Biology summery chapter 1
Photosynthesis
When there is light, photosynthesis takes place in the green parts of plants.
Chloroplasts use the energy of sunlight for converting carbon dioxide and water
into glucose (see figures 1 and 2). Glucose contains a lot of energy. A plant uses
that energy to make all sorts of other substances from glucose in turn, including
the substances that the plant is made of. Photosynthesis also produces oxygen:
water + carbon dioxide + energy → glucose + oxygen
It’s not only plant cells that can convert one substance into another. All
organisms have a metabolism. Substances are constantly being converted
inside the cells in your body as well. This lets you move and keep warm, as well
as letting your body recover and grow. Metabolic processes are needed to stay
alive.
Decomposition
Chloroplasts store energy from sunlight in the form of glucose. The energy-rich
glucose is then transported from the leaves to the other parts of the plant.
Cells use glucose as an energy source. Breaking down glucose releases the
energy stored in it. The cell can use the energy and the breakdown products of
glucose, for instance to make other new substances in turn. That lets the plant
grow and make new parts. Glucose is also broken down in the cells of humans
and other animals to release energy.
The breakdown of glucose happens in mitochondria (singular: mitochondrion).
These are cell organelles that can be found in both plant and animal cells. You
cannot see them with a light microscope, but they are visible in an electron
microscope. In figure 3, the cell organelles have been coloured by computer so
that you can see them more easily. The brown circles and rods in the cell in figure
3 are the mitochondria. Cells that need a lot of energy, such as muscle cells,
have lots of mitochondria. The magnified image shows a single mitochondrion.
Energy
Glucose is broken down in your body to release energy. All the organs in your
body need energy. For example, you need energy for moving and to keep your
body temperature up (at roughly 37 °C).
Respiration
The breakdown of glucose in cells is a form of combustion, a metabolic process
called respiration. The combustion that takes place inside your body does not
need fire but it does need fuel. Cells use glucose as fuel. This combustion –
respiration – takes place in every single cell of your body, day and night. Without
respiration, a cell dies. That is not just true for human cells: it applies to every
living cell in any organism.
Oxygen and carbon dioxide
Combustion needs oxygen as well as fuel. Take a burning candle, for example: if
you put a glass or beaker over a burning candle, it will go out (see figure 2). This
is because the oxygen gets used up.
Body’s respiration
, Your body’s respiration is just the same: it needs a fuel (glucose) and oxygen.
Combustion produces waste products, namely water and carbon dioxide.
Oxygen is therefore needed for converting glucose into carbon dioxide and water
(or water vapour). This releases energy:
glucose + oxygen → water + carbon dioxide + energy
The energy that is released is converted into movement and heat. The heat is
then given off to the surroundings. When you are more active, you need more
energy. The greater the physical effort, the more combustion takes place. Your
heart and lungs are then working harder to make sure that the cells get enough
fuel and oxygen and to get rid of the waste products, water and carbon dioxide.
Respiratory system
Figure 1 is a diagram of the human respiratory system. When you breathe in, air
comes in through the nasal cavity or oral cavity into the throat (pharynx). The air
then flows past the voice box (larynx) into the windpipe (trachea). The windpipe
then splits into two bronchi, which in turn split into smaller and smaller tubes
called bronchioles. At the ends of the bronchioles, there are bundles of air sacs
called alveoli.
The diaphragm is below the lungs. The diaphragm is a tough, muscular
membrane that separates the thoracic cavity (chest cavity) from the abdominal
cavity. The diaphragm can move up and down.
Nasal cavity and oral cavity
Most people breathe through their noses. The nasal cavity is covered with
the nasal lining, which is made up of mucus-producing cells (see figure 2). The
mucus means that the nasal cavity is moist so that the inhaled air also gets
moistened. There are also lots of small blood vessels just under the surface of the
nasal lining. The blood keeps the nasal lining warm and therefore helps warm up
the incoming air.
Clear the air
The air that you breathe in often contains dust particles and germs. In the front
part of the nasal cavity, there are nasal hairs that trap any larger dust particles.
Smaller dust particles and germs stick to the nasal lining. Small hairs
called cilia sweep the mucus along with the dust particles towards the back of
the pharynx where it is then swallowed.
The sense of smell – the olfactory system – is located in the roof of the nasal
cavity. It checks the incoming air and warns you if it contains smelly gases, for
example. When you breathe in through your mouth, the inhaled air is cleaned,
warmed and moistened less. As a result, the mucous membranes in the lungs can
get damaged. You are less able to smell things when breathing through the
mouth too. Breathing through the nose is therefore healthier than breathing
through the mouth.
Pharnyx
After the nasal cavity or oral cavity, the air passes through the pharynx and goes
into the windpipe (trachea). Inhaled air is however not the only thing that goes
through the pharynx: the food you swallow has to go through it too.
The epiglottis makes sure that food cannot get into your windpipe. When you
are breathing, both the oesophagus and the windpipe are open (see figure 3.1).
The air can then flow from your nasal cavity into your lungs through the windpipe
and back out again. When you swallow food, the uvula closes off the nasal cavity
and the epiglottis closes off the windpipe (see figure 3.2). The food is then able to
Photosynthesis
When there is light, photosynthesis takes place in the green parts of plants.
