2025 BIO EXAM SEMESTER 1 Flashcards
(211 cards)
1
Q
What is a cell?
A
A microscopic unit that are essentially the building blocks for all living things. Are living.
2
Q
What is an organelle?
A
Subcellular structures inside cells that perform various jobs/roles.
3
Q
What are the two categories of cells?
A
Prokaryotic and eukaryotic
4
Q
What is an eukaryotic cell?
A
A cell that makes up single or unicellular organisms, has a nucleus and evolved from prokaryotic cells. Their organelles are membrane-bound.
5
Q
What is a prokaryotic cell?
A
Smaller, basic cells that form unicellular protists. They are the oldest types of cell.
6
Q
What is the cell theory & it’s four parts?
A
A scientific theory that states: All living things are made of cells, cells are the basic unit of life, cells come from pre-existing cells, and cells contain DNA.
7
Q
Name the kingdoms that are eukaryotic
A
Protists (unicellular non-bacteria), animals, plants, fungi
8
Q
Name the kingdoms that are prokaryotic
A
Monera (bacteria), all unicellular
9
Q
What are some features/organelles of prokaryotic cells?
A
Cell wall, cell membrane, cytoplasm, capsule, flagella, pili
Simple organelles: ribosomes, nucleoid
10
Q
What do prokaryotic cells lack?
A
Membrane-bound organelles (mbo), nucleus
11
Q
Where is DNA located in prokaryotic cells?
A
Nucleoid
12
Q
What do prokaryotic & eukaryotic cells have in common?
A
Both have DNA, Ribosomes, cytoplasm, and cell membrane
13
Q
Where is DNA located in eukaryotic cells?
A
Nucleus
14
Q
What is unique about eukaryotic organelles?
A
They are membrane-bound
15
Q
What is a cell wall?
A
Outer layer of cell that strengthens and helps cell maintain shape. Located only in plant cells and prokaryotic cells.
16
Q
What are ribosomes and what do they do?
A
Organelle responsible for producing proteins/protein synthesis. Made of rRNA.
17
Q
Where are ribosomes found?
A
Either floating in the cytoplasm or attached to the rough ER.
18
Q
What is the cytoplasm & it’s role?
A
Gel-like fluid inside of a cell. It is not an organelle, rather it is the fluid that holds them. Hold and protect organelles, stores organic molecules for cellular processes.
19
Q
What is the nucleus & it’s role?
A
MBO found in the cytoplasm of plant and animal eukaryotic cells Enclosed by the nuclear envelope, it houses DNA and controls cellular activities.
20
Q
What is a nucleoid & it’s role?
A
A nuclear region found in prokaryotic cells. It is irregularly shaped and holds the DNA of the cell
21
Q
What are pili & their role?
A
Hair-like appendages that extend from the body of a cell to aid attachment.
22
Q
What is the flagella & it’s role?
A
Hair-like tail that extends from bacteria and sperm cells etc. to help movement.
23
Q
What is the smooth endoplasmic reticulum & it’s role?
A
Makes organic (carbon-containing) molecules. The smooth ER makes lipids/fats. Found in animal and plant eukaryotes.
24
Q
What is the rough endoplasmic reticulum & it’s role?
A
Makes organic (carbon-containing) molecules. The rough ER makes proteins. Found in animal and plant eukaryotes.
25
What is mitochondria & their role?
Rod-like MBO found in animal and plant eukaryotic cells
Performs aerobic respiration to make energy available for the cell by producing ATP (an energy-carrying molecule). ATP is broken down to release energy for processes that require energy e.g., active transport of materials into a cell).
26
What are small temporary vacuoles (vesicles) & their role?
MBO found in animal and plant eukaryotic cells
Carries molecules (e.g., proteins) from the Golgi body to the cell membrane to be released out of the cell (secretion).
27
What is a lysosome & it's role?
MBO found only in animal eukaryotic cells
Breaks down damaged organelles.
Helps to digest large food molecules taken into the cell.
28
What is the golgi body & it's role?
MBO found in the membrane of animal and plant eukaryotic cells
Packages molecules made by the cell (e.g., proteins) into small temporary vacuoles for transport
29
What membrane-bound organelles are located in the cytoplasm? (eukaryotic)
Nucleus
Mitochondria
Rough ER
Smooth ER
Golgi Body
Lysosomes (A)
Vesicles
Vacuoles (P)
Chloroplasts (P)
30
What are large permanent vacuoles & their role?
MBO found only in plant eukaryotic cells
Takes up most of the cell
Stores water/dissolved solutes and helps to maintain cell shape.
