chapter 4,5 Flashcards
(227 cards)
1
Q
how does temp affect membrane structure?
A
-Low temperatures:
Phospholipids pack closely, membrane becomes rigid.
Proteins may deform, affecting membrane function.
-High temperatures:
Phospholipids gain kinetic energy, move more, membrane becomes fluid.
High temperatures can denature membrane proteins, leading to loss of structure and permeability.
2
Q
how does solvents affect membrane structure?
A
-Polar solvents (e.g., water):
Maintain the membrane structure by interacting with phospholipid heads.
-Non-polar solvents (e.g., ethanol):
Disrupt phospholipids, dissolve the membrane, increasing permeability.
3
Q
how does ph affect membrane structure?
A
Extreme pH levels can affect membrane proteins by disrupting their bonds and altering their structure.
4
Q
how does saturated or Unsaturated fatty acids affect membrane structure?
A
Saturated vs. Unsaturated fatty acids:
-Membranes with more unsaturated fatty acids are more fluid (kinks in tails prevent tight packing).
-Saturated fatty acids make the membrane more rigid
5
Q
how does cholorestrol affect membrane structure?
A
-At high temperatures: Stabilizes the membrane by reducing fluidity.
-At low temperatures: Prevents the membrane from becoming too rigid by preventing phospholipids from packing too tightly.
6
Q
Diffusion:
A
The net movement of particles from a region of high concentration to a region of low concentration, down a concentration gradient.
It is a passive process (no energy required).
7
Q
Factors Affecting Diffusion Rate:
A
-Concentration Gradient
Steeper gradient = faster diffusion.
-Temperature
Higher temperature = particles move faster = faster diffusion.
-Surface Area
Larger surface area = faster diffusion.
-Thickness of Membrane
Thinner membrane = faster diffusion.
-Size of Molecules
Smaller molecules diffuse faster.
-Nature of Molecules
Lipid-soluble molecules diffuse more easily through cell membranes.
8
Q
where does diffusion occur
A
Occurs in Gases and Liquids
Particles are free to move.
9
Q
What is facilitated diffusion?
A
Facilitated diffusion is the passive movement of large molecules or ions across a membrane via specific transport proteins, from a region of higher concentration to a region of lower concentration.
10
Q
Is facilitated diffusion an active or passive process?
A
Facilitated diffusion is a passive process and does not require energy (ATP)
11
Q
What types of transport proteins are involved in facilitated diffusion?
A
Channel Proteins: Form pores in the membrane for specific ions (e.g., Na⁺, K⁺).
- gated ( part of the channel protein on the inside surface of the membrane can move in order to close or open the pore) allows to control the exchange of ions
Carrier Proteins: Bind to specific molecules (e.g., glucose) and change shape to transport them across the membrane
12
Q
What types of molecules require facilitated diffusion?
A
Large, polar molecules (e.g., glucose, amino acids).
Charged particles/ions (e.g., Na⁺, K⁺, Cl⁻).
13
Q
What factors affect the rate of facilitated diffusion?
A
-Concentration Gradient: Steeper gradient = faster diffusion.
-Number of Transport Proteins: More proteins = faster diffusion, but saturation can occur.
-Temperature: Higher temperature = faster movement of molecules.
-Size and Charge of Molecules: Larger or charged molecules require transport proteins
14
Q
Give two biological examples of facilitated diffusion.
A
Glucose Uptake in Cells: Carrier proteins transport glucose into cells for respiration.
Ion Movement in Neurons: Channel proteins allow Na⁺ and K⁺ ions to move during nerve impulse transmission.
15
Q
What is active transport?
A
movement of molecules or ions across a membrane from a region of lower concentration to a region of higher concentration, against the concentration gradient, using energy (ATP).
16
Q
What is required for active transport to occur?
A
-Energy (ATP): To power the process.
-Carrier Proteins: To transport molecules or ions across the membrane.
17
Q
How does active transport differ from facilitated diffusion?
A
Active Transport Moves substances against the concentration gradient and requires energy (ATP).
Facilitated Diffusion Moves substances down the concentration gradient and does not require energy.
18
Q
What factors affect the rate of active transport?
A
-Energy Availability (ATP): More ATP = faster transport.
-Number of Carrier Proteins: More proteins = faster transport.
-Specificity of Carrier Proteins: Proteins are specific to the molecules they transport.
19
Q
Why is active transport important in cells?
A
-Allows uptake of essential nutrients (e.g., glucose, ions) even when in lower external concentrations.
-Maintains concentration gradients essential for processes like nerve impulses and osmoregulation.
20
Q
process of active transport
A
1)The molecule or ion to be transported binds to a specific carrier protein in the cell membrane.
2)ATP is hydrolyzed to release energy, converting ATP into ADP and a phosphate group.
3)The energy causes the carrier protein to change shape, allowing the molecule or ion to be transported across the membrane.
4)the carrier protein returns to its original shape, ready to transport another molecule or ion.
5)Each carrier protein is specific to the molecule or ion it transports, ensuring selective movement across the membrane.
21
Q
Why does active transport stop if ATP is unavailable?
A
ATP provides the energy required for the carrier proteins to change shape and transport molecules, so without ATP, active transport cannot occur.
22
Q
What is bulk transport?
A
Bulk transport is the process by which large molecules or particles are moved into or out of a cell, typically using vesicles, and requires energy (ATP).
23
Q
What types of molecules are transported by bulk transport?
A
Large molecules (e.g., proteins, polysaccharides) or even entire cells (e.g., bacteria) that cannot pass through the membrane by simple or facilitated diffusion.
24
Q
What are the two main types of bulk transport?
A
Endocytosis: Movement of substances into the cell.
Exocytosis: Movement of substances out of the cell.
25
What is endocytosis?
cells engulf large particles or liquids by wrapping the plasma membrane around them, forming a vesicle that is brought into the cell
26
What are the two main types of endocytosis?
-Phagocytosis: Engulfment of solid particles (e.g., white blood cells engulfing bacteria).
-Pinocytosis: Engulfment of liquid or dissolved substances.
27
What is exocytosis?
cells expel substances by vesicles fusing with the plasma membrane, releasing their contents outside the cell.
28
What is the role of vesicles in bulk transport?
