Module 5: Communication, Homeostasis and Energy Flashcards
(239 cards)
1
Q
How many carbons does the intermediate that reacts with acetyl CoA have?
A
4
2
Q
What happens during the process of Glycolysis?
A
- Glucose(6C) is phosphorylated using two inorganic phosphate from ATP. forming two two ADP. This creates the molecule hexose bisphosphate(3C).
- Hexose bisphosphate(3C) splits into two molecules of triose phosphate(3C). A random inorganic phosphate is added to triose phonsphate(3C) forming triose bisphosphate(3C).
- Triose bisphosphate(3C) is oxidised into pyruvate(3C).
- NAD steals a hydrogen from triose phosphate(3C). This hydrogen is used to reduce NAD forming reduced NAD.
- 2 ADP molecules combine with an inorganic phosphate forming ATP in a process called substrate level phosphorylation.
- Products of Glycolysis:
-A net gain of two ATP molecules (4 ATP molecules).
-2 Pyruvate- to be used in the link reaction then in the krebs cycle.
-2 reduced NAD- to be used in oxidative phosphorylation.
3
Q
What is the final electron and hydrogen acceptor in oxidative phosphorylation?
A
Oxygen
4
Q
What occurs duing Oxidative phosphorylation?
A
- Hydrogen atoms from the reduced NAD and reduced FAD arereleased as they are oxidised. The hydrogen atoms split into to protons and electrons.
- The electrons move along the electron transport chain loosing energy at each carrier.
- This energy is used by the carriers to pump hydrogen ions from the mitochondrial matrix across the inner membrane. Hydrogen ions accumulate in the intermembrane space, and this generates a proton gradient (sometimes referred to as an electrochemical gradient) across the membrane.
- Hydrogen ions then flow back into the matrix through the enzyme ATP synthase which uses the movement of hydrogen ions to add a phosphate group onto ADP to form ATP. The process by which the movement of hydrogen ions produces ATP is called chemiosmosis.
- Once the electrons reach the end of the electron transport chain, they are passed onto oxygen, which is referred to as the ‘final electron acceptor’. Oxygen combines with electrons and hydrogen ions to form water, one of the products of aerobic respiration.
5
Q
What occurs during the Krebs Cycle?
A
- Acetate combines with oxaloacetate to form citrate(6C) The coenzyme A goes back to the link reaction to be used again.
- Citrate is decarboxylated turning it into a 5C molecule. Citrate is dehydrogenated. The hydrogen is used to reduce NAD forming reduced NAD.
- The 5C olecule is decarboxylated and dehydrogenated again. The Hydrogen is used to then reduce 2 NAD and 2 FAD forming 2 reduced NAD and 2 reduced FAD.
- ATP is produced by the direct transfer of a phosphate group from one molecule to ADP . This process is called substrate level phosphorylation.
- Products of the Krebs Cycle:
-1 Coenzyme A- goes back to be used in the link reaction
-Oxaloacetate- regenerated for the next step of the krebs cycle
-2 CO2 - as a waste product.
-1 ATP- used for energy
-3 reduced NAD- used in oxidative phosphorylation.
-2 reduced FAD- used in oxidative phosphorylation.
6
Q
What occurs during the Link Reaction?
A
- Pyruvate is decarboxylated (A carbon molecule is removed in form of CO2).
- NAD collects a hydrogen from pyruvate and uses it to reduce NAD forming reduced NAD and Acetate.
- Acetate combines with Coenzyme A forming Acetyl Coenzyme A.
- Products of the Link Reaction:
-2 Acetyl Coenzyme A- to be used in the krebs cycle
-2 reduced NAD- to be used in Oxidative phosphorylation
-2 CO2- as a waste product. - The link reaction has to occur twice for every glucose molecule.
- No ATP is produced in the link reaction.
7
Q
Where does glycolysis occur?
A
In the cytoplasm
8
Q
Where does the Krebs cycle take place?
A
In the mitochondrial matrix
9
Q
Why are the glycolysis reactions described as anaerobic?
A
It doesn’t involve oxygen
10
Q
Why do animals need energy
A
Active transport
Endo/exocytosis
Synthesis of protein
DNA replication
Cell division
Movement
Activation of a chemical (phosphorylation)
11
Q
Where does photosynthesis take place in plant cells?
A
In the chloroplasts
12
Q
Chloroplatsts contain photosynthetic pigments. What are photosynthetic pigments?
A
Photosynthetic pigments are coloured substances thet absorb light energy for photosynthesis. They are fond in the thylakoid membrane and they are attached to proteins.
13
Q
Describe the stages involved in the light dependent reaction?
A
- Light energy is absorbed by photosynthetic pigments in photosystems 2 (PSII)
This light excites to a high energy level.
The electrons pass through the electron carrier. - The electrons lost need to be replace so a molecule of water is split into hydrogen ions, oxygen and electrons. The elctrons replaces the
lost one. - As the electrons move down the electront transportchain, they loose enerygy.
This energy is used to transport hydrogen ions from the stroma into the thylakoid creating a proton gradient. - The protons are moving down thier concentration gradient so theu loose energy. This energy is used to phosphorylate the conversion or
ADP and Pi into ATP. This processes is called chemiosmosis.
At this point cyclic or non-cyclic phosphorylation - Cyclic Photophosphorylation: Light energy is absorbed at PSI so the elecron is excited again to a higher energy level. This electron and the
hydrogen ions fron the stroma is passed onto NADP forming reduced NADP. - Non- Cyclic Photophosphorylation: The electrons is cycled at PSI , i goes to the elctron transport chain. This means no NADPH is produced and only a small a,ount of ATP is produced.
