13 What's in a cell_

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- GCSE Bitesize - What's in a cell?

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Science

What's in a cell?

Al l animals and plants are made of cells. Animal and plant

cells have features in common, such as a nucleus,

cytoplasm, cell membrane, mitochondria and ribosomes.Plant cells also have a cell wall, and often have chloroplasts

and a permanent vacuole. Note that cells may be

specialised to carry out a particular function.

We use microscopes to see very tiny structures such as

cells.

Bacterial cell structure

Bacterial cells are much smaller than plant or animal cells. They

were first seen under a microscope by Anton van Leeuwenhoek

n 1676. As microscopes have improved, scientists have come

to understand bacterial cell structure better.

Using electron microscopes we now know that bacteria have a

cell wall. This is similar to a plant cell wall but is more flexible.

Bacteria do not have a nucleus. They do have two types of

DNA – plasmid and chromosomal. The chromosomal DNA

carries most of the genetic information. Plasmid DNA forms

small loops and carries extra information. Some bacteria have a

flagellum – a whip like tail. This helps the bacteria to move itself

along. When we talk about these flagellum tails in multiple

bacteria, we call them flagella.





Plant and animal cells

Function of cells which animal and plant cells have in

common

Part Function

Nucleus Contains genetic material, which controls theactivities of the cell

Cytoplasm Most chemical processes take place here,

controlled by enzymes

Cell

membrane

Controls the movement of substances into

and out of the cell

Mitochondria Most energy is released by respiration here

Ribosomes Protein synthesis happens here

Plant cells also have extra parts:

Extra parts of plant cells

Part Function

Structure of a salmonella

bacterium cell

Structure of a bacteria cell





Cell wall Strengthens the cell

Chloroplasts Contain chlorophyll, which absorbs light

energy for photosynthesis

Permanent

vacuole

Filled with cell sap to help keep the cell

turgid [turgid: Having turgor; enlarged and

swollen with water ]

Make sure you can label diagrams of animal and plant cells, like

these:

Microscopes

Microscopes have been in use for approximately 350 years.

Hans and Zaccharias Janssen are credited with constructing the

first usable one in the 1590s.

Generalised animal and plant cell





Early microscopes did not magnify to a great extent and

scientists have worked hard to improve this. We now have

modern light microscopes that can magnify 1,500 times and

electron microscopes that can magnify up to two million times.

This has allowed scientists to see things such as cells in much

greater detail. As a result our understanding of their structure

and function has improved.

Magnification calculations

We can calculate the length of a magnified object by using the

magnification of the lens.

Length of object = length of magnified object ÷

magnification

For example, if a specimen appeared 10mm in length under a

microscope with a magnification of 1,000 times, the calculation

of the actual length would be:

Length of object = 10 ÷ 1000 = 0.01 mm

Now try a Test Bite.

Microscope from the end of

the nineteenth century

Modern microscope

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