Vesicles are membrane-bound sacs that transport substances either into or out of the cell during bulk transport processes (endocytosis and exocytosis).
29
What happens during pinocytosis?
The cell "drinks" extracellular fluid and its dissolved substances by pinching off part of the plasma membrane to form a vesicle
30
Why is bulk transport important for cells?
Bulk transport allows cells to take in large molecules, like nutrients or immune system molecules, and expel waste products or secreted substances, such as hormones and enzymes.
31
What is osmosis?
Osmosis is the passive movement of water molecules across a semi-permeable membrane, from an area of higher water concentration to an area of lower water concentration (potential).
-passive
32
What is hypotonic solution in osmosis?
A hypotonic solution has a lower solute concentration and a higher water potential compared to the inside of the cell. Water enters the cell, causing it to swell.
33
What is hypertonic solution in osmosis?
has a higher solute concentration and a lower water potential compared to the inside of the cell. Water leaves the cell, causing it to shrink.
34
What is isotonic solution in osmosis?
has the same solute concentration as the inside of the cell. There is no net movement of water in or out of the cell, and the cell remains the same size.
35
What happens to a plant cell in a hypotonic solution?
The plant cell gains water, becomes turgid (swollen), but the cell wall prevents it from bursting.
Volume of plant cell increases,expanding protoplast pushes against cell wall, Cell wall withstand increased pressure created, pressure increase until cell turgid.
36
What happens to an animal cell in a hypotonic solution?
The animal cell gains water, swells, and may burst (lysis) if the excess water is not regulated.
37
What happens to a plant cell in a hypertonic solution?
The plant cell loses water, causing the cell membrane and protoplast to pull away from the cell wall, a process called plasmolysis.
38
What happens to an animal cell in a hypertonic solution?
The animal cell loses water, shrinks, and may become crenated (shriveled).
39
What happens to water potential when solutes are added to water?
When solutes are added to water, the water potential becomes more negative because solute potential (Ψs) decreases.
40
What is the water potential of pure water?
The water potential of pure water is 0 (zero), as it has no solutes and no pressure.
41
How does water move in relation to water potential?
Water moves from an area of higher water potential (less negative) to an area of lower water potential (more negative).
42
What are enzymes?
Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process. They are usually globular proteins and lower the activation energy required for reactions to occur
43
What is the lock and key model of enzyme action?
The lock and key model suggests that the enzyme’s active site has a specific shape that exactly fits the substrate, like a key fitting into a lock. This model explains the enzyme's specificity
44
What is the induced fit model of enzyme action?
The induced fit model suggests that when the substrate binds to the enzyme's active site, the enzyme changes shape slightly to fit the substrate more snugly, enhancing the catalytic process.
45
How does temperature affect enzyme activity?
-At low temperatures, enzyme activity is slow because molecules move more slowly.lower frequency of successful collisions
-At optimal temperatures, enzyme activity is highest.
-High temperatures can denature enzymes, causing the active site to change shape permanently and lose its functionality.
46
How does pH affect enzyme activity?
-Enzymes have an optimal pH at which they work -best.
-(disrupts the Ability to bind with the enzyme so reducing number of successful collisions)
Extreme pH levels can denature enzymes by altering the shape of the active site, by breaking the hydrogen and ionic bond
47
what is enzyme-substrate specificity?
Enzyme-substrate specificity refers to the fact that each enzyme can only catalyze a specific type of reaction due to the precise fit between the enzyme's active site and the substrate.
48
What is the role of coenzymes and cofactors in enzyme activity?
-Coenzymes are organic molecules (e.g., vitamins) that assist enzymes in catalyzing reactions by carrying electrons or groups between enzyme
-Cofactors are inorganic ions (e.g., metal ions like Zn²⁺ or Mg²⁺) that help enzymes maintain their active site structure or participate in the reaction.
49
What is competitive inhibition?
Competitive inhibition occurs when a molecule similar to the substrate binds to the enzyme’s active site, preventing the substrate from binding and reducing the rate of the reaction.
50
What is non-competitive inhibition?
Non-competitive inhibition occurs when an inhibitor binds to a site other than the enzyme's active site (allosteric site), causing a conformational change in the enzyme that reduces its ability to catalyze the reaction
51
How do coenzymes differ from metal ion cofactors?
-Coenzymes are organic molecules, usually derived from vitamins, and participate directly in the reaction by carrying atoms or electrons.
-Metal ion cofactors are inorganic ions that help stabilize enzyme structures or assist in the reaction by providing or accepting electrons.
52
what are prosthetic group
cofactors and required by certain enzymes to carry out their catalytic function.
- non-protein, tightly bound, and often permanent component of an enzyme
53
How do prosthetic groups differ from coenzymes?
-Prosthetic groups are tightly or permanently attached to the enzyme.
-Coenzymes are loosely bound and often detach after the reaction to be reused.
54
How do coenzymes work in enzyme catalysis? and can be reused?
Coenzymes often act as carriers, transferring atoms, electrons, or functional groups between enzymes in metabolic pathways. For example, NAD⁺ carries electrons during cellular respiration.
-coenzymes can be recycled and reused in multiple enzyme reactions, unlike prosthetic groups, which are usually permanently attached to the enzyme.
55
What is precursor activation?
Precursor activation is the process by which an inactive precursor enzyme is converted into an active enzyme. This activation is often triggered by changes in environmental conditions or by other molecules.
56
What are intracellular enzymes?
Intracellular enzymes are enzymes that function inside the cell, catalyzing biochemical reactions within various cellular compartments, such as the cytoplasm, mitochondria, or nucleus.
57
How do intracellular enzymes differ from extracellular enzymes?
Intracellular enzymes act within the cell to catalyze metabolic reactions, while extracellular enzymes are secreted from cells to catalyze reactions outside the cell (e.g., digestive enzymes).
58
What are extracellular enzymes?
Extracellular enzymes are enzymes secreted by cells into the extracellular space, where they catalyze biochemical reactions outside the cell, such as digestion or breakdown of organic materials.Eg amylase, ound in saliva and the pancreas that breaks down starch into simpler sugars in the digestive system.
59
What is the digestion of starch?
1)Starch digestion involves the breakdown of starch (a polysaccharide) into smaller sugars, primarily glucose, to be absorbed by the body for energy.