31
What is the chloroplast & its role?
MBO found only in the cytoplasm plant eukaryotic cells containing chlorophyll
Carries out photosynthesis to produce sugars e.g., glucose.
Enables plant cells to obtain energy from the environment.
32
What is the cell membrane?
A selectively permeable membrane that separates the interior of a cell from the outside environment, acting as a selective barrier that regulates the passage of materials in and out. Its flexible barrier protects the cell, contains its contents, and controls movement in and out.
33
Describe the structure of the CM
Structure is a phospholipid bi-layer with hydrophilic phosphate heads facing outwards and hydrophobic lipid tais facing inwards
34
What are phospholipids?
A type of lipid molecule essential to the structure of the cell membrane. They consist of a hydrophilic phosphate head and a hydrophobic lipid tail.
35
What is selectively permeable and why is it important for the CM?
Selectively permeable means it only lets certain things in and/or out of the CM. This allows it to diffuse materials but maintain structure and internal cell environment.
36
How does the phospholipid bi-layer form?
As phosphate heads are hydrophilic, they face outwards. Lipid tails are hydrophobic & repel water, so they face in.
37
What are integral membrane proteins?
Embedded membrane proteins that extend part-way or fully across the CM.
38
What are peripheral membrane proteins?
Membrane proteins found on the outside of the CM. They are soluble and adhere temporarily.
39
What are glycoproteins?
Embedded membrane proteins with a carbohydrate chain attached
40
What are glycolypids?
Phospholipids with a carbohydrate chain attached
41
Where is cholesterol located on the CM & its purpose?
On the surface of the CM
42
How does the CM maintain stability?
The hydrophilic pull of phosphate heads outwards and the hydrophobic attraction of lipids creates a strong structure
43
What is the structure of the CM called?
Fluid mosaic model, phospholipid bi-layer
44
What are carbohydrate chains?
Chains of carbohydrate molecules found on the cell membrane. Can be attached to phospholipids (glycolipids) or proteins (glycoproteins).
45
What are channel proteins?
Integral proteins responsible for diffusing materials, typically larger molecules and water.
46
What are carrier proteins?
Integral proteins that move materials across the CM through pumping.
47
What is simple diffusion?
Passive diffusion is diffusion of small molecules (carbon, oxygen etc.) through the cell membrane from high to low-concentration gradients. The tightly packed phospholipids allow small molecules to pass through whilst larger molecules cannot.
48
What are factors that affect diffusion?
Increased temperature, sa: v, agitation, and shallower concentration gradient
49
What is facilitated diffusion and how does it work?
Passive movement of hydrophilic molecules (eg. glucose) and atoms with a charge (ions like Na+).
As the CM is mostly hydrophobic, channel proteins allow hydrophilic molecules to pass through facilitated diffusion.
Moves with the concentration gradient
50
What is osmosis and how does it work?
Osmosis is a type of passive movement of water molecules across the cell membrane from high to low concentrations.
Water molecules are small enough to diffuse between phospholipids. Specific channel proteins (aquaporins) provide a path for water molecules only to pass, speeding up diffusion.
51
What is binary fission?
Cell division that occurs in prokaryotes and some single-cellular eukaryotes.
It is a form of asexual reproduction.
52
When does diffusion occur/stop?
When equilibrium is reached ie. the concentration of molecules outside & inside of the cell is the same.
53
When does cell division occur?
When the SA: V is too high and the cell is no longer efficient at diffusion
54
What occurs before binary fission?
DNA is replicated inside the cell.
55
First step of binary fission
Cytoplasmic membrane/area elongates, separating the DNA. Simultaneously, DNA attaches to CM.
56
Second step of binary fission
Cell walls grow inwards (furrows) and "pinches" cells. The growth that separates the cells is called the septum.
57
Third step of binary fission
Cell fully divides as septum closes
58
Fourth step of binary fission
2 daughter cells, identical to the parent cell, form. Called cloning.
59
What are the offspring cell of parent cells called?
Daughter cells
60
What is the acronym for mitosis?
IPMAT+C
61
What is mitosis?
A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus. Reproduction, repair, and growth
62
Why is mitosis important?
Without it, dead cells would never be replaced, organisms would never grow or heal.
63
What is interphase?
Pre-mitosis where DNA replication occurs
64
What is early prophase?
Prophase prepares the cell for division. Parent cell begins to break the nucleus down, chromosomes become visible and organised
65
What is late prophase?
Spindle fibres attach to the chromosomes at the centromere
66
Describe metaphase
Chromosomes line up in the middle of the cell to allow them to separate to opposite ends of the cell. Chromatids prepare to be broken apart.
