Cells and Organisation Flashcards
1
Q
What type of cells are animal and plant cells?
A
Eukaryotic cells
2
Q
What are prokaryotes?
A
single-celled organisms
3
Q
What are the 5 subcellular structures of an animal cell?
A
Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes
4
Q
What are the 3 subcellular structures that plant cells have but animal cells don’t have?
A
Cell wall, permanent vacuole and chloroplasts
5
Q
What is the function of the nucleus?
A
contains genetic material that controls the activities of the cell
6
Q
What is the function of the cytoplasm?
A
gel-like substance where most of the chemical reactions happen, contains enzymes that control the chemical reactions
7
Q
What is the function of the cell membrane?
A
Holds the cell together and controls what goes in and out of the cell
8
Q
What is the function of ribosomes?
A
where proteins are made in the cell (protein-synthesis)
9
Q
What is the function of the mitochondria?
A
Where aerobic respiration takes place, it transfers energy that the cell needs to work
10
Q
What is the function of the cell wall?
A
Supports and strengthens the cell
11
Q
What is the cell wall made of?
A
cellulose
12
Q
What is the function of the permanent vacuole?
A
It contains cell sap, a weak solution of sugar and salts
13
Q
What is the function of chloroplasts?
A
Where photosynthesis takes place, which makes food for the plant. Contains chlorophyll that absorbs light for photosynthesis.
14
Q
What do the chloroplasts contain?
A
Chlorophyll
15
Q
What type of cells are bacteria?
A
prokaryotic cells
16
Q
What do eukaryotic cells have the prokaryotic cells do not?
A
Nucleus
17
Q
What do prokaryotes have instead of a nucleus?
A
a single circular strand of DNA that floats freely in the cytoplasm
18
Q
What are plasmids?
A
small rings of DNA
19
Q
What does bacteria not have that animal or plant cells have?
A
Chloroplasts or mitochondria
20
Q
How do light microscopes work?
A
They use light and lenses to form an image of a specimen and magnify it. They let us see individual cells and large subcellular structures.
21
Q
How do electron microscopes work?
A
They use electrons to form an image. They have higher magnification than light microscopes.
22
Q
What are the differences in light microscopes and electron microscopes?
A
Light microscopes
- Use light and lenses
- lower magnification
- lower resolution
- less expensive
Electron microscopes
- Use electrons to form images
- higher magnification and resolution
- expensive
- requires training to operate
23
Q
What is meant by resolution?
A
The ability to distinguish between two points, a higher resolution gives a sharper image.
24
Q
What is the formula for magnification?
A
magnification = image size/ actual size
25
Give the method for the RP on microscopy.
Equipment:
- Light microscope
- Onion
- A slide (glass or plastic)
- Iodine solution
1. Add a drop of water to the middle of a clean slide.
2. Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue.
3. Place the epidermal tissue into the water on the slide.
4. Add a drop of iodine solution.
5. Place a cover slip on top.
6. Observe using the microscope.
26
Why is iodine solution used in microscopy?
It is a stain, makes it clearer for objects in a cell to be seen.
27
Why is the cover slip placed down at an angle?
To reduce air bubbles obstructing the view of the specimen.
28
What are the 6 main parts of a microscope?
Eyepiece
Coarse adjustment knob
Fine adjustment knob
Light
Stage
High and low power objective lens
29
Explain how to use a light microscope.
1. Clip the slide prepared onto the stage.
2. Select the lowest-powered objective lens (lowest magnification)
3. Use the coarse adjustment knob to move the stage up to just below the objective lens.
4. Look down the eyepiece, use the coarse adjustment knob to move the stage down until the image is in focus.
5. Adjust the focus with the fine adjustment knob, until you get a clear image.
6. To see the slide in greater magnification, swap to a higher powered objective lens and refocus.
30
How should you draw your observation?
- Sharp pencil
- No colouring or shading
- Subcellular structures should be in proportion
- Include title and magnification
- label features using straight, uncrossed lines
31
What is differentiation?
The process by which a cell changes to become specialised for its job.
32
When does differentiation typically occur in animals?
As the organism develops but is lost at an early stage.