- Products: - NADPH, ATP.
14
Q
What happens during the light independent stage of photosynthesis?
A
- A CO2 molecule combines with RuBP(a five carbon molecule) forming 2 molecules of glycerate phosphate (a 3C molecule) catalysed by
the enzyme rubisco. - NADPH is oxidised forming NADP and hydrogen ions. The hydrogen ion is used to convert glycerate phosphate into triose phosphate.
ATP provides energy to turn Glycerate phosphate into triose phosphate. - NADP goes back to the light dependent reaction to be used again
- Triose phosphate is converted into useful organic materials like carbohydrate, lipids, and amino acids
- RuBP is reagenerated
15
Q
How many times does the calvin cycle need to turn to make one hexose sugar?
A
6 times
16
Q
Stimulus from different sources often resulting in one response is known as what?
A
Spatial summation
17
Q
State one advantage and disadvantage of a kidney transplant compared to a dialysis
A
ADVANTAGE
– There’s no need for regular visits to the hospital to change dialysis fluid
DISADVANTAGE
– The immune system can reject the kidney because it doesn’t recognse it as “self”
18
Q
What are the three proteins that make up the I-band
A
– Actin
– Tropomyosin
– Troponin
19
Q
Why does the A-band and the I-band look different?
A
– The I-band is usually lighter than the A-band
– The I-band only contains actin filaments while the A-band contains both actin and myosin filaments
20
Q
How different is a contracted muscle to a relaxing muscle?
A
– I-band is shorter
– A-band stays the same
– H-zone is smaller
21
Q
What is a transducer?
Give an example
A
A tranducer is something that converts one form of energy into another
e.g A pancinian corpuscle
22
Q
What is the “All-or-Nothing” principle?
A
– This means that for an action potential to be generated, threshold must be reached.
23
Q
What are liver cells called?
A
Hepatocytes
24
Q
What process does liver cells divide by?
A
Mitosis
25
Where precisely are acetylcholine receptors found?
On the surface of the postsynaptic neurone's membrane
26
What are examples of endocrine glands?
-- pancreas
-- adrenal glands
27
What is the function of the hormone adrenaline?
-- increases heart rate
-- increases blood glucose concentration
28
What is the function of the hormone noradrenaline?
-- increases heart rate
-- increases blood pressure
-- widens pupils
29
What is the function of the hormone glucorticoids?
reglutes metabolism
30
what is the function of the hormone cortisol?
regulation of the metabolism
31
What is the function of the hormone corticosterone?
regulation of metabolism
32
what is the function of the hormone androgens?
regulation of sexual characteristics and cell growth
33
Why is transmission of action potentials along the axon slower than saltatory conduction?
-- This is because an action potential has to be generated alongt he whole length of the axon instead of at the end of each myelin sheath (at the shwann cells).
34
What are the functions of the liver?
-- production of urea in the ornithine cucle
-- removal of amio groups from the the amino acids
-- storage of glucose as glycogen
35
What are examples of cell signalling?
-- The neurotansmitter acetylcholine causing depolaisation
-- The hormone prolactin binding to a cell receptor in breast tissue
-- Epithelial cells releasing cytokines in response to histamine.
36
How is ammonia formed in the ornithine cycle?
By deamination- Removal of an amine group from amino acids
37
what are effectors?
Effectors are cells that bring about a response to a stimulus to produce an effect
38
What is homeostasis?
Homeostasis is the maintenance of a constant internal environment
39
Is positive feedback mechanism involved in homeostasis?
-- No
-- Positive feedback mechanism is not involved in homeostasis because it doesn't keep your internal environment constant.
40
What are the three types of nuerones?
-- Sensory
-- Relay
-- Motor
41
What is the role of the sensory nuerone?
-- Sensory neurone transmitts nerve impulses from the receptors to the central nervous system
42
What is the role of the motor neurone?
The motor neurone transmitts nerve impulses from the central nervous system (CNS) to the effectors
43
What is the role of the relay neurone?
The relay neurone transmits nerve impulses from sensory neurone to the motor neurone
44
What is a transducer?
-- A tranducer is something that converts one form of energy to another
45
What is a resting potential?
-- It is the potential when the cell is at rest
46
Explain how a generator potential is generated when a pancinian corpuscle is stimulated.
-- When a pancinian corpuscle is stimulated, the lamellae is deformed pressing on the sensory nerve ending.
-- This causes deformation of stretch mediated sodium ion channels in the sensory neurones.
-- The sodium ion channels open causing an influx of sodium ion channels.
-- This creates a generator potential.
47
Collagen is found in tendons. Tendons attach muscles to bones. Which property of makes it suitable for the role?
-- Strong
-- Flexible
-- Insoluble
48
Explain why glucose is required for the contraction of skeletal muscle.
-- Glucose is need for respiration
-- To produce ATP
-- ATP is needed (in muscle contraction) for breaking cross-bridges between myosin and actin
49
What is excretion?
-- Excretion is the removal of waste products from the body.
50
How is carbon dioxide excreted from the body?
-- Carbon dioxde is produced as a waste product after respiration. It is excreted when you breathe out.
51
What are the functions of the liver?
-- stores glycogen
-- detoxification
-- formatio of urea
52
What are liver cells?
-- Hepaocytes
53
What are examples of waste products that need to be excreted from the body?
-- Carbon dioxide
-- Nitrogenous waste
54
Why does excretion need to occur?
