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IGCSE Biology > Topic 4 > Flashcards

Topic 4 Flashcards

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1
Q

What is a pathogen?

A

A disease-causing organism

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2
Q

What is a transmissible disease?

A

Pathogens passed on from one host to another.

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3
Q

What is direct contact?

A

Pathogen is passed on from host to host by transfer of bodily fluids (saliva, blood, semen)

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4
Q

What is indirect contact?

A

Pathogen leaves host and is carried in some way to another, uninfected individual

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5
Q

4 methods of transmission:

A
  1. Droplets in the air
  2. Food/Drink
  3. Touching contaminated surfaces
  4. Insect bites
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6
Q

3 ways the body defends itself?

A
  1. Mechanical barriers - skin, hairs in nose
  2. Chemical barriers - mucus, stomach acid
  3. Cells - phagocytosis, producing antibodies
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7
Q

4 ways to prevent the spread of disease?

A
  1. Hygienic food preparation
  2. Personal hygiene
  3. Waste disposal
  4. Sanitation
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8
Q

What is active immunity?

A

The production of antibodies and developing memory cells for future responses to infections.

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9
Q

State 2 ways active immunity can occur:

A
  1. Body has been infected with a pathogen, the lymphocyte makes the complimentary antibody to the antigen
  2. Vaccination
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10
Q

What are antigens?

A

Molecules, such as proteins, projecting from their cell membranes.

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11
Q

What is the role of antibodies?

A

Antibodies can attach to the antigens and cause agglutination (pathogenic cells cannot move around very easily) of pathogens. At the same time, chemicals are released that signal presence of pathogens to phagocytes.

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12
Q

What is immunity?

A

After an encounter with a pathogen, lymphocytes create memory cells, which retain the instructions for making the specific antibody.

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13
Q

What is a vaccine?

A

A weakened/altered form of the pathogen, containing specific antigens to be introduced into the body - cannot cause illness, but can stimulate an immune response

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14
Q

What is passive immunity?

A

Fast-acting, short-term defense against a pathogen by antibodies acquired from another individual. NO MEMORY CELLS MADE.

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15
Q

Process of cholera:

A
  1. Bacteria attach to the wall of the small intestine
  2. Produce a toxin, stimulating the cells lining the intestine to release chloride ions (Cl-) from inside the cells into the lumen of the intestine.
  3. Chloride ions accumulate in the lumen of the small intestine and lower the water potential
    4.Once the water potential is lower in the lumen of the small intestine, water by osmosis starts to move out of the cells, into the intestine - therefore large quantities of water are lost from the body in watery faeces
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16
Q

How is cholera treated?

A

Oral rehydration therapy - drink with small amounts of solutes)

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17
Q

4 Features of gas exchange surfaces:

A
  1. Large surface area = faster diffusion
  2. Thin walls = to aid diffusion
  3. Good ventilation with air = so concentration gradient can be maintained
  4. Good blood supply = maintain high concentration gradient
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18
Q

What is the larynx (voice box)

A

When air passes, it is able to make noise.

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19
Q

What does the alveoli do?

A

Tiny air sacs where gaseous exchange take place.

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20
Q

What is the bronchus?

A

Large tubes branching off trachea.

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21
Q

What is the bronchiole?

A

Connect bronchus to alveoli.

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22
Q

What is the diaphragm?

A

Sheet of connective tissue and muscle at the bottom of the thorax that helps change the volume of the thorax to allow inhalation/exhalation.

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23
Q

What is the trachea?

A

Windpipe that connects the mouth and nose to the lungs - kept open by rings of cartilage.

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24
Q

What do the ribs do?

A

Bone structure that protects internal organs such as the lungs.

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25
Q

What do intercostal muscles do?

A

Muscles between ribs, controlling the movement, causing inhalation/exhalation. Antagonistic pairs.

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26
Q

Is the pleural cavity filled with fluid?

A

Yes

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27
Q

Process of breathing in:

A
  • external intercostal muscles contract
  • ribcage moves up and out
  • diaphragm contracts and flattens
  • volume of thorax increases
  • pressure in the thorax decreases
  • air is drawn in
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28
Q

Composition of oxygen in the atmosphere?