2) Salivary amylase is the enzyme secreted by the salivary glands that begins the digestion of starch into maltose (a disaccharide) in the mouth-and the pancreas (pancreatic amylase) to continue starch digestion in the small intestine.
3)Starch digestion is temporarily halted in the stomach due to the acidic environment, which deactivates salivary amylase.
4)Pancreatic amylase continues the digestion of starch into maltose in the small intestine.
5) Maltase then breaks down maltose into glucose, which can be absorbed.
6)Glucose is absorbed through the walls of the small intestine into the bloodstream, where it is transported to cells for energy production.
60
What is the digestion of protein?
1)Pepsin is the enzyme that starts protein digestion in the stomach. It is secreted as pepsinogen, which is activated by stomach acid into pepsin.
2) Pepsin breaks proteins down into smaller polypeptides by cleaving peptide bonds between amino acids.
3)In the small intestine, the enzyme trypsin, secreted as trypsinogen by the pancreas, continues the breakdown of polypeptides into smaller peptides and amino acids.
4)he small intestine, further breaks down peptides into individual amino acids, which can then be absorbed into the bloodstream.
5)Amino acids are absorbed through the walls of the small intestine via active transport and enter the bloodstream for distribution to body cells.
61
What are the end products of starch and protein digestion?
-The end products of starch digestion are glucose molecules
- the end products of protein digestion are amino acids.
62
How does substrate concentration affect enzyme activity?
As substrate concentration increases, the rate of reaction increases because more substrate molecules are available for the enzyme to act upon. However, once all enzyme active sites are occupied, the rate of reaction levels off (this is called saturation).
63
substate concentration linked with enzyme activity
At high substrate concentrations, enzyme activity levels off because all active sites of the enzymes are occupied, and adding more substrate does not increase the rate of reaction. This is called enzyme saturation.
At low substrate concentrations, the rate of reaction increases nearly proportionally with an increase in substrate concentration, as there are plenty of free enzyme active sites.
64
How do inhibitors affect enzyme activity?
Inhibitors reduce or prevent enzyme activity. They can bind to the enzyme's active site (competitive inhibition) or bind elsewhere on the enzyme (non-competitive inhibition), altering its shape.
65
Describe the process of phagocytosis in the immune response.
Phagocyte (e.g., macrophage) detecting and engulfing pathogens.
The pathogen is enclosed in a phagosome.
A lysosome fuses with the phagosome to release digestive enzymes, breaking down the pathogen.
The phagocyte presents antigen fragments on its surface, triggering an immune response.
66
What is the importance of antigen presentation in the immune response?
Antigen presentation involves displaying pathogen-derived antigens on the surface of phagocytes, which activates helper T cells (TH cells). This is crucial for initiating the adaptive immune response, leading to B cell activation and the production of antibodies.
67
What are the roles of B cells and T cells in the immune response?
B cells: Produce antibodies specific to pathogens, leading to the destruction or neutralization of the pathogen.
T cells:
Helper T cells (TH cells) activate B cells and cytotoxic T cells.
Cytotoxic T cells (TC cells) kill infected cells by inducing apoptosis (cell death).
68
How do antibodies help in protecting the body from infections?
Vaccine?
Vaccines contain weakened or inactive forms of pathogens or their antigens. When introduced into the body, they stimulate the primary immune response to produce memory cells without causing disease, (artifical active immunity)This leads to long-term immunity, allowing the body to respond quickly if exposed to the pathogen in the future.
69
What is the role of the lymphatic system in immunity?
The lymphatic system transports lymph, which contains immune cells such as lymphocytes. It helps to filter out pathogens and debris, and it transports immune cells to sites of infection to mount an immune response.
70
What are antibiotics, and what is antibiotic resistance?
Antibiotics are chemicals used to kill or inhibit the growth of bacteria. Antibiotic resistance occurs when bacteria evolve mechanisms to survive the effects of antibiotics, making infections harder to treat.
71
What are neutrophils, and what is their primary function in the immune response?
Neutrophils are a type of white blood cell and are a key part of the innate immune system. Their primary function is to phagocytose pathogens, especially bacteria, and to destroy them using enzymes in their lysosomes.
72
What are the key characteristics of neutrophils that enable them to carry out their function?
Neutrophils are characterized by:
Multi-lobed nuclei, which allow for flexibility and easier movement through tissues.
Granules containing enzymes (e.g., lysozyme) that help break down pathogens after phagocytosis.
High number of lysosomes, which are used to digest engulfed pathogens.
73
Describe the process of how neutrophils respond to an infection.
Neutrophils:
Chemical released by pathogen attracts neutrophils (chemotaxis)
Neutrophils have receptor proteins on their surfaces that recognise antibody molecules and attach to them
Engulf pathogens via phagocytosis, forming a phagosome.
Fuse the phagosome with lysosomes to form a phagolysosome.
Digest the pathogen using enzymes and release the waste products.
After killing pathogen, neutrophil dies (pus is sign of dead neutrophil)
74
What are antigen-presenting cells, and what role do they play in the immune system?
Antigen-presenting cells (APCs) are cells that process and present antigens on their surface to stimulate an adaptive immune response. They include dendritic cells, macrophages, and B cells. APCs display antigens in association with major histocompatibility complex MHC. Stimulate T cell
can be recognised by lymphocytes
75
Explain the role of MHC molecules in antigen presentation.
MHC class II molecules are found on the surface of APCs and bind to processed antigens from pathogens. These molecules present the antigen to helper T cells (TH cells), which then become activated and stimulate other immune responses (e.g., activating B cells to produce antibodies).
76
What are cytokines, and what is their role in the immune response?
Cytokines are small signaling proteins released by immune cells (e.g., macrophages, T cells) that regulate the immune response. They help to:
Stimulate the activity of other immune cells.
Recruit immune cells to the site of infection (chemotaxis).
Enhance the inflammatory response to infections.
77
How do cytokines contribute to inflammation during an infection?
Cytokines promote inflammation by:
Increasing blood flow to the infected area, leading to redness and warmth.
Increasing vascular permeability, allowing immune cells and proteins to enter the tissue.
Stimulating fever, which helps inhibit pathogen growth.
78
What are opsonins, and how do they assist in the immune response?
Opsonins are molecules (e.g., antibodies, complement proteins) that bind to pathogens, marking them for easier recognition and phagocytosis by immune cells such as neutrophils and macrophages.