67
Describe anaphase
Sister chromatids (previously a chromosome) separate due to spindle fibres pulling them apart. Chromatids are separated to opposite ends of the cell.
68
Describe telophase
CELL IS NOT COMPLETELY SEPARATED
Daughter cells that are formed begin to separate. Nucleus reforms in each cell around DNA and centrioles disappear
69
Describe cytokinesis
Daughter cells split completely.
70
How is the DNA organised in prokaryotic cells?
Single, circular chromosomes
71
How is the DNA organised in eukaryotic cells?
Multiple, linear chromosomes.
72
Define a centromere
Centre of a chromosome. Part of the chromosome where spindle fibres attach
73
What are chromosomes?
An X structure is made of DNA. They allow DNA to be accurately replicated.
74
Define a chromatid
The single strand of a chromosome
75
What is a centriole?
Organisms inside a cell that aid organisation of chroms during mitosis
76
What is the name given to daughter cells of mitosis?
Diploid cells
77
What is an organic molecule?
Large, complex, carbon-containing molecules essential for a cell's function
Controls cells activities
eg. DNA, carbohydrate, protein, lipids, fats
78
What is an autotroph?
Can make organic molecules independently
Usually with chemical reactions (like photosynthesis)
Commonly plants like trees, shrubs grasses
79
What is a heterotroph?
Those that cannot make organic molecules independently. Must source molecules otherwise eg. though food.
Commonly humans and animals
80
What is needed to carry out photosynthesis?
Water and CO2.
light is also needed
81
Photosynthesis produced what?
Glucose and oxygen
82
What are inorganic substances?
Molecules that lack carbon eg. ammonia
Some simple carbon molecules eg. Carbon
83
What other factors (not molecules) are required for photosyntheis?
Chlorophyll and light
84
What is the source of energy for autotrophs?
Light energy
85
How do heterotrophs use aerobic respiration to get molecules?
Under aerobic conditions (oxygen environment) heterotrophs perform aerobic respiration (in mitochondria) to obtain energy. In aerobic respiration glucose is broken down with oxygen to produce carbon dioxide and water. Energy stored in glucose is released. Some is ‘captured’ as chemical energy stored in ATP. Breakdown of ATP supplies energy for energy-needing cell processes e.g., active transport, cell division. This means the source of energy for heterotrophs is chemical energy.
Then, they have to breathe out the CO2, as well as some oxygen.
86
Describe photosynthesis
During photosynthesis light energy is transformed (converted) into chemical energy stored in the chemical bonds of a sugar called glucose (an organic molecule). In chloroplasts, CO2 and water (with light and chlorophyll) produce glucose and oxygen.
87
What is the aerobic respiration word equation?
glucose + oxygen ---> carbon dioxide + water
88
What is the photosynthesis word equation?
carbon dioxide + water --> glucose + oxygen
89
What is ATP?
Adenosine triphosphate is an energy-carrying molecule
90
How do autotrophs obtain chemical energy from photosynthesis?
The energy produced from the glucose made in photosynthesis is then used for aerobic respiration. Glucose is broken down with oxygen to produce carbon dioxide and water and energy stored in glucose is released. Some is ‘captured’ as chemical energy stored in ATP. Breakdown of ATP supplies energy for energy-needing cell processes.
Not available to cell unless its stored in ATP
91
What is fermentation?
Under anaerobic conditions (no oxygen environment) heterotrophs and autotrophs synthesise ATP by performing an energy-releasing process called fermentation.
92
State the word equation for alcohol fermentation
Alcohol fermentation glucose --> ethanol + carbon dioxide
93
State the word equation for lactic acid fermentation
Lactic acid fermentation glucose --> lactic acid
94
What fermentation do heterotrophs/animal cells perform?
Animal cells (and many bacteria) perform lactic acid fermentation.
95
What fermentation do autotrophs perform?
Plant cells (and yeast) carry out alcohol fermentation.
96
When and why does fermentation occur?
#NAME?
97
What are the 3 requirements of cells?
1. need organic molecules
2. need energy
3. must exchange materials with environments
98
What are inputs and examples?
Inputs are things that must enter the cell to help it function. Some examples include: Glucose, oxygen, amino acids, water, ions
99
What are outputs and examples?
Things that must be removed from the cell. Some examples are: CO2, urea, hormones, lactic acid
100
Why do cells need amino acids?
To produce molecules for producing proteins
101
Why do cells need oxygen?
For aerobic respiration, which makes ATP
102
Why do cells need glucose?
