Unit 3 AoS 1 Flashcards
0
Q
Give example of a protein with a regulatory function?
A
Protein hormone insulin.
1
Q
What are the functions of proteins?
A
Regulatory, structural, catalytic, transport, defence, source of energy.
2
Q
Give example of a protein with a structural function?
A
Keratin.
3
Q
Give an example of a protein with transport function?
A
Haemoglobin
4
Q
What elements do carbohydrates consist of?
A
Carbon, Hydrogen & Oxygen
5
Q
What elements do lipids consist of?
A
Carbon, Hydrogen, Oxygen and (Phosphorus)
6
Q
What elements make up proteins?
A
Carbon, Hydrogen, Oxygen, Nitrogen and (Sulfur)
7
Q
What elements does a nucleic acid contain?
A
Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus
8
Q
What are the subunits/building blocks of carbohydrates?
A
Monosaccharides
9
Q
Building blocks/ subunits of lipids?
A
Fatty acids and glycerol
10
Q
Building blocks/subunits of proteins?
A
Amino acids
11
Q
Building blocks/ subunits of nucleic acids?
A
Nucleotides
12
Q
What bonds are formed by carbohydrates?
A
Covalent bonds
13
Q
What bonds are formed by lipids?
A
Covalent bonds, ester linkages
14
Q
What bonds are formed between proteins?
A
Covalent and peptide links
15
Q
What bonds are formed between nucleic acids?
A
Covalent bonds between pentose sugar and phosphate and hydrogen bonds between the nitrogenous bases.
16
Q
Examples of lipids?
A
Cholesterol, phospholipids, triglycerides, waxes, some hormones (e.g steroid hormones), some vitamins, oils/fats.
17
Q
Examples of carbohydrates?
A
- Monosaccharides such as:
- Triose sugars.
- Pentose sugars such as Ribose and Deoxyribose sugars.
- Hexose sugars such as glucose, fructose and galactose.
- Disaccharides such as sucrose, lactose and maltose.
- Polysaccharides such as starch, glycogen, cellulose, inulin and chitin.
18
Q
Examples of proteins?
A
Haemoglobin, enzymes, protein hormones (e.g insulin), antibodies, actin/myosin in muscles.
19
Q
Examples of nucleic acids?
A
DNA (nuclear, mitochondrial, chromosomal, plasmids)
RNA (mRNA, tRNA, rRNA)
20
Q
What are the properties of the inorganic molecule, water?
A
- Polar (cause of hydrogen bonds), *Universal solvent (due to polarity)
- Cohesive: attraction between water molecules (due to polarity)
- Adhesive: attraction between water and other polar molecules (due to polarity)
- High boiling point of 100 deg cel
- Low freezing point of 0 deg cel
- High Specific Heat (takes a longer time to heat up)
- High Latent Heat of evaporation (requires a lot of heat for states conversion)
- High Surface tension (can support aquatic life at surface)
- Reagant in most biochemical reactions
- Transparent (allows light to pass through)
- Low viscosity (ability to flow)
- Highest density at 4 deg cel
21
Q
What are the 3 stages of aerobic respiration in order?
A
1) Glycolysis
2) Krebs Cycle
3) Electron Transport
22
Q
Where does the first stage of aerobic respiration occur?
A
Glycolysis occurs in the cytosol of cells.
23
Q
Where does the second stage of aerobic respiration occur?
A
The Krebs cycle (the citric acid cycle) occurs in the matrix of mitochondria.
24
Where does the third stage of aerobic respiration take place?
Electron transport takes place on the cristae (inner membrane) of mitochondria.
25
What is the equation for aerobic respiration?
C6H12O6+ 6O2 ---> 6CO2+ 6H2O+ 36 (sometimes 38) ATP
26
What is active immunity?
Immunity that develops when an organism makes its own antibodies
27
What are the two types of active immunity?
1) Natural active immunity- when antibodies may be produced naturally in response to chance infection.
2) Induced active immunity- when antibodies may be induced by vaccination.
28
What is passive immunity?
Immunity provided when an individual receives antibodies made by another organism.
29
What are the two types of passive immunity?