79
What is a phagosome, and what role does it play in the immune response?
A phagosome is a vesicle formed when a phagocyte engulfs a pathogen during phagocytosis. The phagosome contains the pathogen and is transported to lysosomes for digestion and destruction of the pathogen
80
What is the function of lysosomes in the immune response?
Lysosomes are organelles in immune cells that contain digestive enzymes (e.g., lysozyme, proteases). They fuse with phagosomes to form a phagolysosome, where the pathogen is broken down and destroyed through enzymatic digestion
81
What are the key steps involved in phagocytosis by neutrophils or macrophages?
The key steps are:
Chemotaxis: Neutrophils are attracted to the site of infection by cytokines.
Recognition and engulfment: The phagocyte recognizes the pathogen and engulfs it into a phagosome.
Fusion with lysosome: The phagosome fuses with a lysosome, forming a phagolysosome.
Digestion: Pathogens are digested and broken down by enzymes inside the phagolysosome.
Exocytosis: Waste products are expelled from the phagocyte.
82
How do phagosomes and lysosomes work together to eliminate pathogens?
After a pathogen is engulfed by a phagocyte, the phagosome forms and contains the pathogen. It then fuses with a lysosome, which contains digestive enzymes. The lysosome breaks down the pathogen inside the phagolysosome, destroying it and allowing the cell to remove the waste products
83
What is the significance of cell signalling in the immune response?
Cell signalling allows immune cells to communicate and coordinate their responses. It enables the activation, differentiation, and regulation of cells involved in the immune response, ensuring a targeted and effective defense against pathogens. Interleukins, which are cytokines, play a crucial role in cell signalling by facilitating communication between immune cells.
84
What are interleukins, and what role do they play in the immune system?
Interleukins are a group of cytokines that act as cell-signalling molecules. They mediate communication between immune cells, regulate the immune response, and help in the activation and differentiation of lymphocytes (e.g., B cells and T cells). Interleukins are essential for T helper cell activation and B cell proliferation.
85
86
87
88
Directions of blood
Body to lungs (deoxygenated blood)
Inferior vena cava, right atrium, tricuspid valve, right ventricle, pulmonary valve, pulmonary artery, lungs
Lungs to body
Lungs, pulmonary veins, left atrium, bicuspid valve,left ventricle, aortic valve, aorta
89
What are the main stages of the cell cycle?
1. Interphase (G1, S, G2)
2. Mitosis (Prophase, Metaphase, Anaphase, Telophase)
3. Cytokinesis
90
Q: What happens during interphase?
• G1 (Gap 1): Cell growth, organelle synthesis, biosynthesis (e.g., protein production).
• S (Synthesis): DNA replication (semi-conservative replication).
• G2 (Gap 2): Further growth, energy stores increase, DNA checked for errors.
91
What are the three key cell cycle checkpoints and their roles?
• G1 Checkpoint: Ensures cell size, nutrient availability, and checks for DNA damage before S phase.
• G2 Checkpoint: Ensures DNA has replicated correctly before mitosis.
• M Checkpoint (Spindle Assembly Checkpoint): Ensures chromosomes are correctly attached to spindle fibers before anapha
92
Why is mitosis important?
• Growth: Produces new cells for growth in multicellular organisms.
• Repair: Replaces damaged or dead cells.
• Asexual reproduction: Produces genetically identical offspring (e.g., in unicellular organisms).
• Genetic stability: Daughter cells are genetically identical to parent cell.
93
What happens during prophase?
Chromosomes condense and become visible, into chromotids.
• Nuclear envelope breaks down.
-nucleolus disappears
• Centrioles move to opposite poles.
• Spindle fibers begin to form from centrioles.
94
What happens during metaphase?
.-centrioles reaches opposite poles
• Chromosomes align at the equator, metaphase plate
.spindle e fibers attach to centromeres.
• The spindle assembly checkpoint ensures correct attachment before progression to anaphase
95
What happens during anaphase?
• Spindle fibers contract, pulling sister chromatids apart.
Each chromatid becomes a separate chromosome.
• Chromatids move to opposite poles of the cell by spindle fibres
96
What happens during telophase?
-chromosomes arrive at opposite pole
• Chromosomes decondense (uncoil).
• Nuclear envelope reforms around each set of chromosomes.
• Spindle fibers break down.
- new nucleoi forms with nucleus
97
How does cytokinesis differ in animal and plant cells?
• Animal cells: Cleavage furrow forms, cell membrane pinches inward, cytoplasm divides.
• Plant cells: Vesicles from the Golgi apparatus form a cell plate, which develops into a new cell wall.
98
Why is meiosis important?
• Produces haploid gametes to maintain chromosome number during fertilization.
• Genetic variation via crossing over (prophase I) and independent assortment (metaphase I & II).
99
What happens during prophase I?
• Chromosomes condense, becoming visible.
• Homologous chromosomes pair up to form bivalents.
• Crossing over of non sister chromtids occurs called chiasma, leading to genetic recombination.
• Nuclear envelope breaks down.
- nucleolus disintegrates
• centrioles move to opp pole and spindle fibers begin to form.
100
What happens during metaphase I?
• Bivalents align at the equator.
• The maternal and paternal chromosomes in each pair position themselves independently of the others, Independent assortment of homologous chromosomes occurs leads to genetic variation.
• Spindle fibers attach to centromeres.
101
What happens during metaphase I?
• Bivalents align at the equator.
• Independent assortment of homologous chromosomes leads to genetic variation.
• Spindle fibers attach to centromeres.
102
What happens during anaphase I?
homologous pairs of chromosomes are separated as pulled by micro tubules
Centromere dont divide
103
• What happens during telophase I and cytokinesis?
Telophase:
- chromosome arrive at opp poles
Spindle fibre break down
• Nuclear envelope reforms (sometimes).
• Cytoplasm divides, forming two haploid cells.
104
What happens during prophase II?
• Chromosomes condense.
• Nuclear envelope breaks down.
• Spindle fibers reform.
105
What happens during metaphase II?
Chromosomes align at the equator.
• Spindle fibers attach to centromeres.
106
What happens during anaphase II?
Sister chromatids separate and move to opposite poles creating 4 groups of chromosomes
107
What happens during telophase II and cytokinesis?
