PAPER 1 Flashcards
(499 cards)
1
Q
What is a light microscope used for?
A
Observing living and dead organisms
2
Q
What are the pros and cons of a light microscope?
A
Pros: cheap, portable, easy to use & can study living specimens
Cons: limited magnification, poor resolution
3
Q
What is a laser scanning confocal microscope used for?
A
Creating a high resolution, high contrast image at different depths of the specimen
4
Q
Whatis a transmission electron microscope be used for?
A
Observing the internal structure of cells under high magnification and resolution
5
Q
What is a scanning electron microscope used for?
A
Viewing the surface of objects under high magnification and resolution
6
Q
What are the pros and cons of an electron microscope?
A
Pros: very high magnification and resolution
Cons: specimens has to be dead, very expensive, large (not portable), requires great skill and training to use
7
Q
What is the difference between a transmission and an scanning electron microscope?
A
TEM sends a beam of electrons through specimen.
SEM bounces electrons off the surface.
8
Q
What is the difference between light and electron microscopes?
A
Light uses lenses to focus beam of light.
Electrons use magnets to focus beam of electrons.
9
Q
What is an eye piece graticule?
A
Small ruler fitted to a light microscope’s eyepiece. Must be calibrated with a stage micrometer before being used to measure specimens.
10
Q
What is a stage micrometer?
A
Millimeter long ruler etched onto a slide. Has 100 divisions, each 0.01mm (10 micrometer). Used to calibrate the eyepiece graticule.
11
Q
Why do we stain specimens?
A
To provide more contrast and make it easier to distinguish between certain parts.
12
Q
What is differential staining?
A
Using a stain to distinguish between either 2 diff organisms or between organelles of a specimen due to preferential absorption of the stain.
13
Q
What is the formula to calculate magnification?
A
Mag = Image / Actual
14
Q
What is magnification?
A
A measure of how much larger the image of a specimen looks under the microscope
15
Q
What is resolution?
A
The ability to distinguish between to adjacent individual points as separate.
16
Q
What are the maximum resolutions of the different microscopes?
A
Light: 200nm; SEM: 10nm; TEM: 0.2nm.
17
Q
What is the maximum magnification of the different microscopes?
A
Light: 1,500X; SEM: 100,000X; TEM: 500,000X.
18
Q
What are the main structures of all eukaryotic cells?
A
Nucleus; nucleolus; cytoplasm; cytoskeleton; plasma membrane;mitochondria; Golgi apparatus; smooth endoplasmic reticulum; rough endoplasmic reticulum; ribosomes.
19
Q
What is the structure and function of the nucleus?
A
Surrounded by a double membrane (the nuclear envelope).
Contains chromatin (DNA wound around histones).
Stores the human genome,
Controls the cell by providing instructions for protein synthesis.
20
Q
What is the structure and function of the nucleolus?
A
Made of RNA, produces ribosomes.
21
Q
What is the structure and function of the nuclear envelope?
A
A double membrane embeded with channel proteins forming pores. Separates the nucleus from the rest of the cell.
Pores allow ribosomes and mRNA to leave the nucleus.
22
Q
What is the structure and function of the rough endoplasmic reticulum (RER)?
A
A system of fluid filled membranes studded with ribosomes.
Continuous with the nuclear membrane.
Large surface area formed by folding, enables lots of protein synthesis. Proteins pinched off in vesicles transported to the Golgi apparatus.
23
Q
What is the structure and function of the smooth endoplasmic reticulum (SER)?
A
A system of fluid filled membranes.
No ribosomes.
Contain enzymes for cholesterol, lipid and phospholipid synthesis.
24
Q
What is the structure and function of the Golgi apparatus?
A
A stack of flattened membrane bound sacs.
Vesicles from the RER join at the cis face.
Here they are modified, by adding sugar to make glycoproteins, adding lipids to form glycolipids.
Folding proteins into their 3D shape.
Modified proteins are pinched off from the trans face into transport vesicles.
25
What is the structure and function of the ribosomes?
2 subunits, large and small. Made of rRNA . Proteins synthesised here.
26
What is the structure and function of the mitochondria?
Double membrane bound. Inner membrane folded into cristae within a fluid filled matrix. Contain own DNA and 70s ribosomes. Site of aerobic respiration.
27
What is the structure and function of the lysosomes?
Membrane bound sacs containing hydrolytic (digestive) enzymes.
Break down old organelles and foreign matter for reuse.
28
What is the structure and function of the chloroplasts?
Double membrane.
Inner membrane forms flat discs filled with chlorophyll called thylakoids, in stacks called granum.
These are surrounded by a fluid matrix called stroma.
Contain their own DNA and 70s ribosomes.
29
What is the structure and function of the plasma membrane?
Phospholipid bilayer, cholesterol, glycoproteins, glycolipids.
Separates cell contents from external environment.
Controls what enters/leaves cell.
Acts as a receptor for various chemicals.
Site of chemical reactions.
30
What is the structure and function of the centrioles?
Present in animals only.
Two bundles of microtubules at right angles.
Used as anchor point to separate chromosomes during cell division.
Form the basis of cilia.
31
What is the structure and function of the cell wall?
Present in plants and Fungi only.
Bundles of cellulose fibers in plants.
Chitin in Fungi.
Provides support and strength, maintains the cell’s shape.
Prevents cell from bursting when turgid.
Permeable to allow solutions through.
32
What is the structure and function of the flagella?
9 pairs of microtubules surrounded by 2 lone microtubules.
Membrane covers the whole thing.
Used for moving unicellular organisms around.
33
What is the structure and function of the cillia?
9 pairs of microtubules surrounded by 2 lone microtubules.
Membrane covers the whole thing.
Present in great numbers.
Move together in a wafting pattern to move a single celled organism.
(On tissue) waft to move fluids such as mucus.
34
Which structures are involved in the production of proteins?
Nucleus
RER
Transport vesicles
Golgi Apparatus
35
What is the structure and function of the cytoskeleton?
Microfilaments made of actin-allow cell movement and cytokinesis.
Microtubules made of tubulin-scaffold-like structures to give cell shape.
Intermediate fibres for mechanical strength=maintain integrity.
36
What do prokaryotic and eukaryotic cells have in common?
Plasma membrane
Cytoplasm
Ribosomes
DNA
RNA
37
What is different between prokaryotic and eukaryotic cells?
Prokaryotes: Don’t have: nucleus, centrioles, membrane bound organelles (mitochondria, RER, SER, Goli apparatus)
Prokaryotes DO have: peptidoglycan cell wall, smaller ribosomes, plasmid DNA
38
How do prokaryotes divide?
Binary fission
39
List out the elements that make up proteins.
Carbon
Hydrogen
Oxygen
Nitrogen
Sulfur
40
Explain the polar nature of water.
O is more electronegative than H
Unequal share of electrons
Results in regions of δpositive H and δnegative O
41
What allows water molecules to have cohesive and adhesive properties?
Hydrogen bonds
42
Describe the structure of amylose, including the bonds involved and the shape.
All 1,4 glycosidic bonds, straight helix
43
Describe the structure of amylopectin, including the bonds involved and the shape.
1,4 and 1,6 glycosidic bonds, branched
44
State the two structures that make up starch.
Amylose
Amylopectin
45
State the reaction that breaks down maltose.
Hydrolysis
46
What is the reaction to join monosaccharides together?
Condensation
47
What are the 3 types of polysaccharides that α-glucose can form?
Amylose
Amylopectin
Glycogen
48
What are the two monosaccharides that join up to make sucrose?
Glucose
Fructose
49
1,6 glycosidic bonds are found on ........
Amylopectin
Glycogen
50
β-glucose can only be found in ........
Cellulose
51
How are the monosaccharides in cellulose arranged?
Alternating β-glucose molecules inverted
52
Based on the arrangement of cellulose molecules, explain why cell walls provide strength and support to plant cells.
Cellulose forms hydrogen bonds w each other to male microfibrils
Microfibrils join to make Macrofibrils
Macrofibrils join to make fibers
Fibers are tough and insoluble
53
What does the Benedict's test test for?