1) Natural passive immunity- when antibodies may be received naturally, ie when a baby receives them from its mother across the placenta or in breast milk.
2) Induced passive immunity- when antibodies may be received through injection.
30
What are the two stages of photosynthesis?
1) The light dependent stage
| 2) The light independent stage
31
Where does the light dependent stage of photosynthesis occur?
In the grana of chloroplasts.
32
Where does the light independent stage of photosynthesis occur?
Inside the stroma of chloroplasts.
33
Define diffusion.
Diffusion is the passive net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.
34
What is the equation for photosynthesis?
6CO2+12H20--light, chlorophyll--> C6H12O6+6O2+6H2O
35
Why is a virus non-cellular?
A virus doesn't contain a cytoplasm, organelles or cell membrane and depends on cells for metabolism and reproduction.
36
Structure and function of cell membrane/ plasma membrane?
A phospholipid bilayer embedded with protein molecules.
Controls the movement of molecules into and out of the cell and is responsible for recognition, adhesion and communication between cells.
37
What are features common to all living cells?
* Cell membrane/plasma membrane.
* Cytosol.
* Ribosomes.
* DNA (Chromosomes)
38
Define osmosis.
Osmosis is the passive net movement of water molecules from a region of high free water molecules to a region of low free water molecules, across a partially permeable membrane, until equilibrium is achieved.
39
What are factors that cause destruction of the cell membrane?
A change in pH, excessive heat, organic solvents (ie ethanol or detergents).
40
Define osmotic pressure.
The pressure exerted by the flow of water into the cell.
| ie Higher the solute concentration of a cell, greater the osmotic pressure.
41
What are factors that affect the rates of enzymatic activity?
Temperature, pH, enzyme concentration, substrate concentration, inhibitors.
42
What is the lock and key model?
A model that explains how substrates bind specifically with the active site of an enzyme.
43
What is a catabolic reaction?
Reactions, such as cellular respiration and digestion, that involve the breakdown of complex molecules to simpler products, releasing energy (exergonic).
44
What is an anabolic reaction?
Reactions, such as protein synthesis, photosynthesis, ATP synthesis, that build up complex molecules from more simple molecules.
45
What is the induced fit model?
A model that explains how enzymes change their shape to accommodate the shape of the substrate.
46
What is a hypertonic solution?
A hypertonic solution has a higher solute concentration than the solution that is is compared with.
47
What is a hypotonic solution?
A hypotonic solution has a lower solute concentration than the solution that it is compared with.
48
What is an isotonic solution?
An isotonic solution has the same solute concentration as the solution that it is compared with.
49
What is the primary structure of a protein?
A unique sequence of amino acids, placed in the correct order by ribosomes under the coded instructions of DNA.
50
What is an organic molecule?
A compound containing both Carbon and Hydrogen (with the exceptions of CO2, CO and carbonates.)
51
What is a biomacromolecule?
A naturally occurring substance of a large molecular weight.
52
What is a condensation reaction?
A condensation reaction is a chemical reaction in which two simple molecules are joined together to form a larger molecule with the removal of one molecule of water.
53
What is a hydrolysis reaction?
A hydrolysis reaction is a reaction in which a water molecule is needed to break up a complex molecule into smaller molecules.
54
What is the general formula of a disaccharide?
C12H22O11
55
Structure and function of starch?
* long straight or branched chains
| * made and stored in plants, not animals
56
Structure and function of glycogen?
* highly branched chains of glucose molecules
| * made and stored in animals and fungi, not plants
57
Describe the role of the polysaccharide cellulose?
Cellulose is the major structural component of plant cell walls.
58
Describe the role of the polysaccharide chitin?
Chitin is the major structural component of the exoskeleton of animals such as insects and spiders.
59
How would cold temperatures affect the rate of diffusion?
* Decreased temperatures decrease the rate of diffusion.
| * There is less kinetic energy so there are less frequent collisions between particles.
60
Why should an experiment be repeated?
* It would decrease the chances of error having a significant effect on the overall result.
* In order to check for reliability.
61
Why should a large sample size be used?
To increase the reliability of any observations made.
62
Possible location of protein enzyme in an animal cell?
Mitochondria (to catalyse aerobic respiration)
63
Why is data averaged in experiments?
