Cells and Energy
Revision
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Plant and Animal Cells
Animal Cells
Plant Cells
Nucleus
Controls the cell's activities and DNA is stored here
Mitochondria
Respiration occurs here
Cell membrane
Controls what enters and leaves the cell
Cytoplasm
A jelly like substance where chemical reactions take place
Mitochondria
Respiration occurs here
Nucleus
Controls the cell's activities and DNA is stored here
Cytoplasm
A jelly like substance where chemical reactions take place
Cell Wall
Gives the cell strength and structure
Chloroplasts
Photosynthesis occurs here
Cell membrane
Controls what enters and leaves the cell
Vacuole
Contains cell sap to keep the cell firm
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Specialised Cells
Specialised Cells
A specialised cell is a cell which is suited to do a particular job.
Sperm Cells
A sperm cell is adapted so that it can fertilise an egg cell.
Red Blood Cells
A red blood cell is desgined to carry oxygen around the body.
Nerve Cells
A nerve cell is designed to carry nerve impulses to different parts of the body.
Root Hair Cells
A root hair cell is designed to absorb water and nutrients for a plant.
A tail to allow the sperm to swim towards the egg cell
Lots of mitochondria to release a lot of energy
No nucleus so that they can carry more oxygen
A biconcave (donut) shape so they have a larger surface area to absorb oxygen
A large surface area so that they can absorb water and minerals more effectively
A thin cell membrane to speed up diffusion
Insulation to increase the speed of a nerve impulse
Very long to send nerve impulses up and down the body
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Respiration
Aerobic Respiration
Glucose + Oxygen → Carbon dioxide + Water + Energy
Comes from food broken down in digestion
Transported in blood cells from the lungs
Exhaled from the body
More than anaerobic respiration
Respiration happens in the mitochondria
Aerobic Respiration
Glucose→Lactic acid + Energy
Not enough oxygen so glucose can’t be fully broken down
Builds up in
muscles and
causes cramps, needs extra oxygen to break it down
Less than aerobic respiration
Cannot be be used for long periods of time because of this
Fermentation Fermentation is a type of anaerobic respiration by yeast in which glucose is broken down and forms ethanol
Glucose→Carbon dioxide + Ethanol
Can be used to make bread and cakes rise
Can be used in alcoholic drinks
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Mitosis
The process of mitosis
Mitosis is a type of cell division in which the cells made are identical to the starting cell
46
92
46
46
The original cell has 46 chromosomes
The chromosomes are copied, so that there are 72 chromosomes
The cell divides in two, with each having 46 chromosomes, each cell is identical to the original cell
Uses of mitosis
Mitosis produces identical cells, it can be used for:
Growth
Replacing dead cells
Asexual reproduction (creating offspring with
only one parent, e.g. in plants)
Where mitosis occurs
Mitosis happens everywhere in the body apart from the sex cells (gametes)
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Stem Cells
Stem Cells
Stem cells are undifferentiated cells, they can divide into many other types of cells.
Embryonic Stem Cells
Embryonic stem cells are found in an embryo (developing baby) and can develop into a wide range of other cells.
Adult Stem Cells
Adult stem cells are found in bone marrow, they can divide into other types of cells, but not as many types as embryonic stem cells.
Uses of Stem Cells
Stem Cells can be used for:
Treating Cancers Treating Paralysis Repairing Injuries
Potential growth of Organs
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Movement of substances
Diffusion
Diffusion is the random spreading of particles, from an area of high concentration to an area of low concentration. It does not need energy.
Osmosis
Osmosis is the diffusion of water from an area of high concentration to an area of low concentration. It does not need energy.
Active transport
Active transport it the movement of substances from an area of low concentration to an area of high concentration. It requires energy to occur.
High concentration
(all close together)
Low concentration
(spread throughout the liquid)
High concentration of water
(a lot of water molecules)
Low concentration of water
(not a lot of water molecules)
Low concentration
(not a lot of molecules)
High concentration
(a lot of
molecules)
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Diffusion In Cells
Diffusion
Diffusion is the random spreading of particles, from an area of high concentration to an area of low concentration.