• Chromosomes decondense.
• Nuclear envelope reforms around each grip of chromosome
Cytokinesis
Cytoplasm divides as new cell surface membranes are formed creating four haploid cells
108
109
What is crossing over, and why is it important?
• Homologous chromosomes form bivalents and exchange genetic material at chiasmata.
• Increases genetic variation in gametes.
110
How does independent assortment generate genetic variation?
• Homologous chromosomes align randomly at the equator in metaphase I.
• Sister chromatids also align randomly in metaphase II.
• Leads to different combinations of maternal and paternal chromosomes in gametes.
111
How does cancer develop?
• Caused by uncontrolled cell division due to mutations in proto-oncogenes or tumor suppressor genes.
• Forms a tumor (benign or malignant).
112
Enzyme concentration
High enzyme concentrations, more active site available, so more enzymes substrate complex formed
Until amount of substrate becomes limiting factor
113
Reversible inhibitors and not
- competive
slow down
-non competitive inhibitors
stop enzyme activity
114
Eg of cofactors
-inorganic ion
Chloride ion (for amylase)
115
Define a pathogen.
A microorganism that causes disease.
116
Name the four types of pathogens and an example of each.
• Bacteria – Mycobacterium tuberculosis (TB)m ring rot
• Virus – HIV (AIDS)
• Fungus – Ringworm (Cattle)
• Protoctist – Plasmodium (Malaria)
117
Describe direct transmission and give an example.
Pathogen is transmitted through direct contact between infected and uninfected individuals.
Example: HIV via sexual contact or exchange of bodily fluids.
118
Describe indirect transmission and give an example.
Pathogen is transmitted via an intermediate (vector, surface, droplet, etc.)
Example: Malaria via mosquito vector.
119
How does climate affect disease transmission?
• Warmer, humid conditions increase pathogen survival (e.g., malaria, fungal infections).
• Cold temperatures may reduce transmission (e.g., influenza spreads more in winter due to indoor crowding).
120
Name three primary non-specific defenses and how they prevent infection.
1. Skin – Physical barrier; secretes antimicrobial compounds.
2. Mucous membranes – Trap pathogens in airways, contain lysozymes.
3. Stomach acid – Kills ingested pathogens via low pH.
121
What is the role of blood clotting in defense?
Prevents entry of pathogens by forming a fibrin mesh at wound sites.
122
123
Describe the process of phagocytosis.
1. Pathogen releases chemicals → attracts phagocytes via chemotaxis.
2. Phagocyte engulfs pathogen via endocytosis into a phagosome.
3. Lysosome fuses with phagosome → forms phagolysosome.
4. Hydrolytic enzymes (e.g., lysozymes) digest pathogen.
5. Antigen presentation on phagocyte surface for T cell activation.
124
What is the role of antigen-presenting cells (APCs)?
Display pathogen antigens to activate the specific immune response.
125
What are the two types of lymphocytes, and what do they do?
• B lymphocytes → Humoral response (produce antibodies). mature in the bone marrow
• T lymphocytes → Cell-mediated response (kill infected cells, activate B cells). Mature in thymus gland
126
Describe clonal selection and clonal expansion.
• Clonal selection – Antigen binds to specific B/T cell receptor, activating it.
• Clonal expansion – Activated B/T cell undergoes mitosis to produce clones.
127
What are the roles of T helper, T killer, and T regulatory cells, T memory cell?
• T helper cells → Release interleukins (type of cytokines) to activate B cells & phagocytes.
• T killer cells → Destroy infected cells via perforins.
• T regulatory cells → Suppress immune response after infection is cleared.
T memory cell: Memory cells remain in the blood, meaning that if the same antigen is encountered again the process of clonal selection will occur much more quickly
128
129
How do antibodies help fight infections?
1. Agglutination – Clump pathogens together, reduces the chance that the pathogens will spread through the body for easier phagocytosis.
2. Neutralization – Acts as anti-toxins(binds to toxins pathogen produce).Block pathogen binding sites.
3. Opsonization – Mark pathogens,by attaching to it for phagocytosis
130
What are the four types of immunity?
1. Natural active – Gained after infection (e.g., recovering from measles).
2. Natural passive – Antibodies from mother via breast milk or placenta.
3. Artificial active – Vaccination (e.g., MMR vaccine).
4. Artificial passive – Injected antibodies (e.g., tetanus antitoxin).
131
How do vaccines provide immunity?
• Contain weakened, dead, or antigenic fragments of pathogen.
• Stimulate primary immune response → memory cells formed.
• Faster & stronger secondary response upon future exposure.
132
What is herd immunity, and why is it important?
• When a large proportion of a population is vaccinated, reducing disease spread.
• Protects those who cannot be vaccinated (e.g., newborns, immunocompromised).
133
Why must antibiotics be used correctly?
• Overuse leads to antibiotic resistance (e.g., MRSA).
• Should only be prescribed for bacterial infections, not viruses.
• Must complete full course to prevent resistant strains from surviving.
134
How can antibiotic resistance be reduced?
• Developing new antibiotics.
• Reducing unnecessary prescriptions.
• Public education on correct antibiotic use
135
What are the two main types of immune response?
1. Non-specific immune response – Immediate, general defense (e.g., phagocytosis, inflammation).
2. Specific immune response – Slower but targeted (e.g., B & T lymphocytes).
136
Name three primary non-specific defenses and their functions.
1. Skin – Physical barrier & secretes (sebum)antimicrobial compounds.
2. Mucous membranes – Trap pathogens & contain lysozymes.
3. Stomach acid – Destroys ingested pathogens with low pH.
137
How does inflammation help fight infection?
• Mast cells release histamines → vasodilation,increase blood flow, through capillaries
• Capillaries become more permeable → allows WBCs to reach infected area.
• Swelling, redness, heat → helps destroy pathogens.-
local response
138
What are the roles of different T cells?
• T helper cells → Release cytokines to activate B cells & phagocytes.
• T killer cells → Destroy infected cells by releasing perforins.
• T regulatory cells → Suppress immune response after infection is cleared.
139
How do B lymphocytes help fight infections?
1. B cells are activated by T-helper cells & antigens.
2. They differentiate into plasma cells (produce antibodies) & memory cells.
140
What is the difference between the primary and secondary immune response?