Data is averaged to reduce variation due to outlying data and to simplify data for analysis of results.
64
Possible location of protein enzyme in a plant cell?
Chloroplast (to catalyse photosynthesis)
65
Possible location of lipid hormone in plant/animal cell?
In cytoplasm, binding to a receptor.
66
Possible location of protein hormone in plant/animal cell?
* Manufactured on Rough Endoplasmic Reticulum.
* Packaged in golgi body.
* In vesicle for exocytosis.
67
Effect of pH on activity of the enzyme?
Different pHs change the shape of the enzyme as they alter the hydrogen bonds. If the shape of the enzyme is altered too much, it becomes denatured as its active site can no longer bind with the substrate efficiently. Some enzymes can regain their shape while other changes are irreversible.
68
What would be the *_____* production at a lower pH than its optimum and a temperature lower than its optimum?
* Reactions would be slower as particles move slower, so the enzyme and substrate would not collide as often.
* The same amount of product would eventually be produced, although this will occur at a slower rate.
69
What does the term "organic catalyst" mean?
Organic- made of protein which contains both Carbon and Hydrogen and is from a living material or organism.
Catalyst- compound that increases the rate of a reaction.
70
Why is a control included in the experimental design?
A control provides known results and acts as a standard of comparison to the effects of treatment.
72
What is the light- dependent stage of photosynthesis and where in the cell does it occur?
Occurs in the grana of chloroplasts. The stage of photosynthesis which is powered by sunlight. During this process, the plant makes energy storing compounds which are used in later stage of photosynthesis and light energy is converted to chemical energy.
73
What is the light- independent stage of photosynthesis and where in the cell does it occur?
Occurs in the stroma of chloroplasts. The stage of photosynthesis which is not dependent on sunlight. The energy storing compounds which were created during the light dependent stage are used to produce sugars and water from the input of CO2, through the Calvin Cycle.
74
What does the 'light intensity' refer to?
The strength of the light.
74
What does 'light duration' refer to?
The length of time which the light is available.
75
What does the 'light quality' refer to?
The wave length of the light.
76
What is the overall process of photosynthesis and its main purpose?
Photosynthesis is the process by which plants use energy from the sun, via chloroplasts, to produce sugars and oxygen.
Its main purpose is to transform light energy into chemical energy.
77
Where is chlorophyll found?
Chlorophyll is found in the grana membranes of chloroplasts.
78
What type of reaction is photosynthesis?
An anabolic reaction because there is build up or synthesis of compounds.
79
What are the adaptations of a leaf to support photosynthesis?
* Flat shape--> large surface area
* Presence of many stomata--> access into leaf for carbon dioxide
* Thinness and internal air spaces--> ready diffusion of carbon dioxide to photosynthetic cells
* Network of xylem vessels that transport water
* Presence of many chloroplasts in photosynthetic cells
80
Define exocytosis
Movement of material out of cells via vesicles in the cytoplasm.
81
Define endocytosis
Bulk movement of solids or liquids into a cell by engulfment.
82
Describe the process of endocytosis
* Large molecules/materials are engulfed into the cell.
* A vesicle is formed from the cell membrane as the materials move into the cell.
* Energy input is required by cell to form vesicles.
83
What is plasmolysis in a plant cell?
Plasmolysis is the withdrawal of water from a plant cell by osmosis when placed in a hypertonic solution, resulting in contraction of cytoplasm and shrinkage of cell membrane away from the cell wall.
84
Describe the process of exocytosis.
* Membrane bound vesicles in the cell surround the chemicals/large materials.
* The secretory vesicles are moved to the outer surface of the cell where they fuse with the cell membrane and empty their contents outside the cell.
* Energy input is required by cell to form vesicles.
85
What is facilitated diffusion?
The passive movement of hydrophilic molecules from a high concentration to a low concentration across the cell membrane via protein channels.
86
What is active transport?
The movement of molecules through selective carrier proteins, from a low concentration to a high concentration (against a concentration gradient) requiring energy/ATP.
87
What is a cofactor?
A non-protein, additional component that is essential for the normal functioning of some enzymes.
88
What is a coenzyme?
