bio mocks Flashcards
(123 cards)
1
Q
characteristics of living organisms:
A
M ovement
R espiration
S ensitivity
C ontrol
G rowth
R eproduction
E xcretion
N utrition
2
Q
what does a typical animal cell contain?
A
-nucleus: an organelle which contains the genetic material that controls the cell’s activities, it is surrounded by its own membrame
-cell membrame: this membrane forms the outer furface of the cell and controls the substances that go in and out
-cytoplasm: a gel-like substance where most of the cell’s chemical reactions happen, it contains enzymes which control these reactions
-mitochondria: small organelles where most of the reactions for aerobic respiration take place
-ribosomes: small organelles where proteins are made in the cell
3
Q
what does a typical plant cell contain?
A
-chloroplasts: photosynthesis, which makes food for the plant happens here, they contain a green substance called chlorophyll, which is used in photosynthesis
-cell wall: a rigid structure made of cellulose, which surrounds the cell membrane, it supports the cells and strengthens it
-vacuole: a large organelle that contains cell sap which helps to support the cell
4
Q
tissues:
A
-a tissue is a group of similar cells that work together to carry out a particular function
-a tissue can contain more than one cell type
5
Q
organs:
A
-an organ is a group of different tissues that work together to perfom a function
-e.g: lungs in mammals and leaves on plants
6
Q
organ systems:
A
-organs work together to form organ systems, each system does a different job
-for example, in mammals, the digestive system is made up of organs including the stomach, intestines, pancreas and liver
organelle -> cell -> tissue -> organ -> organ system
7
Q
eukaryotic organisms:
A
-organisms that have a nucleus and organelles that are found within a plasma membrame
-plants
-animals
-fungi
8
Q
plants:
A
e.g: cereals (maize) and herbaceous legumes (peas)
-plants are multicellular
-they have chloroplasts which means they can photosynthesise
-they have cell walls, which are made of cellulose
-plants store carbonates as sucrose or starch
9
Q
animals:
A
e.g: mammals (humans) and insects (flies)
-animals are multicellular
-they don’t have chloroplast so they can’t photosynthesise
-don’t have cell walls
-most have nervous coordination
-animals store carbonates as glycogen
10
Q
fungi:
A
e.g: yeast (single-cell) or mucor (multicellular)
-some are single-celled
-others have a body called mycelium made up of hyphae (thread-like structures) containing lots of nuclei
-can’t photosynthesise
-have cell walls made of chitin
-most feed by saprotrophic nutrition (they secrete extracellular enzymes into the area outside their body to dissolve their food, so they can absorb nutrients)
-fungi store carbohydrates as glycogen
11
Q
prokaryotic cells:
A
-do not have a nucleus or membrame-bound organelles
-protoctists
-bacteria
-viruses
12
Q
protoctists:
A
e.g: chlorella (plant-cell-like) or amoeba (animal-cell-like)-live in pond water
-these are single-celled and microscopic
-some have chloroplasts and are similar to plant cells
-other are more like animal cells
13
Q
bacteria:
A
e.g: lactobacillus bulgaricus (used to make yoghurt) or pneumococcus (causes pneumonia)
-single-celled and microscopic
-don’t have a nucleus
-they have circular chromosomes of DNA
-some can photosynthesise
-most bacteria feed off other organisms (dead or alive)
14
Q
viruses:
A
e.g: influenza virus (causes the ‘flu’), tobacco mosaic virus (prevents chloroplast formation) or HIV which lead AIDS
-viruses are small particles -not living organisms
-parasitics: can only reproduce within living cells, can infect every type of organisms
-they come in loads of different shapes and sizes
-do not have a cellular structure-they have a protein coat around some genetic material (either DNA or RNA)
15
Q
pathogens:
A
-are disease-causing organisms that include some viruses, protoctists and bacterias
-protoctist: plasmodium, which causes malaria
-bacterium: pneumococcus, which causes pneumonia
-viruses: influenza virus (which cause ‘flu’) and HIV (which causes AIDS)
16
Q
biological molecules:
A
-carbohydrates
-proteins
-lipids
17
Q
carbohydrates:
A
-they are made of carbon, oxygen and hydrogen
-starch and glycogen are large, complex carbohydrates, which are made up of many smaller units joined together in a long chain
maltose (and other simple sugars) -> starch
18
Q
proteins:
A
-proteins are made up of long chains of amino acids
-they all contain carbon, nitrogen, hydrogen and oxygen atoms
amino acids -> proteins
19
Q
lipids:
A
-lipids (fats and oils) are built from fatty acids and glycerol
-lipids contain carbon, hydrogen and oxygen atoms
glycerol & fatty acids -> lipid
20
Q
how to make a food sample:
A
1) get a piece of food and break it up using pestle and mortar
2) transfer the ground up food to a beaker and add some distilled water
3) give the mixture a good stir with a glass rod to dissolve some of the food
4) filter the solution using a funnel lined with filter paper to get rid of the solid bits of food
21
Q
testing for glucose:
A
use the Benedict’s Test to test for glucose:
-if the food sample contains glucose, the solution in the test tube will change from its normal blue colour
-it will become green or yellow in low concentrations of glucose
-it will become brick-red in high concentrations of glucose
22
Q
testing for starch:
A
use Iodine solution to test for starch:
-if the sample contains starch, the colour of the solution will change from browny-orange to black or blue-black
23
Q
testing for proteins:
A
use the Biuret Test to test for proteins:
-if the food sample contains protein, the solution will change from blue to pink or purple
-if no protein is present, the solution will stay blue
24
Q
testing for lipids:
A
use the Sudan III Test to test for lipids:
-if the sample contains lipids, a milky white emulsion will form
-if the sample doesn’t contain lipids, it will remain colourless
25
what are biological catalysts?