For aerobic respiration, which makes ATP
103
Why do cells need water?
MOST IMPORTANTLY: Water provides a medium in the cytoplasm for chem reactions and dissolving of substances.
Also:
Maintaining Shape & Structure, Chemical Reactions, Temperature Regulation (maintain a stable environment), Energy Production (photosynthesis, cellular respiration)
104
Why do cells need ions?
Help provide a medium in the cytoplasm for chem reactions and dissolving of substances.
105
What is the main component of a cytoplasm and why?
Water; allows a medium for certain chemical reactions to occur
106
Why must cells remove lactic acid?
To prevent its accumulation, which can lead to toxic conditions and disrupt normal cellular function.
107
Why must cells remove CO2?
To prevent its accumulation, which can lead to toxic conditions and disrupt normal cellular function.
108
Why must cells remove urea?
Byproducts of protein metabolism; toxic if not eliminated.
109
Why must cells remove hormones?
To regulate body functions, coordinate communication between organs, and maintain homeostasis.
110
What is the importance of organic molecules?
Help carry out fundamental chemical processes.
111
Compare characteristics of living and non-living things
Cellular structure: living things are made up of cells whilst non-living are not
Growth: living grow by cell division or enlargement. non-living do not grow on their own
Reproduction: living can reproduce (sexually or asexually).
non-living cannot reproduce.
Movement: living can move independently whilst non-living cannot
Energy: living require energy to function (e.g., from food or sunlight). Non-living do not require energy.
112
Describe the similarities in structure of prokaryotes and eukaryotes
Both contain DNA, ribosomes, a cytoplasm, and a cell membrane.
113
Describe the differences in structure of prokaryotes and eukaryotes
MBO: eukaryotic have whilst prokaryotic lack
Size: euk. big, prok. small
Cell number: prokaryotes make up single cellular organisms whilst eukaryotic can make up single or multi cellular (mostly multi)
Nucleus: euk has a nucleus whilst prok has a nucleoid region
114
Compare the structure of animal and plant cells.
MBO: Both have a nucleus, mitochondria, rough and smooth ER, a golgi body, small temporary vacuoles.
ONLY Plant cells have large permanent vacuoles and chloroplasts
ONLY animal cells have lysosomes
115
Describe the structure of the selectively permeable membrane.
A phospholipid bi-layer that has embedded and attached (integral & peripheral) membrane proteins. The layer is comprised of hydrophilic heads facing outward and hydrophobic tails facing inward.
The selective permeability allows for small molecules to pass thru the bilayer via diffusion and other molecules to diffuse through channel or carrier proteins whilst maintaining its shape and protecting the cell. Maintains membrane fluidity by preventing it from becoming too rigid or too permeable.
116
Describe how substances move passively across the cell membrane with the concentration gradient.
Substances move passively across the cell membrane with the concentration gradient (from high to low concentration) without requiring energy/ATP.
Molecules diffuse until equilibrium is reached.
1. Simple Diffusion
Movement of small, non-polar molecules (e.g., O₂, CO₂) directly across the phospholipid bilayer.
Example: Oxygen diffusing into cells for respiration.
2. Facilitated Diffusion
Movement of larger or polar molecules (e.g., glucose, ions) across the membrane through transport proteins.
Requires channel proteins (for ions) or carrier proteins (for larger molecules).
Example: Glucose enters cells via carrier proteins.
3. Osmosis (Diffusion of Water)
Water moves across the membrane.
Water moves from an area of high water concentration (low solute) to low water concentration (high solute) through aquaporins (water channels).
Example: Water moving into plant root cells.
117
Explain how a cell membrane controls exchanges of materials (passive or active) between a cell and its environment.
The CM controls the exchange of materials through selective permeability.
This allows some materials to diffuse in and not others, and vice versa. The ability to "replenish" materials and remove wastes keeps the cell in homeostasis.
118
Compare passive and active transport with regard for concentration gradient and energy requirement.
Passive transport requires no ATP. Moves down the concentration gradient (high → low concentration) and doesn't always involve proteins.
Active transport requires ATP, against the concentration gradient (low → high concentration), and is done with the help of carrier or channel proteins.
119
Describe and represent binary fission in prokaryotic cells.
Asexual reproduction undertaken by prokaryotic cells for population growth.
1. DNA Replication
The single circular chromosome duplicates, creating two identical copies.
2. Cell Growth
The cell elongates, separating the two DNA copies.
3. Septum Formation
A new cell wall (septum) begins to form in the middle.
4. Cell Division
The cell splits into two identical daughter cells.