Reducing Sugars
54
Explain how a positive result is formed in Benedict's test.
Reducing sugar reacts w blue Cu2+
Forms: brick Red Cu+
55
How can we test for starch?
Iodine solution
56
How can we use a colorimeter to do a quantitative Benedict's test?
Colorimeter measures absorbance/transmission of light by a coloured solution.
More concentrated solution = more light absorbes/less transmitted.
Plot a graph against concentration and absorbance/transmission.
Compare to data table of known values.
57
What are the two parts that make up a carboxylic acid?
Carboxyl group
Hydrocarbon chain
58
How many water molecule(s) is/are needed when breaking down a triglyceride?
3
59
What is another term for the condensation reaction that makes lipids?
Esterification
60
What is the difference in structure between saturated and unsaturated lipids?
Saturated: all single C-C bonds in fatty acid chain
Unsaturated: all double C=C bonds in fatty acid chain
61
Why do oils contain unsaturated triglycerides rather than saturated?
Unsaturated FA causes molecules to kink/bend
Cannot pack closely together (cannot form hydrogen bonds)
62
What is the difference in structure between triglyceride and phospholipid?
Phospholipid: 2 FA chains + 1 Phosphate group
Triglyceride: 3 FA chains + 1 Glycerol
63
Describe the phospholipid bilayer arrangement.
Hydrophilic heads point outwards
Hydrophobic tails point inwards
64
Describe 2 similarities and 1 difference between phospholipids and sterols.
Similarities: both have dual hydrophilic/hydrophobic characteristics and both make up the plasma membrane
Differences: sterols are complex alcohol molecules, phospholipids are lipids
65
Describe the steps in identifying lipids and state the positive result.
Mix sample w ethanol.
Mix solution w H2O and shake
White emulsion layer forms = lipid is present
66
State the monomer of a protein.
Amino Acids
67
What are the components that make up an amino acid?
Central Carbon
Hydrogen atom
Amine group (NH2)
Carboxyl group (COOH)
68
Name the bond formed between two amino acids.
Peptide bond
69
What is the primary structure of a protein?
Amino acid sequence
70
What is the secondary structure of a protein?
α-helix and β-pleated sheets
71
What is the tertiary structure of a protein?
Folding into a 3D shape
72
What is the quaternary structure of a protein?
Binding with other tertiary sub-units
73
State the bond involved in the primary structure of a protein.
Peptide bond
74
Stat the bond involved in the secondary structure of a protein
Hydrogen bond
75
State the bond involved in the tertiary structure of a protein.
Ionic
Covalent
Hydrogen
Hydrophobic interactions
Disulphide bridges
76
State the bond involved in the quaternary structure of a protein.
Ionic
Covalent
Hydrogen
Hydrophobic interactions
Disulphide bridges
77
Name the reaction that breaks down proteins.
Hydrolysis
78
What is the solution used to test for the presence of proteins?
Biurets solution
79
Describe a positive result for proteins.
Using biurets solution
Colour change Blue → Purple
80
What is thin layer chromatography?
Technique used to separate individual components of a mixture (e.g Amino Acids)
81
Based on what principles are the amino acids separated in TLC?
Depends of interactions (hydrogen bonds) the AA forms with silica gel in stationary phase.
Depends on solubility in the mobile phase
82
Why should the chromatography plate be only handled by the edges?
Prevent contamination with proteins on hands
83
What are the three types of proteins?
Globular
Conjugated
Fibrous
84
Explain why insulin is soluble in blood.
Hydrophilic AA are folded on the protein’s surface
85
What are prosthetic groups?
Non-protein components in a conjugated protein
86
Give an example of a conjugated protein.
Haemoglobin
Catalase
87
Compare the haem groups in haemoglobin and catalase.
Hb: Fe2+ bonds reversibly with O2 in the blood
Catalase: Fe2+ allows catalase to interact with H2O2 (hydrogen peroxide) to speed up its breakdown)
88
How many haem groups do a haemoglobin contain?
4
89
Explain why keratin is relatively strong, inflexible and insoluble.
Many strong disulfide bridges
90
Briefly describe the structure of collagen.
3 polypeptides wound together in a long, strong rope-like structure
91
What bonds do DNA/RNA polymerase catalyse?
Phosphodiester bonds
92
Name the monomer of a nucleic acid.
Nucleotide
93
State the five possible bases of a nucleotide.
Adenine
Guanine
Thymine
Cytosine
Uracil
94
State the three components to a DNA nucleotide.
Deoxyribose
Nitrogenous base
Phosphate group
95
The two strands of the double helix are ............. to each other.
Antiparallel
96
Thymine, cytosine and uracil belong to a group of bases. Name the group.
Pyrimidines
97
Adenine and guanine belong to a group of bases. Name the group.
Purines
98
State the complementary base pairings.
A-T/U
C-G
99
State the number of hydrogen bonds formed between adenine and thymine/uracil.
2
100
State the number of hydrogen bonds formed between cytosine and guanine.
3
101
Why is DNA replication described as semi-conservative?
Each new DNA molecule is made up of 1 new and 1 old(template) strand
102
State the enzymes involved in DNA replication.
DNA helicase
DNA polymerase
103
State the function of DNA polymerase.
Catalyses formation of phosphodiester bonds between DNA molecules
104
State the function of DNA helicase.
Unzips DNA double helix and breaks hydrogen bonds
105
The free nucleotides pair up with the exposed bases on the DNA strands based on ...... (which principle?)
Complementary base pairing
106
DNA polymerase can only build phosphodiester bonds on the daughter strand in a particular direction. What is this direction?
5’ to 3’
107
In which direction of the template strand does the DNA polymerase move in?
3’ to 5’
108
Define 'genetic code'.
The sequence of bases in DNA that codes for the sequence of AA in protein production
109
The genetic code is described as 'degenerate'. What does that mean?
Many different codons can code for the same AA
110
Define 'gene'.
A section of DNA containing the base sequence that codes for a protein
111
What is a codon?
Triplet bases on RNA that code for AA
112
What are the two differences between DNA and RNA?
DNA: deoxyribose sugar and Thymine base
RNA: ribose sugar and Uracil base
113
Name the enzymes involved in transcription.
DNA helicase
RNA polymerase
114
Why is the antisense strand needed even though it does not code for proteins?
Acts as template strand to form complementary mRNA w the same base sequence as the sense strand
115
What type of bond does mRNA have?
Phosphodiester bonds
116
Even though DNA codes for proteins directly, why is mRNA needed to be made for making proteins?
DNA is to large to leave the nucleus through the nuclear pores
117
How is rRNA involved in catalysing translation?
Contains enzyme that transfers one AA to another
118
Which part of tRNA binds to the mRNA?
Anticodon loop
119
Name the amino acid that is always at the start of a protein.
Methionine
120
Describe what happens to the amino acid chain to make it a fully functional protein.
AA chain folds into secondary then tertiary structure.
May undergo further modification at Golgi Apparatus
121
State the two stages of protein synthesis.
Transcription
Translation
122
Name the product of transcription.
mRNA
123
Name the product of translation.
Polypeptide, which then becomes a functional protein after modification in the Golgi apparatus
124
State the location where translation occurs.
Ribosomes
125
What are the three main types of activities in cells that require energy?
Synthesis
Transport
Movement
126
What does 'ATP' stand for and what is it?
Adenosine Triphosphate
Energy currency
127
Draw the structure of ATP.
Ribose sugar (pentose w Oxygen at top)
Adenine on C1
x3 phosphate groups on C5
128
How does ATP release energy?
ATP hydrolysed into (ADP + Pi) and releases Energy
129
State 3 properties of ATP.
Small-easy to move in/out of cells
Water soluble-release energy in small quantities so no heat lost
Easily regenerated by phosphorylation of ADP
130
What are metabolic reactions?
All reactions in an organism
131
What are anabolic reactions?
Building up larger molecules from smaller molecules
132
What are catabolic reactions?
Breaking down molecules into smaller components
133
What are enzymes?
Biological catalysts that speed up chemical reactions wo being used up
134
Name the energy that is required to start a reaction.