Many waste products are toxic so allowing them to build up in the body can cause damage
55
What are the funtions of a liver?
-- Breaks down excess amino acids
-- Removes harmful substances from the blood
-- Stores glycogen
56
How are excesss amino acids broken down in the liver?
-- Nitrogen from the nitrogen conatining compounds are removed forming ammonia and organic acids.
-- The organic acids can then be respired to give ATP and converted into carbohydrates and be stored as glycogen
-- The ammonia combines with carbon dioxide in the ornithine cycle ceating urea.
-- Urea is released from the liver into the blood where it can be filtered out by the kidney.
57
How is alcohol (ethanol) broken down by the liver?
-- Ethanol is converted into ethanal
-- Ethanal is then broken down into acetic acid
58
Which harmful substances the liver can remove from the blood?
-- ethanol/alcohol
-- paracetamol
-- insulin
59
what is the function of the hepatic artery?
-- The hepatic artery supplies the liver with oxygenated blood from the heart. This is so that the liver has good supply of oxygen for respiration.
60
what is the function of the hepatic vein?
The hepatic vein takes deoxygenated blood away from the liver.
61
What is the function of the hepatic portal vein?
-- The hepatic portal vein brings blood from the duodenum and ileum (small intestine) so it is rich in products of digestion. This means that any harmful substances can be filtered out and broken down straight away.
62
What is the function of the bile duct?
Takes bile (produced by the liver to emusify fats) to the gall bladder to be stored.
63
What are the function of kupfer cells?
-- They remove bacteria and break down red blood cells
64
What are effectors?
Cells that produce a response are.
65
What are ectothermic organisms?
Ectothermic organisms are unable to physiologically control their own body temperature.
66
What are endothermic organisms
Endothermic organisms maintain a constant internally controlled body temperature, regardless of environmental changes in temperature.
67
Nitrogen containing compounds are harmful to the body, then why are they in the body?
-- They are made from the metabolism of protein.
68
What are the hormones that control blood glucose concenration?
-- Insulin and Glucagon
69
What organ monitors the bloodglucise concentration in the blood?
-- The cells in the pancreas
70
What cell secretes insulin into the blood?
-- Beta cells
71
What cells secretes glucagon into the blood?
-- Alpha cells
72
What feedback level keeps the blood glucose concentration normal?
-- Negative Feedback Mechanism
73
What happens when the blood glucose concentration is too high?
-- Beta cells secrete insulin.
-- Insulin binds to specific receptors on the surface of liver cells and muscle cells.
-- This increases the permeability of cell membrane so the cells take up more glucose.
-- insulin activates specific enzymes that allow the conversion of glucose into glycogen.
-- Cells store glycogen in thier cytoplasm as energy sources.
-- The process of converting glucose into glycogen is known as glycogenesis.
-- Insulin increases the rate of respiration of glucose especially in muscle cells.
74
what happens when you blood glucose concentration is too low?
-- Alpha cells secrete glucagon
-- Glucagon binds to specific receptors on the cell membranes on liver cells
-- Glucagon activates enzymes that break down of glycogen into glucose.
-- This process is called glycogenolysis
-- Glucagon promotes the conversion of glycerol and fatty acids into glucose.
-- This process is called gluconeogenesis.
-- Gluacgon also decreases the rate of respiration of glucose in cells.
75
Beta cells secrete insulin when they detect high blood glucose concentration.
How do they secrete insulin?
-- When blood glucose concentration is high, more glucose enters the beta cells by facillitated diffusion.
-- This causes rate of respiration to increase so more ATP is made.
-- The presence of ATP causes potassium ion channels in the beta cell memvrane to close.
-- Potassium ion cannot diffuse out of the cell so they build up inside teh cell.
-- This makes inside the cell less negatively charged because potassium ions are positiely charged so the membrane is depolarised.
-- This causes calcium ion channels to open. Calcium ions diffuse into the beta cells.
-- The vesicles fuses with the beta cell membrane releasing insulin by exoctosis
76
What is deamination?
Deamination is the process by which ammonia is converted to urea
77
Why must deamination occur?
• Urea is less soluble and less toxic than ammonia so it can be passed back into the blood to the kidneys
78
What are the main functions of the kidney?
-- The kidney excretes waste products
-- The kidney regulates blood water potential
79
What is urine usually made up of#?
-- Water
-- Urea
-- Hormones
-- Excess vitamins
80
How do you distinguish between a strong stimulus and a weak stimulus
--A strong stimulus is likely to reach threshold but a weak stimulus will not unless it is carried out frequently
81
What are the 4 main functions of the cytoskeleton?
-- Microtubules and microfilaments help provide support by keeping the organelles in place.
-- Microtubules and microfilaments provide strength and maintain its shape.
-- Microtubules and microfilaments help to move materials around e.g the movement of the spindle during mitosis
-- Microtubules help to move organelles aro8nd e.g cillia and flagella
82
Why must ammonia be converted to urea?
-- Ammonia is too toxic for mammal to excrete it directly so it is combined with carbon dioxide to form urea
83
What is a synapse?
-- A synapse is a gap between two neurone.
84
What is the all or nothing principle?
This means that threshold has to be reached for an action potential to be generated.
85
How does your brain know the type of stimulus?
using receptors
86
What is a myelin sheath?
-- An electrical insulator
87
What makes up myelin sheath?
-- Schwann Cells
88
What are in between schwann cells?
-- Nodes of Ranvier
89
Where does depolarisation occur?