An organic compound (ie vitamin) that acts with an enzyme to increase the rate of reaction.
89
What is the function of cofactors/coenzymes?
* Increases the reaction rate.
* Binds to the active site of an enzyme and aids in forming the enzyme- substrate complex.
* Unchanged by the reaction.
90
How does cholesterol assist the cell membrane?
Cholesterol makes the cell membrane:
* more fluid,
* more stable,
* more fluid in colder temperatures
* decreases the permeability of the phospholipid bilayer to small water-soluble molecules.
91
What is the tertiary structure of a protein?
The folding of 1 polypeptide chain, due to interactions between amino acid R groups and their environment, into its conformational 3D shape. Some proteins are complete at the tertiary level, ie myoglobin.
Possible bonding: hydrogen bonding, disulphide bonds, ionic bonds and hydrophobic interactions.
92
Which are the pyrimidine and purine nitrogen bases?
Pyrimidine: Cytosine, Thymine and Uracil (single ring structures)
Purine: Adenine and Guanine. (double ring structures)
93
How does the active site of an enzyme help to lower the activation energy?
The R group amino acid lining the active site form molecular interactions with substrate, weakening the bonds within the substrate, hence lowering the activation energy.
94
What is competitive reversible inhibition?
Inhibitor competes directly with substrate. Inhibitor has same complementary shape and takes position of active site but does not last long. It prevents the binding of enzyme and substrate.
95
What is non-competitive reversible inhibition?
Inhibitor bonds to part of the enzyme, away from the active site. Inhibitor changes conformational shape of the enzyme, decreasing effectiveness of the substrate binding to the active site.
96
What is irreversible inhibition?
Irreversible inhibitors bind covalently (tightly) to the active site, causing permanent loss of catalytic activity. Such molecules (eg heavy metal cations, nerve gases and natural toxins) are toxic.
97
How is denaturation of enzymes caused by high temperatures?
High temperatures break hydrogen bonds. This destroys the characteristic 3D structure of the protein and the active site is altered, so it can no longer bind to the substrate. Enzyme denaturation by high temperatures is permanent and irreversible.
98
What is the function of a semi permeable membrane?
The semi permeable nature of the cell membrane allows only selective substances into the cell and secretes or voids selective substances outside of the cell In order to maintain its structure and function.
99
What are the factors that affect photosynthesis?
* Light quality (type of light/wavelength of light- red, green, blue)
* Light intensity
* Availability of water
* Concentration of CO2
* Temperature
* Amount of chlorophyll
100
What is rational drug design?
Rational drug design involves designing an inhibitor that is complementary in shape to the enzyme that is being inhibited in order to block the active site, so the substrate can't bind to it, and the product (which may be harmful) can not form.
101
What are the factors that increase the rate of diffusion?
* Increase in temperature
* Increase in concentration gradient
* Increase in surface area to volume ratio
102
What is plasmodesmata?
The gap between plant cells that allow transfer of hormones, ions and molecules across the cell membrane.
103
What is the function of chlorophyll during photosynthesis?
Chlorophyll absorbs light energy and converts it to chemical energy (in the form of sugars) in a series of many enzyme- controlled reactions/
It mainly absorbs the red and blue-violet wavelengths of the light spectrum and reflects green light.
104
Examples of stored chemical energy?
Glycogen, starch.
105
Most readily used form of stored chemical energy?
Glucose.
106
What is the immediate source of energy?
ATP
107
What is signal transduction?
Signal transduction involves the conversion of an external stimulus into one or more internal events
through binding of the hormone to a specific receptor which triggers a cascade of events (one signal converted into another by a series of relay molecules) that initiates an amplified cellular response.
108
In what ways can the glucose produced in photosynthesis be used up?
1) Metabolised to produce ATP (ie cellular respiration in plants)
2) Stored as starch (e.g. in seeds and underground stems and roots)
3) Transported to the rest of the plant as sucrose (Not as glucose, because sucrose reduces the number of solute particles by half which means the impact on its osmotic pressure is also halved)
4) Converted to structural polysaccharides such as cellulose
5) Converted to other types of organic molecules (i.e. PGAL gets converted)
109
What is photosynthesis?