Activation energy
135
What are enzymes' effect on the activation energy of a reaction?
Provide alternative route with lower activation energy
136
Name the area on the enzyme that binds to and reacts with the substrate.
Active site
137
The active site has a _____ shape to the substrate.
Complementary/specific
138
Name the two models used to illustrate enzyme actions.
Lock and key
Induced fit
139
Name the structure where the enzyme and substrate are bound together.
Enzyme-Substrate complex
140
What is the difference between the lock-and-key model and the induced fit model?
Lock and Key: no movement
Induced fit: slight movement of AS to allow better binding w substrate
141
Name an intracellular enzyme.
Catalase
142
Name an extracellular enzyme.
Amylase
Trypsin
143
Define the term ‘denaturation’.
Loss of AS shape
144
Explain how an increase of temperature increases enzyme activity.
Increases particles Kinetic energy
Particles move faster and collide more often
Increase chance of more successful collisions between AS and substrate
145
Explain how high temperatures can denature enzymes.
Lead to more vibrations that breaks bonds that hold proteins together
146
What is the temperature coefficient (Q10)?
A measure of how much the ROR increases with a 10°c increase
147
How are the enzymes in organisms that live in cold environments adapted?
Enzymes are more flexible and less stable
Can move in lower KE environments so they can bind w substrate
148
How are the enzymes in organisms that live in hot environments adapted?
Enzymes are more stable (more bonds in tertiary structure)
More resistant to denaturation by high heat
149
How does a change in pH affect enzyme structure?
Change in pH = change in H+ concentration
H+ ions interact w polar-groups and charged-R-groups in tertiary structures
Breaks the bonds/interactions between R groups = loss of tertiary structure
150
Explain why an increase in substrate concentration increases rate of reaction.
Higher successful collision rate between AS and substrate
Forms more ES-complexes
151
What does it mean by a ‘reversible’ inhibitor?
Inhibitor can be released from enzyme to resume the enzyme’s function
152
Most competitive inhibitors are reversible or irreversible?
Reversible
153
Explain how Vmax of the enzyme can be unchanged in competitive inhibition.
Adding more substrates to outcompete inhibitors
More substrate = more successful collisions between enzymes and substrates = more ESC formed
Therefore, less enzymes are available for inhibitors to bind to
154
What types of inhibitor does aspirin belong to?
Irreversible
Competitive
155
Explain the difference between competitive and non-competitive inhibition mechanisms.
Competitive: binds to AS = substrate no longer able to bind to AS
Non-Competitive: inhibitor binds to allosteric site = changes 3D tertiary structure of enzyme = changes AS shape = substrate no longer able to bind to AS
156
Explain how an increase in substrate concentration affects the rate of reaction in non-competitive inhibition.
No change
157
State an example of irreversible, non-competitive inhibitor for human use.
Proton pump inhibitor = treat long-term indigestion
158
What is end-product inhibition?
The product of an enzyme-catalysed reaction acts as the inhibitor
159
How does ATP regulate its own production by end-product inhibition?
ATP binds to allosteric site of the enzyme
Prevents a second phosphorylation of glucose
Therefore, Glucose is not broken down to produce more ATP
160
State the difference between cofactors and coenzymes.
Cofactor: non-protein component that aids enzymes to carry out their functions
Coenzymes: organic cofactors
161
From which chemical are cofactors derived from?
Minerals
162
From which chemical are coenzymes derived from?
Vitamins
163
Name the cofactor found in amylase.
Chloride ion
164
Name the cofactor invovled in photosynthesis.
NADP
165
Name the cofactor invovled in respiration.
NAD
FAD
166
State the difference between cofactors and prosthetic groups.
Cofactors: temporarily bound to enzyme
Prosthetic groups: permanently bound to the enzyme
167
Name the prosthetic group in haemoglobin.
Fe2+ ion in Haem group
168
Name the prosthetic group in carbonic anhydrase.
Zn2+
169
What are the three ways that an enzyme can be activated by changing the tertiary structure?
adding a cofactor
Adding another enzyme
Change in pH
170
Why is it important that some enzymes are produced in its inactive form?
So it doesn’t damage the cell that it was produced in
171
What is an apoenzyme?
Inactive form of an enzyme
172
What is an apoenzyme?
Active form of an enzyme
173
What is the fluid mosaic model?
Cell membrane formed from a sea of phospholipids embedded with proteins
174
What is a glycolipid?
A lipid w a carbohydrate molecule attached
175
What is a glycoprotein?
A protein with a carbohydrate molecule attached
176
State four functions of membranes at the surface of cells
Separates cell’s components from its external surroundings to ensure conditions inside cell remain unaffected.
Regulates transports of materials in/out cell.
Surface antigens so the body’s immune system recognises cell as ‘self’ and contains receptors for chemical signals (hormones, drugs etc).
Site of chemical reactions.
177
State 4 functions of membranes within cells
Maintains conditions inside cell so metabolic reactions can take place.
Inner mitochondrial membrane highly folded for large SA for electron carrier proteins.
Thylakoid membrane contain chlorophyll for light-dependent stage of photosynthesis.
Vesicle production for exocytosis.
178
Define the term diffusion.
The net movement of a substance from an area of high concentration to an area of low concentration. It is passive, does NOT require ATP.
179
Define the term facilitated diffusion
Movement of molecules from a high concentration to a low concentration, across a partially permeable membrane, via specific channel or carrier proteins. It is passive, does NOT require ATP
180
What is a channel protein?
A protein which creates a fluid filled pore in the cell membrane through which ions and small polar molecules can pass.
181
What is a carrier protein?
A protein which changes shape to allow larger molecules to pass through the membrane. In facilitated diffusion this requires no energy, in active transport it requires ATP.
182
What types of molecules can diffuse directly across the phospholipid bilayer?
Small molecules such as oxygen and carbon dioxide; lipid-soluble molecules such as steroid hormones and alcohol
183
Describe the movement of water across the phospholipid bilayer
Water is polar and insoluble in lipid, BUT because it is present in such high quantities, significant direct, simple diffusion does occur. In membranes (e.g. collecting duct) where a very high rate of water movement is required, special channel proteins known as aquaporins are inserted into the membrane.
184
State 5 factors that affect the rate of simple diffusion
Temperature, surface area, diffusion distance, size of molecule, concentration gradient
185
Define the term active transport
Movement of molecules, against their concentration gradient (using energy liberated from ATP hydrolysis) using specific protein channels or carriers
186
Describe how carrier proteins are used in active transport
Molecule binds to specific site in carrier protein; ATP binds to separate binding site; carrier protein changes shape (conformational change) and transports molecule across membrane
187
Define bulk transport and give two examples
The movement of large molecules that are too big to pass across the plasma membrane. Endocytosis (phagocytosis or pinocytosis) brings large molecules INTO the cell, enclosed in a vesicle. Exocytosis transports large molecules OUT of cells.
188
Define and describe phagocytosis
The intake of solid particles into the cell by engulfing. Pseudopodia surround the particles, the membrane fuses together, to form a vesicle.
189
Define and describe pinocytosis
The intake of liquids into the cell by engulfing. The plasma membrane invaginates, and the membrane fuses around the substance, forming a vesicle.
190
Define and describe exocytosis
ATP is required to provide energy for the movement of vesicles along microtubules of cytoskeleton (via motor proteins); ATP is needed to fuse vesicle membrane and plasma membrane together (PM is changing shape)
191
Describe the role of ATP in bulk transport
ATP is required to provide energy for the movement of vesicles along microtubules of cytoskeleton (via motor proteins); ATP is needed to fuse vesicle membrane and plasma membrane together (PM is changing shape)
192
What is the main difference between active transport and facilitated diffusion?
Active transport requires ATP; facillitated diffusion is passive
193
Define the term osmosis
The movement of water molecules from a region of higher water potential to a region of lower water potential, across a partially permeable membrane
194
What is water potential?
The tendancy of water molecules to move from one region to another.
195
What substance has the highest possible water potential of 0 kPa?
Pure water
196
State the equation that links water potential, solute potential and pressure potential
WP = SP + PP
197
As more solute is added to a solution, what happens to the solute potential and hence the water potential?
