Transcript B4 The Processes of Life

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B4 The Processes of Life
OCR Additional Science
M Barker
Shirebrook Academy
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B4.1 How do Chemical Reactions
take place in living things?
Photosynthesis Introduction
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Basically, photosynthesis is the process through which a plant
makes large food molecules using carbon dioxide and water and
it happens in plants as well as some micro organisms:
That’s a nice plant. I’m
going to put it in the sun and
give it lots of water and air…
CO2
H2O
Respiration Introduction
I enjoy taking samples using quadrats. In
order to do this, I need energy. Where does
this energy come from?
All living things, including plants, get their
energy from respiration. Respiration is
basically the process of breaking down the
large food molecules that were probably
originally made in plants.
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Enzyme use in nature
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Enzymes are proteins that speed up chemical uses. Here are
two important natural uses for them:
Cells use glucose to generate
energy – this process is called
“respiration”. Respiration
happens in mitochodria and is
catalysed by enzymes.
Photosynthesis is
catalysed by enzymes
in the cells.
Enzymes
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Enzymes are biological catalysts. They help the reactions
that occur in our bodies by controlling the rate of reaction.
An enzyme is basically a protein molecule made
up of long chains of amino acids. Cells make
enzymes according to the instructions carried in
their genes.
The enzyme’s shape helps another
molecule “fit” into it:
Enzyme
This shape can be destroyed by
high temperatures or the wrong
pH:
Substrate
The “Active Site”
Active site
Enzyme
Substrate
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Enzymes
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Enzymes work best in certain conditions:
Enzymes are
denatured
beyond 40OC
Enzyme
activity
400C
Temp
Could be
protease (found
in the stomach)
Could be amylase
(found in the
intestine)
pH
Enzymes are used in industry to bring about reactions at
normal temperatures and pressures that would otherwise be
expensive. However, most enzymes are denatured at high
temperatures and can be costly to produce.
pH
B4.2 How do Plants make food?
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Photosynthesis – the 4 things you need
SUNLIGHT
Gives the plant energy
CHLOROPHYLL
WATER
Travels up
from the roots
CARBON DIOXIDE
Enters the leaf through small
holes on the underneath
The green
stuff
where the
chemical
reactions
happen
Photosynthesis equations
Carbon dioxide + _____
Sunlight
Chlorophyll
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glucose + _____
Sunlight
6CO2
+ 6H20
Chlorophyll
C6H12O6 + 6O2
The GLUCOSE produced by photosynthesis is used by the
plant for _______ (through ____________). It is stored
in the plant as ___________.
Words – respiration, starch, water, oxygen, energy
What is the glucose used for?
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1) Glucose (sugar) can be used to make long chains of insoluble starch…
Glucose
molecules
Starch
molecule
2) Glucose can be used to make cellulose for cell walls…
Glucose
molecules
Cellulose
3) Glucose can be combined with nitrates to make proteins (for growth)…
Glucose
molecules
Proteins
Glucose can also be used for respiration,
either by the plant or by what eats it!
A Typical Plant Cell:
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Cell wall – made
of cellulose which
strengthens the cell
Cell membrane
– controls what
comes in and out
Large vacuole –
contains sap and
helps support the
cell
Chloroplasts – contains
chlorophyll and enzymes for
photosynthesis reactions
Nucleus – controls
what the cell does and
stores genetic info for
making proteins
Cytoplasm –
Chemical reactions
happen here
2 common nutrients…
Nitrates:


Used to make proteins
Lack of it leads to stunted growth
Magnesium:


Used to make chlorophyll
Lack of it leads to yellow leaves
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Diffusion
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Diffusion is when something travels from an area of high
concentration to an area of low concentration. For example,
consider the scent from a hamburger…
The “scent particles” from
this hamburger are in high
concentration here:
Eventually they will
“diffuse” out into this area
of low concentration:
Carbon dioxide and oxygen pass in and out
of leaves by diffusion.
Diffusion Summary
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Diffusion is when particles spread from an area of high
concentration to an area of ___ concentration. The particles
move along a “concentration _____” and this process takes no
_____ (it’s a “passive” process”). Diffusion can be accelerated
by increasing the _______ of the particles, which makes them
move _______.
Words – faster, low, gradient, temperature, energy
Osmosis
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Osmosis is a “special kind of ___________”. It’s when water
diffuses from a __________ area to a less concentrated area
through a partially permeable _________ (i.e. one that allows
water to move through but not anything else):
Water
Sugar solution
In this example the water
molecules will move from
left to right (along the
concentration ______) and
gradually _____ the sugar
solution. Plants use osmosis
to take in water through
their roots.
Words – membrane, concentrated, dilute, diffusion, gradient
Potato cells
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Strong
sugar
solution
Medium
sugar
solution
Weak
sugar
solution
Active Transport
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In diffusion substances moved along a concentration gradient.
In active transport, substances move against this gradient:
Outside cell
Inside cell
Cell membrane
This process takes ______ and
this comes from ___________.
It enables cells to take in
substances even though there
are in very small __________.
Root hair cells take in ______
using active transport.
Words – concentration, energy,
respiration, nutrients
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Diffusion and Active Transport in plants
Mineral
More
concentrated
Carbon dioxide diffuses
into the leaf through
holes in the bottom
surface.
Less
concentrated
…while plant nutrients are taken
in by root hair cells using active
transport.
Encouraging Photosynthesis
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Using knowledge of limiting factors, explain how plant growth
is encouraged in a greenhouse:
Limiting Photosynthesis
What factors could limit the rate of photosynthesis?
1. Temperature – the best temperature is
about 300C – anything above 400C will
slow photosynthesis right down
2. CO2 – if there is more carbon dioxide
photosynthesis will happen quicker
3. Light – if there is more light
photosynthesis happens faster
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Drawing graphs of these factors
1. Temperature
Photosynthesis is controlled by
enzymes – these are destroyed
at temperatures above 400C
2. Carbon dioxide
Photosynthesis increases at
first but is then limited by a
lack of increase in temp or light
3. Light
Photosynthesis increases at
first but is then limited by a
lack of increase in temp or CO2
Fieldwork techniques
Using quadrats
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Recording light
levels
Fieldwork techniques also involve using a key to identify plants.
B4.3 How do living organisms obtain
energy?
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Uses for energy from respiration
Animals and plants have many uses for the energy they
generate from respiration:
1) To perform the life processes, such as moving, _____ etc
2) To build up body _______
3) To maintain a constant body ___________ (warm-blooded
mammals only)
4) To build up sugars, ________ and other nutrients in plants
5) Active __________
Words – nitrates, tissue, proteins, transport, growing
Synthesis
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“Synthesis” means “making large molecules out of small ones”.
Two examples:
1) Glucose (sugar) can be used to make long chains of insoluble starch…
Glucose
molecules
Starch
molecule
2) Glucose can be combined with nitrates to make proteins (for growth)…
Glucose
molecules
Proteins
Respiration Introduction
I enjoy taking samples using quadrats. In
order to do this, I need energy. Where does
this energy come from?
Our energy comes from a process called
respiration, which basically involves turning
food and oxygen into energy and this
reaction is controlled by enzymes.
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(Aerobic) Respiration
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All living organisms have to move, _____, reproduce etc. Each
of these life processes needs ENERGY. ___________ is the
process our bodies use to produce this energy:
Glucose + oxygen
water + carbon dioxide + ENERGY
The glucose we need comes from ______ and the oxygen from
_________. Water and carbon dioxide are breathed out.
The MAIN product of this equation is _________.
Respiration happens in _________ in cells.
Words – breathing, energy, grow, respiration, food,
mitochondria
Muscles and exercise
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When we exercise our muscles are supplied with more oxygen
and glucose, increasing the rate of respiration.
Muscles store glucose as glycogen
which can then be converted back
into glucose during exercise.
Anaerobic respiration
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Unlike aerobic respiration, anaerobic respiration is when
energy is provided WITHOUT needing _________:
Glucose
lactic acid + a bit of energy
This happens when the body can’t provide oxygen quick enough
for __________ respiration to take place.
Anaerobic respiration produces energy much _______ than
aerobic respiration but only produces 1/20th as much.
Anaerobic respiration can also take place in other low-oxygen
conditions, such as plant roots in _________ soil or
bacteria in ________ wounds.
Words – oxygen, aerobic, quicker, puncture, waterlogged
Making Ethanol
Ethanol is an important chemical. Many
countries are increasing the amount of
ethanol put into their petrol supplies:
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Ford Escape E85 –
runs on 85% ethanol
Ethanol is another product of anaerobic respiration in plant
cells and some micro organisms:
Sugar
ethanol + carbon dioxide + energy
Bacteria
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Consider a bacteria cell in more detail:
Bacteria – containing
cytoplasm and a membrane
surrounded by a cell wall.
The genes are NOT in a
distinct nucleus.
The cell contains a number of features,
including:
1) Chromosomal DNA, containing the
genetic info of the cell
2) Plasmid DNA, containing extra
information such as defence
mechanisms
3) Flagella, which helps the cell move
The Structure of Bacteria
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Bacteria also have plasmids
(circular strands of DNA) that
can be copied and move
between different bacteria.
This means that resistance to
antibiotics can be passed on
without the need for
reproduction.
Respiration in Cells
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Notice that plant and animal cells (and bacteria) have many
features that help respiration:
1) Cytoplasm where enzymes are
made
2) Nucleus – carries
genetic info for
making enzymes
3) Cell Membrane –
controls what comes in
and out
4) Mitochondria –
contain enzymes for
respiration reactions
In bacteria cells, this job
is done by circular DNA
Using Anaerobic Respiration
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Anaerobic respiration in micro organisms is used to make fuels
through:
1) Manure or other waste that can be
used to release methane (biogas)
2) Corn or sugar cane that can be broken
down in a fermenter to produce
alcohols like bio-ethanol.
Anaerobic respiration is also
used in fermentation to make
bread and alcohol.