-- At the nodes of ranvier
90
What biological molecule makes up schwann cells?
-- Lipids
-- Protein
91
How does myelination affect the speed at which an action potential is generated?
-- Action potentials are tansmitted faster because depolarisation only occurs at the nodes of ranvier instead of along the whole length of the axon.
92
How does saltatory conduction?
-- Saltatory conduction is when electrical impulse is conductued at every node of ranvier because impulses jump from node to node
93
what factors affect the speed of conduction?
-- Axon diameter
-- Myelination
-- Temperature
94
What is a stimulus?
A stimulus is a change in internal or external environment
95
What detects a stimuli?
-- Receptors
Each receptors are specific to a stimuli, they only detect one type of stimulus.
96
How do cells communicate with distant and adjacent cells?
Via cell signalling
97
What is the difference between sensory neurones and motor neurones?
-- Sensory neurones have longer dendrites
98
Describe resting potential. {2 marks}
-- Naᐩ/Kᐩ pump are actively transporting Naᐩ out of the cell and Kᐩ into the cell becaus ethe cell is not permeable to Naᐩ.
-- Naᐩ and Kᐩ voltagegated channels are closed so resting potential is maintained at -70mV.
99
What do cones detect?
-- Cones detect color
100
What do rods detect?
-- Rods detect images in black and white.
101
How does a neurotransmitter transmit nerve impulses between neurones?
-- Action potential arrives at the pre-synaptic synaptic knob
-- This stimulates voltage gated calcium ions to open causing and influx of calcium ions diffuse into knob by facillitated diffusion.
-- This causes synaptic vesicles containing neurotransmitter to fuse with presynaptic membrane releasing neurotransmitter into synaptic cleft.
-- Neurotransmitter binds to the complementary receptor on postsynaptic membrane and stimulates the opening of of sodium ion channels.
-- The influx of sodium ions cause depolarisation and when threshold is reached action potential is generated.
-- The neuroteansmitter is removed from the synaptic cleft so the reaction does not keep happeneing
102
What happens during depolarisation?
-- If threshold is reached, voltage gated sodium ion channels open, sodium ions rapidly enter the cell causing the membrane potential to decrease.
-- As more sodium ions diffuse into the cell, more sodium ion channels open (positive feedback mechanism)
103
What happens during repolarisation?
-- Sodium ion channels close, preventing the further influx of sodium ions.
-- Voltage gated potassium ion channels open, allowing potassium ions to diffuse out of the cell (negative feedback mechanism)
104
What happens during hyperpolarisation?
-- Potassium on channels are too slow to close so there is an overshoot of potassium ions.
105
Why can't the neurone of a cell membrane be excited again?
-- This is because the ion channels are recovering (sodium ion channels are closed during repolarisation and potassium ion channels are closed during hyperpolarisation). This is referred to as the refractory period.
106
Why is impulse carried faster when there is a high temperature?
At higher temperatures, the ions have more kinetic enerygy hence they will move faster.
However too high a temperature, the proteins in the membrane may denature.
107
Why is inpulse carried faster when there is a wider axon diameter?
The wider the lumen of the axon, there is less resistance to the flow of ions.
108
What is the hormonal system made up of?
-- The endocrine gland and hormones
109
How does the endocrine system wok?
-- The endocrine system secretes hormones directly into the blood.
110
Howdoe sthe exocrine system work?
-- The secrete molecules into a duct so they can travel to where they are needed.
111
What are examples of an endocrine gland?
-- Pituitary Glands
-- Adrenal Glands
112
What are some examples of hormones?
-- Adrenaline
-- Noradrenaline
113
How do hormones trigger a response?
-- Adrenaline is the first messenger so it binds to specific receptors on the surface of target cell.
--This causes the receptor to change shape activating G-protein.
-- G-protein actiavtes adenyl cyclase.
-- Adenyl cyckase activates the conversion of ATP into cAMP.
-- cAMP is the second messenger, it activates enzymes in the cell which brings about a response in the cell
114
Where does ultrafiltration take place?
-- In the bowman's capsule
115
Why is there a high pressure in the glomerulus?
-- This is because the afferent arteriole is bigger than the efferent arteriole
116
What occurs during ultrafiltration?
-- The blood enters the afferent arteriole into the glomerulus then leaves through the efferent arteriole.
-- The high pressure in the glomerulus forces liquid and small molecules from the capillary into the bowman's capsule.
-- The blood passes through the capillary wall (basement membrane- epithelium of the bowman's capsule).
-- Large molecules like proteins are too big so theyvstay in the blood.
117
Where does selective reabsorbtion take place?
Proximal convoluted tubule
118
What happenes during selective reabsorbtion?
-- Many of the molecules lost into the nephron are needed by the body so selective reabsorption takes place.
-- Glucose amino acids ad vitamins are reabsorbed by active transport and facilliated diffusion.
-- Water(by osmosis) and salts are also reabsorbed here.
-- Urea is reabsorbed by diffusion.
119
How are the cells linning the PCT adapted for selctive reabsorption?
-- Microvilli: For a large surface area
-- Lots of mitochondria: Provides energy in the form of ATP for active transport
-- Co-transporter protein: For the transport ofglucose and amino acids
--Tightly packed
120
How is water and salt reabsorped at the loop of henle?
The descending limb is permeable to water and not ions so as filtrate flows down this part of the loop its water potential decreases.
The ascending limb is impermeable to water but it is permeable to ions so Na+ and Cl- are actively pumped in to the medulla.
