L1 -Introduction to Biology, Cell Theory

Grade 10 Science

Nicole Klement

What is Biology

Bio : Life Ology: Study of Life

In Grade 9 Science you studied Ecosystems & Human activity in your biology unit (the Large picture)

This year (Grade 10) year we will study cells, tissues & organs (the middle picture)

If you take Grade 11 Biology you will focus on microbiology (the small picture)

What is Life?

How can you tell something is living…..

Talk to the members at your lab bench and brainstorm a list of characteristics that belong to ALL living things.

Characteristics of Living Things

All living things have common characteristics: Require food for energy Respire break down food for energy Limited lifespan Respond to the environment Grow Reproduce Produce waste Are made of CELL(S)

Did you know?

That viruses do not actually meet the definition of life as described in the cell theory?

They are made up of DNA (or RNA), encased in a protein shell.

You are living. Where did you come from?

Since you fulfill all the criteria for a living organism you are alive.

If you are alive you are made of cells.

Where did these cells come from?

Cell Theory

Original Cell Theory

The original Cell Theory, developed mainly in the 1800s, claimed that:

1. All living things are composed of one or more cells.

2. Cells come from pre-existing cells.

3. Cells are the smallest unit of life.

Modern Cell Theory

The Modern Cell Theory has added several refinements because of technological advances that have given scientists a better idea of what actually happens at the cellular level.

Cells contain DNA (deoxyribonucleic acid) which contains their genetic information and it is passed on each time a cell divides.

All cells are similar with regards to chemical composition and metabolic functions.

All basic chemical and physiological functions are carried out inside the cell, such as digestion and locomotion.

Cell activities are dependent upon sub-structures known as organelles.

History of cell study

Robert Hooke (1665) coined the word “cell” when studying cork cells

Antonie Van Leewenhoek ( ) created the first basic microscope allowing him to be the first to visualize single cells

Robert Brown (1831) discovered the nucleus Theodore Schwann (1838) viewed animal cells

in cartilage and stated “cells may be the basic unit of plants and animals”

Virchow (1858) “all cells come from cells”

Did you know?

That very little progress was made for about 150 years after Hooke and Leuwenhoek, mainly due to a belief in something called Spontaneous Generation? This theory claimed that life could be generated spontaneously and did not have to come from pre-existing organisms.

For example, people believed that maggots came from dead meat, and frogs came from mud. This was because people didn't know about things they couldn't see, like fly eggs laid on meat and frog eggs buried in mud.

Cells

Cell SizeCells are small (1-100µm)

Cell Surface Area

Cells are small for good reason (transport):

a) Surface-to-volume ratio

b) Distance from surface to centre

Cell types

Until high school you learn about TWO cell types.

a) Animal

b) Plant

These are important to distinguish.

Cell Sub-types

Animal cells are not just of one type (as you have learned to date).

There are variations.

Different types of Animal cells

But there is more too categorizing cells

There are varieties among animal cells:a) Prokaryotic

Ex: Bacteria cell; no nucleus (or other membrane bound organelles), circular DNA, ribosomes

b) Eukaryotic

Ex: YOU are made of Eukaryotic cells; larger, nucleus, linear chromosomes and membrane bound organelles

Cell Structure

To review cell structure we visited: the virtual image gallery “cells alive”

Be sure you are comfortable with the following terms and functions….

Part of a cell - Organelles

Cells are made up of smaller parts called organelles.

These organelles perform the functions that the cell needs in order to live, much like your organs do for you.

Similarities among cells

All cells you’ve study have the same components: Plasma membrane (phospholipid bilayer) DNA (deoxyribonucleic acid; the Genetic material in

nucleus) Cytoplasm (water, salts and organelles) Endoplasmic reticulum (synthesis & packaging, rough;

proteins, smooth; lipids) Golgi Apparatus (packaging and transport) Lysosomes (digest or destroy) Mitrochondria (provides energy) Cytoskeleton (network of fibres to which organelles

attach)

Differences among Plant & Animal CellsPlant cells Have cell walls Have vacuoles Have chloroplasts (in charge of photosynthesis)

Animal Cells No cell walls No vacuoles No chloroplasts (or photosynthesis)

Organelles specific to Animal vs Plant cells The Animal Cell: In addition to the organelles

listed on the previous page, animal cells contain centrioles. They play a role in the reproduction of the cell.

The Plant Cell: In addition to the organelles listed on the previous page, plant cells contain chloroplasts and have a cell wall. Chloroplasts contain chlorophyll, the chemical that enables plants to convert sunlight into a useable type of energy in the form of sugar. Without chlorophyll, life could not exist. Plant cells also contain plastids, which store chemicals and pigments.

Why do plants wilt?

Plants have vacuoles that maintain turgor pressure. That’s why water is so important for plants!

Did you know?

Did you know that crickets can regenerate their legs?

Humans have a limited ability to regenerate lost organs. However, up to 75% of the liver may be lost and have regeneration.

Children up to the age of 12 may regenerate severed fingertips.

Tomorrow

Tomorrow’s lecture will cover “cell reproduction” and will explain how humans are able to grow and regenerate

Links

Inside a cellhttp://learn.genetics.utah.edu/content/begi

n/cells/insideacell/Cell mitosishttp://www.cellsalive.com/cells/cell_model.

htmHistory of cellhttp://library.thinkquest.org/12413/

theory.html

For review if needed….

Parts of a Cell

All cells, whether animal or plant, contain the following parts: 1. Cell membrane - This is a semi-permeable (it allows some things to pass through it and stops

others) membrane that surrounds a cell and allows it to keep its integrity. Think of it like your skin.

2. DNA - This is the genetic code that dictates what the cell will be like and what function it will have. For example, people have 46 chromosomes (bundles of DNA) in their cells. Dogs have 78 chromosomes.

3. Cytoplasm - This is a gel-like material that fills the spaces inside a cell. It contains water and nutrients for the cell.

4. Endoplasmic Reticulum - This is the circulatory system for the cell and it moves materials around in the cell. It is like your blood vessels. It can be smooth or rough. If it is rough, then it has ribosomes stuck to it.

5. Ribosomes - They make protein for the cell and they can be free-floating or attached to the endoplasmic reticulum.

6. Golgi Bodies - They store energy for the cell in the form of ATP (adenosine triphosphate). 7. Mitochondria - They act like your stomach in that they digest food, releasing energy for the

cell. They are known as the powerhouses of the cell. 8. Lysosomes - They contain chemicals that break down dead organelles and other types of

cell waste. 9. Vacuoles - They are storage areas where the cell can place chemicals and other substances,

like food, that it will need later. Think of them like your fat cells. Animal cells have many small vacuoles, while plant cells have a few large ones.