Solute potential decreases, hence water potential decreases
198
Describe what would happen to a red blood cell placed in a solution with a more negative water potential than that of its cytoplasm
Water would move OUT, down a WP gradient, shrinking to crenation
199
Describe what would happen to a liver cell placed in a solution with a more positive WP than its own cytoplasm
Water would move IN, down a WP gradient, swelling the cell and causing it to burst (CYTOLYSIS) due to the presence of no cell wall
200
Describe what would happen to a root hair cell placed in a solution with lower WP than its own cytoplasm/vacuole
Water would move OUT, down a WP gradient, causing the cell to become flaccid and then plasmolysed
201
Describe what would happen to a guard cell placed in a solution of less negative WP than its own cytoplasm
Water would move IN, down a WP gradient, causing the cell to swell and become TURGID
202
State three events that occur in G1 phase of the cell cycle
Cells grow and increase in size; proteins from which organelles are made are synthesised (transcribed and translated); organelles replicate
203
What happens during the S phase of the cell cycle?
This is the synthesis phase, DNA is replicated.
204
What happens during the G2 phase?
Second growth phase, proteins which involved in making the chromosomes condense are synthesised (transcribed and translated).
205
Describe what may happen in G0 phase of the cell cycle
Cells may undergo apoptosis, differentiation or senescence
206
State three cell cycle checkpoints and briefly describe what is being checked for at each
G1/S - checks for size, growth factors, nutrients, DNA damage; G2/M - checks DNA has been properly replicated; spindle assembly - checks chromosomes have correctly attached to spindle fibres
207
State three purpose of mitosis in life cycles
Asexual reproduction; growth; tissue repair; replacement of cells
208
Describe the main events of prophase
Nuclear envelope breaks down; chromatin condenses (DNA supercoils); nucleolus disappears; spindle fibres start to form from centrioles
209
Describe the main events of metaphase
Chromosomes line up along equator (metaphase plate); spindle fibres attach through centromeres
210
Describe the main events of anaphase
Sister chromatids pulled to opposite poles of the cell by shortening tubulin spindle fibres
211
Describe the main events of telophase
Nuclear envelope reforms around each set of chromosomes; chromatin relaxes; nucleolus reappears
212
Describe how cytokinesis differs between dividing animal cells and plant cells
Animal cells - cleavage furrow forms and plasma membrane is pulled inwards, splitting the cytoplasm; plant cells - vesicles assemble around metaphase plate and fuse; new plasma membrane and cellulose cell wall are laid down
213
Why would we use the root tip for investigating mitosis?
It is the location of meristematic tissue (source of stem cells) in a plant, i.e. cells are actively dividing
214
Explain why we warm the root tips in hydrochloric acid when preparing a root tip squash
To break the links between cellulose cell walls in plant cells; this ensures the stain penetrates the cells and binds to the chromosomes
215
Which stain would we use to stain chromosomes in a root tip squash?
Acetic orcein
216
What is meiosis?
The formation of gametes. Genetically unique with half the genetic information of a somatic cell.
217
Describe how meiosis produces genetic variation in the gametes produced
Crossing over in prophase I; independent assortment in metaphase I; independent assortment in metaphase II
218
Describe the difference between anaphase I and anaphase II
In anaphase I, a homologous pair of chromosomes is separated so the chromosome number halves (2 haploid cells made); in anaphase II, sister chromatids of each chromosome are separated so chromosome number stays the same (haploid number maintained)
219
In which stage of meiosis is the chromosome number halved
Anaphase/telophase I
220
Explain why genetic variation is important for a population of organisms
More likely that some individuals are adapted to a change in the environment, so the population can survive
221
What is differentiation?
The process by which a cell develops to become more distinct in form and function
222
Describe and explain how erythrocytes are adapted for their function
Very small so have a large SA:vol (biconcave shape also ensures this) meaning oxygen can reach all regions inside the cell; well-developed cytoskeleton allows the erythrocytes to change shape and move through very narrow capillaries; no nucleus or organelles so more space for Hb molecules
223
Explain why a neutrophil contains many lysosomes
These contain hydrolytic enzymes which digest pathogens
224
Describe and explain how sperm cells are adapted for their function
Acrosome in head contains enzymes to penetrate the egg follicle during fertilisation; many mitochondria to generate ATP for flagellar movement; large haploid nucleus in head to fertilise haploid ovum
225
Describe how guard cells open in sunny conditions
Light energy --> ATP; ATP used to actively transport potassium ions from epidermal cells into guard cells; water potential of guard cells lowered; water moves in by osmosis and guard cells become turgid
226
Describe the purpose of cytoskeleton threads and motor proteins in palisade cells
Moves the chloroplasts to areas of appropriate light intensity
227
Describe how a root hair cell plasma membrane is adapted for transport of mineral ions
Contains specialised carrier proteins to transport specific mineral ions in by active transport
228
Describe how cartilage is adapted for its function
Connective tissue that contains elastin and collagen fibres; prevents ends of bones from rubbing together
229
Define the term tissue
A group of cells working together to perform a particular function
230
State three types of muscle tissue, giving an example of where each is found
Skeletal - bicep/tricep etc.; smooth - digestive tract, blood vessels; cardiac muscle - heart walls
231
Give four features of meristematic cells that means they can differentiate easily
Thin walls with very little cellulose; no chloroplasts; no large vacuole; divide by mitosis and have the ability to differentiate into many cell types
232
Describe the differences between multipotent, pluripotent and totipotent stem cells
Multipotent - found in bone marrow and can form a range of different cells including blood cells; pluripotent - found in early embryos (embryonic stem cells) and can form all tissue types except extra-embryonic cells; totipotent - found in first 16 cells post-zygote and can form all tissue types including extra-embryonic tissue (e.g. placenta, umbilical cord)
233
State three characteristics of stem cells
Undifferentiated; all genes able to be expressed; self-renewing; able to differentiate into any cell type
234
State the three main factors that affect the need for an exchange system
Size, SA:Vol ratio and level of activity
235
Explain why smaller organisms have a lower demand for oxygen than larger organisms
Smaller organisms have a larger SA:V ratio than larger organisms; simple diffusion can be sufficient for unicellular organisms but due to many-layered multicellular organisms, it would be too slow. Multicellular organisms therefore need transport systems
236
Describe and explain three features of a good exchange surface
Large SA (folded walls; provides more space for relevant molecules to pass through); thin, permeable barriers (reduces diffusion distance); good blood supply (keeps high concentration gradients for rapid diffusion)
237
Describe how human alveoli are adapted to reduce diffusion distances
Alveolus wall one cell thick; capillary wall one cell thick; walls of alveoli/capillaries contain squamous (flattened) cells; caoillaries are in close contact with alveoli walls; capillaries are narrow to restrict RBC movement
238
Describe the role of surfactant in alveoli
Coats the internal surface of the alveoli to reduce cohesive forces between water molecules, preventing collapse
239
Describe the mechanism of inspiration
Diaphragm contracts (moves down and flattens); external intercostal muscles contract to push ribcage up and out; volume of thorax increased and so pressure decreases below atmospheric pressure; air rushes into lungs down a pressure gradient
240
Why do alveolar walls contain elastic fibres?
To stretch during inspiration and recoil , pushing air out, during expiration
241
Which tissue type comprises alveolar walls?
Squamous epithelium
242
The trachea is lined with ciliated epithelial tissue and goblet cells. Describe the functions of these.
Goblet cells produce mucus onto the tracheal lining, trapping dust and microorganisms. The cilia then beat and move the mucus away from the lungs and towards the throat
243
The trachea and bronchi are lined with cartilage. Describe why.