A

21%

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29
Q

Composition of nitrogen in the atmosphere?

A

78%

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30
Q

Composition of carbon dioxide in the atmosphere?

A

0.04%

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31
Q

Composition of oxygen in exhalation?

A

16%

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32
Q

Composition of carbon dioxide in exhalation?

A

4$

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33
Q

What is secreted by goblet cells and why?

A

Mucus secreted. Mucus traps particles, pathogens and prevents them from getting into lungs and causing damage. Cillia push mucus away from the lungs toward the throat

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34
Q

What is respiration?

A

Chemical process that involves the breakdown of nutrient molecules in order to release energy stored within the bonds of these molecules.

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35
Q

6 uses of energy in the body:

A
  1. Maintenance of a constant body temperature
  2. Cell division and growth
  3. Active transport
  4. Passage of nerve impulses
  5. Muscular contractions
  6. Protein synthesis
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36
Q

What is aerobic respiration?

A

Requires oxygen and is defined as chemical reactions in cells that use oxygen to break down nutrient molecules to release energy. Complete breakdown of glucose to release a relatively large amount of energy/

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37
Q

Word and symbol equation of aerobic respiration:

A

glucose + oxygen -> carbon dioxide + water

C6H12O6 + 6O2 -> 6CO2 + 6H2O

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38
Q

What is anaerobic respiration?

A

Incomplete breakdown of a nutrient molecule, resulting in energy and lactic acid in animals.

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39
Q

Word equation for anaerobic respiration in animals:

A

glucose -> lactic acid

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40
Q

Anaerobic respiration word and symbol equation:

A

Glucose -> Alcohol + carbon dioxide

C6H12O6 -> 2C2H5OH +2CO2

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41
Q

What is oxygen debt?

A

Lactic builds up in muscle cells, making them more acidic by lowering the pH of cells and blood. This could denature the enzymes in the cells so it needs to be removed. Cells excrete lactic acid into the blood, passing through the liver. The lactic acid is taken into the liver cells and oxidised.

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42
Q

Organs specialised for removal of carbon dioxide:

A

Lungs

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43
Q

What is excretion?

A

Removal of the waste substances of metabolic reactions, toxic materials and substances in excess of requirements

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44
Q

Why does CO2 need to be excreted?

A

It dissolves in water easily to form an acidic solution - lowering the pH of cells (can reduce activity of enzymes in the body which are essential for controlling the rate of metabolic reactions.

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45
Q

What do the kidneys do?

A
  • Regulate water content of blood (maintains blood pressure)
  • Excrete toxic waste products of metabolism
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46
Q

Waste substances to be removed from the blood via kidneys:

A
  1. Urea
  2. Creatinine
  3. Uric acid
  4. Ammonia
  5. Excess Hormones
  6. Excess water
  7. Excess salts
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47
Q

Where are the nephrones in the kidney?

A

Start in the cortex of the kidney, loop down into the medulla and back into the cortex.

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48
Q

What is ultrafiltration?

A

Arterioles branch off renal artery and lead to each nephron where they form a knot of capillaries that get narrower as they get further into the glomerulus, increasing the pressure. This causes smaller molecules carried in the blood to be forced out of the capillaries into the bowmans capsule, where they form a filtrate.

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49
Q

What substances are filtered out during ultrafiltration?

A

Glucose, water, urea and salts.

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50
Q

What is selective reabsorption?

A

After the glomerular filtrate enters the Bowmans capsule, glucose is the first to be absorbed at the proximal convoluted tubule via active transport (proximal convoluted tubule is adapted for this by having many mitochodria to provide energy for active transport)

As filtrate drips through loop of Henle, necessary salts are reabsorbed back into the active transport. As salts are reabsorbed back into the blood, water follows by osmosis.

51
Q

Where else can water be absorbed in the kidney?

A

The collecting duct - depending on how much water the body needs at the time.

52
Q

What is deamination?

A

Breakdown of amino acids by enzymes in the liver. The nitrogen-containing amino group is removed and converted into ammonia and then urea, to be excreted.

53
Q

After deamination, what happens to the carbon?

A

Stored as glycogen.

54
Q

What happens when you have urea levels that are too high?