-a catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction
26
enzymes:
-they are protein molecules and the shape of the enzyme is vital to its function
-this is because each enzyme has its uniquely shaped active site where the substrate binds (joins)
-a simplified way to look at it is the Lock and Key Hypothesis:
-a substrate is a molecule that is changed in a reaction, it must have the correct shape to fit into the active site
27
how does temperature affect enzyme function?
-the optimum is around 37ºC (body temperature)
-the rate of reaction increases with an increase in temperature up to this optinum, but above this temperature it rapidly decreases and eventually the reaction stops
-when the temperature becomes too hot, the bonds in the structure will break
-this changes the shape of the active site, so the substrate can no longer fit in, which means it is denatured
28
practical: investigate how enzyme activity can be affected by changes in temperature
1) Starch solution is heated to set temperature
2) Amylase is added
3) Iodine is added to each well after a minute
4) Measure the time it takes until the iodine stops turning blue-black (meaning starch is present)
5) Repeat the test with different temperature
29
how does pH affect enzyme function?
-the optinum pH for most enzymes is 7, but some that are produced in acidic conditions, such as the stomach, have a lower optinum pH
-if the pH is too high or too low, the forces that hold the amino acids chains will be affected
-this will change the shape of the active site, so the substrate can no longer fit in
-the enzyme is said to be denatured and can no longer work
30
diffusion:
-diffusion is the spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration
-it is a passive process as no energy is required
-the molecules have to be small in order to be able to move accross, for example oxygen, glucose, amino acids and water, but larger molecules such as starch and proteins cannot
31
osmosis:
-> the movement of water from a less concentrated solution to a more concentrated one through a partially permeable membrame
-water moves from a dilute solution to a concentrated solution because it moves from ana area with high water potential to low water potential- down a concentration gradient
-it is a passive process
32
What is an Isotonic solution?
If the concentration of sugar in a external solution is the same as the internal, there will be no movement and the solution is said to be isotonic to the cell
33
What is a Hypertonic solution?
If the concentration of sugar in an external solution is higher than the internal, water moves out, and the solution is said to be hypertonic to the cell
34
What is a Hypotonic solution?
if the concentration of sugar in external solution is lower than the internal, water moves in, and the solution is said to be hypotonic to the cell
35
active transport:
-active transport is the movement of particles from an area of lower concentration to an area of higher concentration, i.e: against a concentration gradient
-this requires energy from respiration as it is working against the gradient, which is why its called active
36
concentration gradient: affecting rate of movement
the greater the difference in concentration, the faster the rate of diffusion because more particles are randomly moving down the gradient than are moving against it
37
temperature: affecting rate of movement
the greater the temperature, the greater the movement of particles, resulting in more collisions and therefore a faster rate of diffusion
38
surface area:volume ratio: affecting rate of movement
the greater the surface area, the more space for particles to move through, resulting in a faster rate of diffusion
39
distance: affecting rate of movement
the further the particles have to travel the longer it will take
40
practical: investigate diffusion in non-living systems
1) cut a 1cm^3 cube of agar made of sodium hydroxide and phenolphthalein
2) place cube in solution with hydrochloric acid
3) remove the cube and wash with water to stop further reaction
4) cut the cube in half and measure the distance that the acid has caused agar to become colourless from outside inwards
5) repeat the experiment two more times and calculate the mean
6) repeat with different concentrations of hydrochloric acid
41
practical: investigating osmosis in potatoes
1) place different sucrose solutions including 0% for a control, in different boiling tubes
2) dry potato strips on a paper towel and measure the masses
3) place each potato strip into each surcrose solution for 20 mins and record how the mass changed
4) repeat tests at each solution several times with potato strips of similar masses
42
photosynthesis:
-photosynthesis is the process of making glucose from sunlight in the leaves of the plant
-it is an endothermic reaction in which light energy is converted into chemical energy within the chloroplasts
43
word equation for photosynthesis:
carbon dioxide + water (light)-> glucose + oxygen
CO2 + H20 -> C6H12O6 + O2
balanced: 6CO2 + 6H02 -> C6H12O6 + 602
44
factors affecting photosynthesis: temperature
-with an increase in temperature, the rate of photosynthesis increases
-however, as the reaction is controlled by enzymes, this trend only continues up to certain temperature until the enzymes begin to denature and the rate of reaction decreases
45
factors affecting photosynthesis: light intensity
-for most plants, the higher the light intensity, the rate of photosynthesis increases
-as the distance between the light source and the plant increases, the light intensity decreases, i.e. it is inversely proportional to the square of the distance: light intensity∝ 1/distance^2