33
True or false : Lots of plant cells don’t ever lose the ability to differentiate.
True
34
What are cells that differentiate in mature animals used for?
Repairing and replacing cells
35
What are undifferentiated cells called?
Stem cells
36
Give 3 examples of specialised cells in animals?
Sperm cells
Nerve cells
Muscle cells
37
How are sperm cells specialised?
Long tail- to help swim
Streamlined head- to help swim
Lots of mitochondria- provide energy
Enzymes- helps digest through egg cell membrane
38
How are nerve cells specialised?
Long- cover more distance
Branched connections- to connect nerve cells and form a network
39
How are muscle cells specialised?
Long- so have space to contract
Lots of mitochondria- provides energy needed for contraction
40
Give 3 examples of specialised plant cells?
Root Hair cells
Phloem
Xylem
41
How are root hair cells specialised?
Large surface area- absorbs more water and mineral ions from the soil
42
What are embryonic stem cells?
Stem cells found in human embryos that can differentiate into any type of cell.
43
What are adult stem cells?
Stem cells found in adults, often in bone marrow. However, can’t turn into any type of cell, only certain cells like blood cells.
44
What is the difference between embryonic stem cells and adult stem cells?
Embryonic stem cells can differentiate into any cell, adult stem cells can only differentiate into certain cells.
45
What can stem cells be used for?
Can be grown in a lab to produce clones and made to differentiate into cells used for medicine or research.
46
What is therapeutic cloning?
An embryo could be made to have the same genetic information as the patient, so wouldn’t be rejected by the patient’s body.
47
What are the risks of using stem cells in medicine?
If grown in a lab, they could be contaminated and could pass on disease to the patient.
48
Why are some people against stem cell research?
- Religious beliefs that human embryos shouldn’t be used for experiments as each one is a potential human life
- In some cases, embryos that aren’t used are destroyed
- Scientists should focus on developing other types of stem cells
49
Where are stem cells found in plants?
meristems
50
How do stem cells work in plants?
They can differentiate into any type of plant cell throughout the plant’s entire life. They can produce clones quickly and cheaply. They can be used to grow rare plants to reduce risk of extinction. Can be used to create identical plants with desired features in farming.
51
Where are chromosomes found?
The nucleus of cells
52
What are chromosomes?
coiled up lengths of DNA molecules.
53
What do genes control?
The development of characteristics
54
How many copies of a chromosome do body cells have?
Two
55
How many pairs of chromosomes are in a human cell?
23
56
What are the two stages of the cell cycle?
1- Growth and DNA replication
2 - Mitosis
57
What does the cell cycle make cells for?
Growth, development and repair
58
In what stage of the cell cycle do cells divide?
Mitosis
59
What is produced at the end of the cell cycle?
Two new cells, identical to the original cell with the same number of chromosomes.
60
What happens during the growth and DNA replication stage of the cell cycle?
The DNA is spread out in long strings. Before it divides it must grow and increase the amount of subcellular structures such as mitochondria and ribosomes. It then duplicates its DNA so there is one copy for each new cell. The DNA is copied and forms X-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate.
61
What happens during mitosis?
1. Once DNA has been copied, the chromosomes line up at the centre of the cell and cell fibres pull them apart.
2. Each ‘arm’ of the chromosome goes to opposite ends of the cell.
3. Membranes form around each of the sets of the chromosomes, creating a nuclei of the two new cells. (Nucleus divides)
4. The cytoplasm and cell membrane divides.
5. Two new daughter cells are produced. They are identical and contain the exact same DNA.
62
How do prokaryotic cells divide?
Binary fission.
63
How do prokaryotic cells replicate by binary fission?
1. The circular DNA and plasmid(s) replicate.
2. The cell gets bigger and the circular DNA strands move to opposite ends of the cell.
3. The cytoplasm begins to divide and new cell walls begin to form.
4. The cytoplasm divides and two daughter cells are produced. Each cell has one copy of the circular DNA but can have variable copies of the plasmids.
64
A bacterial cell has a mean division time of 30 minutes. How many cells will it have produced after 2.5 hours?
2.5 x 60 = 150 minutes
150/30 = 5 divisions
2^5 = 32 cells
65
Explain how to grow bacteria in a lab.