• Primary response – Slower (first exposure), B cells need time to produce antibodies.
• Secondary response – Faster & stronger (due to B memory cells).
141
What is an autoimmune disease?
When the immune system attacks self-cells, mistaking them for foreign antigens.
142
Give an example of an autoimmune disease and its cause.
• Rheumatoid arthritis → Immune system attacks joints.
• Type 1 diabetes → Immune system destroys insulin-producing β cells in pancreas.
143
144
What basal metabolic rate
the metabolic rate of an organism when at rest. The BMR is significantly lower than when an organism is actively moving
145
Features of Exchange Surfaces
Large surface area
Short diffusion distance (thin)
Good blood supply
Ventilation mechanism
146
What is counter current system
the blood flow is in the opposite direction to the flow of water
147
What exchange does fish have
Counter current system
148
Why counter current used and what is is
ensures theres always a concentration gradient is maintained along the whole surface. There is still a difference in concentration so diffusion of oxygen into the blood still occurs
149
Where does gas exchange in human takes place
Thorax , in the chest cavity
150
151
Passage of Air
Nose / mouth
Trachea (windpipe)
Bronchi
Bronchioles
Alveoli
152
Process of inspiration/inhalation
- EXTERNAL INTERCOSTAL MUSCLES CONTRACT
- RIBCAGE MOVES UP AND OUT
- DIAPHRAGM CONTRACTS AND FLATTENS
- VOLUME OF THORAX INCREASES
- PRESSURE INSIDE THORAX DECREASES (lower than the atmospheric pressure)
- AIR IS DRAWN
153
Process of expiration/exhalation
- EXTERNAL INTERCOSTAL MUSCLES RELAX
- RIBCAGE MOVES DOWN AND IN
- DIAPHRAGM RELAXES AND BECOMES DOME - SHAPED
- VOLUME OF THORAX DECREASES
- PRESSURE INSIDE THORAX INCREASES
The recoil of elastic fibres surrounding alveoli causes the air to be forced out
- AIR IS FORCED OUT
154
What is Vital capacity
maximum volume of air that can be breathed in or out in one breath
the greatest volume of air that can be expelled from the lungs after taking the deepest possible breath.
155
Tidal volume?
volume of air that is breathed in or out during normal breathing (at rest)
Measuered by difference between the top and bottom of the trace
156
Breathing rate?
number of breaths taken in one minute (one breath = taking air in and breathing it back out again)
157
Oxygen uptake?
volume of oxygen used up by someone in a given time
158
Why is co2 absorbed in spirometer
Absorbed by soda lime Removes CO₂ to prevent buildup.
159
How to find oxygen uptake in spirometer
Oxygen Uptake:Measured by decreasing air volume as oxygen is absorbed.
160
residual volume?
small amount of air is always retained in the lungs
161
Gas exchange/Tracheal system in insects
-rigid exoskeleton with a waxy coating that is impermeable to gases
-Spiracles are openings in the exoskeleton, allow air to flow into the internal system of tubes
known as the tracheal system
Tracheae tubes within the insect respiratory system which lead to narrower tubes known as tracheoles
Rigid rings of chitin keep the tracheae open
162
What are tracheae
are tubes within the insect respiratory system which lead to narrower tubes known as tracheoles
163
tracheoles in insects
Ends are filled with tracheal fluid; gases can dissolve in this fluid before diffusing to the cells for gas exchange
large number of tracheoles that are in contact with the muscle cells provides a large surface area for gas exchange
164
165
Gas exchange in insects at rest
energy requirements are low= diffusion alone is fast enough to supply oxygen to the cells so insects may close their spiracles to reduce water loss by evaporation
166
Gas exchange of insects when active
rapid supply of oxygen = rapid supply of oxygen = pressure changes inside tracheae = drawing air in and out
167
Gas exchange of insects during flight
the tracheal fluid at the narrow ends of the tracheoles is drawn into the respiring muscle = removing fluid from the tracheoles reduces the diffusion distance between the air and the muscle cells, speeding up diffusion
168
Structure of fish gills
Series of gills on each side of the head
Each gill arch is attached to two stacks of filaments
On the surface of each filament, there are rows of lamellae
The lamellae surface consists of a single layer of flattened cells that cover a vast network of capillaries
169
Gas exchange mechanginism for fish
The capillary system within the lamellae ensures that the blood flow is in the opposite direction to the flow of water - it is a counter-current system
The counter-current system ensures the concentration gradient is maintained along the whole length of the capillary
The water with the lowest oxygen concentration is found adjacent to the most deoxygenated blood
170
Ventallion mechanism in fish
• Mouth Opens → Buccal cavity floor lowers → Volume ↑, Pressure ↓
• Water Flows In (higher external pressure)
• Mouth Closes → Buccal cavity floor rises → Pressure ↑
• Water Moves from buccal cavity (high pressure) → gill cavity (low pressure)
• Operculum Opens → Water exits, ensuring oxygen-rich flow over gills
• Cycle Repeats for continuous gas exchange
171
Water flow (in pressure
always flow from an area of high pressure to an area of low pressure
172
173
Compare lungs to trachea in insects
*Similarities:*
• Thin walls → Fast diffusion
• Highly branched → Large SA: V ratio
• Supported structure → Cartilage (lungs), chitin (insects)
• Tracheal fluid & moist lining → Gas diffusion
• Ventilation movements in both
*Differences:*
• Lungs rely on pressure changes, insects use diffusion & muscle contraction
• Insects have spiracles, lungs do not
• Insects’ tracheae are not compact or linked to a circulatory system
• Oxygen carried by RBCs in lungs, but diffuses directly to cells in insects
174
175
What circulatory system does fish have
Single circulatory
176
Single circulatory system in fish
Deoxygenated blood is pumped to the gills from the heart
The gills are the exchange site where oxygen and carbon dioxide are exchanged with the atmosphere and the blood
The oxygenated blood flows from the gills to the rest of the body
It travels through the capillaries in organs, delivering oxygen and nutrients
The blood returns to the heart
The heart only has one atrium and one ventricle
177
What is the circulation called from heart lungs
Pulmonary circulation
178
What is the circulation called from heart to body
Systemic circulation
179
Advantages of double circulation
-When blood enters a capillary network the pressure and speed drops significantly
-In a double circulatory system, the blood only passes through one capillary network before returning to the heart
As a result, the double circulation maintains higher blood pressure and average speed of flow
This increased pressure and speed helps to maintain a steeper concentration gradient which allows for the efficient exchange of nutrients and waste with the surrounding tissues
180
What us double circulation
the blood passes throught the heart twice during a single circuit of the body
181
What is closed circulatory system
blood is pumped around the body and is always contained within a network of blood vessels
182
What is open circulatory system
blood is not contained within blood vessels but is pumped directly into body cavities
183
Define systemic circulatory system
Blood then returns to the left side of the heart, so that oxygenated blood can be pumped efficiently (at high pressure) around the body
184
Define pulmonary circulation system
The right side of the heart pumps blood deoxygenated blood to the lungs for gas exchange
185
Circulatory system in insects
Open circulatory system
1 main blood vessel dorsal vessel
The tubular heart,in the abdomen, pumps haemolymph (this is what blood in insects is called) into the dorsal vessel
The dorsal vessel delivers the haemolymph into the haemocoel (body cavity)
Haemolymph surrounds the organs and eventually reenters the heart via one-way valves called ostia
186
187
Structure of arteries
-three layers: tunica adventitia/externa, tunica
media and tunica intima
-tunica intima = made up of an endothelial layer, a layer of connective tissue and a layer of elastic fibres
-tunica media= made up of smooth muscle cells and a thick layer of elastic tissue
-have a thick tunica media
-layer of muscle cells strengthen the arteries so they can withstand high pressure. enables them to contract and narrow the lumen for reduced blood flow
-elastic tissue, maintain blood pressure in the arteries.