-this means that if a lamp is 2 metres away from a plant, then light intensity of the lamp is a 1/4 of its original value -> 1/2^2 = 1/4
46
factors affecting photosynthesis: carbon dioxide concentration
-carbon dioxide is also needed to make glucose
-as the concentration of carbon dioxide increases, the rate of reaction increases
47
structure of a leaf:
-waxy cuticle: helps to reduce water loss by evaporation and is a protective layer found at the top of a leaf
-upper epidermis: very thin and transparent in order to let light in to the palisade mesphyll
-palisade mesophyll: contain lots of chloroplasts so that photosynthesis can happen rapidly
-spongy mesophyll: have lots of air spaces to allow gases to diffuse in and out of cells faster
-lower epidermis: contains guard cells and stomata (gaps)
-guard cell: kidney-shaped cells that open and close the stomata by absorbing or losing water(when lots of water is available, the cells fill and open stomata)
-stomata: where gas exchange and loss of water by evaporation takes place- opens during the day and closes at night
48
plants require 2 main types of mineral ions:
-mineral ions: for growth
-magnesium: required for chlorophyll production, deficiency -> causes leaves to turn yellow
-nitrate: required to produce amino acids, deficiency
-> causes stunted growth and turns leaves yellow
49
practicals investigating photosynthesis:
-use water plants, such as Elodea which release bubbles of oxygen when photosynthesising
-a lamp with an LED bulb is set up beside the beaker of water containing the water plant. An LED is best as it will not raise the temperature of the water
-sodium hydrogen carbonate (NaHCO3) is added to the water to supply carbon dioxide
-this can set up can be used to investigate the evolution of oxygen from a water plant
50
practical: investigating the effect of light intensity:
1) place pondweed in water and set up a desk lamp next to alongside a ruler so that you can measure the distance between the light and the beaker
2) move a lamp away by 10 cm
3) leave for 5 minutes to allow for the pondweed to adapt
4) count the number of bubbles given off in 1 minute and record
5) repeat steps 2-4
the rate at which pondweed produces oxygen corresponds to the rate at which it's photosynthesising - the faster the rate of oxygen production, the faster the rate of photosynthesis
51
practical: investigating the effect of carbon dioxide:
-complete the experiment of light but instead of testing the variable of light intensity using a lamp, use different concentrations of sodium hydrogen carbonate solution, whilst keeping the other variables the same
52
practical: investigating starch production:
1) cover half of a small leaf with foil
2) place the plant on a windowsill for 48 hours so that ligh can reach it
3) put the leaf into boiling water to kill and preserve it
4) put the leaf in a boiling tube containing hot ethanol for 10 minutes (this removes the chlorophyll pigment)
5) dip the leaf in boiling water to soften it
6) put lead in a Petri dish and cover with iodine solution
7) the covered half of the leaf will remain orange-brown, whereas the exposed half will change to blue-black (as iodine solution changes colour in the presence of starch, as photosynthesis tuned the glucose into starch for storage)
53
experiment provide photosynthesis require chlorophyll:
-repeat the experiment of starch production but with a variegated leaf
-variegated plants are white and green and only contain chlorophyll in the green parts, therefore only the green areas of the plant will test positive for starch (i.e. turn blue-black) as a result of photosynthesis occuring
-the white areas that do not contain chlorophyll remain an orange-brown colour
54
nutrition in humans:
-humans need to eat a balanced diet in order to mantain their health
-this should consist of carbohydrates, proteins, lipids, dietary fibre, vitamins, minerals and water
55
nutrient sources and functions:
-carbohydrates: pasta, rice, sugar -> provide energy
-proteins: meat, fish -> needed for growth + repair of tissue, and to provide energy in emergencies
-lipids: butter, oily fish -> provide energy, act as an energy store and provide insulation
-dietary fibres: wholemeal bread, fruit -> aids the movement of food through the gut
-vitamin A: carrots, green vegetables -> helps improve vision and keep skin and hair healthy
-vitamin C: fruit, e.g: oranges -> helps to prevent scurvy
-vitamin D: eggs -> needed for calcium absorption
-calcium: milk, cheese -> needed to make bones and teeth
-iron: red meat -> needed for haemoglobin for healthy food
-water: food and drink -> just about every bodily function relies on water-we need a constant supply to replace water lost through urinating, breathing and sweating
56
factors affecting energy requirements: age
-children and teenagers need more energy than older people-they need energy to grow and they're generally more active
57
factors affecting energy requirements: activity levels
-if you are more active then you will need more energy for movement
58
factors affecting energy requirements: pregnancy
-pregnant women need more energy than other women- they've got to provide the energy their babies need to develop
59
the alimentary canal:
-the alimentary canal is the passage food moves through once it has been eaten-mouth
-oesophagus
-stomach
-liver
-gall bladder
-pancreas
-large intestine
-small intestine
-rectum
60
human alimentary canal: mouth
-mechanical digestion: teeth break up large food piece into smaller pieces (food bolus)
-salivary glands produce saliva to lubricate the food bolus so it can be swallowed easily