1. Make an agar plate by pouring hot agar jelly into a petri dish.
2. When the jelly is cooled and set, inoculating loops can be used to transfer microorganisms to the culture medium. Alternatively, a sterile dropping pipette and spreader can be used to get an even covering of bacteria.
3. Place a lid over the top and store upside down in a lab at around 25°C.
66
What are bacteria grown in?
A culture medium
67
What does a culture medium contain?
The carbohydrates, minerals, proteins and vitamins that the bacteria need to grow.
68
Give 2 examples of culture mediums.
A nutrient broth solution or solid agar jelly
69
What can be seen when bacteria grow on agar jelly?
Colonies on the surface of the jelly or will spread out to give an even covering of bacteria.
70
Why are cultures of microorganisms not kept above 25°C in a school lab?
Harmful pathogens are more likely to grow above this temperature and grow a lot faster at higher temperatures.
71
What can you do to make sure that cultures are not contaminated?
1. Petri dishes and culture medium must be sterilised before use (heat to high temp), to kill unwanted microorganisms.
2. Inoculating loop must be sterilised by passing through hot flame.
3. After transferring the bacteria, the lid must be taped on to stop microorganisms in the air getting in.
4. The petri dish should be stored upside down to stop drops of condensation falling onto the agar surface.
72
Explain how you can test the effect of antibiotics on bacterial growth.
1. Place paper discs soaked in different (types or concentrations) of antibiotics on an agar plate containing an even covering of bacteria. Leave some space between disks.
2. The antibiotic should diffuse into the agar jelly.
3. Use a control by placing a paper disc that has not been soaked in antibiotic but soaked in sterile water onto the agar jelly.
4. Leave the plate at 25°C for 48 hours.
5. The more effective the antibiotic is, the larger the inhibition zone will be.
73
What is an inhibition zone?
When no bacteria is growing.
74
How do you measure an inhibition zone?
πr^2
75
What is a bacterial colony?
groups of bacteria on a surface
76
What is diffusion?
Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration.
77
Complete the sentence: Diffusion happens in both __________ and __________ because the particles are free to ___________ ___________.
solutions, gases, move, randomly
78
Complete the sentence: The bigger the concentration gradient the _________ the diffusion rate.
faster
79
What is a concentration gradient?
The difference in concentration
80
Give an example of diffusion.
Small molecules such as oxygen, glucose, amino acids and water diffuse through cell membranes.
81
Complete the sentence: The __________ the surface area, the faster the diffusion rate.
larger
82
What is osmosis?
Osmosis is the movement of water molecules across a partially permeable membrane from an area of high water concentration to an area of low water concentration.
83
What is a partially permeable membrane?
A membrane with small holes that only tiny molecules can pass through.
84
Explain the effect of sugar solutions on plant tissue (potato). RP
IV- Concentration of sugar solution
DV - Change in mass
CV- surface area of potato, volume of solution, time in solution, temperature, type of sugar
1. Cut up a potato into equal cylinders.
2. Fill some beakers with equal volumes of different sugar solutions. One should be pure water and another should be a very concentrated sugar solution. The rest should be in between.
3. Measure the starting mass of each cylinder.
4. Leave a cylinder in each beaker of solution for 24 hours.
5. Take out of the solution and pat dry.
6. Measure the mass of the cylinders and calculate the % change.
85
If the potato cylinders increase in mass, what has happened?
Water has moved in by osmosis.
86
What is active transport?
Diffusion against a concentration gradient, moving from a lower concentration to a higher concentration.
87
What does active transport require?
energy
88
Explain how root hair cells take in minerals and water.
The concentration of minerals is usually higher in a the root hair cell than in the soil around them. Minerals are absorbed by the root hair cells by active transport from an area of low mineral concentration to an area of high mineral concentration.
89
Give an example of active transport in humans.
Making glucose from the gut and kidney tubes.
90
Complete the sentence: How easily something moves between an organism and its environment depends on its __________ ________ to ___________ _______.
surface area, volume, ratio
91
True or false : The smaller an organism is, the smaller its surface area to its volume.
False - The larger an organism is, the smaller its surface are to its volume.