-The tunica adventitia covers the exterior of the artery and is mostly made up of collagen
-narrow lumen which helps to maintain a high blood pressure
-pulse is present
188
189
Factors affecting rate of transpiration :
Abiotic:
• ↑ Light → More stomata open → Faster transpiration.
• ↑ Temperature → ↑ ke of water molecules, ↑ rate of evaporation from spongy mesophyll into air spaces in leaf, Faster diffusion & evaporation.
• ↑ Wind → Removes humid layer around edge of leaf (boundary layer) replaced by less humid air → Increases water potential gra → Increases rate.
• ↓ Humidity → Increases water potential gra, increase rate of diffusion of h20(g) out of leaf, ↑ rate of evaporation higher rate
190
Potometer Experiment (Measuring Transpiration Rate)
• Measures water uptake, not exact transpiration rate.
• Key steps:
1. Cut stem underwater to prevent air bubbles.
2. Seal joints with petroleum jelly.
3. Introduce air bubble and measure movement.
4. Keep conditions constant (light, temp, wind).
191
What is the cohesion-tension theory?
A mechanism explaining water movement in the xylem:
• Cohesion: Water molecules stick together via hydrogen bonding, forming a continuous column.
• Tension: Transpiration pulls water up, creating negative pressure.
• Adhesion: Water sticks to xylem walls, preventing column breakage.
192
What evidence supports the cohesion-tension theory?
1. Xylem under tension: When a xylem vessel is cut, water does not leak out but air is drawn in.
2. Diameter changes: Tree trunks shrink during high transpiration due to tension in xylem.
3. Broken water column stops transport: If a xylem vessel is punctured, air enters and stops upward flow.
193
What is the role of the Casparian strip in transpiration?
Forces water into the symplast pathway, preventing harmful substances from entering the xylem
194
Why do multicellular plants require transport systems?
• Large size → Diffusion alone is too slow.
• High metabolic rate → Need efficient transport of nutrients & gases.
• Small SA:V ratio → Limits direct exchange.
195
What is the function of xylem, and what are its key components?
• Function: Transports water & minerals from roots to leaves.
• Components:
• Xylem vessels: Hollow, lignified tubes for transport.
• Tracheids: Narrower tubes for support.
• Fibers: Provide structural strength.
• Parenchyma: Stores nutrients.
196
What is the function of phloem, and what are its key components?
• Function: Transports assimilates (e.g., sucrose) via translocation.
• Components:
• Sieve tube elements: Form transport tubes, lack nuclei.
• Companion cells: Provide ATP for active transport.
• Plasmodesmata: Connect sieve tubes & companion cells.
197
What is transpiration, and why does it occur?
• Definition: Loss of water vapor via stomata due to evaporation.
• Driven by: Water potential gradient → Water moves up xylem via cohesion-tension theory.
198
What are the pathways of water movement in plants?
1. Apoplast pathway: Water moves through cell walls (fastest).
2. Symplast pathway: Water moves through cytoplasm via plasmodesmata.
3. Vacuolar pathway: Water moves through vacuoles.
199
What is the cohesion-tension theory?
• Cohesion: Water molecules stick together (hydrogen bonds).
• Tension: Transpiration pulls water up, creating negative pressure.
• Adhesion: Water sticks to xylem walls.
200
Name adaptations of xerophytes to reduce water loss.
Thick waxy cuticle: Reduces evaporation.
• Sunken stomata: Traps moist air.
• Hairy on insides of leaves: Reduces air movement.
• Rolled leaves: Traps humid air.
201
Name adaptations of hydrophytes.
• Large air spaces: Aid buoyancy.
• Stomata on upper surface: Allow gas exchange.
• Thin cuticle: Less need to prevent water loss.
202
What is translocation, and how does it work?
• Definition: Active transport of organic compounds/assimilates (e.g., sucrose) in phloem, from source to sink and requires the input of metabolic energy (ATP)
• Source: Site of sugar production (e.g., leaves).
• Sink: Site of sugar use/storage (e.g., roots)
203
Step for how sucrose is loaded apoplast route
diffuses through the cell walls to companion cells
H+ ions are pumped out of the companion cells into the cell wall space using ATP-powered proton pumps (active transport).
• This creates a proton gradient (more H+ outside than inside the cell).
• H+ ions flow back in through co-transporter proteins, bringing sucrose with them into the companion cells and then into sieve tube elements.
Result:
• Sucrose concentration increases in sieve tubes, lowering water potential.
• Water enters by osmosis from the xylem, creating high hydrostatic pressure at the source.