5. Daughter Cells
Each new cell has one copy of the original DNA and is genetically identical to the parent cell.
120
Describe and represent mitotic division in eukaryotic cells.
Mitosis produces two genetically identical daughter cells, ensuring an organism's growth, repair, and maintenance.
Interphase (Pre-Mitosis)
The cell prepares for division by replicating its DNA and growing.
Prophase
Chromosomes condense and become visible.
The nuclear membrane breaks down.
Spindle fibers begin to form.
Metaphase
Chromosomes align at the center (equatorial plate).
Spindle fibers attach to the centromeres of chromosomes.
Anaphase
Spindle fibers pull sister chromatids apart toward opposite poles.
Telophase
Chromatids reach the poles and decondense into chromatin.
The nuclear membrane reforms around each set of chromosomes.
Cytokinesis (Final Step)
The cytoplasm splits, forming two identical daughter cells.
121
Compare binary fission with mitotic division.
Mitosis:
Eukaryotes (Animals, Plants, Fungi, Protists), growth, repair, and asexual reproduction, Genetically identical, more complex, involves multiple linear chromosomes
Binary fissions:
Prokaryotes (Bacteria), Asexual reproduction, Genetically identical, simple process, single circular chromosome
122
Compare the sources of organic molecules and energy for autotrophs and heterotrophs.
Autotrophs make organic molecules independently whilst heterotrophs must consume their own. Autotrophs use light energy to perform photosynthesis whilst heterotrophs get chemical energy from aerobic respiration.
123
Explain why cells need to exchange materials (inputs)
Materials must be exchanged to maintain homeostasis/constant environment.
Absorb:
Oxygen (O₂): for aerobic respiration, producing ATP
Glucose: for aerobic respiration, producing ATP
Water: chemical reactions and maintaining cell structure
Ions: Crucial for nerve signals, enzyme function, and maintaining osmotic balance.
124
Explain why cells need to exchange materials and the need for removal of wastes.
Lactic Acid: Prevent accumulation, which leads to toxic conditions and disrupts cell function
CO2: Prevent accumulation, which leads to toxic conditions and disrupts cell function
Urea: Byproduct of protein synthesis; toxic
Hormones: Regulate body functions, coordinate communication
125
What are the three types of microorganisms?
Protists, bacteria, unicellular fungi
126
Discuss the effects of factors on bacterial growth.
Temperature (20-45 degrees C growth, 0-4 near zero, 50-100 kills), pH level (ideal 7, 1-3 kill), water (lack of reduces growth near zero), nutrients (Less nutrients = less growth as most are autotrophs), removal of waste (if cannot = dies)
127
What is disease?
A condition that disrupts the regular function of an organism.
An organism that is growing and carrying out life’s processes ‘with ease’ is said to be in a good state of health or healthy. ‘Dis-ease’ results if good health breaks down.
128
What is infectious disease?
Disease that spreads from organism to organism is called infectious disease e.g. ‘flu’, COVID-19 (coronavirus disease 2019). These contagious diseases are caused by pathogens.
129
What is non-infectious disease?
Disease that cannot be transmitted tor other organisms. Either genetic or lifestyle diseases
130
What is a "lifestyle" disease?
Disease caused by long-term "unhealthy" habits. eg. diabetes or heart disease.
131
What is genetic disease?
Hereditary disease that is passed on to offspring. Inherited condition caused by a change in DNA. EG: pulmonary fibrosis
132
What is a pathogen?
Agent that causes infectious disease. Can be living eg. parasite or non-living eg. virus
133
What are the characteristics of a pathogen?
1. have ways of increasing numbers
2. need a food source from in between cells
3. live on or enter a host to replicate or obtain nutrients
4. have adaptations
5. have ways of avoiding the immune system
134
What are the five main pathogens?
Bacteria, protists, viruses, parasites, and fungi.
135
What are the characteristics of bacteria?
Unicellular prokaryotes. Upon entering the host’s bloodstream, they move into (infect) tissues where they may reside for a period of time. Bacteria release chemical’s that disrupt cell function (toxins). They divide (by binary fission) to produce large numbers of new bacteria that damage tissues causing disease. EG: tooth decay, food poisoning, tuberculosis (TB), and cholera.
136
What are the characteristics of fungi?
Unicellular organism (yeast) or multicellular (mould) eukaryotes. Mould: if left in contact with warm and moist skin, they increase in numbers causing the skin to crack = bacterial infection = inflammation. EG: athletes foot
137
What are the characteristics of viruses?