92
What are exchange surfaces?
Surfaces that are adapted to maximise the exchange of a substance.
93
Which type of organism has a smaller surface area to volume ratio?
multicellular organisms
94
How are exchange surfaces adapted?
- Thin membrane (short distance to diffuse across)
- Large surface area (lots of substance can diffuse at once)
In animals :
- lots of blood vessels to get stuff in and out od the blood fast
- gas exchange surfaces are ventilated so air can move in and out
95
Explain how gas exchange happens in the lungs.
The lungs contain millions of little air sacs called alveoli where gas exchange takes place.
Alveoli have a huge surface area, moist lining, thin walls and a good blood supply to maximise the diffusion of oxygen and carbon dioxide.
In the alveoli, carbon dioxide from the blood capillary diffuses into the alveolus whilst oxygen diffuses into the blood stream.
96
What gases are involved in gas exchange in the lungs?
Carbon dioxide and oxygen.
97
Where does gas exchange take place in the lungs?
in alveoli which are attached via bronchiole.
98
What are villi?
Tiny projections inside the small intestine that increase the surface area so digested food is absorbed much more quickly into the blood.
99
How are villi adapted for their function?
- Single layer of surface cells
- very good blood supply to assist quick absorption
100
Explain gas exchange in leaves.
The underneath of a leaf is its exchange surface. It contains little holes called stomata which carbon dioxide diffuses through. Oxygen and water vapour also diffuse out through the stomata.
The size of the stomata is controlled by guard cells that close the stomata if water is being lost faster than it is being replaced. The flattened shape of the leaf increases its surface area so that gas exchange is more effective.
101
What is the size of stomata controlled by?
Guard cells
102
Explain how gills work.
1. Water (containing oxygen) enters the fish through its mouth and passes out through the gills.
2. Oxygen diffuses from the water into the blood in the gills and carbon dioxide diffuses out of the blood and into the water.
3. Each gill is made up of thin plates called gill filaments that have a large surface area for gas exchange.
4. The gill filaments are covered in tiny structures called lamellae, which increase the surface area.
5. The lamellae have lots of blood capillaries to speed up diffusion.
6. They also have a thin surface layer to minimise the distance that the gases have to diffuse.
7. Blood flows through the lamellae in one direction, water flows in the opposite. This maintains a large concentration gradient.
8. The concentration of oxygen is always higher in the water than blood.
103
What is a tissue?
A group of similar cells that work together to carry out a particular function.
104
Give 3 examples of tissues in mammals.
Muscular tissue - contracts to move what it is attached to
Glandular tissue - makes and secretes enzymes and hormones
Epithelial tissue - covers some parts of the body e.g. the inside of the gut
105
What are tissues organised into?
Organs
106
What is an organ?
A group of different tissues that work together to perform a certain function.
107
Give an example of an organ.
Stomach, Heart, Lungs, Brain, Liver, Kidney
108
How are organs organised?
into organ systems
109
What is an organ system?
A group of organs working together to perform a particular function.
110
Give an example of an organ system.
The digestive system.
111
What organs does the digestive system contain?
Glands
Stomach
Liver
Small intestine
Large intestine
112
What to organ systems work together to make?
Organisms
113
What are enzymes?
Catalysts produced by living things, biological catalysts.
114
What is a catalyst?
A catalyst is a substance which increases the speed of a reaction without being changed or used up in the reaction.
115
Complete the sentence : Enzymes are all large _________ made up of chains of ________ ________.
proteins, amino acids
116
Complete the sentence : Enzymes have special ________ so they can catalyse reactions.
shapes
117
Explain the lock and key model of enzyme action.
Every enzyme has an active site with a unique shape that fits onto the substance. The substrate and the active site fit together like a lock and a key. If the substrate doesn’t match the enzymes active site then the reaction wont be catalysed.
118
What happens to an enzyme if the temperature of the reaction increases too much?
Some of the bonds holding the enzyme break, changing the shape of it’s active site. The enzyme is denatured and wont catalyse the reaction.
119
What is meant by the optimum temperature for an enzyme to function?
The best temperature where the enzyme is most active.
120
What effects enzymes?
Temperature and pH.