More commonly used
204
Process of Water Movement in the Apoplast Pathway:
1. Water enters root hair cells from the soil by osmosis.
2. Moves through the cortex via the apoplast (cell walls & spaces between cells). due to cohesive forces between water molecules:
.
3. Reaches the endodermis (surrounding vascular bundle).
4. Casparian strip blocks apoplast pathway → Forces water into the symplast pathway to regulate ions before entering the xylem.
5. Water enters the xylem via osmosis due to the water potential gradient.
205
Importance of the Apoplast Pathway:
✔ Fastest route for water transport.
✔ Ensures bulk flow of water, driven by transpiration pull.
✔ Casparian strip forces selective uptake, preventing harmful substances from reaching the xylem.
206
Key Features of the Apoplast Pathway:
1. Fastest Route – Water moves freely through the cell walls due to the absence of membrane resistance.
2. Bulk Flow – Water moves via capillary action and hydrostatic pressure, rather than osmosis.
3. Passive Movement – No metabolic energy (ATP) is required.
4. Blocked at the Endodermis – The Casparian strip in the endodermis (made of suberin) forces water into the symplast pathway, ensuring selective absorption before entering the xylem.
207
What is the cardiac cycle
the series of events that take place in one heart beat, including muscle contraction(systole) and relaxation (diastole)
208
209
Arterial systole
1) walls of the atria contract
2) Atrial volume decreases
3) Atrial pressure increases
4) pressure in the atria rises above that in the ventricles, forcing the atrioventricular (AV) valves open
5) Blood is forced into the ventricles (slight increase in ventricular pressure and chamber volume as the ventricles receive the blood from the atria)
6) The ventricles are relaxed
210
Ventricular systole
1) walls of the ventricles contract
2) Ventricular volume decreases
3) Ventricular pressure increases
4) pressure in the ventricles rises above that in the atria
This **forces the AV valves to close**, preventing back flow of blood
5) pressure in the ventricles rises above that in the aorta and pulmonary artery
This ** forces the semilunar (SL) valves open **so blood is forced into the arteries and out of the heart
211
Diastole
1) **ventricles and atria are both relaxed**
2) pressure in the ventricles **drops below that in the aorta and pulmonary artery, ** forcing the **SL valves to close**
3) The atria continue to fill with blood
**Blood returns to the heart **via the vena cava and pulmonary vein
4) Pressure in the atria rises above that in the ventricles, **forcing the AV valves open**
5) **Blood flows passively into the ventricles **without need of atrial systole
6) The cycle then begins again with atrial systole
212
Tachycardia (ecg)
When the heart beats too fast it is tachycardic
Peaks being too close
213
Bradycardia
When the heart beats too slow
Peaks being too far apart
214
Ectopic heartbeat
This condition is caused by an early heartbeat followed by a pause
215
Fibrillation
An irregular heartbeat will disrupt the rhythm of the heart
216
Formation of hydrogen carbonate ions
Carbon dioxide diffuses from the plasma into red blood cells
carbon dioxide combines with water to form H2CO3
enzyme carbonic anhydrase which catalyses the reaction between carbon dioxide and water
Carbonic acid dissociates readily into H+ and HCO3- ions. The H+ ions changes the ph. Causing heamogoblin to release oxygen
The hydrogen carbonate ions diffuse out of the red blood cell into the blood plasma where they are transported in solution
Cl- ion move into rbc to counteract the ph change (the chloride shift)
217
What is the Bohr effect?
The Bohr effect describes how an increase in carbon dioxide (CO₂) concentration lowers the affinity of hemoglobin (Hb) for oxygen, promoting oxygen release in tissues.
218
How does CO₂ cause hemoglobin to release more oxygen?
CO₂ dissolves in blood, forming carbonic acid (H₂CO₃), which dissociates into H⁺ ions. These H⁺ ions compete with O₂ for binding to hemoglobin, reducing hemoglobin’s oxygen affinity and encouraging oxygen unloading.
219
How does the Bohr effect shift the oxygen dissociation curve?
The oxygen dissociation curve shifts right under high CO₂ conditions, indicating that hemoglobin releases oxygen more readily
220
Why is the Bohr effect essential for respiration?
It ensures oxygen is released in active tissues (where CO₂ is high) to support aerobic respiration.
221
How does the Bohr effect differ in the lungs compared to respiring tissues?
• Lungs: Low CO₂ → Higher O₂ affinity → Oxygen binds to hemoglobin.
• Respiring Tissues: High CO₂ → Lower O₂ affinity → Oxygen is released.
222
Oxygen dissociation curve
LOW PARTIAL PRESSURE OF 02 at respiring tissue.
High partial pressure at lungs
-Haemoglobin has a low affinity for oxygen at low pO2, so saturation percentage is low
223
How does sucrose loading affect hydrostatic pressure?
Actively loading sucrose into sieve tubes lowers water potential, causing water to enter by osmosis and increasing hydrostatic pressure at the source.
224
What happens when sucrose is unloaded at the sink?
Solutes leave the phloem, increasing water potential, so water exits by osmosis, lowering hydrostatic pressure and maintaining the pressure gradient
225
Mass flow theory translocation
MEMORISE
1. Active transport/active movement of sugar (sucrose) at the source into phloem causes the water potential of phloem contents to become more negative.
2. Therefore water moves into the phloem by osmosis.
3. This means the hydrostatic pressure in phloem increases at the source (higher than the sink), which causes mass flow from source to sink.
4. At another part of the plant the sucrose and other organic solutes are removed from the phloem (a sink) increasing the water potential so water moves out by osmosis. This lowers the hydrostatic pressure.
226
Key Differences Between Apoplast and Symplast Routes translocation
Apoplast Route:
Pathway= through cell wall and intercellular spaces
Energy= requires atp (active transport)
Symplast route
Pathway= through cytoplasm via plasmodesmata
Energy= passive (no atp needed)
227
Coordination of cardiac cycle
1) the sino atrial node near the vena cava in the right atrium wall initiates an electric impulse
2) wave of excitation spreads across the atria but is stopped by a non conducting collagen disc between atria and ventricle.
3) atria contracts Before the ventricles
4) impulses reaches Atrioventricular node in right atrium and is delayed
5) impulses conducted down the septum via the purkyne tissue to apex
6)impulses conducts spreads out from apex.
7) ventricle muscle contract from bottom up after the atria
