Overview of Cell Theory, Elements & Properties: Cells, Tissues & Physical Attributes, Study notes of Chemistry

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BTEC Applied Science

Unit 1 Revision Guide

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EXAM DATE:

Monday 5th June 2016,

9:00am, 1h 30m

1. Outline the similarities and differences between eukaryotic and prokaryotic cells.
2. Briefly outline how cell theory has de- veloped over the past 400 years.

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CELL THEORY

The cell is the fundamental unit of life. All organisms, whatever their type or size, are composed of cells. The modern theory of cellular organisation states:-

• All living things are composed of cells and cell products.
• New cells are formed only by the division of pre-existing cells
• The cell contains inherited information (genes), which is used as instructions for growth, functioning and development.
• The cell is the functioning unit of life; the metabolic reactions of life take place within the cells.

Eukaryotic Prokaryotic

Eukaryotic cells make up multi- cellular organisms such as plants and animals. They are complex cells with a nucleus and membrane-bound orga- nelles.

Prokaryotic cells are single- celled organisms. They are sim- ple structures and do not have a nucleus or any membrane- bound organelles.

Plants and animals Bacteria

1665: Robert Hooke first described cells

1674 – 1683: The first living cell was observed Anton van Leeuwenhoek was the first person to observe bacteria and protoctista from pond water samples, after developing powerful glass lenses.

1831: Nucleus observed Robert Brown an English botanist was the first to observe and describe the nucleus in a plant cell.

1674 – 1683: Universal cell theory Matthias Schleiden suggested that all plant material is composed of cells. Jan Purkyne observed that animal tissue is composed of cells and the structure is similar to plant tissue. The scientist credited for the Universal Cell Theory is Theodor Schwann, a German physiologist. He proposed that ‘all living things are composed of cells.

1852: Evidence for the origin of new cells Robert Remak observed cell division in animal cells. His findings were not accepted at the time, but in 1855 Rudolf Virchow published the findings as his own to show new cells form from existing ones.

1860: Spontaneous generation disproved Louis Pasteur demonstrated that bacteria will only grow in sterile nutrient broth after it has been ex- posed to air. This disproved the theory of spontaneous generation of cells.

Robert Hooke

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MY NOTES/EXAM PRACTICE

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MY NOTES/EXAM PRACTICE

1. State two functions of the Golgi appa- ratus.
2. Draw from memory a labelled diagram of an animal cell.
3. Outline the functions of each cell com- ponent.

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Make sure you can link the structure of a cell organelle with its function.

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ANIMAL CELLS

One of the key functions of a cell is to synthesise proteins for use inside the cell, to lead to cell multiplication and for secretion out of the cell for example, insulin.  Proteins are synthesised on ribosomes attached to rough endoplasmic reticulum.  The newly synthesised proteins are transported through the cisternae of the rough ER and packaged into vesicles.  They are transported to the Golgi apparatus, where vesicles fuse with the sur- face of the Golgi apparatus and the proteins enter.  It is here that the newly synthesised proteins are modified and then packaged into vesicles. Secretory vesicles will transport proteins that are to be released from the cell to the cell surface membrane.  They will fuse with the membrane and release the protein by exocytosis.

1. Name an organelle found in a plant cell that is not present in this animal cell.
2. Outline the function of each plant cell component.

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Make sure you can link the structure of a cell organelle with its function.

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PLANT CELLS

Plasmodesma: Microscopic channels which cross the cell walls of plant cells. Enable transport and communication be- tween individual plant cells.

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1. Briefly explain how to carry out gram staining.

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GRAM STAINING

It is important that microbiologists can correctly identify bacteria that cause infections to enable them to decide the most effective treatment.

During the staining technique, two stains are added to the bacterial smear: crystal violet and safranin.

Gram Positive Gram Negative

If you see a purple stain when ob- serving the smear under a micro- scope it shows that Gram-positive bacteria are present.

If the smear has retained the pink safranin stain, this shows that Gram-negative bacteria are pre- sent. This is because their thinner cell walls and lipid membranes allow ethanol (applied during the method) to wash off all the crystal violet purple stain and to then re- tain the pink safranin stain.

Scientists researching fertilisation in humans need to understand how sperm cells are adapted for their specific function. The diagram shows a human sperm cell. Complete the miss- ing labels, X and Y, on the diagram.

1. Explain how the mid-piece of a human sperm cell is specialised to support the function of its tail.

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Do you understand the meaning of the key terms ‘gametes’ and ‘water potential’?

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SPECIALISED CELLS (I)

Palisade mesophyll cells Root hair cell Sperm cell

Palisade mesophyll cells found in leaves are rectangular box shaped cells that con- tain chloroplasts. The chloroplasts are able to absorb a large amount of light for pho- tosynthesis. They also move around in the cytoplasm in order to maximise the amount of light absorbed.

These cells are found at a plant’s roots, near the growing tip. They have long hair- like extensions called root hairs. The root hairs increase the surface area of the cell to maximise the movement of water and minerals from the soil into the plant root.

Sperm cells are male gametes in animals. They have a tail like structure called a un- dulipodium so they can move. They also contain many mitochondria to supply the energy needed for this movement. The sperm head is 3 μm wide and 4 μm long. It is made up of an acrosome, which contains digestive enzymes. These enzymes are released when the sperm meets the egg, to digest the protective layer and allow the sperm to penetrate. The sperm’s function is to deliver genetic information to the egg cell or ovum (female gamete). This is ferti- lisation

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MY NOTES/EXAM PRACTICE

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1. What is the name of the lung tissue that con- tains ciliated cells?

A columnar endothelium

B columnar epithelium

C squamous endothelium

D squamous epithelium

2. Chemicals in cigarette smoke reduce the movement of the cilia on ciliated cells in the human lung. Explain how reducing the move- ment of these cilia can result in a smoker hav- ing to cough.

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EPITHELIAL TISSUE

Squamous epithelial tissue Ciliated columnar epithelial tissue Endothelial tissue

Location: lines organs and surfaces Location: line the trachea in the respirato- ry system, column-shaped ciliated cells with hair-like structures called cilia cover- ing the exposed cell surface

Location: found lining the heart, blood vessels and lymphatic vessels

Function: one cell thick, form thin, smooth, flat layers. Ideal for rapid diffu- sion e.g. alveoli in lungs - rapid diffusion of oxygen

Function: protect the lungs from infection by sweeping away pathogens and se- creting mucus to trap pathogens

Function: The cells provide a short diffu- sion pathway for the movement of various substances, such as:  products of digestion into blood capillaries  blood plasma and tissue fluid in and out of blood capillaries.

Damage caused by smoking: Smoking irritates and causes inflammation and scar- ring in the epithelium tissue of the lungs. The alveoli walls become thicker due to scarring and produce more mucus. The damage to the air sacs causes emphysema and the lungs lose their natural elasticity.

How the lungs are protected: They se- crete mucus to help trap any unwanted particles that are present in the air that you breathe in. This protects your lungs because it prevents bacteria reaching the alveoli.

How arteriosclerosis develops: Carbon monoxide and high blood pressure can damage the inner lining of the arteries. White blood cells repair the damage and encourage the growth of smooth muscle and the deposition of fatty substances such as cholesterol under the endothelium lining of arteries, not on the surface. This process of deposition is called atheroscle- rosis

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