121
If the pH of a substance is too high or too low, what could happen to the enzymes?
They could denature.
122
What is the optimum pH for enzymes to function in the stomach?
pH 2.
123
Explain how to investigate the effect of pH on enzyme activity.
IV- pH of buffer solution
DV - time taken for starch to be broken down
CV - concentration & volume of amylase solution, temperature
Amylase catalyses the breakdown of starch to maltose. Starch can be detected using iodine solution. If starch is present it will change from browny-orange to blue-black.
1. Put a drop of iodine solution into every well of a spotting tile.
2. Place a bunsen burner on a heatproof mat and a tripod and gauze over it. Put a beaker of water on the gauze and heat until 35°C.
3. Use a syringe to add 1cm^3 of amylase solution and 1cm^3 of a buffer solution with a pH of 5 to a boiling tube.
4. Put the tube into the beaker of water for 5 minutes.
5. Add 5cm^3 of starch to the boiling tube.
6. Immediately mix the contents and start a stop clock.
7. Use continuous sampling to record how long it takes for the amylase to break down the starch. To do this use a dropping pipette to take a fresh sample from the tube every 30 seconds and put a drop into a well.
8. When the iodine solution remains brown, starch is no longer present.
9. Repeat the whole experiment with buffer solutions of different pH values.
124
How do you calculate the rate of reaction?
Rate = 1000/time
125
What is the unit for rate of reaction?
S^-1
126
At pH6, the time taken for amylase to break down all of the starch in a solution was 90 seconds. Calculate the rate of reaction.
1000/90 = 11 s^-1
127
What do digestive enzymes break down?
big molecules into smaller ones
128
Give 3 examples of big molecules.
Starch, protein, fats
129
Give 4 examples of smaller molecules.
sugars (glucose and maltose), amino acids, glycerol and fatty acids
130
What does carbohydrases convert?
carbohydrates into simple sugars
131
What does proteases convert?
Proteins into amino acids
132
What does lipases convert?
Lipids into glycerol and fatty acids
133
What is amylase?
A carbohydrase that breaks down starch.
134
Where are the 3 places that amylase is made?
1. Salivary glands
2. Pancreas
3. Small intestine
135
Where are the 3 places that protease is made?
1. Stomach
2. Pancreas
3. Small intestine
136
Where are the 2 places that lipase is made?
1. Pancreas
2. Small intestine
137
What is starch broken into?
simple sugars
138
What are proteins broken into?
amino acids
139
What are lipids broken into?
Glycerol and fatty acids
140
What is bile and where is it produced?
Bile is alkaline and neutralises acids in the small intestine to allow enzymes to function correctly. It is produced in the liver and stored in the gall bladder before released.
141
What does bile do?
Neutralises stomach acids and emulsifies fats.
142
What does the stomach do in the digestive system?
Pummels food with muscular walls, produces the protease enzyme pepsin, produces hydrochloric acid that kills bacteria and creates the right pH (2).
143
Where is the digested food absorbed out of the digestive system and into the blood?
Small intestine
144
What is the function of the large intestine?
Where excess water is absorbed from the food.
145
Where is bile stored?
The gall bladder
146
Where is bile produced?
The liver
147
How do you prepare the food samples for a food test?
1. Break down the piece of food using a pestle and mortar.
2. Transfer the ground up food to a beaker with some distilled water.
3. Stir the mixture with a glass rod to dissolve some of the food.
4. Filter using a funnel lined with filter paper to remove solid bits of food.
148
What is the food test for sugars?
The Benedict’s Test
149
Explain how the Benedict’s test is used to test for sugars.
1. Prepare a food sample. Transfer 5cm^3 to a test tube.
2. Prepare a water bath at 75°C.
3. Add 10 drops of Benedict’s solution to the test tube using a pipette.
4. Place the test tube in the water bath for 5 minutes. Point the tube away from you.
5. If the food sample contains a reducing sugar the solution will change from blue to green, yellow or brick red depending on how much sugar the food contains.
150
What colour will Benedict’s solution turn in the presence of sugar?
Green, Yellow or Brick red from blue
151
What is the food test for starch?
Iodine solution
152
Explain how iodine solution is used to test for starch.