A
  • Cell death
  • Reduced response to insulin
  • Deposits inside blood vessels.
55
Q

What does the human nervous system consist of?

A
  • Central Nervous system (CNS): brain, spinal cord
  • Peripheral Nervous System (PNS): all the nerves in the body
56
Q

What does the nervous system allow us to do?

A

Coordinate and regulate body functions, make sense of our surroundings and make responses to them.

57
Q

What do sensory neurones do?

A

Carry impulses from sense organs to the CNS

58
Q

What do relay/intermediate nerves do?

A

Found inside the CNS and connect sensory and motor neurones.

59
Q

What do Motor neurones do?

A

Carry impulses from CNS to effectors.

60
Q

What are effectors?

A

Muscles or glands.

61
Q

How are neurones optimised for their job?

A
  • Long axon
  • Dendrite
62
Q

What is a voluntary response?

A

When you make a conscious decision to carry out a particular action, therefore it starts with your brain.

63
Q

What is an involuntary response?

A

Automatic and rapid response to a stimulus. Doesn’t involve brain as the coordinator of the reaction (you aren’t aware you have completed it until after you take action). It is essential for basic survival and is rapid.

64
Q

What is the reflex pathway?

A

stimulus -> receptor -> sensory -> relay -> motor -> effector -> response ->

65
Q

What is a synapse?

A

The junction between two neurones

66
Q

What do synapses ensure?

A

Ensures the impulses only travels in one direction.

67
Q

How does a synapse work?

A

Electrical signal/impulse travels along the first axon, triggering the nerve ending of the presynaptic neurone to release chemical messengers called neurotransmitters in vesicles that diffuse across the synaptic cleft to bind with the receptor molecules on the membrane of the second neurone (postsynaptic membrane). This stimulates the second neurone to generate an electrical impulse that travels down the second axon. The neurotransmitters are then destroyed to prevent continued stimulation of the second neurone which would cause repeated impulses to be sent.

68
Q

What part of the nervous system are messages chemical?

A

Synapses

69
Q

Where do drugs work?

A

Synapses

70
Q

What are receptors?

A

Receptors are a group of specialized cells that detect a change in the environment and stimulate electrical impulses in response.

71
Q

What is skin sensitive to?

A

Pressure, heat, and pain.

72
Q

What can skin sense?

A

Touch and temperature.

73
Q

What is the tongue sensitive to?

A

Chemicals in food/drink.

74
Q

What is the tongues sense?

A

Taste.

75
Q

What is the nose sensitive to?

A

Chemicals in the air.

76
Q

What is the nose’s sense?

A

Smell.

77
Q

What is the ear sensitive to?

A

Sound and movement.

78
Q

What is the ears sense?

A

Hearing and balance.

79
Q

What is the eye sensitive to?

A

Light.

80
Q

What is the eye’s sense?

A

Sight.

81
Q

What does the cornea do?

A

Transparent lens that refracts light as it enters the eye.

82
Q

What does the pupil do?

A

The pupil is a hole that allows light to enter the eye.

83
Q

What does the lens do?

A

Transparent disc that can change shape to focus light onto retina.

84
Q

What does the optic nerve do?

A

Sensory neurone that carries impulses between eye and brain.

85
Q

What does the retina do?

A

Contains light receptor cells:
rods = light intensity
cones = colour

86
Q

Where is the blind spot and what does it do?

A

At the point where the optic nerve joins with the retina, there are no rod or cone cells on that part of the retina - leading to our brain ‘filling in’ from surrounding light.

87
Q

What is the fovea?

A

Has the highest concentration of cone cells.

88
Q

What does the ciliary muscle do?

A

Affects the size of lense.

89
Q

What does the suspensory ligaments do?

A

Connect the lense to the ciliary muscles.

90
Q

What does the iris do?

A

Act as a ‘shutter’ for the pupils.

91
Q

What is the pupil reflex?

A

Reflex action carried out to protect retina from damage in the bright light and protect us from not seeing objects in the dim light.

92
Q

What does the pupil do in dim light?

A

The pupil dilates in order to allow as much light into the eye as possible.

93
Q

What does the pupil do in the bright light?