C-shaped rings of cartilage line these tubes, preventing collapse during inspiration. The C-shape allows food to pass down the oesophagus behind the trachea
244
Describe how the nasal cavity is adapted for exchange
Large SA with a good blood supply, warming air to body temperature; lined with hair (which secretes mucus) to trap dust and MOs, protecting from infection; moist surfaces to increase the humidity of the incoming air, reducing evaporation from exchange surfaces
245
Describe the roles of smooth muscle and elastic tissue in the airways
Smooth muscle can contract to constrict airways (not under conscious control, i.e. involuntary); elastic fibres elongate smooth muscle again, recoiling the airway to its original shape and size (dilates airway)
246
Describe precautions that must be taken when using a spirometer
Subject should be free of asthma; there should be no air leaks in the apparatus; mouthpiece should be sterilised; soda lime should be fresh and functioning
247
Describe what is meant by 'vital capacity' and state the factors that it depends upon
The maximum volume of air that can be moved by the lungs in one breath; measured by taking one deep breath and expiring all the possible air from the lungs. Depends on: size (height) of person; age/gender; exercise levels.
248
State the usual range for vital capacity
2.5 - 5.0 dm3
249
Describe what is meant by 'inspiratory reserve volume'.
The maximum volume of extra air you can breathe in forcibly (vital capactiy - tidal volume - ERV)
250
Describe what is meant by 'expiratory reserve volume'.
The maximum volume of extra air you can breathe out forcibly (vital capacity - tidal volume - IRV)
251
Describe what is meant by 'residual volume' and state the standard volume
Describe what is meant by 'residual volume' and state the standard volume
252
Describe what is meant by 'tidal volume' and state a typical figure
Volume of air moved in and out with each breath at rest. A normal value would be 0.5 dm3 (500cm3)
253
What is the difference between 'ventilation rate' and 'breathing rate'?
BR = no. of breaths taken per min; VR = total volume of air inhaled per min
254
The normal breathing rate of a healthy 50 year old woman is 18 breaths per minute and her tidal volume is 500 cm3. During strenuous exercise, her ventilation rate increases to 45 000 cm3min-1 and she is breathing 30 times a minute. Calculate her tidal volume during this exercise and state how much higher than normal this figure is.
TV = 1500 cm3 ...1 dm3 higher than normal
255
Most bony fish have 5 pairs of gills which are covered by a bony flap, known as the …? What is the function of this bony flap?
Operculum; protects the gills and ensures a constant flow of water
256
Describe the structure of gills in bony fish
Two rows of gill filaments; these are slender branches of tissue known as primary lamellae and are attached to a bony arch. Each gill filament is folded into secondary lamellae providing a very large surface area
257
Describe ventilation in bony fish
Buccal cavity (mouth) can change volume; floor of mouth moves downwards, drawing water into the buccal cavity; mouth closes and water is pushed through the gills. As water is pushed from the buccal cavity through the gills, the operculum moves outwards
258
How is air supplied to respiring tisses in an insect?
How is air supplied to respiring tisses in an insect?
259
How does air enter the tracheal system in an insect?
Spiracle
260
The ends of tracheoles in insects are filled with tracheal fluid. What is the function of this fluid?
Gaseous exchange occurs between air in tracheole and the tracheal fluid
261
When an insect is active, what changes occur in the insect to increase their oxygen supply?
Tracheal fluid can be withdrawn into the body fluid to increase the surface area of the tracheole wall exposed to air
262
Describe three features of an effective transport system
A fluid to carry nutrients/oxygen/wastes around the body (blood); a pump to create pressure that will push the fluid around the body (heart); exchange surfaces (capillaries)
263
Describe three disadvantages of single circulatory systems, as seen in fish
Blood pressure drops as blood passes through the gill capillaries; blood flows slowly through as it is under low pressure; the rate of delivery of oxygen/nutrients to respiring tissues is limited (and removal of CO2 and urea)
264
Explain why fish do not need as much energy as mammals
They are not as metabolically active as mammals as they do not maintain their body temperature
265
Describe what is meant by the term open circulation
Blood is not always held in vessels, but it circulates throughout the body cavity and the tissues and cells bathe directly in blood
266
State two disadvantages of open circulatory systems
Blood pressure is low and blood flow is therefore slow; circulation can be affected by body movements (or lack of)
267
State four advantages of closed circulation over open circulation
Blood travels at higher pressure and therefore flow is faster; oxygen/nutrients supplied and CO2/urea removed more quickly; transport is independent of body movements.
268
What is the inner tissue lining of a blood vessel called? What is its role?
Endothelium; reduced friction with the flowing blood
269
Describe the three structural layers of an artery
Tunica intima - thin layer of elastic tissue which allow walls to stretch and recoil (opposes muscle); tunica media - thick layer of smooth muscle; tunica adventitia - thick layer of collagen and elastic tissue providing strength to withstand the high pressure and recoiling against the muscle
270
What is the role of arterioles?
Take blood from artery to capillary; they have a layer of smooth muscle which contracts restricting and slowing blood flow
271
Describe how capillaries are adapted for exchange
Narrow lumen (squeezes red blood cells against walls so transfer of oxygen is better to the tissues); walls consist of single layer of endothelial cells (reduces diffusion distance); walls are permeable (allows blood plasma and dissolved substances to leave the blood)
272
Describe the function of a venule
Takes blood from the capillaries to the veins
273
Describe how veins are adapted to carry blood back to the heart
Wide lumen to ease blood flow; thin layers of elastic/muscle/collagen in walls as no need to stretch and recoil; valves to prevent backflow of blood
274
Where is hydrostatic pressure created of the blood created?
In the ventricles of the heart
275
What is oncotic pressure?
The pressure created by the osmotic effects of the solutes
276
What substances might affect the oncotic pressure of the blood?
Dissolved solutes such as mineral ions, sugars and proteins
277
State the cell types that are most likely to be found in blood plasma, tissue fluid and lymph
Blood plasma - red blood cells, neutrophils, lymphocytes; tissue fluid - neutrophils (especially during infection); lymph - lymphocytes
278
Why can proteins known as plasma proteins not leave the blood plasma?
They are too large to pass between the squamous cells of the capillary wall
279
Why can neutrophils enter the tissue fluid but erythrocytes cannot?
Neutrophils can change shape very easily (multilobed nucleus) and squeeze themselves between cells. Erythrocytes cannot change shape as much
280
Describe the role of the lymph fluid
A system of tubes that returns excess tissue fluid to the blood system
281
A system of tubes that returns excess tissue fluid to the blood system
Tissue fluid surrounds body cells so exchange occurs across plasma membranes
282
Describe the simple structure of haemoglobin
Four subunits (each with a polypeptide chain and a haem group); haem groups each contain an Fe2+ ion at the centre; iron ions can attract and hold an oxygen molecule
283
What is the process known as by which oxyhaemoglobin releases its oxygen to respiring cells?
Dissociation
284
What is the main difference between foetal haemoglobin and adult haemoglobin?
It has a higher affinity for oxygen than adult haemoglobin
285
Describe three ways in which carbon dioxide is transported
5% dissolved directly in the plasma; 10% directly with haemoglobin in the form of carbaminohaemoglobin; 85% in the form of hydrogencarbonate ions
286
5% dissolved directly in the plasma; 10% directly with haemoglobin in the form of carbaminohaemoglobin; 85% in the form of hydrogencarbonate ions
Carbon dioxide from the blood plasma diffuses into RBCs anf combines with water to form carbonic acid (catalysed by carbonic anhydrase); carbonic acid then dissociates into hydrogencarbonate ions and protons
287
Describe how the charge inside a RBC is maintained when hydreogencarbonate ions diffuse into the plasma
Chloride ions move into the RBCs from the plasma (chloride shift)
288
Describe how the pH inside a RBC is buffered as hydrogen ions build up inside, making the RBC very acidic
Hydrogen ions are taken out of solution and combined with haemoglobin to form haemoglobinic acid (HHb)
289
What is the net result of the Bohr effect?
More oxygen is released where more carbon dioxide is produced in respiration
290
With reference to protein structure, explain how increasing hydrogen ion levels affects haemoglobin.
More hydrogen ions --> lower pH (more acidic cytoplasm); tertiary structure of Hb altered which reduces its affinity for oxygen
291
What is the purpose of semilunar valves?
To prevent backflow of blood from arteries to the ventricles
292
Why is the left ventricular wall so much thicker than the right ventricular walls?