Photosynthesis is a two stage process by which inorganic molecules (CO2+H20) are converted into organic molecules (C6H12O6) during which process radiant energy is converted into chemical energy.
110
How do prokaryotes carry out photosynthesis, considering they have no plastids?
Chlorophyll/pigments are dissolved in the cytosol and photosynthetic enzymes could be attached to the cell membrane.
111
Which colours of the spectrum are most effective in carrying out photosynthesis?
Red and blue/violet
112
What is the light compensation point on a graph?
The LCP is the light intensity at which the rate of photosynthesis equals the rate of cellular respiration.
113
What is true at the Light compensation point?
* Cellular respiration and photosynthesis occur at the same rate.
* There's no net exchange of CO2 or O2
* No net synthesis or breakdown of glucose.
114
Purpose of myoglobin?
An emergency store of oxygen. More muscles=more myoglobin.
115
What are properties of the DNA triplet code?
* Degenerate (redundant): More than one triplet code can code for the same amino acid.
* Unambiguous: A particular code can code for only ONE amino acid (ie TAC can code only for methionine and not any other amino acid)
* Universal: The codes code for the same amino acid in almost all living cells.
116
What are genes?
Sections of the DNA molecule which code for proteins and RNA's
117
What is a chromosome composed of?
A chromosome is composed of a DNA molecule wrapped around histone proteins.
118
What is the difference between an RNA nucleotide and an ATP molecule?
In ATP, the base is always Adenine and the number of phosphates differ between the two.
119
What is cellular respiration?
Cellular respiration is the process by which organic compounds are broken down sequentially to produce energy that is usable immediately.
120
What is phosphorylation?
The covalent addition of a phosphate group to a molecule.
121
What is the need for fermentation, considering that the process does not yield any ATP?
Fermentation helps to remove any excess pyruvates since its accumulation can lead to a negative feedback which could slow down glycolysis.
122
Three types of cells likely to have a high number of mitochondria?
Liver, muscle and heart cells.
123
What happens during starvation?
During starvation, energy is obtained in the following order:
*Glucose in the blood
*Fat tissue
*Proteins
When proteins from muscle and other tissue are used up, the animal reaches a critical condition (autophagia).
124
Photosynthesis is carried out by what organisms?
Autotrophic organisms such as:
* Green plants
* Algae
* Photosynthetic bacteria
* Chemosynthetic organisms such as some bacteria
125
What is homeostasis?
Homeostasis is the maintenance of a relatively stable internal environment within a small range of tolerance, in the face of a changing external environment.
126
What is the stimulus-response model?
Stimulus--> Receptor--> Control Centre--> Effector (muscle/gland) --> Response
127
What is the nervous system made up of?
* The Central Nervous System (brain+spinal cord)
| * The Peripheral Nervous System (includes the nerves and sense organs ie receptors)
128
What are receptors?
Specialised structures capable of receiving specific stimuli (change in temperature, change in light etc)
129
What variables are subject to homeostasis?
* Nutrients
* Temperature
* Water
* Ions, such as Na+, Ca2+, Cl-
* pH (hydrogen ion concentration)
* blood volume
* blood pressure
* oxygen
* carbon dioxide
* red blood cells
130
What are pheromones?
Pheromones are species specific chemical signalling molecules that travel through the air and are used as sex attractants and can alter the behaviour in animals/insects through binding to specific receptors.
131
What is a common description of a hormone in plants?
Chemicals produced in small amounts in cells in one part of a plant that act on other cells involved in growth and development.
132
What is a common description of a hormone in animals?
Animal hormones are chemical messengers produced in small amounts by endocrine glands. They are transported through the bloodstream to all parts of the body but will only have an effect on specific target organs. Hormones modify the activity of cells as a result of interaction with specific receptors. (some hormones are involved in autocrine signalling and paracrine signalling.)
133
Type of auxin responsible for apical dominance?
Indoleacetic Acid (IAA)
134
Explain how positive phototropism works.
* Auxin is produced at tip of plant.
* Auxins move towards shaded side of the plant OR Auxin is inhibited by light.
* Auxins accumulate on shaded side and diffuse down the phloem to cause increased cell elongation on the shaded side.
