Discovering Cells

LIVING ORGANISMS

Plants, animals and other organisms respond to the same basic needs. Aside

from a few exceptions, anything classified as

living has the following characteristics:

LIVING ORGANISMS

• It is made up of cells.• It needs water and food for energy in order to

live.

• It needs carbon dioxide (CO2) OR oxygen to release energy.

• It grows.• It is able to reproduce (asexually or sexually).• It is able to respond to changes in its

environment.• It gives off waste.• It needs a place to live.

LIVING ORGANISMS

ENERGY is the KEY to all of these functions. Living things

consume food to get the energy they need to organize their cells, to reproduce, and to

respond to changes. All living things need energy to grow and

reproduce. Energy ultimately comes from the SUN!

CELLS

Likewise, a single cell has the same needs as an entire organism!

For each cell to stay alive, it must carry out many of the same functions as the entire organism!

CELLS

It needs water and food for energy in order to live.It needs oxygen to release energy.It is able to reproduce (asexually: by duplicating

(copying) its genetic information and then dividing This process of reproduction, called MITOSIS produces “daughter cells” that are identical copies of the parent cell!)

It is able to respond to changes in its environment.It is gives off waste.It needs a place to live.

Parent cell

Identical daughter cells

Cell vs Living Organism

CELL THEORY

Spontaneous generation was the idea that living things came from non-living things.

This idea became a theory and was accepted for several hundred years.

In the mid- 1800’s Louis Pasteur, a French chemist, provided enough evidence to

disprove the theory of spontaneous generation.It was replaced with Biogenesis which is the

theory that living things come only from other

living things.

The following experiments helped

to prove that… LIVING THINGS COME ONLY

FROM Living Things

Redi’s Experiment

1. Maggots developed in the open container.

2. Maggots appeared on the netting of the covered container because the flies were still laying eggs. No maggots developed on the meat.

3. No maggots developed on or in the closed container. The flies were unable to sense the meat.

Pasteur’s Experiment

1. Broth was poured into the flask. 2. The broth was boiled to kill all of the microbes (bacteria).3. Dust collected in the “S” of the flask BUT the flask did NOT

turn cloudy. 4. The broth did not turn cloudy (indicating that there was

bacteria present) until the flask was tipped OR until the “S” shape was removed & the broth was exposed to the dust.

Dust

SEEING CELLS

Robert Hooke: • In 1665, Robert Hooke used a

microscope to observe a thin slice of cork.

•The cork appeared to be made up of empty little boxes or rooms. Hooke called these spaces cells.

SEEING CELLS

Leeuwenhoek: Around 1674, Leeuwenhoek notice single- celled organisms in a drop of lake water and scrapings from teeth & gums using a microscope that he had built. He called these moving organisms animalcules,

meaning “little animals”.

SEEING CELLS

During the mid- 1800’s other scientists made further cell discoveries leading to the development of the CELL

THEORY.

SEEING CELLS

Schleiden concluded that all plants are made of cells

Schwann concluded that all animals are made of cells

Virchow proposed that cells divide to form new cells and that all cells come from existing cells.

The Cell Theory…

1. All organisms are made

up of one or more cells.

An organism can be one cell (single- celled or unicellular) or have many cells (multi-cellular) like most plants and animals.

2. The cell is the basic unit of structure and function in organisms.

Even in complex organisms, like humans, the cell is the building block of all living things!

3. All cells come from other

cells.

Most cells divide to form two, identical cells.

BASIC CELL PARTS

All plant and animal cells have 3 basic parts: Cell Membrane- surrounds the cell;

controls what comes in and what goes out of the cell

Nucleus- control center of the cell; controls all of the cell’s activities- the “brain”

Cytoplasm- liquid-like substance that stores wastes and allows movement of materials from one part of the cell to another part

Plants have MORE…

Plants have additional organelles or tiny structures inside a cell, that

animal cells do not have. Cell Wall- supports and protects

the cellChloroplasts- is where the plant makes its own food using the Sun’s

energy

BODY ORGANIZATION

Cells Tissue Organ

Organ System Organism… You!

You try it!

How many times does a compound light microscope

w/ an eyepiece lends of 10Xand an objective of 10X

magnify objects?10X x 10X = 100X

How many times does a compound light microscope w/ an eyepiece lends of 12X

and an objective of 4X magnify objects?

12X x 4X = 48X

How does material move in and out of the cell?

The Cell Membrane controls HOW materials move into or out of a cell.

• Every cell (plant and animal) is surrounded by a Cell Membrane

• The cell membrane is selectively permeable, which means that some substances can pass through the membrane while others CAN NOT!

Transport

There are TWO process that allow materials to pass through a cell

membrane1. ACTIVE transport

2. PASSIVE transport

Passive Transport

Passive Transport is the movement of dissolved materials across a cell membrane without using energy

Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration H L

Osmosis is the diffusion of H2O

Materials that move through a cell by Passive Transport: CO2, oxygen, water

Passive Transport

Facilitated DIFFUSION

Some molecules, like sugar, can NOT pass easily through the membrane so the proteins in the cell membrane form “channels” through which the sugars (glucose) can pass. These channels make it easier for the sugars to reach the opposite side of the cell membrane. NO ENERGY is used in facilitated diffusion so it is another form of passive transport!

Active Transport• Active Transport is the movement of materials across a cell

membrane using cellular energy • Energy is required for active transport because the materials are

moving from an area of LOWER concentration to an area of higher concentration! L H

This requires WORK for the cell!

• Using the cells energy, the proteins pick upmolecules and carry them across the membrane• Materials that move through a cell by Active Transport:

calcium, proteins and sodium

protein

ATP = Energy!