Biology - enzymes and organ systems Flashcards
structure of nervous system
sensory organs contain receptors which detect changes in the environment - e.g. eyes detect light
central nervous system (CNS) consists of brain and spinal cord, and is responsible for coordinating a response
nervous system consists of different types of neurons
sensory neurons
carry signals from receptors to central nervous system
made up of
- receptor cell
- cell body
- axon terminal
- fatty sheath
relay neurons
carry signals from sensory neurons to motor neurons
made up of:
- dendrites
- cell body
- axon
- axon terminal
motor neurons
carry signals from CNS to muscles and glands (effectors)
made up of:
- cell body
- fatty sheath
- dendrites
- axon terminal
what are axons
a long structure containing cytoplasm and surrounded by a cell membrane, the axon carried the electrical impulse along the neuron
what is the cell body
contains a nucleus enclosing dna , codes for proteins needed by cell
what are dendrites
branched structures that allow different neurons to communicate
what is a synapse
‘gap’ between two neurons
‘gap’ is very small and slowest part of neuronal pathway
order of events at neuron
- nerve impulse travels down axon of first neuron
- impulse triggers release of chemical transmitters
- chemical transmitters diffuse across synapse
- chemical transmitters bind to receptors on second neuron
- nerve impulse is initiated in second neuron
(chemical transmitters released from end of one neuron and diffuse passively across synapse)
how does ecstasy affect the actions of synapse
- changes way serotonin is removed from synapse
- serotonin is a ‘mood hormone’ - changes things like pain and aggression
- ecstasy causes a lack of removal of serotonin, meaning the concentration of serotonin increases
- normally leads to mood being enhanced
what is a reflex
- unconscious actions that do not require any thought in order to carry out
- protective
- reflexed are involuntary, rapid and automatic responses to simuli
how electrical impulse travels through a reflex arc
- stimuli is detected by receptors
- electrical impulses travel along sensory neuron
- in spinal cord, sensory neuron and relay neuron synapse
- impulses are further passed to a motor neuron via a synapse to an effector (muscle/gland)
respiration
process of releasing energy from glucose and occurs in every living cell
process is catalysed by enzymes
aerobic respiration
glucose + oxygen –> carbon dioxide + water + energy
most efficient way to release energy
anaerobic respiration
glucose –> lactic acid + energy
insufficient oxygen - incomplete breakdown of glucose and releases less energy than aerobic
lactic acid is produced which causes muscles to fatigue
what is glucose stored as
glycogen
during vigorous exercise, glycogen is converted back to glucose for use
structure of respiratory system
- air enters through mouth and nose and then passes to larynx
- continues to trachea
- trachea splits into 2 main tubes called bronchi
- bronchi split into progressively smaller tubes called bronchioles
- bronchioles split into alveoli (site of gas exchange)
how is alveolus adapted for efficient gas exchange
- walls of alveolus are one cell thick to minimise diffusion distance and time
- have large surface area to increase rate of gas exchange
- capillary networks surround alveoli to maintain high concentration gradient
what is ventilation
process of breathing in and out
what happens when breathing in
- intercostal muscles contract
- diaphragm contracts and flattens
- intercostal muscles cause rib cage to move up and out
- thorax volume increases
- since volume increases, air in thorax remains same, thoracic pressure decreases causing air to be draw into lungs in inhalation
what happens when breathing out
- intercostal muscles relax
- diaphragm relaxes
- intercostal muscles cause rib cage to move down and in
- thorax volume decreases
- since volume decreases, thoracic pressure increases causing air to be pushed out of lungs in inhalation
human circulatory system
- double circulatory system
- one pumps oxygenated blood to body, other pumps deoxygenated blood to lungs
structure of heart
- upper chambers called atria
- lower chambers called ventricles
- valves that prevent backflow of blood
features of arteries
thick walls
small lumen
high blood pressure
muscular and elastic walls to withstand high pressure
features of veins
thin walls
large lumen
low blood pressure
veins have valves to prevent backflow of blood
features of capillaries
walls are one cell thick
very small lumen
high blood pressure
walls are very thin to give a high diffusion rate
heart rate
- rate at which heart beats is determined by bodys demand for oxygen
- affected by activity and conditions in body
- during exercise, heart rate increases from resting to cope with extra oxygen demand
what is heart rate controlled by
- pacemaker cells in heart
- clusters of these cells are known as sinoatrial node (atrial contraction) and antrioventricular node (ventricular contraction)
how can you trace heart’s electrical activity
- electrocardiogram (ECG)
- diagnostic test that can show heart attacks and irregular heartbeats
- ECG below shows two full heart beats for a healthy individual