Blood is pumped throught the aorta and needs sufficient pressure to overcome the resistance of the systemic circulation
293
Why are there so many mitochondria in cardiac muscle?
Supply energy for contraction
294
What is the purpose of intercalated discs between adjacent muscle cells?
Ensures an even, synchronised contraction
295
Briefly outline the events of atrial systole
Left and right atria contract together; blood is squeezed from the atria through the atrioventricular valves into the ventricles, down a pressure gradient.
296
Briefly outline the events of ventricular systole
Ventricular blood pressure rises very quickly to a level above the arteries; semilunar valves open and blood rushes out of ventricles into the arteries
297
Briefly outline the events of diastole
Once ventricular contraction is complete, heart muscle starts to relax, heart starts to fill with blood again and semilunar valves close
298
What is meant by the term myogenic?
Cardiac muscle can initiate its own contractions
299
What tissue is responsible for initiating the heartbeat?
Sinoatrial node (SAN)
300
What tissue propagates the electrical signal from the atria to the ventricles, resulting in ventricular systole?
Atrioventricular node (AVN)
301
Why is there a delay before the AVN depolarises the ventricular walls?
To allow the atria to finish contracting
302
Describe the role of the Purkyne tissue
Specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles
303
What do the letters PQRST indicate in an ECG?
P = atrial excitation; QRS = ventricular excitation; T = diastole
304
What terms describe a slow and a fast heart rate?
Bradycardia; tachycardia
305
What happens in atrial fibrillation?
Atria beat more frequently than ventricles, meaning no clear P wave can be seen on ECG
306
What is an ectopic heart beat?
An early ventricular beat
307
Plant transport systems consist of 2 major specialised vascular tissues. Name these, state their transport material and the direction of transport
Xylem - water, soluble mineral ions (upwards); phloem - assimilates (up or down)
308
What tissue is found in between the xylem and phloem? What is its function?
Meristematic tissue (source of stem cells)
309
What is the purpose of parenchyma cells in xylem tissue?
To separate and support the vessels (act as packing tissue)
310
What is the purpose of lignin in xylem vessels?
Strengthens vessel wall and prevents collapse
311
How do bordered pits form and what is their purpose?
Where lignification is incomplete, leaving gaps in the cell wall; the bordered pits in 2 adjacent vessels are aligned to allow water to leave one vessel and pass into the next, as well as leave the xylem
312
Describe three adaptations of xylem vessels that relate structure to function
1) Dead cells aligned end to end to form a continuous column; (2) Tubes are narrow so water column doesn't break easily and capillary action can be effective; (3) Bordered pits allow sideways movement of water between vessels; (4) Lignin allows stretching of xylem (spiral, annular or reticulate patterns) as plant grows
313
What two components of phloem tissue are concerned with transport?
Sieve-tube elements and companion cells
314
Why do sieve tube elements contain no nucleus and very little cytoplasm?
Allows space for mass flow of sap to occur
315
How are companion cells adapted for active loading?
Many mitochondria to produce ATP
316
Describe 2 major pathways taken by water to move between cells
Apoplast - through spaces in cell walls and between cells (mass flow…not osmosis); symplast - moves through cytoplasm and between cells via plasmodesmata
317
What allows water to move through cells via the symplast pathway, and by which mechanism of movement?
Different water potential of cytoplasm of adjacent cells; Water moves by osmosis
318
What allows water to move continuously via the apoplast pathway?
Cohesion, by diffusion
319
Why does the presence of starch in the endodermis suggest that an active process is involved?
Starch acts as a store of sugars, which can be released and respired to release energy for active processes
320
What is the Casparian strip?
A band of waterproof, waxy suberin around each endodermis cell (on cell wall)
321
Explain the significance of the Casparian strip
Waterproof hence locks the apoplast pathway between the cortex and the medulla, forcing water and dissolved mineral ions to pass through the selectively permeable membrane into the cytoplasm, filtering out toxic chemicals
322
Describe how water is lost via stomata (refer to gradients)
Water vapour in higher concentration in air spaces than in space outside leaf; water diffuses down water vapour potential gradient
323
Describe the effects of light intensity, humidity and wind speed on the rate of transpiration
Light intensity (increased LI…increased rate as stomata more open); humidity (incr. humidity in air…decr. Rate as lower water vapour potential gradient); wind speed (incr. wind…incr. rate as maintaining high water vapour potential gradient)
324
State two precautions that should be taken to ensure no air bubbles are in the potometer setup
Set up u/w; cut stem u/w to prevent air entering xylem
325
The distance moved by the meniscus in a potometer is 45mm in 5 minutes. The radius of the capillary tube is 0.5 mm. Calculate the rate of transpiration.
7.1mm3/min
326
Describe how water moves up the stem via the transpiration pull
Loss of water by evaporation at the top of the plant must be replaced by water from the xylem. This puts water at the top of xylem under tension. Tension pulls the column of water up the xylem as water molecules are cohesive.
327
What property of water causes cohesion?
The polarity of the water molecule, which produces hydrogen bonds between the molecules
328
Define the term translocation
Transport of assimilates from source to sink (tissue that needs them)
329
State two sinks (for translocation) in a plant
Roots growing or active uptaking mineral ions; actively dividing meristematic tissue; part plants that are laying down food stores (e.g. developing seeds, fruits etc)
330
What is the difference between active loading and active transport?
Active transport is the movement of particles against their concentration gradient using metabolic energy (ATP). Active loading is a more extensive process which involves active transport at some stage. In this case, active loading uses active transport to pump hydrogen ions out of the companion cells. This results in movement of sucrose molecules by facilitated diffusion and diffusion.
331
Describe the role of hydrogen ions in active loading
The hydrogen ions are pumped out of the companion cells, creating a hydrogen ion concentration gradient across the cell membrane. The hydrogen ions can diffuse back into the companion cells through special transport proteins – but they only move if sucrose is carried in with them (cotransport). 8
332
Why is sucrose transported in phloem and not glucose?
More stable hence less likely to be metabolised in the transport process
333
How does sucrose move from the companion cells into the sieve tube elements?
Increasing sucrose conc causes water to also move into companion cells, which builds up turgor pressure (and water potential). The water carrying assimilates (sucrose) then enters sieve tubes down the pressure/WP gradient through plasmodesmata
334
Based on what principle does mass flow work in sieve tubes?
"Turgor pressure difference - sieve tubes at source has higher turgor pressure due to ""intake"" of sucrose and water, whereas sieve tubes at sinks has lower turgor pressure due to the cells removing the sucrose from the sieve tubes"
335
Based on what principles does phloem unloading work?
Diffusion of sucrose - by rapidly moving into surrounding cells or by converting into glucose, decreasing sucrose conc within cells hence maintaining sucrose conc difference between cells in sink and sieve tube
336
Describe 3 adaptations of marram grass (xerophyte) and explain their importance
Leaf rolled longitudinally trapping air inside (air becomes humid and reduces water loss from the leaf); thick waxy cuticle on upper epidermis (reduces evaporation); stomata on lower epidermis inside rolled leaf (protected by enclosed air space); stomata are in pits in lower epidermis which is folded and covered by hairs (reduces air movement and hence water loss); spongy mesophyll very dense with few air spaces (less surface area for evaporation of water)
337
Cacti are succulents. What does this mean?
They store water in their stems which become fleshy and swollen
338
Why is it advantageous for some xerophytes to have a low water potential inside their leaf cells?
Reduces evaporation of water from the cell surfaces as the water potential gradient between the cells and the leaf air spaces is reduced
339
Describe two adaptations of roots that could help a plant survive in arid conditions
Roots could be very long to reach water deep in soil; roots could be very widespread to absorb water from a large area when it does rain.
340
What is a response?
A behavioural or physiological change in an organism as a result of a stimulus.
341
What is a stimulus?
A change in the internal or external environment of an organism.
342
What is homeostasis?
Responses that maintain a constant internal environment inside an organism.
343
Name 4 internal conditions that are maintained by an organism's homeostasis.
Body temperature, blood glucose concentration, blood water potential, carbon dioxide concentration
344
Put the following aspects of a feedback mechanism in order: processor, stimulus, effector, response, receptor
stimulus, receptor, processor, effector, response
345
What are the 2 communication systems in mammals?