Chloroplasts use the energy of sunlight for converting carbon dioxide and water
into glucose (see figures 1 and 2). Glucose contains a lot of energy. A plant uses
that energy to make all sorts of other substances from glucose in turn, including
the substances that the plant is made of. Photosynthesis also produces oxygen:
water + carbon dioxide + energy → glucose + oxygen
It’s not only plant cells that can convert one substance into another. All
organisms have a metabolism. Substances are constantly being converted
inside the cells in your body as well. This lets you move and keep warm, as well
as letting your body recover and grow. Metabolic processes are needed to stay
alive.
Decomposition
Chloroplasts store energy from sunlight in the form of glucose. The energy-rich
glucose is then transported from the leaves to the other parts of the plant.
Cells use glucose as an energy source. Breaking down glucose releases the
energy stored in it. The cell can use the energy and the breakdown products of
glucose, for instance to make other new substances in turn. That lets the plant
grow and make new parts. Glucose is also broken down in the cells of humans
and other animals to release energy.
The breakdown of glucose happens in mitochondria (singular: mitochondrion).
These are cell organelles that can be found in both plant and animal cells. You
cannot see them with a light microscope, but they are visible in an electron
microscope. In figure 3, the cell organelles have been coloured by computer so
that you can see them more easily. The brown circles and rods in the cell in figure
3 are the mitochondria. Cells that need a lot of energy, such as muscle cells,
have lots of mitochondria. The magnified image shows a single mitochondrion.
Energy
Glucose is broken down in your body to release energy. All the organs in your
body need energy. For example, you need energy for moving and to keep your
body temperature up (at roughly 37 °C).
Respiration
The breakdown of glucose in cells is a form of combustion, a metabolic process
called respiration. The combustion that takes place inside your body does not
need fire but it does need fuel. Cells use glucose as fuel. This combustion –
respiration – takes place in every single cell of your body, day and night. Without
respiration, a cell dies. That is not just true for human cells: it applies to every
living cell in any organism.
Oxygen and carbon dioxide
Combustion needs oxygen as well as fuel. Take a burning candle, for example: if
you put a glass or beaker over a burning candle, it will go out (see figure 2). This
is because the oxygen gets used up.
Body’s respiration
, Your body’s respiration is just the same: it needs a fuel (glucose) and oxygen.
Combustion produces waste products, namely water and carbon dioxide.
Oxygen is therefore needed for converting glucose into carbon dioxide and water
(or water vapour). This releases energy:
glucose + oxygen → water + carbon dioxide + energy
The energy that is released is converted into movement and heat. The heat is
then given off to the surroundings. When you are more active, you need more
energy. The greater the physical effort, the more combustion takes place. Your
heart and lungs are then working harder to make sure that the cells get enough
fuel and oxygen and to get rid of the waste products, water and carbon dioxide.
Respiratory system
Figure 1 is a diagram of the human respiratory system. When you breathe in, air
comes in through the nasal cavity or oral cavity into the throat (pharynx). The air
then flows past the voice box (larynx) into the windpipe (trachea). The windpipe
then splits into two bronchi, which in turn split into smaller and smaller tubes
called bronchioles. At the ends of the bronchioles, there are bundles of air sacs
called alveoli.
The diaphragm is below the lungs. The diaphragm is a tough, muscular
membrane that separates the thoracic cavity (chest cavity) from the abdominal
cavity. The diaphragm can move up and down.
Nasal cavity and oral cavity
Most people breathe through their noses. The nasal cavity is covered with
the nasal lining, which is made up of mucus-producing cells (see figure 2). The
mucus means that the nasal cavity is moist so that the inhaled air also gets
moistened. There are also lots of small blood vessels just under the surface of the
nasal lining. The blood keeps the nasal lining warm and therefore helps warm up
the incoming air.
Clear the air
The air that you breathe in often contains dust particles and germs. In the front
part of the nasal cavity, there are nasal hairs that trap any larger dust particles.
Smaller dust particles and germs stick to the nasal lining. Small hairs
called cilia sweep the mucus along with the dust particles towards the back of
the pharynx where it is then swallowed.
The sense of smell – the olfactory system – is located in the roof of the nasal
cavity. It checks the incoming air and warns you if it contains smelly gases, for
example. When you breathe in through your mouth, the inhaled air is cleaned,
warmed and moistened less. As a result, the mucous membranes in the lungs can
get damaged. You are less able to smell things when breathing through the
mouth too. Breathing through the nose is therefore healthier than breathing
through the mouth.
Pharnyx
After the nasal cavity or oral cavity, the air passes through the pharynx and goes
into the windpipe (trachea). Inhaled air is however not the only thing that goes
through the pharynx: the food you swallow has to go through it too.
The epiglottis makes sure that food cannot get into your windpipe. When you
are breathing, both the oesophagus and the windpipe are open (see figure 3.1).
The air can then flow from your nasal cavity into your lungs through the windpipe
and back out again. When you swallow food, the uvula closes off the nasal cavity
and the epiglottis closes off the windpipe (see figure 3.2). The food is then able to