1. Make a food sample and transfer 5cm^3 to a test tube.
2. Add a few drops of iodine solution and gently shake to mix the contents.
3. The colour of the solution will change from browny-orange to blue-black if starch is present.
153
What colour will iodine solution change to in the presence of starch?
From browny-orange to blue-black
154
What is the food test for proteins?
The Biuret test.
155
Explain how biuret solution can be used to test for proteins.
1. Prepare a food sample and transfer 2cm^3 to a test tube.
2. Add 2cm^3 of biuret solution and mix by gently shaking.
3. If the sample contains protein, the solution will change from blue to pink or purple.
156
What colour will biuret solution change to in the presence of proteins?
Pink/purple from blue
157
What is the food test for lipids?
The Sudan III test.
158
Explain how Sudan III stain solution can be used to test for lipids.
1. Prepare a food sample (doesn’t need filtering) and transfer 5cm^3 to a test tube.
2. Use a pipette to transfer 3 drops of Sudan III stain solution to the test tube and gently shake.
3. If the sample contains lipids, they will become stained and the mixture will separate into two layers. The top layer will be bright red.
159
What will happen if lipids are present when mixed with Sudan III solution?
The mixture will separate into two layers, the top layer will be bright red.
160
What are the hazards of food tests?
Iodine - irritant
Biuret solution - contains dangerous chemicals
Water bath - very high temp
Sudan III stain solution - flammable
161
Where are the lungs located in the body?
the Thorax
162
What is the thorax?
The top part of your body.
163
What is the thorax separated from, by what?
The lower part of your body by the diaphragm.
164
What are the lungs protected by?
The ribcage.
165
What are the lungs surrounded by?
pleural membranes
166
How does air enter the lungs?
Through the mouth, down the trachea, split into two tubes (bronchi) and into each lung.
167
What are the bronchi split into?
Progressively smaller tubes called bronchioles.
168
What is at the end of bronchioles?
Alveoli - small air sacs.
169
Where does oxygen diffuse out of and from what concentration?
The alveolus from high concentration to low concentration.
170
Where does carbon dioxide diffuse out of and from what concentration?
Out of the blood from a high concentration to low concentration.
171
What happens when the blood reaches body cells?
Oxygen is released from red blood cells and diffuses into the body cells.
Carbon dioxide diffuses out of body cells and into the blood to be taken back to the lungs.
172
How can you calculate breathing rate?
breaths per minute = number of breaths/ number of minutes
173
What does the circulatory system do?
Carries food and oxygen to every cell in the body.
174
What is the circulatory system made up of?
The heart, blood vessels and blood.
175
What type of circulatory system do humans have?
A double circulatory system - two circuits joined together.
176
What happens in the first circuit of the circulatory system?
The right ventricle pumps deoxygenated blood to the lungs via the pulmonary artery to take in oxygen. The blood then returns to the heart via the pulmonary vein.
177
What happens in the second circuit of the circulatory system?
The left ventricle pumps oxygenated blood around the other organs of the body. The blood loses oxygen at the body cells. The deoxygenated blood returns to the heart via the vena cava to be pumped to the lungs again.
178
What is the heart?
A pumping organ that keeps the blood flowing around the body. Mostly made of muscular tissue.
179
What are valves for?
To make sure that blood flows in the right direction preventing it flowing backwards.
180
What are the four chambers of the heart?
Right atrium, Right ventricle, Left atrium, Left ventricle
181
Where does blood flow into in the heart?
The two atria.
182
Where does blood flow into the heart from the body?
Through the vena cava, into the right atrium.
183
Where does blood flow into the heart from the lungs?
Through the pulmonary artery into the left atrium.
184
Where does blood leave the heart to go to the lungs?
It leaves the right ventricle through the pulmonary artery.
185
Where does the blood leave the heart to go to the rest of the body?
It leaves the left ventricle through the aorta.
186
True or false : Arteries carry blood to the heart.
False - They carry blood away from the heart.
187
Complete the sentence: Veins carry blood ________ _____ the heart.
Back to
188
What are the three types of blood vessels?
Arteries, Capillaries and Veins
189
What are the features of Arteries?