Non-living, acellular infectious agents. Viruses may enter cells through the cell membrane. Once it has infected the host cell, the virus may use it to produce new viruses (viral replication). These new viruses soon leave the host cell where they can infect more cells, either in the same body or in a new host organism. Some viruses, however, remain dormant in the host cell for a period before the replication processes begins. EG: influenza, Covid-19
138
What are the characteristics of protists?
Unicellular, non-fungi eukaryotes. It can restrict nutrient absorption and infect cells. EG: Malaria
139
What are the characteristics of parasites?
An organism that lives on or in another organism (host). Harm the host, but not enough to cause death.
140
Describe the structure of a virus
A virus is genetic material (DNA or RNA) enclosed in a lipid membrane ‘coat’ with proteins on its surface.
141
What is a vector?
Term for a way a disease can be transmitted eg. animal vector
142
What are the 6 main vectors?
Air, dust, food, feces, animals, direct/indirect contact
143
How do faeces vectors transmit diseases?
Microscopic pieces of faeces from a pathogen-infected person end up in water or food that is then consumed by non-infected people. eg. Giardia infection (‘gastro’), hepatitis A and cholera.
144
How do air vectors transmit diseases?
Spread by droplets containing a pathogen (e.g. a virus) released into air when an infected person coughs or sneezes that are breathed in by other people nearby. The closer someone is to an infected person (or the longer they are in close contact with them), the more likely the droplets are to end up in their mouth, nose or eyes. eg. ‘flu’, COVID-19, and the ‘common cold’.
145
How do dust vectors transmit diseases?
Infectious disease is spread by dust with pathogen attached to it. These travel on air currents after which they are inhaled by non-infected persons. eg. pneumonia and tuberculosis (TB).
146
How do direct and indirect contact vectors transmit diseases?
DIRECT: When a pathogen-infected person’s skin comes into contact with the skin of other non-infected people. eg. chicken pox. spread by shaking hands.
INDIRECT: When a non-infected person’s skin comes into contact with surfaces contaminated by a pathogen. eg. contracting COVID-19 by touching contaminated door handles or tabletops
147
How do animal vectors transmit diseases?
When non-infected humans touch or are bitten by a pathogen-infected animal. eg. bird flu (bird handling) and rabies (dog bite)
148
How do food vectors transmit diseases?
When food is consumed by people (or other animals) that contains a pathogen. eg. meat that is infected with the bacterium Salmonella that leads to food poisoning (Salmonellosis).
149
What is a host?
Organism/living thing that a pathogen resides on or in.
150
Define a "reservoir"
Place where a pathogen typically resides in. Can be living (eg. humans) or non-living (eg. water). eg. oncoviruses' reservoir is humans
151
What are carriers?
Animal vectors (humans, dogs, rats, etc)
152
How can new infectious diseases outbreak?
The result of a pathogen (e.g. a virus carried by an animal) that previously could not infect humans developing the ability to do so.
Pathogens have hence been able to have "jumped to humans".
153
Explain what is meant by a pathogen to have "jumped to humans"
Pathogen is said to have ‘jumped to humans’. This means it has acquired the ability to replicate and infect the human body, and to spread between people.
154
What is an epidemic?
Once a virus starts to spread quickly between people causing many people to be infected at the same time, the outbreak is called an epidemic. Epidemics may occur in a local populations, populations nationally or in several countries.
155
Define a pandemic
Epidemic spread over large geographical location, in many countries, affecting a large percentage of the population of them at the same time. eg. the COVID-19 pandemic
156
How does the persistence of pathogens in a host determine the spread of infectious disease?
The persistence of the pathogen refers to its ability to survive within a host. Bacterial and viral pathogens have mechanisms to increase their persistence in hosts. In the case of many bacteria this includes thermal resistance or tolerating increases in host body temperature post-infection (fever). In viruses this includes ways of being able to evade the host’s immune system. One example involves spike proteins that become suited to binding to cell receptors (thus allowing their entry into human cells and shelter from certain components of the immune system).
157
How do immunized populations determine the spread of infectious disease?
Immune An individual whose immune system has been ‘boosted’ to make them immune to a pathogen is said to be immunised. Immunisation involves introducing into the body a vaccine (e.g. by injection). The greater the proportion of people in a population who are immune or who have been immunised the less potential hosts there are for the pathogen to infect that, in turn greatly reduces the spread of infectious disease.
158
How does the transmission mechanism determine the spread of infectious disease? How can thsi be impacted?
How have pathogens evolved to do this?