61
human alimentary canal: oesophagus
-tube from mouth to the stomach
-food bolus moves down due to unidirectional wave-like contractions (peristalsis) created by circular muscles and longitudinal muscles that create a squeezing action
62
human alimentary canal: pancreas
-produces carbohydrase, protease and lipase enzyme
-secretes enzymes into the stomach and small intestine
63
human alimentary canal: stomach
-it pummels the food with its muscular walls
-produces the protease enzyme, pepsin
-produces hydrochloric acid to: kill bacteria and give the optinum pH for pepsin to work
64
human alimentary canal: small intestine-> duodenum
duodenum:
-the first part of the small intestine
-carbohydrases, proteases and lipases digest food here
-bile is released into the duodenum, bile is produced in the liver and stored in the gallbladder, it has 2 roles:
1) it is alkaline to neutralise the hydrochloric acid which comes from the stomach, the enzymes in the small intestine have a higher (more alkaline) optinum pH than those in the stomach
2) it breaks down large drops of fat into smaller ones (emulsifies it), the larger surface area allows lipase to chemically break down the lipids into glycerol and fatty acids faster
-peristalsis also occurs here
65
human alimentary canal: small intestine -> ileum
ileum:
-lined with vili to absorb maximum absorption of digested, soluble food molecules into the blood
-it's very long, so there's time to break down and absorb all the food before it reaches the end
-big surface area for absorption, because the walls of the small intestine are covered in millions of vili
-each cell on the surface of a villus has its own microvilli-they increase the surace area even more
-villi have a thinlining and a good blood supply to assist quick absorption
66
human alimentary canal: large intestine
-also called colon
-water is absorbed here, to produce faeces
-faeces is stored in the rectum and the removed through the anus (the last part of the large intestine)
67
digestive enzymes:
carbohydrates (starch):
-broken down by carbohydrases
-starch -> maltose by amylase
-maltose -> glucose by maltase
proteins:
-broken down by proteases in the stomach and small intestine
-proteins -> amino acids
lipids:
-broken down by lipases
-lipids -> glycerol + 3 fatty acids
68
respiration:
-respiration occurs in every cell in the body of all livings things to supply ATP (adenosine triosphate) to cells
-cellular respiration is an exothermic reaction
-there are 2 types of respiration: aerobic and anaerobic
69
aerobic respiration:
-this uses oxygen
-it yields the most energy
-most of the reactions that make up aerobic respiration occur in the mitochondria
glucose + oxygen -> carbon dioxide + water
C6H12O6 + O2 -> CO2 + H2O
balanced C6H12O6 + 6O2 -> 6CO2 + 6H2O
70
anaerobic respiration:
-occurs when there is not enough oxygen
-it does not yield as much energy as aerobic respiration
-it is only used as a last resort, for example during a sprint where it is difficult to breathe in enough oxygen
in animals:
glucose (C6H12O6) -> lactic acid
in plant and yeast cells it is (called fermentation):
-glucose (C6H12O6) -> ethanol (C2H6O) + carbon dioxide (CO2)
71
practical: investigate the evolution of carbon dioxide from respiring seeds or other suitable living organisms
1) connect a capillary tube from the air into a flask containing sodium hydroxide, which will absorb carbon dioxide
2) connect this flask with a capillary tube to another flask containing hydrogen carbonate indicator (which is red at neutral pH and yellow at low pH, i.e. when carbon dioxide is present)
3) connect the second flask to a third flask containing either germinating seeds or respiring animals, such as worms
4) connect the third flask to another flask containing hydrogen carbonate indicator, such as in step 2
results: the sodium hydroxide solution in the first flask will absorb carbon dioxide from the air, which will turn the second flask red, as it will have a neutral pH. However, the respiring organism will produce carbon dioxide and will therefore turn the indicator yellow
72
practical: investigate the evolution of heat from respiring seeds or other suitable living organisms
1) use 2 vacuum flasks, one containing living germinating seeds and the other containing dead or boiled seeds (as a control)
2) put a thermometer wrapped in cotton wool (to prevent heat from escaping) to measure temperature
3) measure initial temperature
4) leave seeds for a few days and then measure end temperature
-the live germinating seeds will release heat due to aerobic respiration and so the temperature will increase
73
structure of thorax:
-ribs: bone 'cage' surrounding the lungs to provide protection of internal organs
-intercostal muscle: muscles found between the ribs that control inhalation and exhalation
-diaphragm: muscular dome at the bottom of the thorax that changes the pressure in order to control inhalation and exhalation
-trachea: the windpipe, where air enters the thorax and flows to the lungs
-bronchi: the trachea divides into 2 bronchi-one to each lung
-bronchioles: the bronchi further divide into smaller tubes that connect to the alveoli
-alveoli: tiny air sacs that are the place of gas exchange
-pleural membrames: found on the outside of the lungs and inside of chest cavity to lubricate the lungs-reducing friction when breathing
74
intercostal muscles and diaphragm in ventilation:
-intercostal muscles: inhalation -> contract, exhalation -> relax
-ribcage: inhalation -> up and out, exhalation -> down and in
-diaphragm: inhalation -> contracts downwards, exhalation -> relaxes upwards