A

The pupil constricts to prevent too much light from entering and damaging the retina.

94
Q

What are photoreceptors?

A

Rod and cone cells.

95
Q

What type of muscle action do pupils do?

A

Antagonistic.

96
Q

3 features of pupil in dim light:

A
  1. Dilated pupil
  2. Radial muscles contracted (stretch in length)
  3. Circular muscles are relaxed
97
Q

3 features of pupil in bright light:

A
  1. Constricted pupil
  2. Radial muscles are relaxed
  3. Circular muscles are contracted (decrease in diameter)
98
Q

What happens to the eye when an object is up close?

A
  1. Ciliary muscles contract
  2. Suspensory ligaments loosen - lens becomes fat
  3. Light refracted more
  4. Constriction of pupil
99
Q

What happens when an object is far away?

A
  1. Ciliary muscles relax (increase in diameter)
  2. Suspensory ligaments tighten - making lens become thinner
  3. Light is refracted less
  4. Pupil contracts
100
Q

What are the 3 types of cone cells?

A

Blue, green and red.

101
Q

Where are the rod cells found?

A

All over the retina.

102
Q

Where are the cone cells found?

A

Almost all in the fovea.

103
Q

What is a hormone?

A

A chemical substance produced by a gland and carried by the blood. Alters the activity of one or more target organs.

104
Q

What is glucagon?

A

Hormone produced when blood glucose levels falls, stimulating the liver and muscle cells to convert stored glycogen into glucose and to be released in the blood.

105
Q

What is glycogen?

A

Stored form of glucose (starch).

106
Q

What is adrenaline?

A

The ‘fight or flight’ hormone as it is produced in situations where the body might be in danger.

107
Q

What is adrenalines affect on the body?

A
  • Increases blood glucose (from glucagon) to ensure muscles are prepared for high levels of activity by increased respiration.
  • Increases pulse and breathing rate so glucose and oxygen can be delivered to muscles cells + removal of carbon dioxide.
  • Dilating pupils
  • Diverting blood flow towards muscles
108
Q

What is homeostasis?

A

The maintenance of a constant internal environment.

109
Q

What is the role of insulin?

A

Secreted into the blood at times when blood glucose levels are high. Insulin temporarily converts excess glucose into glycogen, stored in liver + muscles. Glycogen is converted back to glucose several hours later when blood glucose levels have dipped due to respiration.

110
Q

What is negative feedback?

A

Occurs when the conditions change from the ideal/set point and returns conditions to this set point.

111
Q

What is type 1 diabetes?

A

Condition where blood glucose levels are not able to be regulated as insulin secreting cells in the pancreas are unable to produce insulin.

112
Q

What are symptoms of type 1 diabetes?

A
  • Too high blood glucose levels (can’t be regulated)
  • Extreme thirst
  • Fatigue
  • Blurred vision
  • Weight loss
113
Q

How to treat symptoms of type 1 diabetes?

A

Injecting insulin.

114
Q

How can people with type 1 diabetes control blood glucose level?

A

Exercise and diet.

115
Q

What is gravitopism?

A

When the stimulus of gravity is detected, and growth is positively/negatively responsive.

116
Q

What is phototropism?

A

When the stimulus of light is detected, and growth is positively/negatively responsive.

117
Q

What is auxin?

A

A growth hormone, produced in the tips of growing stems/roots. Stimulates the cells behind the tip to elongate; the more auxin, the faster growth.

118
Q

What is drugs?

A

A substance taken into the body that modifies or affects chemical reactions in the body.

119
Q

What are antibiotics?

A

Chemical substances made by certain fungi/bacteria that affect the working of bacterial cells by disrupting their structure or function or by preventing them from producing.

120
Q

Are antibiotics effective against viruses?

A

No, only bacteria.

121
Q

What happens to a cell that has been targeted by antibiotics?

A

Cell ruptures and dies when it tries to grow.

122
Q

What are some reasons of antibiotic resistance?

A
  • Overuse
  • Failing to finish full prescribed course
  • Large scale use in farming
123
Q

What do we call bacteria that have developed antibiotic resistance?

A

Super bugs - e.g MRSA

IGCSE Biology (10 decks)

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