Thick walls
Smaller lumen
Strong and elastic walls
Thick layers of muscle
190
True or false : Veins carry blood at lower pressures than arteries.
True
191
What are capillaries?
Small blood vessels that arteries branch into to carry blood close to cells to exchange substances.
192
What are the features of capillaries?
Thin wall (1 cell thick)
Very small lumen
Permeable walls
193
What are the features of veins?
Large lumen
Thinner walls than arteries
Contain valves
Elastic fibres and smooth muscle
194
What is blood?
A tissue
195
What are the four main things in blood?
Red blood cells
White blood cells
Platelets
Plasma
196
What is the function of red blood cells?
Carry oxygen from the lungs to all the cells in the body. They contain haemoglobin that binds to oxygen to form oxyhaemoglobin.
197
What are the features of red blood cells?
- No nucleus so more room to carry oxygen
- Biconcave disc that gives a larger surface area for absorbing oxygen
198
True or false : White blood cells contain a pigment called haemoglobin.
False - Red blood cells contain a red pigment called haemoglobin.
199
What is the function of white blood cells?
They defend against infection.
200
What are the two types of white blood cells?
Phagocytes and Lymphocytes
201
What do phagocytes do?
Engulf pathogens/ unwanted microorganisms via phagocytosis.
202
What so lymphocytes do?
Produce antibodies to fight microorganisms as well as antitoxins to neutralise any toxins produced by the microorganism.
203
What do white blood cells have that red blood cells do not have?
A nucleus
204
What are platelets?
Small fragments of cells that have no nucleus. They help the blood clot.
205
What can a lack of platelets cause?
Excessive bleeding and bruising
206
What is plasma?
A pale straw-coloured liquid that carries everything in the blood.
207
Give 3 examples of things that plasma carries.
Any 3 from:
- Red and white blood cells
- Platelets
- Nutrients (glucose, amino acids)
- Carbon dioxide
- Urea
- Hormones
- Proteins
- Antibodies and antitoxins
208
What is cardiovascular disease?
A term to describe diseases of the heart or blood vessels.
209
What is coronary heart disease?
When the coronary arteries that supply the blood to the muscles of the heart get blocked by layers of fatty material building up.
210
How can coronary heart disease result in a heart attack?
The arteries become narrow so blood flow is restricted. The lack of oxygen to the heart muscle can result in a heart attack.
211
What can be used to treat coronary heart disease?
Stents or statins
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What is a stent?
Tubes that are inserted into the arteries. They keep them open making sure blood can pass through. They lower the risks of heart attacks for people with coronary heart disease and are effective for a long time. However, there is a risk of infection and also blood clots. Therefore patients must take anti-clotting tablets.
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What are statins?
Drugs that reduce the amount of ‘bad’ cholesterol present in the blood stream. This slows down the rate of fatty deposits forming.
214
Give an advantage and disadvantage of statins.
Advantages
- reduce the risk of strokes, coronary heart disease and heart attacks due to lower cholesterol
- increase the amount of beneficial cholesterol in the bloodstream
- can help prevent other diseases
Disadvantages
- Long term drug that must be taken regularly
- Can have negative side effects (headaches to kidney failure, liver damage, memory loss)
- The effect is not instant, takes time to work
215
Where is the natural pacemaker located in the heart?
The right atrium wall.
216
What is a pacemaker?
A group of cells that produce a small electrical impulse which spreads to the surrounding muscle cells causing them to contract.
217
What is used to treat someone with an irregular heartbeat?
An artificial pacemaker.
218
What is an artificial pacemaker?
A small device implanted under the skin and has a wire going to the heart. It produces an electric current to keep the heart beating regularly.
219
What is used to treat heart failure?
A heart transplant or artificial heart.
220
What is a disadvantage of a heart transplant?
- Could be rejected by the patients body
- donor organs aren’t always available right away
221
What are artificial hearts?
A temporary mechanical device that pumps blood around a persons body whose own heart has failed. In some cases, they are used as a permanent fix.
222
What is the advantage of an artificial heart?
They are less likely to be rejected by the body’s immune system than a donor heart.
223
How can faulty heart valves be treated?