-pressure: inhalation -> decreases, exhalation -> increases
-air movement: inhalation -> moves in, exhalation -> moves out
75
alveoli adaptations:
-thin cell walls: one cell thick so there is a shorter distance of diffusion
-folded: to increase surface area for diffusion
-large network of tiny capillaries: increases concentration gradient between air in alveoli and the blood
76
consequences of smoking:
-damages the walls inside the alveoli, reducing the surface area for gas exchange and leading to diseases like emphysema
-the tar in the cigarettes damages the cilia in you lungs and trachea making chest infections more likely
-tar also irritates the bronchi and bronchioles, encouraging mucus to be produced which can't be cleared well by damaged cilia-this causes smoker's cough and chronic bronchitis
-the carbon monoxide in cigarette smoke reduces the amount of oxygen the blood can carry, to make up for this, heart rate increases-which lead to an increase in blood pressure, high blood pressure damages the artery walls, making the formation of blood clots more likely which increases the risk of coronary heart disease (e.g. heart attacks)
-tobbaco also contains carcinogens-chemical that can lead to cancer
77
practical: investigating the effect of exercise on breathing rate
1) sit for five minutes
2) for one minute, count the number of breaths you take
3) do four minutes of exercise and as soon as you stop count your breaths for a minute
4) repeat the steps above, and work out the average results for resting and after exercise
5) you could also pester two other people to do the same so you get three sets of results to compare
results: your results show that exercise increases breathing rate, this is because you muscle respire more during exercise. They need to be supplied with more O2 and have more CO2 removed, so your breathing rate increases
-in this experiment you need to control the time exercising, and the temperature
78
practical: investigating the effect of release of carbon dioxide in your breath
1) set up 2 boiling tubes and put the same amount of limewater in each
2) put your mouth around the mouthpiece and breathe in and out several times
3) as you breathe in, air from the room is drawn in through boiling tube A. This air contains very little carbon dioxide so the limewater in this boiling tube remains colourless
4) when you breathe out, the air you exhale bubbles through the limewater in boiling tube B. This air contains CO2 produced during respiration, so the limewater in this boiling tube turns cloudy
results: since the limewater in tube A remains clear, you can tell the carbon dioxide in the exhaled air was from respiration-it wasn't inhaled through boiling tube A. if you'd inhaled in the carbon dioxide, the limewater in boiling tube A would've turned out cloudy too
79
Why do unicellular organisms rely on diffusion for the movement of substances?
-in small single-celled organisms can use diffusion to transport molecules into their body from the air-this is because they have a relatively large volume surface : volume ratio
-due to their low metabolic demands, diffusion accross the surface of the organism is sufficient enough to meet its needs
80
the need for a transport system in multicellular organisms:
-multicellular organisms have a small surface area : volume ratio so they cannot rely on diffusion alone
-instead, surfaces and organ systems have a number of adaptations that allows molecules to be transported in and out of cells, examples (alveoli in the lungs, villi in the small intestines and root hair cells in plants)
81
transporting substances in plants: phloem
-the phloem transport sugars, like sucrose and amino acids where they're made in the leaves to other parts of the plant
-this movement of food substances around the plant is known as translocation
82
transporting substances in plants: xylem adaptations
-the xylem carry water and mineral salts from the roots up the shoot to the leave in the transpiration stream
83
composition of blood: plasma
-the liquid which carries the components in the blood
-plasma is important for the transport of red and white blood cells, platelets, carbon dioxide, digested food products, urea, hormones and heat energy
84
composition of blood: red blood cells
-carry oxygen molecules from the lungs to all the cells in the body
-contain haemoglobin: a red protein that combines with oxygen for transport
-no nucleus: to create more space for haemoglobin
-biconcave shape: to maximise surface area for oxygen to be absorbed
-flexible: so they can fit through very narrow blood vessels
85
composition of blood: white blood cells
-they are part of the immune system, which is the body's defence against pathogens, there are 3 types:
1) Phagocytic wbc: one types of wbc can do a process called phagocytosis, where the pathogen is engulfed and killed + as they are able to do this with any type of pathogen they are non specific
2) producing antibodies (lymphocytes): each pathogen has an antigen on their surface, once antibodies begin to bind to the pathogen, they start to clump together, resulting in it being easier for wbc to find them + if you become infected again with the same pathogen, the specific complementary antibodies will be produced at a faster rate. The individual will not feel the symptons of the illness, they are said to be immune
3) producing antitoxins: wbcs neutralise the toxins released by the pathogen by binding to them
86
human circulatory system: the heart
-the heart is an organ in the circulatory system, it carries oxygen and nutrients to every cell in the body and removes the waste products
