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Cells PowerPoint PPT Presentation

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Cells. Bacterial cell – genetic information not contained within a nucleus. Diffusion is the net movement of particles from a high concentration to a low concentration down the concentration gradient until an equilibrium is reached. Cell . Tissue. Organ. Organ system.

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Bacterial cell – genetic information not contained within a nucleus

Diffusion is the net movement of particles from a high concentration to a low concentration down the concentration gradient until an equilibrium is reached




Organ system

Organs are made of tissues. The stomach is an organ that contains:

■ muscular tissue, to churn the contents

■ glandular tissue, to produce digestive juices

■ epithelial tissue, to cover the outside and the inside of the stomach.


Examples of plant tissues include:

  • epidermal tissues, which cover the plant

  • mesophyll, which carries out photosynthesis

  • xylem and phloem, which transport substances around the plant







Taken in through holes in the leaves as a gas in air

Taken in through the roots from soil

Made by photosynthesis and stored as starch in leaves, roots, stems, etc.

waste product exhaled

With light and


We know that plants make their own food from sunlight. They are the producers in the food chain. This is done in the green parts of the plant, e.g. upper surface of the leaves.





Paraffin lamps have traditionally been used in greenhouses. Their use increases the rate of photosynthesis because as well as the light generated from the lamps, the burning paraffin produces heat and carbon dioxide too

The use of artificial light allows photosynthesis to continue beyond daylight hours. Bright lights also provide a higher-than-normal light intensity.

The use of artificial heating allows photosynthesis to continue at an increased rate.

Converted into insoluble starch for storage

Used in respiration


To produce fats and oils for storage

To produce cellulose for cell walls

To produce proteins

To produce proteins, plants also use nitrate ions that are absorbed from the soil.





  • Proteins act as:

    • structural components of tissues such as muscles

    • hormones

    • antibodies

    • catalysts

  • Catalysts increase the rate of chemical reactions. Biological catalysts are called enzymes. Enzymes are proteins.

Enzymes are protein molecules, and so are made up of long chains of amino acids. Most enzymes contain between 100 and 1,000 amino acids.

These long chains are folded to produce a unique 3D shape which enables other molecules to fit into the protein.

  • The shape of an enzyme is vital for the enzyme’s function. High temperatures change the shape. Different enzymes work best at different pH values.

This is what happens at the active site





enzyme-reactant complex









If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes.

This affects the shape of the active site and means that the enzyme will no longer work.

When this happens the enzyme is denatured.

Effect of pH…

A change in the pH changes the shape of the protein molecule, the enzyme loses its active site and so can no longer act as a catalyst.

Effect of temperature…


  • What are biological catalysts called?

  • What are enzymes made of?

  • What is the place on the enzyme where the reactant molecule binds called?

  • What does it mean when an enzyme is denatured?

  • What two factors can affect enzyme action?

Some enzymes work outside the body cells.

The digestive enzymes are produced by specialised cells in glands and in the lining of the gut. The enzymes then pass out of the cells into the gut where they come into contact with food molecules.

They catalyse the breakdown of large INSOLUBLE molecules into smaller SOLUBLE molecules.

The stomach produces hydrochloric acid to create the optimum conditions for the protease enzymes in the stomach

Bile neutralises the acid that was added to food in the stomach. This provides alkaline conditions in which enzymes in the small intestine work most effectively.


  • Name the enzyme that breaks down fats?

  • Name the enzyme that breaks down proteins?

  • Name the enzyme that breaks down carbohydrates?

  • What are fats broken down into?

  • What are proteins broken down into?

  • What are carbohydrates broken down into?

  • Where is amylase made?

  • Where is protease made?

  • Where is lipase made?

  • Where is bile produced?

  • Where is it stored?

  • What does it do?


From microorganisms

More effective at low temperatures than other washing powders

Isomerase – converts glucose into fructose

  • In industry, enzymes are used to bring about reactions at normal temperatures and pressures that would otherwise require expensive, energy-demanding equipment.

  • However, most enzymes are denatured at high temperatures and many are costly to produce.


  • What type of organisms produce enzymes that are used in industry?

  • What enzymes are found in washing powders?

  • What enzyme converts glucose into fructose?

  • Why is fructose used in slimming foods rather than glucose?



waste product exhaled

waste product exhaled

from the digestive system

from the breathing system

AEROBIC Respirationis the process that the body uses to release energy from digested food (glucose):







Happens in all cells all the time in plants & animals inside mitochondria

Which cells contain more mitochondria? Why?

  • Muscles, liver and kidneys

  • They require more energy

  • They use energy at a higher rate, especially during exercise

The folded layers produce a large surface area for the chemical reactions

The large surface area means more enzymes can attach to the substrates to catalyse the reactions


  • Respiration releases energy from the food we eat so body cells can use it

  • Builds large molecules up from smaller ones to make new cell material (synthesis reactions) – example – sugars and nitrates are built into amino acids which are then used to make proteins

  • Makes your muscles contract – whether aware of or not – e.g. sleeping – heart beats, breathe, gut churns!

  • On cold days we use energy to keep warm and on hot days use energy to sweat and keep cool – WARM BLOODED


  • Write the equation for aerobic respiration

  • Where does respiration occur?

  • Which cells contain more mitochondria?

  • Give two reasons for respiration

  • What changes happen during exercise?

What do these changes mean?

  • Increase the blood flow to the muscles and so increase the supply of glucose and oxygen and increase the rate of removal of carbon dioxide.

If insufficient oxygen is

available during exercise

what type of respiration


  • Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid


  • As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration.

  • Anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise lactic acid to carbon dioxide and water.


  • If muscles are subjected to long periods of vigorous activity they become fatigued, i.e. they stop contracting efficiently.

  • One cause of muscle fatigue is the build-up of lactic acid in the muscles. Blood flowing through the muscles removes the lactic acid.


  • What does anaerobic mean?

  • What is produced in anaerobic respiration?

  • Why is more energy produced with aerobic than anaerobic respiration?

  • What is the ‘oxygen debt’?

  • What is one cause of muscle fatigue?


  • In body cells the chromosomes are normally found in pairs. Body cells divide by mitosis. The chromosomes contain the genetic information

  • When a cell divides to form gametes:

    • copies of the genetic information are made

    • then the cell divides twice to form four gametes, each with a single set of chromosomes.


  • How do body cells divide?

  • Where are the chromosomes found?

  • How many daughter cells does mitosis produce?

  • How many daughter cells does meiosis produce?

  • Where does meiosis occur?

  • What does meiosis produce?

  • Most types of animal cells differentiate at an early stage whereas many plant cells retain the ability to differentiate throughout life.

  • In mature animals, cell division is mainly restricted to repair and replacement


  • Cells from human embryos and adult bone marrow, called stem cells, can be made to differentiate into many different types of cells, e.g. nerve cells.

  • Human stem cells have the ability to develop into any kind of human cell.

  • Treatment with stem cells may be able to help conditions such as paralysis.

  • Sexual reproduction gives rise to variation because, when gametes fuse, one of each pair of alleles comes from each parent

Each gene may have different forms called alleles



Gene is a small section of DNA

Chromosomes are made of DNA

Each gene codes for a particular combination of amino acids which make a specific protein

Each person (apart from identical twins) has unique DNA. This can be used to identify

individuals in a process known as DNA fingerprinting


  • What is a stem cell?

  • Where are they produced?

  • What is an allele?

  • What is a gene?

  • What are chromosomes made of?

  • Why does sexual reproduction give rise to variation?


Embryo screening?

Cystic fibrosis

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