Nervous, hormonal
346
What is cell signalling?
The release of a chemical from a cell that is complementary to a receptor in a target cell, bringing about a response in the target cell.
347
What is an effector?
A cell or tissue that bring about a response to a stimulus.
348
What are the 3 types of effector?
Muscle cell, gland cells, liver cells
349
What is meant by the potential difference across a membrane?
The difference in potential between inside and outside the cell.
350
What is meant if a membrane is polarised?
The inside of the cell has a more negative potential than outside.
351
What is the resting potential value of a resting neurone?
-60mV
352
What 3 things maintain the resting potential of a resting neurone?
Presence of large organic anions inside the cell, 3 Na+ out, 2 K+ in by Na+/K+ pump, membrane is more permeable to K+
353
Where is the highest concentration of Na+ at resting potential?
Outside the cell
354
Name 3 types of neurone
motor, sensory and relay
355
motor, sensory and relay
Their cell body is located in the CNS and they have a long axon carrying the action potential to the effector.
356
Describe the structure and function of a sensory neurone?
Have a long dendron carrying the action potential from a sensory receptorto the cell body, positioned outside the CNS. They have a short axon carrying the action potential into the CNS.
357
Describe the structure and function of a relay neurone?
They connect the sensory and motor neurones in the CNS. They have short dendrites and short axon
358
They connect the sensory and motor neurones in the CNS. They have short dendrites and short axon
The neurone is insulaterd by a myelin sheath, which is schwann cells wrapped tightly around the neurone.
359
Describe any advantages of myelination of neurones?
An action potential can be transmitted much quicker as the signal jumps between the nodes of Ranvier.
360
Where are non myelinated neurones found?
They are often used to coordinate body functions such as breathing or digestion, carrying action potentials over shorter distances.
361
What is a sensory receptor?
A cell or tissue that monitors an aspect of an organism's internal or external environment.
362
What do sensory neurones do?
What do sensory neurones do?
363
Name 6 examples of sensory receptors.
Thermo, chemo, baro, photo, proprio, osmo
364
Sensory neurones act as a tranducer. What is a tranducer?
Something that converts one form of energy into another.
365
What is a processor?
A tissue or organ that coordinates the input from sensory receptors and communicates the output response to the relevant effector.
366
What is a Pacinian corpuscle?
A pressure sensor that detects changes in pressure or vibration in the skin.
367
Describe the structure of a Pacinian corpuscle?
The corpuscle is oval shaped with a series of rings of concentric conective tissue, wrapped around the end of a nerve cell.
368
How does a Pacinian corpuscle detect pressure changes?
The corpuscle is sensitive to changes in pressure tat deform the rings of connective tissue. Therefore no response when the pressure is constant.
369
How are cell membrane proteins involved in neural communication?
Some proteins are channels allowing the movement of ions across the membranes by facilitated diffusion, while others are transport proteins that actively move ions across the membrane requiring energy in form of ATP.
370
What happens if a stimulus is too weak?
The generator potential will not reach the threshold level and so there is no action potential
371
Where is the highest concentration of K+ at resting potential?
Inside the cell
372
Describe how a sodium/potassium pump in the cell menbrane functions?
3 Sodium ions are actively pumped out of the cell, with 2 potassium ions going into the cell
373
What is meant if a membrane depolarises?
The inside of the cell has a less negative potential than outside.
374
What causes a membrane to depolarise?
Some Na+ channels open, allowing Na+ to diffuse down its concentration gradient.
375
What happens in the neurone membrane if threshold potential is reached?
Voltage-gated Na+ channels open for bigger influx of Na+
376
What is the action potential value of a stimulated neurone?
+40mV
377
What happens in the neurone membrane at +40mV?
Voltage-gated Na+ channels close, voltage-gated K+ channels open
378
What is repolarisation?
Return of membrane potential difference to more negative inside the cell than outside.
379
What causes repolarisation?
Diffusion of K+ out of the cell down their concentration gradient.
380
What is hyperpolarisation?
Overshoot of membrane potential difference so that inside is more negative than outside than at resting potential.
381
What happens in the neurone membrane at -70mV?
Voltage-gated K+ channels close
382
What causes hyperpolarisation?
Voltage-gated K+ channels only close at -70mV so K+ continues to diffuse out of the cell.
383
What is the refractory period?
A short period of time after an action potential when it is impossible to stimulate the membrane into another action potential.
384
What are the 2 purposes of the refractory period?
What are the 2 purposes of the refractory period?
385
What is a local current in a neurone?
Diffusion of Na+ from point of entry to area of low concentration adjacent to the next region of membrane.
386
What is an electrochemical gradient?
A concentration gradient of ions
387
What is saltatory conduction in a neurone?
Elongated local currents in myelinated neurones so that action potentials only occur at nodes of Ranvier.
388
How does changing the intensity of the stimulus affect the action potential?
Makes them more frequent.
389
What is a synapse?
A junction between 2 or more neurones.
390
What is a synaptic cleft?
A small gap between 2 neurones.
391
What is a synaptic cleft?
A small gap between 2 neurones.
392
What is a neurotransmitter?
A chemical released from the pre-synaptic neurone that causes a new action potential in the post-synaptic neurone.
393
What are 4 examples of neurotransmitters?
Acetylcholine, adrenaline, dopamine, GABA
394
Name one example of an excitatory neurotransmitter.
Acetylcholine
395
Name one example of an inhibitory neurotransmitter.
GABA
396
What is the difference between excitatory and inhibitory neurotransmitters?
Excitatory: causes depolarisation of postsynaptic neurone, causes action potential to be triggered; Inhibitory: causes hyperpolarisation of postsynaptic neurone, prevents action potential to be triggered
397
What is a cholinergic synapse?
A synapse that uses acetylcholine as a neurotransmitter.
398
What are the 4 specialisations of the pre-synaptic bulb?
Many mitochondria, complex SER, many vesicles containing neurotransmitter, voltage-gated Ca2+ channels
399
What is the specialisation of the post-synaptic membrane?
Neurotransmitter-gated Na+ channels
400
What is acetylcholinesterase?
Enzyme that hydrolyses acetylcholine into acetic acid and choline.
401
"What is the ""all or nothing"" principle?"
Each action potential is the same size and intensity.
402
What is an excitatory post-synaptic potential (EPSP)?
A small depolarisation in the post-synaptic neurone caused by a small number of neurotransmitter molecules being released from the pre-synaptic neurone.
403
What is summation?
The reaching of threshold potential in the post-synaptic neurone due to the combination of several EPSPs.
404
What is temporal summation?
The reaching of threshold potential in the post-synaptic neurone due to the combination of several EPSPs consecutively from the same pre-synaptic neurone.
405
What is spatial summation?
The reaching of threshold potential in the post-synaptic neurone due to the combination of several EPSPs from the several different pre-synaptic neurones.
406
What is an inhibitory post-synaptic potential (IPSP)?
A small hyperpolarisation in the post-synaptic neurone caused by a small number of neurotransmitter molecules being released from the pre-synaptic neurone.
407
What are the 2 divisions of the nervous system?
Central, peripheral
408
What are the 2 organs of the central nervous system?
Brain, spinal cord
409
What organ connects the central and peripheral nervous systems?
Spinal cord
410
What type of neurones is the brain mostly composed from?
Relay
411
What are the 2 divisions of the peripheral nervous system?
What are the 2 divisions of the peripheral nervous system?
412
What are the 2 divisions of the motor nervous system?
Somatic, autonomic
413
What is the function of the somatic nervous system?
Conduct action potentials to effectors that are under voluntary / conscious control.
414
What are 2 structural features of the somatic nervous system?
Mostly myelinated neurones, single neurone connects CNS to effector
415
What effectors are controlled by the somatic nervous system?
Skeletal muscles
416
What is the function of the autonomic nervous system?
Conduct action potentials to effectors that are not under voluntary / conscious control.
417
What are 3 structural features of the autonomic nervous system?