* The plant bends towards the light.
135
Explain positive geotropism at roots.
* Auxin accumulates in the lower parts of the roots.
* Auxin inhibits growth at roots- the top section of root grows faster than the bottom section and the root bends towards gravity.
136
Explain negative geotropism at shoots.
* Auxin accumulates in the lower parts of shoots.
* Auxin stimulates cell growth at shoot.
* Bottom section of shoot grows faster than top section
* Therefore, shoot bends away from gravity.
137
What is a tropism?
The growth of a plant in response to a stimulus.
138
What is positive tropism?
Plant growth towards a stimulus.
139
What is negative tropism?
Plant growth away from a stimulus.
140
What are the functions and features of the plant hormone auxin?
* Inhibit lateral growth
* Cause cell elongation
* Cell differentiation
* Acts with cytokinin to determine whether root cells or shoot cells are developed
* Inhibited by fire and light
141
What are the functions and features of the plant hormone gibberellin?
'Growth’: stimulate cell division and elongation.
| ‘Gorgeous’: stimulate fruit enlargement, flowering, seed germination.
142
What are the functions and features of the plant hormone ethylene?
* Increases rate of cellular respiration (breaks down starch to glucose) and other processes of fruit ripening
* Promotes abscission, flowering and fruits
* Growth
* Stimulates growth in dormant seeds
144
What are the functions and features of the plant hormone cytokinin?
* Cell division and differentiation
* Produced in the roots.
* Ratio of cytokinins: auxins determines differentiation of new cells
* Acts on shoots, roots and fruits.
144
What does apoptosis involve?
1. Cell receives ‘death’ signal (signal transduction begins)
2. Cells activate caspase enzymes and send a signal to attract phagocytes to the area
3. Cells starts to shrink and develop small bumps (blebs) on their surface. Caspases enter nucleus and break down the DNA and proteins inside, mitochondria also break down
4. Cell fragments
5. Phagocyte digests cell fragments
145
What are the functions and features of the plant hormone abscissic acid?
* Made in chloroplasts
* Stimulates closing of stomata (eg drought and defence to pathogenic infection)
* Promotes seeds to be dormant
* Inhibits shoot growth
* Inhibited by auxins
146
Under what types of circumstances does apoptosis occur?
* Cell are no longer required(eg cells between fingers and toes in developing foetus)
* Cells haven’t fully developed (eg embryonic brain cells)
* There are too many cells (eg overproduction of immune cells, eg Bplasma)
* Damaged or old cells
147
Difference between apoptosis and necrosis?
Necrosis is a form of cell injury that results in premature death of cells whereas apoptosis is programmed cell death.
148
What is apoptosis?
Programmed cell death.
149
Dendrite
receives signals from other neurons or receptors and gives information to nucleus
150
What are examples of cellular responses initiated by signal transduction?
* the DNA to produce or not produce proteins (e.g. enzymes). That is, genes are regulated (switched on or off)
* the production/secretion of another hormone
* activation or inhibition of enzyme action
* protein channels to open or close
* transport vesicles to be moved to the plasma membrane to secrete cellular products.
* protein production
151
Cell body
contains nucleus which determines whether electrical signal is sent or not
152
Myelin sheath
layer of fatty substances enclosing nerve fibres. Insulates axon like a rubber sheath. (speeds up electrical signal)
153
Axon
transmit electrical signal along the neuron away from the cell body.
154
Axon terminals/nerve ending
transmit chemical message (neurotransmitters) to next neuron/effector
155
Synapse
gap between one neuron to another or gap between neuron and effector
157
What is a reflex arc?
A reflex arc is an automatic response that occurs without the involvement of the brain.
158
What is the importance of the reflex arc response
* It brings about an immediate or fast response to protect the body from tissue damage.
* It is used when the speed of the response must be particularly quick (ie jerking hand away from a sharp pin.)
159
Properties of fibrous proteins?
Insoluble, provides support (due to parallel arrangement of protein fibres) , strength and protection. e.g. collagen (supports body tissues), keratin (nails and hair),
160
Properties of globular proteins?
Soluble and are functional proteins involved in chemical reactions/metabolic processes.