For an infectious disease to spread between people, transmission from the reservoir to an person must occur first (e.g. touching a door handle). Then the infected individual must transmit the pathogen to other individuals nearby (e.g. by coughing). Pathogens have evolved a wide variety of ways to achieve this the success of which are influenced by factors including human behaviour (e.g. hand-washing practices), density of the human population (city vs rural), the numbers of suitable carriers and the local environment (climate, season).
159
How does the mobility of people in a population determine the spread of infectious diseases?
Very mobile individuals who come into contact with many people (e.g. shopping, going to school). greatly increases the probability that they will come in contact with the pathogen either directly or indirectly. More people who do this = more likely exposure = greater spread.
160
What is meant by an "immune person"?
A person who is naturally not susceptible to a pathogen or who has been infected by it and recovered is described as being immune. An individual whose immune system has been ‘boosted’ to make them immune to a pathogen is said to be immunized.
161
What is disease control?
A variety of measures quickly put in place to reduce the spread of disease.
162
How does the immune system contribute to disease control?
Because it strives to kill or greatly reduce the number of pathogens in the body.
163
What are some disease controls?
(IMMUNE SYSTEM) Controlling carriers, killing pathogens, reducing transmission, isolating carriers
164
Explain how controlling carriers is a disease control
Carriers of infectious disease (e.g. mosquitoes, fleas) can be controlled by: use of insecticides to kill insect carriers, promoting the use of nets that serve as barriers, and encouraging the proper storage and disposal of food (=lack of food source), and covering up (by wearing long-sleeved clothing and long pants).
165
Explain how killing the pathogen controls disease
Pathogens are killed using chemicals applied outside the body (e.g. antiseptics, disinfectants) or chemicals introduced into the host’s body (antibiotics, antivirals). An antiseptic is spread over living tissue (e.g. skin) to kill pathogens that may be residing there (e.g. hand sanitisers). Disinfectants are used on non-living objects to kill pathogens (e.g. floor cleaning products, toilet cleaners). Antibiotics taken by a host kill bacterial pathogens that are inhabiting the body (e.g. penicillin, streptomycin). Antivirals are taken to kill viral pathogens that have infected a host (e.g. Rapivab and Tamiflu that are used separately to combat ‘flu’ in humans).
166
Explain how reducing transmission is a disease control
Including regular hand-washing, social distancing, wearing of masks, and quarantining. Reducing transmission reduces the likelihood of infecting hosts.
167
How does isolating disease carriers a disease control?
Quarantining or isolation aims to stop infected persons from spreading disease to others.
168
What are pathogen adaptations? Give examples
A structure or behaviour that helps an organism or virus survive. Pathogens have adaptations that facilitate their entry into hosts and their tissues and cells.
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What are some adaptations of bacteria and viruses?
Adaptations to increase the time they can survive (or persist) in their host. eg. thermal resistance (allows pathogen to persist when the body temperature of the host increases, as in fever), production of proteins to neutralise stomach acid (to persist in the stomach of a mammal).
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What is an adaptation of protists?
One protist, Plasmodium has evolved to exist in different forms: in the mosquito carrier to be injected straight into the hosts bloodsteam.
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How can viruses/bacteria adapt to enter tissue/blood?
BOTH VIRUS AND BACTERIA: After crossing the one-cell thick exchange surfaces that line alveoli (in lungs) and villi (in the small intestine). they enter other host tissues by leaving blood in capillaries by crossing the equally thin capillary walls.
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How can bacteria adapt to enter tissue/blood?
Those that can enter host cells have adaptations like viruses that permit them to be recognised. This triggers their uptake into the host cell by a process similar to endocytosis called phagocytosis.
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What are cell receptors?
Protein molecules on the surface or within a cell that bind to specific molecules/proteins
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How do viruses enter and infect cells? (STEP BY STEP PROCESS)
1. Attachment (Adsorption)
Virus attaches to the host cell by binding to specific receptor proteins on the cell’s surface. This interaction is highly specific—like a key fitting into a lock—so a virus can usually infect only certain types of cells.
2. Entry (Penetration)
The virus/its genetic material enters the host cell.
3. Uncoating
Once inside, the virus sheds its protein coat to release its genetic material (DNA or RNA) into the host cell.
4. Replication and Transcription
The host cell's machinery is hijacked to replicate the viral genome and produce viral RNA.
5. Viral proteins are synthesized
6. New virus particles are assembled
7. New viruses leave the cell
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Why do pathogens enter cells?
1. Replicate and reproduce
2. Obtain nutrients
3. Ideal living conditions
4. Block immune system
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How many lines of defense does the immune system have?
Three
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Define the immune system
The organ system that defends the human body against infection by pathogens. This complex network of organs, tissues, cells and proteins enables many infections to be avoided, or limited.