They can be replaced. Surgeons can replace valves with ones taken from other humans or mammals (biological valves). Alternatively, mechanical valves can be used but can cause problems with blood clots.
224
What is artificial blood?
A blood substitute (e.g. a salt solution) used to replace a lost volume of blood. It can keep a person alive even if they lose 2/3 of their red blood cells as long as no air bubbles get in. Otherwise, a blood transfusion is needed.
225
What are plant cells organised into?
Tissues and organs.
226
Give 3 examples of organs in plants.
Stems, roots, leaves
227
Name an organ system in a plant.
Transporting substances.
228
Give 5 examples of plant tissues.
Epidermal tissue, palisade mesophyll tissue, spongy mesophyll tissue, xylem & phloem, meristem tissue
229
What type of plant tissues do leaves contain?
epidermal, mesophyll, xylem and phloem
230
What are the epidermal tissues on a leaf covered with?
A waxy cuticle to reduce water loss.
231
What is the upper epidermis of a leaf?
A transparent layer that allows light to pass through to the palisade layer.
232
What does the palisade layer contain a lot of?
chloroplasts
233
What do the xylem and phloem form?
A network of vascular bundles which deliver water and other nutrients to the leaf and transport glucose away from the leaf. They also support the structure.
234
How are the tissues of leaves adapted for efficient gas exchange?
The lower epidermis contains small holes called stomata, which let co2 diffuse into the leaf and o2 out. The opening and closing of stomata is controlled by guard cells in response to environmental conditions. The air spaces in the spongy mesophyll tissue increases the rate of diffusion.
235
What are the two types of vessel in plants?
Phloem and Xylem.
236
What do phloem tubes transport?
Sugars made by photosynthesis from the leaves to the rest of the plant. Food substances are also transported to organs to be stored for the winter.
237
True or false : The transport in phloem goes in both directions.
True
238
What is the term for the movement of dissolved substances from the leaves to the rest of the plant?
Translocation
239
What is phloem made of?
Living tissue.
240
What is Xylem made up of?
Dead cells joined end to end with no end walls between them and a hole down the middle. They are strengthened by lignin.
241
What is xylem strengthened by?
Lignin
242
What does the xylem carry?
Water and mineral ions from the roots to the stem and leaves.
243
What is the direction of movement through the xylem?
From the roots out of the leaves.
244
What is the transpiration stream?
The movement of water from the roots, through the xylem and out of the leaves.
245
What is transpiration?
The loss of water from a plant.
246
What is transpiration caused by?
The evaporation and diffusion of water from a plants surface.
247
Where does most transpiration take place?
The leaves
248
Why is water needed throughout the plant?
For photosynthesis and to hold itself upright.
249
What are the 4 factors that affect the rate of transpiration?
Light intensity, temperature, air flow and humidity.
250
How does light intensity affect the rate of transpiration?
The brighter the light, the greater the transpiration rate.
Stomata begin to close as it gets darker since photosynthesis can’t occur in the dark. This reduces the amount of water lost.
251
How does temperature affect the rate of transpiration?
The warmer it is, the faster the rate of transpiration. When it is warm, more water evaporates as particles move faster so diffuse out of the stomata at a faster rate.
252
How does airflow affect the rate of transpiration?
The better the air flow around a leaf, the greater the transpiration rate. If air flow around a leaf is poor then water vapour just surrounds the leaf and doesn’t move away. If there is good air flow then water moves away faster so diffusion happens more quickly.
253
How does humidity affect the rate of transpiration?
The drier the air around a leaf, the faster transpiration happens. If the air is humid then a lot of water surrounds the leaf creating a low concentration gradient. Therefore diffusion happens at a slower rate. However in dry conditions, transpiration can happen at a faster rate as the concentration gradient is greater.
254
What can be used to estimate transpiration rate?
A potometer
255
What does a potometer measure?
The uptake of water.
256
How are guard cells adapted to open and close stomata?
- Kidney shape
- when turgid, causes stomata to open
- when flaccid, causes stomata to close to reduce water loss
- Thin outer walls, thick inner walls
- sensitive to light and close at night
- on the underside of leaf so less water is lost due to reduced light & cooler temps
