products of digestion are absorbed
Colon
The first part of the large intestine where water is reabsorbed
Rectum
Part of the large intestine where faeces is stored
Palisade mesophyll
A tissue found in plant leaves that is specialised to carry out photosynthesis
Spongy mesophyll
A tissue found in plant leaves that is specialised for gas exchange
Stomata
Small holes found on the surface of a leaf that allow carbon dioxide and oxygen to diffuse in and out of the leag for photosynthesis
They also control water loss
Waxy cuticle
A layer on top of the leaf that reduces water evaporation, but does not block sunlight
Aerobic respiration
A form of respiration that uses oxygen to release energy from the breakdown of molecules like glucose
glucose + oxygen –> carbon dioxide + water
Anaerobic respiration
A form of respiration that releases energy from the breakdown of molecules like glucose without using oxygen
glucose –> lactic acid
ATP
A molecule that releases energy quickly
Alveoli
Tiny air sacs in the lungs that serve as the gaseous exchange surface
Bronchi
The two airways branching from the trachea that lead into the lungs
Bronchioles
The small airways branching from the bronchi in each lung
Trachea
The windpipe connecting the lungs to the mouth and nose
Diaphragm
The muscle separating the thorax and the abdomen
Intercostal muscles
Group of muscles situated between the ribs
They are responsible for the movement of the ribs during breathing
Pleural membranes
The airtight membranes covering the lungs and the chest wall
Heart
An organ that pumps blood around the body in a double circulatory system
Artery
A type of blood vessel that carries blood at high pressure away from the heart to the tissues
Vein
A blood vessel that carries blood at low pressure back to the heart
Aorta
The main artery that takes oxygenated blood away from the heart to the body
Vena cava
The main vein that takes deoxygenated blood back to the heart from the body
Pulmonary artery
The main artery that takes deoxygenated blood away from the heart to the lungs
Hepatic artery
The artery that supplies the liver with oxygenated blood
Hepatic vein
The vein that carries blood away from the liver
Pulmonary artery
The artery that takes deoxygentaed blood back to the heart from the lungs
Pulmonary vein
The main vein that carries deoxygenated blood back to the heart from the lungs
Renal arteries
The arteries that supply blood to the kidneys
Renal veins
The veins that take blood away from the kidneys
Atria
The two upper chambers of the heart that receive blood from the veins and pump blood into the ventricles
Ventricles
The two lower chambers of the heart that receive blood from the atria and expel blood into the artieries
Blood
A tissue containing red blood cells, white blood cells, platelets and plasma
Red blood cells
Cells in the blood that transport oxygen
They have a biconcave shape, no nucleus, and contain haemoglobin
Haemoglobin
The red protein found in red blood cells that transports oxygen in the blood
White blood cells
Cells of the immune system that protect the body from invading pathogens via the production of antibodies and antitoxins
Phagocyte
A type of white blood cell that ingests pathogens
Lymphocyte
A type of white blood cell that produces specific antibodies against a pathogen
Memory cell
An immune cell that can recognise a pathogen previously encountered (either from infection or vaccination) and produce antibodies against the pathogen quickly
Plasma
The straw-coloured liquid in blood that transports carbon dioxide, urea, digested food, hormones and heat energy
Platelets
Tiny fragments of cells found in the blood that are involved in clotting
Xylem
A plant transport tissue that is specialised to transport water and dissolved minerals from the roots of the plant to the leaves
Phloem
A transport tissue found in plants which is specialised to transport sugars from sources to sinks
Excretion
The removal of waste products and toxic substances from the body
Organs of excretion
The lungs, kidneys and skin. The lungs excrete carbon dioxide and water vapour, the kidneys excrete water, urea and salts and the skin excretes water and salts
Bladder
The organ that collects and holds urine
Ureters
The tubes that carry urine from the kidneys to the bladder
Urethra
The tube that carries urine from the bladder to outside the body during urination
Nephron
The functional unit of the kidney
Convoluted tubules
Tubes of the nephron through which filtrate flows
Substances from the filtrate are reabsorbed into blood in the convoluted tubules
Glomerulus
A collection of capillaries that is involved in the filtration of blood under high pressure
Bowman’s capsule
The cup-like strcture at the start of a mephron where the filtrate from the glomerulus is collected and taken to the tubules
Loop of Henle
Part of the nephron in which water and salts are reabsorbed
Collecting duct
The final part of the nephron before the ureter in which water is selectively reabsorbed
Its permeability to water is altered by ADH
ADH
A hormone produced by a pituitary gland that increases the reabsorption of water in the kidney tubules
Ultrafiltration
The filtration of the blood at the glomerulus to produce a filtrate which contains water, ions, glucose, urea and other molecules
Proteins and cells are not present in the filtrate
Adrenaline
A hormone produced by the adrenal glands in response to fear or stress
It increases the heart rate and boosts the delivery of blood to the brain and muscles as part of the fight or flight response
CNS
The brain and spinal chord
It coordinates the response of effectors
FSH
A hormone produced by the pituitary gland that stimulates the growth of follicles in the ovary and the secretion of oestrogen
Homeostasis
The maintenence of a stable internal environment in the body despite fluctuations in internal and external conditions
Vasodilation
The dilation of blood vessels near the surface of the skin to lose heat
Vasoconstriction
The constriction of blood vessels near the surface of the skin to conserve heat
Insulin
A hormone secreted by the pancreas when blood glucose concentration is too high
It reduces blood glucose concentration
Reflex arc
The pathway of neurones involved in a reflex action
Stimulus - receptor - sensory neurone - interneurone - motor neurone - effector - response
Effectors
Muscles or glands which bring about responses to restore optimum levels
Stimulus
A change in an organism’s internal or external environment