what is blood composed of
- plasma
- red blood cells
- white blood cells
- platelets
plasma description
- watery part of blood where cells are transported
- contains dissolved glucose, amino acid, urea, carbon dioxide and proteins
- distributes heat
red blood cells description
- contain haemoglobin to carry oxygen in form of oxyhaemoglobin
- cells are concave in shape
- do not have nucleus so that the cell can carry as much oxygen as possible
white blood cells description
- fight infection
- phagocytes can change shape in order to engulf microorganisms
- lymphocytes also produce antibodies in order to neutralise microorganisms
- do have a nucleus
platelets description
- causes blood to clot at the site of a wound
- fibrinogen is converted into fibrin through a series of enzymes, creating a mesh that traps platelets and red blood cells to stop blood loss
- no nucleus
blood groups
assigned depending on antigens on surface of individual’s red blood cells
A antigens and B antigens
you can have A, B, AB, or O
blood group A qualities
antigens = A
antibodies = anti-B
can donate blood to = A and AB
can receive blood from = A and O
blood group B qualities
antigens = B
antibodies = anti-A
can donate blood to = B and AB
can receive blood from = B and O
blood group AB qualities
antigens = A, B
antibodies = none
can donate blood to = only AB
can receive blood from = anyone
blood group O qualities
antigens = none
antibodies = anti-A, anti-B
can donate blood to = anyone
can receive blood from = only O
which blood group is universal donor?
O
which blood group is the universal recipient
AB
when does an agglutination reaction occur
if patient is given red blood cells with antigens corresponding antibodies in their blood
this reaction can be fatal
structure of digestive system
- mouth
- oesophagus
- stomach
- small intestine
- large intestine
what is peristalsis
food is moved through this process where wave-like muscle contractions move food along digestive tract
mechanical digestion
e.g. ground by teeth
chemical digestion
e.g. bile and enzymes in stomach
enzymes
- break down large insoluble molecules into smaller soluble molecules
- biological catalysts
- proteins
- can be altered by temperature and pH
lock and key model
active site (where substrate binds) of enzyme is specific to substrate and only catalyses specific reaction
what enzyme breaks starch down into what products
starch broken by amylase into maltose
maltose broken by maltase into glucose
what enzymes break protein down into what products
protein broken down by proteases into amino acids
what enzyme breaks lipids into what products
lipids broken by lipases into glycerol and fatty acids
where is amylase produced
salivary glands
pancreas
small intestine
where are proteases produced
stomach
pancreas
small intestine
where are lipases produced
pancreas
small intestine
where are lipases produced
pancreas
small intestine
what is emulsification
- bile is made in the liver and is stored in the gall bladder until needed
- bile is then released into the small intestine
- large lipid droplets are broken down into smaller droplets, therefore increasing surface area
- rate of digestion increases
food absorption
- small intestine is main site of absorption which has villi that increase surface area
- villi contain blood capillaries so high conc. gradient is maintained
- nutrients are absorbed through diffusion and active transport and water is absorbed through osmosis
- absorbed nutrients used in order to make new macromolecules, for respiration, growth and repair or energy storage
- the parts of the food that are unable to be digested (e.g. cellulose) leaves the body as faeces, which is brown due to bile pigments
- faeces egested out of anus
excretory system: liver
- excess amino acids are broken down by liver through DEAMINATION
- the nitrogen parts of these are converted into UREA - a toxic substance which is then excreted by kidneys
- breaks down haemoglobin to create BILIRUBIN, which is excreted with faeces
excretory system: lungs
- removes carbon dioxide from the body, which is a waste product of aerobic respiration
excretory system: skin
- produces sweat, containing sodium chloride and small amounts of urea dissolved in water
- skin is not an excretory organ in the same way that the lungs or kidney are
excretory system: kidneys
- removes urea
- adjusts water content
- adjusts ion levels
kidneys structure
- receives blood from renal artery
- filtered blood returned to renal vein, which forms vena cava
- each kidney contains millions of nephrons
- each nephron there is a glomerulus, which is a ball of capillaries that are surrounded by a Bowman’s capsule
- leads to a proximal convoluted tubule, the loop of Henle, the distal convoluted tubule and the collecting duct
how is filtrate formed
- large cells and substances, such as rbc and proteins, cannot filter through the glomerulus and therefore stay within the capillaries
- smaller molecules such as water, urea and dissolved ions are forced through the wall through ULTRAFILTRATION (filtration under pressure)
- forming FILTRATE
selective reabsorption
filtrate passes through tubule and selective reabsorption of glucose, some salt and water occurs