Factors which will speed up diffusion
High concentration
(all close together)
Low concentration
(spread throughout the liquid)
Diffusion in cells
Diffusion occurs across the cell membrane.
A higher temperature
A gas rather than a liquid
A larger surface area
High concentration of water
(a lot of water molecules)
Low concentration of water
(not a lot of water molecules)
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Kinetic Energy
Kinetic Energy
Kinetic energy is the energy of movement, it is measured in joules
Kinetic Energy = 0.5 x mass x speed x speed
(kg) (m/s) (m/s)
Kinetic energy and mass
The greater the mass, the greater the kinetic energy
Example
A car is moving with a speed of 10 m/s and has a mass of 2500 kg. What is the kinetic energy of the car?
Kinetic energy = 0.5 x mass x speed x speed
Kinetic energy = 0.5 x 2500 x 10 x 10
Kinetic energy = 125 000 J
Kinetic energy and mass
The greater the speed, the greater the kinetic energy
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Gravitational Potential Energy
Gravitational Potential Energy
Gravitational potential energy is the energy because of the position of an object, it is measured in joules
Gravitational Potential Energy = Mass x Gravity x Height
(kg) (N/kg) (m)
Gravitational Potential energy and mass
The greater the mass, the greater the gravitational potential energy
Example
A book with a mass of 0.25 kg is placed on a shelf with a height of 1.7 m. If the value of gravity on Earth is 9.81 N/kg, what is the gravitational potential energy of the book?
Gravitational potential energy = mass x gravity x height
Gravitational potential energy = 0.25 x 9.81 x 1.7
Gravitational potential energy = 4.17 J
Gravitational Potential energy and gravity
The value of gravity is different on different planets, the greater the value of gravity, the greater the gravitational potential energy
Gravitational Potential energy and height
The greater the height, the greater the gravitational potential energy
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Power
Power
Power is a measure of how quickly energy is transferred, it is measured in Watts
Power = Energy ÷ Time
(W) (J) (s)
Factors affecting power
The more powerful an appliance is the faster it will transfer energy
The less time to transfer energy, the more powerful the device will be.
The more time used to transfer energy, the less powerful the device will be.
Example
A light bulb transfers 1000 J of energy in 20 seconds. What is the power of the light bulb?
Power = energy ÷ time
Power = 1000 ÷ 20
Power = 50 W
Power rearrangements
Power = Energy ÷ Time
(W) (J) (s)
Energy = Power x Time
(J) (W) (s)
Time = Energy ÷ Power
(s) (J) (W)
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Efficiency
Kinetic Energy
Efficiency is a measure of how much energy is used usefully in a situation, the lower the wasted energy the more efficienct a device is.
Efficiency = (useful energy ÷ total energy) x 100
Increasing efficiency
Efficiency can be increased by reducing wasted energy, examples of how to do this include:
Using lubricants to prevent moving parts rubbing together
For heaters reducing wasted energy to the surroundings by using insulation
Example
A light bulb has 500 J of electrical energy provided to it, if 200 J is transferred as light, what is the efficiency of the light bulb?
Efficiency = (useful energy ÷ total energy) x 100
Efficiency = (200 ÷ 500) x 100
Efficiency = 40 %
Useful and wasted energy
Useful energy is the energy released which is used by the appliance
Wasted energy is any other form of energy given out, usually this can be thermal and sound
Input: Electrical Energy
Useful:
Light Energy
Wasted:
Thermal Energy
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Renewable and Non Renewable Energy
Non Renewable energy
Non renewable energy resources will run out, they cannot be replaced within your lifetime
Renewable energy
Renewable energy resources will not run out, they can be replaced within your lifetime
Nuclear power uses radioactive materials to heat water and turn a turbine to generate electricity
Fossil fuels (coal, oil and natural gases) are burned in a power station to heat water and turn a turbine to generate electricity
Wind turbines use the wind to generate electricity
Solar panels convert energy from the sun into electricity
Hydroelectric energy uses falling water to turn turbines and generate electricity
Geothermal uses the heat of rocks to heat water which will turn a turbine to generate electricity