This makes the medulla more concentrated so more more Na+ and Cl- move out of the ascending limb.
Water diffuses out of the distal convoluted tubule by osmosis.
Water in the medulla is re-abasorbed back in to the blood through the capillary network.
121
When a person is dehydrated, it can be said that the person has a low water potential. How is water reabsorbed back into the blood?
-- Osmoreceptors in the hypothalamus (in the brain) sends nerve impulses to posterior pituitary gland to release antidiuretic hormone (ADH) into the blood.
-- ADH insertts aquaporin channels into the walls of the membrane.
-- This makes walls of DCT and collecting duct more permeable to water therefore increasing the reabsorption of water by osmosis from the tubules into the blood.
122
What happens when a person is hydrated?
-- The water content of the blood is high so the water potential of the blood increases.
-- This is detected by osmoreceptors in the hypothalamus.
-- The posterior pituitary gland releases less ADH
-- This means that little to no aquaporuin channels are inserted into the DCT so water is not reabsorbed back into the blood by osmosis
-- A large ammount of dilute urine is produced.
123
What can cause kiney failure?
-- Kidney infections
-- High Blood pressure
124
Whatare the effecs of kidney failure?
-- Waste products build up
-- Ion imbalance
-- Accumulation of fluid in tissue
-- Anaemia
-- Mortality
125
what are the two types of dialysis??
-- Haemodialysis
-- Peritoneal dialysis
126
What are the two types of kidney treatment?
-- Renal dialysis (haemodialysis and peritoneal dialysis)
-- Kidney transplant
127
how does haemodialysis occur?
Haemodialysis – removes blood from the body and pumps it through a machine where the blood is run in countercurrent flow alongside dialysis fluid. These fluids are separated by an artificial membrane so must rely on diffusion gradients for molecules to move from one fluid to the other. A blood thinning agent must be added to avoid the blood clotting outside of the body.
128
How does peritoneal dialysis occur
Peritoneal dialysis – dialysis fluid is put into the body cavity so that exchange can happen across the body’s own peritoneal membrane. The fluid must be drained and replaced.
129
Advantages of a kidney transplant
-- It is cheaper than to keep a person on a dialysis machine for a long time.
-- It is more convineient for daily activities
130
Disadvantages of a kidney transplant?
-- A trnsplant is a very risky operation.
-- The person might have to take immunosupressant drugs so the body does not reject the transplant.
131
How can the urine be used to test if a person is pregnant?
-- The person urinates.
-- hCG bound to the free antibody (and by extension the dye enzyme) enters the test site. Here, the hCG-free antibody complex will bind to immobilised antibody using the hCG.
-- There is fixed antibody in the control site. This will bind to any free antibody (not bound to hCG), and cause a colour change here.
-- If a person is not pregnant, the free antibody moves through the test site, and instead binds to the fixed antibody in the control site, causing a colour change here.
-- If a person is pregnant, the hCG-free antibody complex will form in the reaction site, and this complex binds in the test site, causing a colour change here. Some free antibody will still pass to the control site, so you will see two stripes.
132
Where are adrenal glands located?
-- Above the kidney
133
Why would the medulla secrete adrenaline?
The medulla secretes adrenaline in response to danger, stress or excitement which is involved in the fight or flight response.
134
What is function of cortisol and corticosterone?
cortisol and corticosterone which stimulate an increase in blood glucose concentration.
135
What produces mineralocorticoids?
-- Adrenal cortex
136
Type of mineralocorticoids?
aldosterone
137
What is the function of aldosterone?
-- Aldosterone targets the kidney and gut to control the concentration of sodium and potassium ions in the blood.
138
Types of glucocorticoids?
-- cortisol
-- corticosterone
139
What is special about the pancreas?
The pancreas functions in both an endocrine and exocrine way.
140
What is is the endocrine function of the pancreas?
The Islets of Langerhans have an endocrine function which involves secreting insulin from beta cells and glucagon from alpha cells directly into the blood.
141
What is the exocrine function of the pancreas?
The exocrine function of the pancreas involves secreting digestive enzymes such as amylase, trypsin and lipase to the duodenum via the pancreatic tract.
142
Describe an excitatory synapse
— At an excitatory synapse, neurotransmitters depolarise the post synaptic membrane making it fire an action potential if threshold is reached.
143
What is spatial summation?
This is when signals from multiple stimuli is coordinated into a single response.
144
What are the features of a sensory neurone?
-- They are specific to a single type of stimulus
-- They act as a transducer
145
What are types of a sensory receptors?
-- Mechanoreceptors
-- Chemoreceptos
-- Thermoreceptors
-- Photoreceptors
146
How are cells able to communicate with each other?
Cell releases a chemical, which has an effect on a target cell
147
What is an autoimmune disease?
A disease causing the body’s immune system to attack its own cells
148
How does the body detect between a small stimulus and a large stimulus?
The larger the stimulus the more frequent the nerve impulses/action potentials
149
Describe what would happen if a refracory period did not exist?
-- The axon could be immediately depolarised after an action potential
-- Therefore the action potential could travel backwards / in both directions / not reach target cell
150
Describe resting potential.
-- Sodium potassium pump actively transports sodium and potassium ions
-- Three sodium ions moved out, two potassium ions moved in
-- Potassium ions can diffuse out through open potassium ion channels becaus ethe membrane is permeable to potassium ions
-- This makes the membrane more positive outside than inside the axon.
151
What effect does alcohol have on the nervous system?