-the heart pumps blood around the body in a double circulatory system, this means there are 2 circuits, mammals require this double system because the metabolic rate is higher and so need a faster system
system 1: right atrium
-deoxygenated blood flows into the right atrium and then into the right ventricle which pumps it to the lungs to undergo gas exchange
system 2: left atrium
-oxygenated blood flows into the left atrium and then into the left ventricle which pumps oxygenated blood around the body
87
structure of the heart:
-muscular walls to provide a strong heartbeat
-the muscular wall of the left ventricle is thicker because blood needs to be pumped all around the body rather than just to the lung like the right ventricle
-4 chambers that seperate the oxygenated blood from the deoxygenated blood: 2 atria above and 2 ventricles below
-valves to make sure blood does not flow backwards
-coronary arteries cover the heart to provide its own oxygenated blood supply
88
process of the heart:
1. blood flows into the right atrium through the vena cava, and left atrium through the pulmonary vein
2. the atria contract forcing the blood into the ventricles
3. the ventricles then contract, pushing the blood in the right ventricle into the pulmonary artery to be taken to the lungs, and blood in the left ventricle to the aorta to be taken around the body
4) as this happens, valves close to make sure the blood does not flow backwards
89
structure of blood vessels:
pulmonary arteries: carry blood AWAY from the heart
-layers of muscle in the walls make them strong
-elastic fibres allow them to stretch
-this helps the vessels resist the high pressure created by the pumping of the heart
-the largest artery in the body is the aorta
pulmonary veins: carry blood TOWARDS the heart
-the lumen (the actual tube in which blood flows through) is wide to allow the low pressure blood to flow through
-they have valves to ensure the blood flows in the right direction
-capillaries- they carry the blood really close to every cell in the body to exchange substances with them
-one cell thick walls create a short diffusion pathway
-permeable walls so substances can move accross them
90
heart rate changes: exercise
-when exercising, muscles require energy and so will be respiring at a higher rate
-this means that the heart rate will increase in order for the heart to pump more oxygen and nutrients around the body and to remove the waste carbon dioxide from respiring muscle
-stroke volume will also increase, meaning that the heart will pump more powerfully as well as faster
-when anaerobic respiration occurs during high intensity exercises, such as sprintm an oxygen debt is created, which is then needed to be transferred around the body quickly so that the lactic acid produced by the anaerobic respiration does not cause muscle cramps
91
heart rate changes: adrenaline
-adrenaline is a hormone produced by the adrenal glands above the kidney
-it is responsible for the 'fight or flight' reaction
-increased heart rate to deliver more oxygen to respiring muscles that will be contracting more frequently
-increased breathing rate, so more gas exchange occurs and more oxygen diffuses into the blood and more carbon dioxide diffuses out
-blood flow is diverted away from digestive system and towards respiring muscles
-adrenaline also causes other body changes, such as pupils to dilate to let in more light
92
coronary heart disease:
-the coronary arteries supply blood to the heart and in CHD these arteries become blocked, due to a build-up of fatty plaques (astherosclerosis). This can cause ischaemia (lack of blood and oxygen) which can eventually lead to a muscle death and therefore a heart attack
causes:
-Poor diet: a diet rich in saturated fat increases choresterol levels, which can increase the chance of fatty plaques building up + high levels of salt can increase blood pressure which damages the blood vessels and increases the chance of fatty deposists building up
-smoking: the carbon monoxide in cigarette smoke reduces the amount of oxygen the blood can carry, to make up for this, heart rate increases-which lead to an increase in blood pressure, high blood pressure damages the artery walls, making the formation of blood clots more likely
-stress: hormones produced in times of stress can increase blood pressure which can damage the artery walls
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the kidneys and excretion:
-three main roles:
-removal of urea from the blood, urea is produced in the liver from excess amino acids
-adjustment of salt levels in the blood
-adjustment of water content of the blood
-they do this by filtering stuf out of the blood under high pressure, and then reabsorbing the useful things, the end product is urine
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coordination and response:
-homeostasis is the maintenance of a constant internal environment, for example, mantaining body temperature or body water content
-coordinating responses there needs to be a stimulus (such as heat), a receptor which detects the stimulus (such as the skin on the fingertip) and then an effector which produces the response (such as arm muscles moving the hand away)
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positive phototropism:
-shoots grow towards the light
-when a shoot tip is exposed to light, it accumulates more auxin on the side that's in the shade than the side that's in the light
-this makes the cells grow (elongate) faster on the shaded side, so the shoot bends towards the light
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negative phototropism: (roots???)