161
Factors that increase the rate of nerve impulse transmission?
* Presence of myelin sheath around axon
* Wider axon
* Less synapses involved in pathway
162
Difference between endocrine and exocrine glands?
Endocrine glands are ductless (hormones aren't released through ducts) whereas exocrine glands have ducts.
163
When do we undergo anaerobic respiration?
When the rate of cellular respiration is greater than the rate of oxygen consumption, we undergo anaerobic respiration.
163
Why is it important for the hormone to be inactivated after it has carried out its action?
Hormones circulate in the bloodstream and continue to act on tissues until they are inactivated. Different hormones take different times to act but excessive action may lead to excessive effect of the hormone. Excessive action is avoided by the hormone being broken down through metabolic pathways.
164
Differences between plant and animal hormones?
* Plant hormones are generally produced in growing regions of roots and shoots whereas animal hormones are produced by special glands or particular groups of cells in those glands.
* The tubular system through which animal hormones are transported includes a pump (the heart) that facilitates rapid movement of hormones from one to another area of a human body; pumps are not present in plant transport systems.
166
Sensory neuron/Afferent neuron
Detects change in the external or internal environment and transmits information from the receptor to the CNS.
167
Interneuron/Connecting neuron
Located in the CNS and carries signal from neuron to neuron.
167
What is the stimulus-response pathway in the nervous system?
Stimulus --> Receptor --> (Control Centre) --> Effector--> Response
168
Motor neuron/Efferent neuron
Carries signals from CNS to effector and causes it to respond.
170
Describe the neural pathway that controls an action reflex?
A signal is picked up by a receptor and travels through the sensory neuron to the interneuron. (However, this does not involve interneurons of the brain but instead goes to the interneurons of the spinal cord.) A signal is then sent via the motor neuron to the effector and initiates a response (usually muscle movement) from there.
171
How does the electrical impulse travel down the axon?
*This occurs through the generation of the action potential
o A resting neuron is always negative on the inside
o When the neuron is stimulated beyond threshold, the sodium ions enter the axon, causing the inside of the axon to become more positive, and outside to be negative- an action potential is created
o When the inside of the axon becomes positive, the K+ ions move out of the cell and the inside becomes negative again, and the outside positive
o The sodium potassium pumps then transport the ions back to where they were at the resting stage
172
What is an action potential and when is it generated?
* Action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls
* Action potential is an all-or-nothing response- action potential generated only if neuron is stimulated beyond threshold (-50mV)
172
What is signal amplification?
When one hormone molecule causes the production of many second messenger molecules.
173
How does the electrical impulse travel down the axon and to the next neuron/effector?
.• Electrical impulse generated along axon
• Sodium ions accumulate. Causing calcium ion channels to open at the end of axon
• Influx of calcium ions causes acetylcholine (neurotransmitter) to be released into synaptic junction
o Neurotransmitters are synthesised and stored in synaptic vesicles (type of secretory vesicles)
o They are released into synapse by exocytosis
• Neurotransmitters diffuse across the synapse (synaptic junction) to the next neuron/ effector
• Neurotransmitters may bind to receptors on the next neuron or on effectors
o Acetylcholine binds to protein receptors on the next neuron, changing the shape of ion channels and causing sodium ions to enter the neuron, hence generating an action potential
o OR Acetylcholine may bind to receptors on effector, causing a response
175
Explain the action of peptide hormones in signal transduction.
* Hormone binds to specific receptor on cell membrane
* This activates a protein (G-protein) that activates an enzyme that results in the production of many secondary molecules (eg cAMP)
* Note: A secondary molecules is one that helps to relay signal from membrane receptors to target molecules in cytoplasm or nucleus
* These trigger a cascade of events which result in an amplified cellular response
176
Explain the action of steroid hormones in signal transduction.
* Hormone binds to specific intracellular receptor
* Hormone-receptor complex forms (series of events)
* Hormone-receptor complex enters nucleus and binds to DNA and regulates gene expression (cellular response)
177
Similarities between animal and plant hormones?
* Both kinds of hormone are produced in relatively small amounts.
* Both kinds of hormones are signal molecules.
