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What does every organism (except viruses) contain one or more of?
cells
In plant cells, there is a cell wall, chloroplast and a large permanent vacuole. What about animal cells?
They have no cell wall or chloroplasts present, or a permanent vacuole.
What does the cell membrane do?
Controls substances entering and leaving the cell
What does the cytoplasm do?
Its a gel-like substance where most of the chemical reactions happen
What is the function of the nucleus?
The nucleus contains chromosomes which carry genetic information and control the activities of the cell
What does the cell wall do?
It contains cellulose - supports the plant's structure
What is the chloroplast's function?
Absorbs light for photosynthesis
What does the vacuole do?
It contains cell sap and helps maintain the shape of the cell
What does cell sap contain?
A dilute solution of sugars and mineral salts
What is the mitochondria the site of?
aerobic respiration
What chemical is used to examine animal and plant cells?
Methylene blue or iodine
What is the calculation for magnification?
Magnification = size of image ÷ size of real object
What is the maximum light microscopes can magnify?
1000x
How do you achieve total magnification?
It is achieved by the multiplication of the power of the eyepiece lens
What do electron microscopes use?
It uses a beam of electrons instead of light
What is the maximum electron microscopes can magnify?
up to 50,000,000x
What is a disadvantage of electron microscopes?
You can only study dead cells
What did electron microscopes allow scientists to discover?
Internal structures of cells
What does an iodine stain do?
It makes the nucleus more obvious and stains any starch present
What does methylene blue stain?
It stains acidic parts of the cells blue and make the nucleus more obvious
Which stain is most commonly used to stain plant cells?
Iodine
Which stain is most commonly used to prepare slides of animal cells and bacteria?
Methylene blue
What are the simplest forms of living organisms called? (only one cell)
Unicellular organisms
What are organisms that consist of many cells called?
multicellular
How many cells are humans made up of?
34 to 37 trillion
Give an example of a specialised cell
muscle cells
What are tissue cells?
Groups of similar cells with a similar function
Give an example of tissue cells
Muscle cells contract and therefore shorten
What are organ cells?
Several tissues performing specific functions, eg. the heart pumps blood
What is an organ system?
A group of organs working together to perform a particular function, eg. the circulatory system carries substances around the body
What do molecules of liquids and gases do?
Collide against each other all the time
What passes through the cell membrane by diffusion?
Oxygen and carbon dioxide
Molecules diffuse from an area of high concentration to an area of...?
low concentration
Does the process of diffusion require energy?
No
In diffusion, all liquid and gas molecules have ..... energy.
kinetic energy - they are constantly moving and mixing
The greater the difference in concentration between two areas...
the faster the rate diffusion happens
As the temperature increases...
the rate of diffusion increases (molecules have more kinetic energy)
If there is high pressure, the molecules...
will quickly move from the area of high pressure to low pressure
Where does every substance that enters or leaves the cell cross?
cell membrane
What kind of membrane is the cell membrane?
selectively permeable membrane
What does the term 'selectively permeable membrane' mean?
The membrane allows certain molecules to pass through, but not others.
What is an example of a small molecule?
water
What is an example of a large molecule?
minerals, sugars
What can you use to model how the cell membrane?
visking tubing
Define aerobic respiration
Aerobic respiration is a process that happens in cells when oxygen is available. It is a series of reactions controlled by enzymes.
When does respiration occur?
all the time
What is the equation for aerobic respiration?
glucose + oxygen --> carbon dioxide + water + energy (ATP)
Define anaerobic respiration.
the release of a relatively small amount of energy by the breakdown of food substances in the absence of oxygen
Anaerobic respiration is less efficient than aerobic respiration because..
less ATP is produce per molecule of glucose (glucose molecule isn't completely broken down)
What is the equation for anaerobic respiation?
Glucose -> lactic acid
Name an advantage of anaerobic respiration
Muscles can release energy for a short period when not enough oxygen is available, e.g. 100m sprints.
Name 2 disadvantages of anaerobic respiration
• Lactic acid is released which is harmful to the body. In the muscles, lactic acid can cause pain (cramp).
• It is not suitable for activities that require energy release over a long period of time, e.g. a long-distance run.
What is an oxygen debt?
The amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells
It is a good measure of fitness to see how quickly you can recover from an 'oxygen debt'.
A fit person can:
o Breathe in a greater volume of air.
o Produce less lactic acid,
o Break down lactic acid faster.
Why do large organisms require a complex respiratory system?
To obtain sufficient volume of oxygen to maintain a high level of aerobic respiration + remove an equivalent volume of waste carbon dioxide.
What is the function of the respiratory system?
• get oxygen into the blood
• remove carbon dioxide from the blood.
What are alveoli covered by on the outside?
blood capillaries
What diffuses across the walls of the alveoli (from the air into the blood)?
Oxygen
What goes from the blood into the air?
Carbon dioxide
How are alveoli adapted for gas exchange?
• large surface area
• good blood supply
• thin - short diffusion pathway
• moist - dissolve gases
What is the difference between inspired air and expired air?
Inspired air is breathed in and expired air is breathed out
What does the body absorb from inspired air?
Oxygen
What does the body add to expired air?
Carbon dioxide and water vapour
What does expired air have more than inspired air?
Carbon dioxide and water vapour
What does inspired air have more than expired air?
Oxygen
How do you test for carbon dioxide?
Bubble limewater through a straw - it goes cloudy
What gas stays the same during breathing?
Nitrogen
Why does the air need to be cleaned before it reaches the alveoli?
The alveoli are very delicate
What does the mucus trap?
dust and other small particles (bacteria)
What moves the mucus upward?
cilia + in a wave like motion
What happens to the mucus pushed?
You swallow it and acid in your stomach destroys any bacteria
What is a trend?
A trend is a pattern or change over a long period of time
How long does tobacco smoke paralyse cillia in the trachea and bronchi for?
about an hour after the cigarette is smoked
What irritates lungs, then clogs mucus?
Dry dust and chemicals
What happens if mucus builds up and becomes infected?
It can cause bronchitis
___ damages alveolar walls
Coughing
What happens when the alveolar walls are damaged?
It reduces surface area for gas exchange and results in the sufferer being short of oxygen
What does tar do?
It collects in the lungs as the smoke cools and paralyses cilia
What does carbon monoxide do?
It binds permanently to haemoglobin, and prevents oxygen from being delivered to tissue as much as 15%
What are the effects of nicotine?
Increased alertness and concentration, appetite suppression, and vasocontriction. It is also very addictive
What does tar contain?
carcinogens
__ of lung cancers are thought to be caused by smoking
90%
What are the statistics for death from lung cancer?
1 in 10 moderate smokers, and 1 in 5 heavy smokers die from lung cancer
What is the function of the respiratory system?
supply the body with oxygen and dispose of carbon dioxide
Why do large organisms need to obtain a sufficient volume of oxygen?
to maintain a high level of aerobic respiration
What does chlorophyll do?
absorbs light energy
What is the equation for photosynthesis?
Carbon dioxide + water -> glucose + oxygen
What can be used to measure the rate of photosynthetic activity?
Note 
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