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What is the first line of defence?
Barriers, which block and prevent pathogens from entry.
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Define and give examples of a physical barrier
A part of the first line of defence, physical barriers are "sheilds" that prevent entry of pathogens. EG: Skin, cornea
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Define and give examples of chemical barriers
A part of the first line of defence, chemical barriers are molecules that prevent pathogen entry by killing pathogens that come into contact with them.
EG: tear enzymes, stomach enzymes, ear wax molecules
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How can physical barriers be enhanced?
With the use of disinfectants/antiseptics
eg. skin barrier is enhances with hand washing
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What is an antigen?
A protein or other substance that initiates an immune response.
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How is the detection and destruction of pathogens inside the body possible?
Via molecular recognition involving antigens
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What is meant by pathogens "breaching" a barrier?
Pathogens pass the barriers that defend the body against them, enter the bloodstream, and begin to move through the body. Triggers immune response.
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What is the body's immune response?
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Describe how the immune response works
The body uses immune cells and their receptors to attach to pathogen antigens. If recognised as foreign, the body is signaled to attack the pathogen.
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How does the body detect pathogens?
Immune cells produce receptors on their surface that recognise and bind to antigens on the surface of pathogens. If they are recognised as foreign antigens, an immune system response is activated, leading to the pathogen's destruction.
The detection of pathogens depends on the body’s ability to distinguish the pathogen (non-self) from its own cells (self).
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Where can you find antigens?
On the surface of various molecules eg. blood cells.
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What are foreign antigens?
Substances that originate from outside the body and trigger an immune response. Typically appear on pathogens.
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What are self antigens?
Molecules that are naturally present in the body and are recognized by the immune system as belonging to the "self." They are not usually attacked by the body unless there is a disorder (eg. alopecia)
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What can be taken to kill bacterial pathogens?
Antibiotics
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What can be taken to kill viral pathogens?
Antivirals
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What is the name of the first line of defence?
Barriers
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What is the name of the second line of defence?
Innate immune system
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What is the name of the third line of defence?
Adaptive immune system
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Distinguish the difference between infectious and non-infectious disease
Infectious diseases are spreadable diseases that can be passed from organism to organism. They can be spread by vectors.
Non-infectious disease cannot be passed to other organisms and is either genetic or "lifestyle".
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Describe the general characteristics of a pathogen
Pathogens can replicate, have ways of avoiding the immune system, live on or in a host to obtain nutrients and survive, and have adaptations
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What factors determine the spread of infectious disease?
Mobility of population, immunized populations, density of population, transmission mechanisms, and persistence of pathogen in hosts
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Compare foreign antigens with self-antigens
Foreign antigens come from outside the body (e.g., bacteria, viruses), whereas self-antigens are produced by the body itself. Self-antigens have self-markers whilst foreign antigens don't.
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How can pathogens breach the first line of defense?
Pathogens (inhaled) can travel through the thin lining of the alveoli, travel thru breaks in the skin, etc.
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What is meant by the innate immune system being "non-specific"?
The term "non-specific" in relation to the innate immune system means that it doesn't target specific pathogens or foreign substances, but rather responds to a broad range of potential threats in a generalized way.
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Name some characteristics of the innate immune system
Non-specific, fast-acting,
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What are the three immune cells inolved in the innate response?
Phagocytes (white blood cells), natural killer cells (NKC), and the complement system proteins
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What organisms display an innate immune response?
Organisms, including plants and animals (invertebrates, vertebrates) display innate immune responses.
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What are phagocytes and how do they fight pathogens?
Phagocytes are white blood cells that consume pathogens. They engulf pathogens that breach the first line of defense (eg. a virus) by binding their receptors to antigens on pathogen's surface. When recognised as non-self, phagocyte "eats" it via endocytosis & destroys it using digestive enzymes.
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How do NKC eradicate pathogens?
NKC have receptors that recognise abnormal self-antigens on infected/cancerous body cells. Following recognition, NKC relase toxins into the infected cell, hence preventing spread of pathogen into body.
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What is the complement system?
The complement system is made up of about 30 proteins present in blood plasma.
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How does the compliment system help fight bacterial pathogens?
It destroys bacteria by binding to antigens on its surface and creating holes in their membrane (called membrane attack complexes). This causes an inrushing of fluid and eventual exploding/lysis.
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What is the inflammatory response and how does it operate?
Response triggered by the signaling of histamine or other molecules at the site of tissue damage (sent out by mast cells).
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Name two types of phagocytes
Neutrophils, macrophages