-roots grow away from light
-if a root starts being exposed to some light, more auxin accumulates on the more shaded side
-the auxin inhibits cell elongation on the shaded side, so the root bends downwards, back into the ground
-roots that are underground aren't exposed to light, they grow downwards due to positive gravitropism
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negative geotropism: (s. gravity???)
-when a shoot is growing sideways, gravity produces unequal distribution of auxin in the tip, with more auxin on the lower side
-this causes the lower side to grow faster, bending the shoot upwards
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positive geotropism: (roots + sideways)
-root bends downwards
-a root growing sideways will also have more auxin on its lower side
-but in a root the extra auxin inhibits growth, this means the cells at the top elongate faster, and the root bends downwards
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the human nervous system: nervous vs endocrine system
-the nervous system is made up nerve cells that carry impulses around the body
-the endocrine (hormonal) system is made up of glands that produces hormones that stimulate changes in the body
both systems require stimuli, receptor and effectors and chemicals are involved in both, but there are also key differences between them:
nervous system:
-type of signal: electrical
-transmitter: nerve cells
-speed of response: very fast
-duration of response: short
endocrine system:
-type of signal: chemical
-transmitter: hormones in bloodstream
-speed of response: slower
-duration of response: long
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the CNS:
-the nervous system is made up of all of the neurones in your body, there are 3 types of neurone: sensory neuron, relay neurones and motor neurones
-the CNS consists of the brain and the spinal cord only
-when recepetors in a sense organ detect a stimulus, they send electrical impulses along sensory neurones and motor neurones to the CNS
-the CNS then sends electrical impulses to an effector along a motor neurone, the effector then responds accordingly
-the job of the CNS is to coordinate the response (which always need a stimulus, receptor and effector)
-because neurones transmit information using high speed electrical impulses, the nervous system is able to bring about very rapid responses
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synapses:
-synapses are the connection between two neurones
-the nerve signal is transferred by chemicals called neurotransmitters which diffuse accross the gap
-these chemicals then set off a new electrical signal in the next neurone
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the reflex arc:
-the reflex arc is a subconscious response to a dangerous stimuli which involves the CNS
1) a stimulus is detected by receptors
2) impulses are sent along a sensory neuron
3) in the CNS the impulse passes to a relay neuron
4) impulses are sent along a motor neuron
5) the impulse reachers an effector resulting in the appropiate response, such as a contraction
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the eye:
-cornea: the transparent outer part of the eye -> it refracts light to reach the retina
-iris: the coloured part of the eye that does not allow light to go through -> controls how much light enters eye + in bright light, the circular muscles contract and radial muscles relax to make the pupil smaller + in dim light, the circular muscles relax and the radial muscles contract to make the pupils larger, so more light can enter to create a better image
-lens: transparent, biconvex disc that attaches to ciliary muscles by the suspensory ligaments + focuses light onto the retina
-retina: contains light receptors -> contains rods (respond to dim light) and cones (respond to colour)
-optic nerve: carries impulses between the eye and the brain
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accomodation:
near object:
-ciliary muscles contract
-suspensory ligaments slacken
-this allows the lens to become fatter so the light is refracted more
-light converges on the retina
distanct object:
-ciliary muscles relax
-suspensory ligaments stretch
-this allows the lens to become thin so the light is refracted less
-lighy converges on the retina
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mantaining temperature:
when it is hot:
-sweat is produced by sweat glands
-vasodilation (blood vessels close to the surface of the skin widen)
-hairs lie flat
when it is cold:
-sweating stops
-skeletal muscles contract rapidly (shivering) to generate heat
-hair stands on end to create an insulating layer, trapping warm air
-vasconstriction means blood does not flow so close to the surface, resulting in less heat lost
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the endocrine system:
-hormones are chemical messengers that are secreted by endocrine glands into the bloodstream
-source, roles and effects:
-adrenaline: adrenal gland, prepares the body for 'fight or flight' response, increases heart rate and breathing rate
-insulin: pancreas, helps control blood sugar levels, stimulates the liver to turn glucose into glycogen for storage
-testosterone: testes, main sex hormone in males, produces secondary sexual characteristics in males (e.g: hair growth, depper voice)
-progesterone: ovaries, mantains pregnancy, mantains the uterus lining so that the fertilised egg can implant
-oestrogen: ovaries, main sex hormone in females, produces secondary sexual characteristics in females, (e.g: breasts developing) and control menstrual cycle
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asexual reproduction: + some advantages and disadvantages
-> involves only one parent, the offspring have identical genes to the parent
-more efficient in both time (faster) and energy (less energy required)
-since they’re identical, their is risk that they could all die if conditions become unfavorable
-mitosis: produce genetically identical cells
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sexual repoduction: + some advantages and disadvantages
-> involves the fusion of male and female gametes, because there are two parents, the offspirng contains a mixture of their parents’ genes
-produces variation of offspring
-requires time (longer) and energy (more energy is required)
-meiosis: produce genetically different cells
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what is fertilisation?
-> involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo
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sexual reproduction in plants:
structures of plants:
the stamen: (male part of the reproductive part in a plant)
-the anther -> contains pollen grain, these produce the male gametes (sperm)
-the filament -> is the stalk that supports the anther
the carpel: (female part of the reproductive part in a plant)
-the stigma -> the end bit that the pollen grains attach to
-the style -> the rod-like section that supports the stigma
-the ovary -> contains the female gametes (eggs) inside ovules
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insect pollinate: adaptations of features for pollination
petals: large and bright to attract insects
nectar: scanted with nectar to attract insects
pollen grains: sticky and in moderate amounts
anthers: inside flower, stiff and attached so that insects can brush apart
stigma: inside flower, sticky pollen grains stick to it when an insect brushes past
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wind pollinated: adaptations of features for pollination
petals: small and dull-usually green or brown
nectar: no scent or nectar
pollen grains: smooth and light so they can be easily carried in the wind and in large amounts to make sure some reach other flowers
anthers: outside flower, loose on long filaments so that pollen can be released easily
stigma: outside flower, forms network to catch pollen grains drifting in the wind
filament: long filaments that hang the anthers outside flower so that a lot of pollen gets blown away
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seed and fruit formation:
pollen grains land on stigma
pollen tube grows out of the pollen grain into the ovule
the ovary will become the fruit of the plant which will be the method of transport of the cell
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practical: understand the conditions needed for seed germination
germination is the process in which seeds begin to develop into a new young plant
-water: needed to activate enzymes to break down the starch food reserves in the seeds
-oxygen: needed for aerobic respiration to release energy for growth
-warmth: optimum temperature for enzymes will increase growth rate
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practical: understand the conditions needed for seed germination/ method
1) set up 4 boiling point with 10 cress seeds in each, sitting on a cotton wool
2) Tube A should have dry cotton wool and kept at 20ºC
3) Tube B should have moist cotton wool and kept at 20ºC
4) Tube C should have boiled water that has been cooled, covered with a layer of oil and kept at 20ºC
5) Tube D should have moist cotton wool but is kept at lower temperature (4ºC)
-the results will show that seeds germinate in test tube B only because it has the water, temperature and oxygen required for germination. Tube A does not have water, the oil in tube C does not allow for oxygen and tube D is not kept at optimum temperature
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germination:
-> process in which seeds begin to develop into a new young plant
conditions they need:
-water
-oxygen
-suitable temperature
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structures of seeds:
-embryo: young root and shoot become the adult plant
-food store: starch for the plant to use until it is able to carry out photosynthesis
-seed coat: a protective covering
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asexual reproduction: natural & artificial
1) Natural: runners
2) Artificially (cloning): cuttings
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structure of the male reproductive system:
structure, description:
-sex gland: produces semen that contains sperm cells
-sperm duct: sperm passes through this
-testis: contains in scrotum (bag of skin) and produces sperm and testosterone
-penis: passes urine and semen out of the body
-urethra: tube inside the penis to carry urine or semen, a ring of muscle inside stops the two mixing
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structure of female reproductive system:
structure, description:
-ovary: contains ova (female gametes) which develop when FSH is released
-oviduct: connects ovary to the uterus
-uterus: has a thick lining so that fertilised eggs can be implanted
-cervix: ring of muscle at lower end of uterus to ensure foetus remains in place during pregnancy
-vagina: muscular tube that leads to the inside of the body
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secondary sexual characteristics:
females: oestrogen
-breast development
-menstrual cycle begins
-growth of body hair
-widening of hips
-increased height
males: testosterone
-growth of penis and testes
-production of sperm
-growth of facial and body hair
-muscle development
-voice lowering and breaking
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the menstrual cycle:
the menstrual cycle last 28 days and the egg is usually released on day 14 (ovulation)
oestrogen:
-causes thickening of the uterus in preparation for implantation of an egg
-levels peak on day 10 and then begin to fall
progesterone:
-maintains the thick lining of the uterus
-inhibits the release of LH and FSH
-the egg matures on day 14 and progesterone starts increasing after this until it reaches its peak 3 days later
if the egg is not fertilised progesterone levels fall and the uterus lining breaks down in a period that lasts for around 5 days
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developing an embryo:
-the placenta allows diffusion of glucose, oxygen and amino acids from the mother's blood to the developing foetus for growth
-amniotic fluid is a liquid contained in a bag (amnion) in the uterus that surrounds the foetus, it protects the foetus and cushions any rough movement, when labour begins the amnion breaks and the fluid come out-often known as a woman's 'water breaking'