-- Alcohol binds to GABAA receptors
-- This changes shape of receptor allowing more neutrotransmitter (GABA) to bind.
-- This increases activity of the neurotransmitter, GABA decreases the activity of the brain by preventing nervous transmission.
152
How does synapses ensure impulses are only transmitted in one direction?
Neurotransmitter receptors are only present on the postsynaptic membrane, so it can only cause depolarisation of this membrane resulting in action potential
153
Similarity between a spatial summation and a temporal summation?
-- They both result in a build-up of neurotransmitter in the synapse / both result in an action potential being triggered.
154
Differences between a spatial summation and a temporal summation?
–- Spatial is a result of neurotransmitter being released from many neurones into the same synapse, temporal is a result of small amounts of neurotransmitter being released from a neurone several times in a short period.
155
What are the roles of a synapse?
-- They ensure impulses are unidirectional
-- They can allow an impulse to be transmitted to a number of neurone at multiple synapses
156
What does the central nervous system consist of?
-- The brain
-- The spinal cord
157
What does the peripheral nervpus system consists of?
-- Neurones (motor and sensory neurones)
158
Feature of the somatic nervus system?
-- The person is under consious control
-- Volountary
e.g moving your arm
159
Features of the autonomic nervous system?
-- Works constantly
-- Under subconcious control
e,g the heart beating
160
What is the autonimic nervous system divided into?
-- The sympathetic and the parasympathetic nervous system
161
What protects the brain?
-- The skull
162
What protective membrane surround the brain?
-- Meninges
163
What does the cerebrum control?
-- It controls volountary actions e.g personality, consious thought, memory, learning.
164
What does the cerebellum control?
-- It controls the unoncious functions e.g posture, balance and non-volountary movement.
165
What is the function of the medulla oblongata?
-- used in the autonomic control e.g controls heart rate and breathing rate, swallowng, peristalsis amd coughing.
166
What is the function of the hypothalamus?
-- It regulates tempertaure and water balance in the body
-- Produces hormones
-- Controls patterns of behaviour such as sleeping, aggression and feeding
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What is the function of the pituitary glands?
-- It stimulates hormones and glands e.g adrenal glands.
168
State the differences between the posterior and the anterior pituitary gland.
-- Anterior pituitary produces hormones, posterior pituitary stores and secretes hormones produced by the hypothalamus.
169
Types of reflexes?
-- Knee-jerk reflexes
-- Blinking reflexes
170
What are the three types of muscle in the body?
-- Sleletal muscle
-- Cardiac muscle
-- Involountary muscle
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What si meant by the term myogenic?
They can contract without the need for a nervous stimulus.
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How can a reflex action improve an organism's chances of survival?
-- reflex arc formed does not include the brain which decreases the time taken for the body to react to the situation.
173
Why do muscle fibres have lots of mitichondria?
This is to povide ATP for muscle contraction
174
What protein makesup myofibrils?
-- Actin
-- Myosin
175
Professional sprinters have a hgh level of creatine phosphate in thier muscle cells. Describe why?
-- During a sprint, muscles work so hard oxygen cannot be replaced as quickly as it is used up
-- Anaerobic respiration required
-- Creatine phosphate is a source of phosphate, the more creatine phosphate, the more ADP can be phosphorylated so muscles can perform at maximum rate for longer
176
After a person's death, thier body can no longer produce ATP. This results in the stiffening of muscles (rigor mortis). Explain why a lack of ATP prevents muscles relaxing?
-- ATP is needed to break bond/cross-bridge between actin and myosin
-- If no ATP available actin remains bonded to myosin
-- Filaments remain in contracted state / filaments can’t slide back to original position.
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What are reflexes?
Reflexes are immediate and very fast response to stimulus which do not involve decision making by brain
178
How is the hormone- adrenaline involved in cell signalling?
1. Adrenaline acts as first messenger.
2. Binding of adrenaline to its receptor on body cells such as hepatocyte.
3. Adenylyl cyclase on inner surface on hepatocyte activates.
4. It catalyses formation of cyclic AMP (cAMP) from ATP.
5. cAMP activates glycogenolysis (conversion of glycogen to glucose) via cascade of reactions.
179
What is flight or flight?
Flight and flight response: when an organism feels threat, its body prepare itself for action.
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What are some actions that occur during fight or flight?
1. Sensory neurons send impulse to hypothalamus.
2. This condition activates hormonal and sympathetic nervous system.
3. Hypothalamus stimulates pituitary gland to secrete ACTH.
4. ACTH via blood stream reaches adrenal cortex which secretes steroidal hormones.
5. Due to this sympathetic nervous system activates and trigger release of adrenaline from adrenal medulla.
6. Heart rate increases and blood is pumped faster throughout the body.
7. Bronchiole muscle relax causing deep breathe.
8. Glycogenolysis convert glycogen to glucose which muscles used to respire.
9. Arteriolar muscles supplying skin and gut constrict and those supplying to heart, lungs and skeletal muscles dilate.
10. Blood is diverted from skin and gut to heart, lungs and skeletal muscles.
11. Erector pili muscles present of skin contract which makes hairs to stand on end and thus the animal appear larger.
181
Effects of hormone and nervous mechanism on high blood pressure?
-- High blood pressure → detected by baroreceptors → impulses goes to medulla → medulla sends signal to vagus nerve → secretion of acetylcholine and binding to SAN→ cardiac muscles relax → slowing down of heart rate and decrease in blood pressure.
182
Effects of hormone and nervous mechanism on low blood pressure?