* Both kinds of hormone are produced in one kind of cell or a group of cells and most commonly act on other types of cells.
* Both kinds of hormones are transported through tubular systems, such as the circulatory system in mammals and the phloem in flowering plants.
178
In mammals, how does a simple reflex reaction pathway differ from the pathway involved when a conscious decision is made?
Information involved in reflex arcs can involve 2 or 3 neurons and no connection to the brain. If a conscious decision is involved, the impulse must travel to the brain before travelling to motor neurons.
179
Differences between nervous control and hormonal control?
* Actions controlled by hormones are much slower to be initiated than actions controlled by nerves.
* Hormone-controlled actions are sustained for longer than nerve-controlled actions.
180
What is the essential difference between an intracellular and an extracellular fluid?
An intracellular fluid is the cytosol that is contained within the cell membrane and surrounds the nucleus. An extracellular fluid is the tissue fluid and the plasma that is outside cells and bathes their outer membranes.
181
Why do nerve cells contain many mitochondria/require large amounts of ATP?
ATP is needed for:
* Active transport of Na+ and K+ in and out of the neuron
* The synthesis of neurotransmitters/ secretory proteins and synthesis of synaptic vesicles for exocytosis.
182
What are 5 examples of receptors and what is the stimuli that they detect?
* Chemoreceptor- smell, taste
* Mechanoreceptor- pressure, touch, sound
* Photoreceptor- light
* Thermoreceptor- temperature
* Pain receptor- pain
183
What is a neurotransmitter and what is its function?
* A chemical substance released from a nerve ending (neuron axon) in response to a nerve impulse.
* A neurotransmitter interacts specifically with receptors on a target cell, carrying the action potential across a synaptic cleft.
* The neurotransmitter will stimulate or inhibit the target cell.
184
Why are chemicals involved in paracrine signalling only used on nearby cells?
Paracrine hormones can only be used on nearby cells because they break down (become chemically bound or destroyed) soon after they are released and nearby cells are the only cells with appropriate receptors to bind to these chemicals.
185
Action of chemicals in endocrine signalling?
Chemicals involved in endocrine signalling are released into the bloodstream and act on distant target cells.
186
What is the stimulus-response pathway involved in a conscious response? (ie a person tugging at your hand)
Stimulus(person tugging hand)--> Receptor(Mechanoreceptor[touch] in skin)--> Sensory neuron (transmits impulse to CNS) --> Interneuron (Transmits impulses within CNS[through spinal cord and to brain] Brain processes the signal and sends impulse to motor neuron)-->Motor neuron (Transmits impulse to effector)--> Effector (Muscle contracts)-->Response (Turn neck to look at person tugging your hand.)
187
What is a neurohormone?
* Hormones produced by neurons and released into the bloodstream.
* They travel to the cells of the target organ where the signal is transducted.
e. g. neurohormones produced by the hypothalamus travel via blood to the pituitary gland.
188
What is a hormone?
A hormone is a chemical messenger that binds to specific receptors in target cells, initiating a cellular response.
189
What happens after the action of the neurotransmitter has been achieved?
Neurotransmitter is either returned to the axon terminal or enzymes will break down and destroy the left over neurotransmitter, thus terminating stimulation of the post synaptic cleft.
190
What is the threshold potential?
The minimum amount of excitatory signal needed to generate an action potential.
ie. Only when the neuron is stimulated beyond threshold, an action potential occurs.
191
What is the function of second messenger molecules in signal transduction?
It helps to relay signal from the membrane receptors to target molecules in cytoplasm or nucleus.
192
Why does hyperventilating cause a person to become unconscious?
A lower level of carbon dioxide reduces the urge to breathe, resulting in a person running out of oxygen before carbon dioxide builds up to a level to stimulate breathing.
193
Why do underwater pearl divers hyperventilate?
* If writing about prior to dive, hyperventilation increases carbon dioxide loss, therefore reduced levels of carbon dioxide reduce the urge to breathe, therefore it allows divers to remain under water for longer, as it takes longer for carbon dioxide to build up in the blood.
* If writing about after the dive, because of rapid deep breathing to restore oxygen levels or to reduce carbon dioxide levels.