Mostly non-myelinated neurones, at least 2 neurones connects CNS to effector, connections between neurones called ganglia
418
What 3 effectors are controlled by the autonomic nervous system?
Smooth muscle, glands, cardiac muscle
419
What are the 2 divisions of the autonomic nervous system?
Sympathetic, parasympathetic
420
What is the function of the sympathetic nervous system?
Prepare the body for activity.
421
What is the function of the parasympathetic nervous system?
Conserve energy.
422
What are 3 effects of the sympathetic nervous system being more active than the parasympathetic nervous system?
What are 3 effects of the sympathetic nervous system being more active than the parasympathetic nervous system?
423
What are 3 effects of the parasympathetic nervous system being more active than the sympathetic nervous system?
Decreased heart rate, decreased ventilation rate, increased digestion
424
What are 3 structural features of the sympathetic nervous system?
Ganglia close to CNS, 1:1 nerve:effector ratio, acetylcholine as neurotransmitter
425
What are 3 structural features of the parasympathetic nervous system?
Ganglia close to effector, 1:many nerve:effector ratio, noradrenaline as neurotransmitter
426
What are 4 main regions of the brain?
Cerebrum, cerebellum, hypothalamus / pituitary complex, medulla oblongata
427
What is the function of the cerebrum?
Coordinates higher functions such as conscious thought & actions, emotions, speech and memory.
428
What part of the brain connects the 2 cerebral hemispheres?
Corpus callosum
429
What are the 4 lobes of the cerebrum?
Frontal, parietal, temporal, occipital
430
What are the 3 areas found in each lobe of the cerebrum?
Sensory, association, motor
431
What is the function of the cerebellum?
Coordinates balance and fine movement control.
432
What part of the brain connects the cerebellum to the cerebrum?
Pons
433
What is the function of the hypothalamus / pituitary complex?
Coordinates homeostatic mechanisms such as thermoregulation and osmoregulation.
434
What is the function of the medulla oblongata?
Coordinates physiological processes such as heart rate, blood pressure and ventilation rate.
435
What is a reflex action?
A response that requires no processing from the brain.
436
What are 2 examples of a reflex action?
Blinking,/knee jerk/spinal/cramial/corneal
437
What is a cranial reflex?
A reflex action with a nervous pathway through the brain.
438
What is a spinal reflex?
A reflex action with a nervous pathway through the spinal cord.
439
What does a corneal reflex do?
A reflex action with a nervous pathway through the brain, causing the eyelid to blink.
440
What part of the medulla oblongata controls heart rate?
Cardiovascular centre
441
What are 2 stimuli that would lead to an increase in heart rate?
Muscle stretch, low blood pH
442
What is a stimulus that would lead to a decrease in heart rate?
High blood pressure
443
What are the 3 types of muscle?
Skeletal, smooth, cardiac
444
What are 3 features used to identify smooth muscle?
Small, discrete cells, non-striated, longitudinal / circular layers
445
What are 3 features used to identify cardiac muscle?
Long, branched fibres, striated, intercalated discs
446
What is an intercalated disc?
Specialised cell surface membrane that allow action potentials to be easily conducted.
447
What are 3 features used to identify skeletal muscle?
Long, unbranched fibres, striated, multinucleate
448
What is a sarcolemma?
Cell surface membrane of a muscle fibre.
449
What is a sarcoplasm?
Cytoplasm of a muscle fibre.
450
What is a sarcoplasmic reticulum?
Endoplasmic reticulum of a muscle fibre.
451
What is the sarcomere?
The distance between the two Z lines, where the filaments are held together.
452
What happens when the muscle contracts?
Contraction of sacromeres as the myosin and actin filaments slide over on another.
453
Decribe the structure of the myosin filaments?
They have globular heads and are hinged so they can move back and forth, with a binding site for actin and a binding site for ATP.
454
Describe the structure of a actin filament?
They have binding sites for myosin heads, called actin-myosin binding sites.
455
Describe the sliding filament hypothesis of muscle contraction?
During contraction of the muscle the light band and H zone gets shorter so the Z lines move closer together and the sacromere gets shorter.
456
What causes a muscle contraction?
The myosin heads attach to the actin and move causing the actin filament to slide past the myosin filament.
457
What does tropomysin do in a resting muscle?
It blocks the actin-myosin binding site, so the myosin heads cannot bind to the actin for muscle contraction
458
What triggers a muscle contraction in the sacromere?
An action potential from a motor neurone tiggers an influx of Calcium ions.
459
What is the function of Ca ions in triggereing a muscle contraction?
They bind to troponin, changing it's shape pulling the attached tropomycin out of the actin-myosin binding site.
460
How is ATP released to provide the energy for a muscle contraction?
Calcium ions activate the enzyme ATPase.
461
When ATP is hydrolysed in the sacromere, what does it trigger?
Provides energy for the myosin head to return to its original position
462
What is the endocrine system?
A communication system using hormones as signalling molecules.
463
What are the 2 types of hormone?
Steroid, non-steroid
464
Name 3 examples of non-steroid hormones.
Adrenaline, insulin, glucagon
465
Name 2 examples of steroid hormones.
Oestrogen, testosterone
466
What are the 2 types of gland?
Endocrine, exocrine
467
Where does an endocrine gland secrete into?
Blood
468
Where does an exocrine gland secrete into?
Through ducts into organs or surface of body
469
Name 3 examples of endocrine glands.
Pituitary, adrenal, pancreas, (thyroid, ovaries, testes)
470
Name 3 examples of exocrine glands.
Salivary, liver, pancreas, (stomach)
471
What is a target cell of a hormone?
A cell in which the hormone causes an effect.
472
What do target cells of non-steroid hormones have?
Complementary receptors on their cell surface membrane.
473
What is a first messenger?
A non-steroid hormone.
474
What is a second messenger?
A signalling molecule that stimulates a change in a cell.
475
Name an example of a second messenger.
cAMP
476
What are the 2 main regions of the adrenal gland?
Adrenal cortex, adrenal medulla
477
What hormone is secreted from the adrenal medulla?
Adrenaline / noradrenaline
478
What type of hormone is adrenaline?
Non-steroid
479
Name 3 target cells of adrenaline.
Smooth muscle, cardiac muscle, hepatocyte
480
Name 7 effects of adrenaline on the body.
Increased tidal volume, increased stroke volume, increased heart rate, vasoconstriction, pupil dilation, piloerection, inhibition of digestion
481
What is the function of noradrenaline?
Works with adrenaline to respond to stress
482
What is the function of the androgens(sex hormones)?
Regulate the production of gametes and development of secondary sexual characteristics.
483
Name 2 examples of androgens.
Oestrogen, testosterone
484
What are the exocrine glands found in the pancreas?
Acini
485
What is secreted by acini?
Digestive enzyme precursors
486
What enzymes are found in the pancreatic duct?
pancreatic amylase, trpsinogen and lipase
487
What are the endocrine glands found in the pancreas?
Islets of Langerhans
488
What 2 cells make up the islets of Langerhans?
Alpha, beta
489
What hormone is secreted by the alpha cells of the islets of Langerhans?
Glucagon
490
What hormone is secreted by the beta cells of the islets of Langerhans?
Insulin
491
What range of blood glucose concentration is considered normal?
4-6 mmol dm-3 OR 90mg 100cm-3
492
What hormone is secreted if blood glucose concentration is above normal?
Insulin
493
What hormone is secreted if blood glucose concentration is below normal?
Glucagon
494
What is the effect of insulin on blood glucose concentration?
Decrease
495
What is the effect of glucagon on blood glucose concentration?
Increase
496
What are the 2 target cells of insulin?
Hepatocytes, muscle cells
497
What 4 effects does insulin have on its target cells?
Glucose transporter proteins added to cell surface membrane, glycogenesis, glucose converted to lipids / proteins, increased rate of cellular respiration
498
How does insulin cause an affect on target cells?
Insulin binds to the glycoprotein receptor, which causes a conformational change in the glucose transport protein channels (part of a complex with the receptor); 2. Activates enzymes to convert glucose to glycogen and fat
499
What is glycogenesis?
Condensation of glucose molecules to form glycogen.