-- High blood pressure → detected by baroreceptors → impulses goes to medulla → medulla sends signal to accelerator nerve → secretion of noradrenaline and binding to SAN →cardiac muscles contract → speeding up of heart rate and increase in blood pressure.
183
Effects of hormone and nervous mechanism on high blood O2, low blood CO2 and high pH?
-- High blood O2, low blood CO2 and high pH → detected by chemoreceptors → impulses goes to medulla → medulla sends signal to vagus nerve → secretion of acetylcholine and binding to SAN→ cardiac muscles relax → slowing down of heart rate and O2, CO2 and pH back to normal
184
Effects of hormone and nervous mechanism on low blood O2, high blood CO2 and low pH?
-- Low blood O2, high blood CO2 and low pH → detected by chemoreceptors → impulses goes to medulla → medulla sends signal to accelerator nerve → secretion of noradrenaline and binding to SAN→ cardiac muscles contract → speeding up of heart rate and O2, CO2 and pH back to normal.
185
What is the sliding filament model of muscular contraction?
1. Motor neuron stimulates muscle cell.
2. Depolarisation of muscle cell and signal reaches to sarcoplasmic reticulum.
3. Sarcoplasmic reticulum releases Ca++ ions into sarcoplasm.
4. Ca++ binds to troponin and conformational change of troponin.
5. Tropomyosin comes out of actin-myosin binding site on actin filament.
6. Exposure of binding site and myosin head binds.
7. Bond between myosin head and actin filament is actin-myosin cross bridge.
8. Ca++ ions breaks down ATP to release energy for muscle contraction.
9. This energy moves myosin head that pulls actin filament in a rowing action.
10. The energy provided by ATP also dislodges myosin head from actin filament.
11. It breaks actin-myosin cross bridge.
12. The cycle continues repeatedly till Ca++ ions are bound to troponin.
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The action of neuromuscular junctions?
1. Synapse between motor neuron and muscle cell.
2. Pre-synaptic knob (motor neuron) releases acetylcholine into synaptic cleft.
3. Receptors at postsynaptic cleft binds to acetylcholine.
4. Depolarisation of muscle cell.
5. Muscle contraction when depolarisation is at threshold level.
187
What are the limiting factors of photosynthesis?
-- Light intensity
-- CO2 concentration
-- Temperature
188
The respiratory quotient (RQ) formul?
-- RQ = carbon dioxide produced / oxygen consumed
189
RQ of carbohydrates?
1
190
RQ of lipids?
0.8
191
RQ of proteins?
0.9
192
Anaerobic respiration in mammals?
-- In mammals, pyruvate is converted to lactate.
-- Pyruvate acts as the hydrogen acceptor to enable NADH to be reoxidised to NAD which can then be used to continue the reactions in glycolysis
-- Lactate can then be converted back to pyruvate in the liver cells when the oxygen levels rise again.
193
Anaerobic respiration in plants?
-- In this process Pyruvate is decarboxylated to EthanAl which in turn is reduced to ethanOl reoxidising NAD in the process.
-- So ethanAl is the hydrogen acceptor. The first step in this process produces CO2 and therefore this is an irreversible reaction.
194
What are the three main type sof hormones produced by the adrenal cortex?
-- Glucocorticoids
-- Mineralcorticoids
-- Androgens
195
What is the function of glucocorticoids?
-- They include cortisol which regulate show the body converts fats, carbohydrates and protein into enerygy sources.
196
What is the function of mineralcorticoids?
-- Produced by aldosterone
-- Helps to control blood pressure by maintaining the balance between salt and water concentrations in the body fluids and in the blood
197
Where are the adrenal glands located?
-- They are located above the kidneys
198
What makes up the adrenal glands?
Adrenal medulla and the adrenal cortex
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What hormones ae secreted by the adrenal medulla?
Noradrenaline and adrenaline
200
What is the function of adrenaline?
It increases heart rate by sending blood quickly to the muscle and the brain.
201
What is the function of noraadrenaline?
works together with adrenaline in response to stress and produces effects such as widening of pupils, increased heart rate, widening of air passage ways, widening of essential blood vessels in essential organs.
202
What is a function of an endocrine gland?
they produce and secrete hormones
203
Describe the pathway triggered by a stimulus in hormonal communication
-- Stimulus detected → gland stimulated → hormone secreted → travels in blood (plasma) → target cell → binds to receptor/triggers response
204
What are the functions of a pancreas?
-- Endocrine glands: produces enzymes and releases them via a duct into the duodenum
-- Exocrine glands: produces hormones and releases them into the blood
205
What is an ectotherm?
-- Animals that use heat from their surroundings to warm their bodies so their core body temperature is heavily dependent on their environment (1).
206
Examples of ectotherms?
-- Lizard
-- Locust
207
What is auxins role in plants?
-- Control cell elongation
-- Prevents leaf fall (abscission)
-- Maintains apical dominance
-- Stimulates the release of ethene which is involved in fruit ripening
208
What is gibberellins role in plants?
-- Cuases stem elongation
-- Stimulates pollen tube growth in fertilisation.
-- Triggers the mobilisation of food stores in a seed at germination.
209
What is the role of ethene?
-- causes fruit ripenning
-- Promotes abscission in deciduous trees
210
What is the role of abscisic acid (ABA)?
-- Mantains dormancy of seed and buds
-- stimulates cold protective responses e.g antifreeze production
-- Stimulates stomatal closing
211
What is a tropism?
A plants growth response to an external stimulus
212
What is a positive tropism?
-- A positive tropism is a plants growth towards the stimulus
213
What is a negative tropism?
-- A plant's growth response away from the light
214
Types of Tropism?
Phototropism
Geotropism
Hydrotropism
Thermotropism
Thigmotropism
215
how does auxin and gibberellin have a synergistic effect?
-- Auxin and gibberellin go hand in hand to make the plant very tall. This is because auxin stimulates apical growth and gibberellins stimulates stem elongation.
216
How can auxin and giberellins have an antagonistic effect?
-- Auxin inhibits lateral shoot growth whereas gibberellin stimulates lateral shoot growth.
217
What are deciduous plants?
Deciduous plants are plants that loose thier leaves in winter
218
Why do deciduous leaves loose thier leaves during winter?
-- This helps them conserve water during winter when it might be difficult to absorb water and when there is less light for respiration.
219
How do auxins and ethene have an antagonistic effect?
-- Auxin inhibits leaf loss but ethene stimulates leaf loss
220
Why do plants need to close thier stomata?
-- To reduce water loss by transpiration
221
Why are chemicals so important in coordinating the growth of plants?
-- Plants are multicellular and often large so need coordination
-- Plants don’t appear to have nervous systems so no electrical coordination system
-- Chemicals can be carried in plant transport systems and move from cell to cell to coordinate responses
222
Why are chemicals like auxin, gibberelins, ethene, abscisic acid etc considered as hormones?
They are involved in coordination and control of the plant
They are made in one place and carried through the transport system to another region where they have an effect
223
What effect does auxin have on plant tissue?
-- Auxin produced in tip of growing shoot stimulates growth in some regions of the plant and inhibits growth in others – the apical shoot grows and lateral shoots are inhibited
-- If tip of leading apical shoot is removed, growth in that shoot slows as stimulation of auxin removed
-- Lateral shoots grow faster as auxin inhibition removed
-- Replace auxin artificially on leading shoot
-- Apical shoot stimulated and grows fast again
-- while lateral shoots inhibited again and growth slows
224
Why is it important for plants to be able to respond to thier surroundings?
-- They are rooted to the ground so cannot move their bodies therefore very important that they are sensitive so they can grow in the right direction and make the best of the circumstances where they have germinated
225
Why do so many trees in temperate climate loose all thier leaves in winter?
-- The amount of photosynthesis that can take place decreases as day length is reduced and temperatures fall
-- so the amount of glucose produced by photosynthesis falls
-- the amount of glucose needed for respiration to maintain leaves through the winter
-- and produce chemicals to prevent freezing damage increases
-- it becomes more efficient to lose the leaves and become dormant until the days lengthen and temperatures increase again
226
How do plant hormones protect plant cells from damage in freezing cinditions?
-- Chemicals such as abscisic acid
-- trigger gene switching
-- so plants make chemicals such as sugars or proteins
-- which lower the freezing point of the cytoplasm
-- or protect the cells against damage by ice crystals if they do freeze
227
Which plant hormone trigger stomatal closure?
Abscissic acid (ABA)
228
How does ABA trigger stomatal closure?
-- ABA binds to receptors on the guard cell membranes.
-- This causes calcium ion chnnels to open allowing an influx of calcium ions into the cytosol of the vacuole.
-- The increased concentration of calcium ions in the cytosol causes potassium ion channels to open.
-- Potassium ions leave the guard cells raising the water potential of the cells.
-- Water then leaves the guard cells by osmosis.
-- The guard cell because flaccid and the stomata closes.
229
What is herbivory?
Herbivory is the process by which herbivores eat plants.
230
What are some examples of chemical defences against herbivory by animals, how do they protect plants and how are they used by people?
-- Tannins: -bitter taste puts animals off eating leaves OR toxic to insects.
-flavour tea and red wine.
-- Alkaloids: -affect metabolism,
-often poison animals
-prevent germination in plants
-stop roots of neighbouring plants spreading
-taste bitter
-- Insecticide terpenoids: -toxic to insects
-repel insects;
-used as insect repellent
231
How can plant hormone be used to control fruit ripening?
-- Ethene involved in natural fruit ripening so it is used to ripen fruit such as bananas, mangos, tomatoes etc. at desired time
-- Cytokinins and gibberellins can be used to delay fruit ripening
232
Why is it commercilly important to be able to control fruit ripening?
-- Ripe fruit is easily damaged in transport, once fruit is ripe it has a finite life before it goes off.
-- If fruit is transported unripe and hard, it is much less likely to be damaged and doesn’t start to go off,
-- Controlled ripening when needed gives uniform product which and minimises waste.
233
What are some commercial uses of auxin?
-- Rooting powder
-- Selective weedkillers
-- Development of seedless fruit
-- Leaf fall
234
What are the commercial uses of ethene?
-- Controlled ripening
-- Fruit dropping
-- Leaf fall
235
What are some commercial uses for the gibberellins?
-- Delays fruit ripening
-- Increases fruit size
-- Speeds up the brewing process
236
What are some commercial uses of cytokinins?
-- Prevent ageing of ripened fruit and lettuces
-- Micropropagation to control tissue development
237
Why do cool conditions slow the rate of ripening even if ethene is present?
-- Ripening is the result of many enzyme-controlled reactions, at lower temperatures reactions occur more slowly, so ripening occurs more slowly even with ethene present.
238
State the precise location of photosynthetic pigments in a chloroplasts
-- In the photosystems in the thylakoid membrane
239
When the p-value is greaer than the t-value, what conclusion can be made?
-- The difference is not significant
