Section 3: Cells

Unit 1: Life Processes

Where does life come from?

• Up until ~1600s, most scientists thought that life developed spontaneously from non-living things.

Ex. Leaving a piece of meat alone for a couple of weeks develops maggots…therefore, maggots developed spontaneously from the meat!

• The scientific process and proper experimentation allowed scientist to refute the idea of spontaneous generation.

• Over time, the Cell Theory was developed.

• The Cell Theory is how biologist gauge whether or not an object is living.

I. Cell Theory

1. All living things are made up of one or more cells.

2. All living things come from other cells.

3. The cell is the basic unit of life.

Why was the development of the cell theory important to the progress of science?

• Scientists finally had a way to describe what LIFE was!

What would have been the limitations of this “new science” when cells were discovered?

• Microscopes were not powerful enough to see the inner workings of the cell.

Viruses

• They consist of a piece of DNA, covered by a protective protein coat.

• Viruses reproduce by injecting their DNA into a host cell, tricking it into manufacturing new viruses.

• The viruses accumulate in the cell preventing the cell from functioning properly (causing disease).

• Viruses are extremely small – they can only be seen by electron microscopes

Would you consider a virus to be a living organism? Why or why not?

I. Cell Theory

1. All organisms are made up of one or more cells.

2. The cell is the basic unit of life.

3. Cells are produced from other cells.

• Unicellular: describes a single-celled living thing.

• Multicellular: describes a living thing made up of many cells.

• Two main types of cells:

§Prokaryotic Cells§Eukaryotic Cells

Venn Diagram:

Prokaryotic vs. Eukaryotic Cells• Prokaryotic cells contain

organelles which are NOT surrounded by a membrane.

• Eukaryotic cells contain organelles which ARE surrounded by a membrane.

• All multicellular organisms (and some unicellular organisms such as amoeba) are composed of eukaryotic cells.

Organelle Structure and Function(Eukaryotic Cells)

• Organelles: smaller structures within cells that carry on life functions.

• The organelles inside the cell serve many functions together including…

The organelles inside the cell serve many functions together including…

1. Providing structure and form2. Forming a barrier between the cell and the

environment.3. Building and repairing cells4. Synthesizing materials5. Storing and releasing energy6. Getting rid of waste material7. Multiplying in number

Most cells share similar characteristics. It is these characteristics that we are going to learn about.

II. Cell StructuresThree Major Cell Parts• Cell Membrane – thin flexible structure that

surrounds the cell. Regulates what enters and exits the cell.

• Nucleus - “brain” of the cell. Controls functions of the cell. Contains genetic information – Deoxyribonucleic acid (DNA)

• Cytoplasm – jelly-like fluid in which organelles are found. This is where many chemical reactions take place within the cell.

Other Major Organelles:• Mitochondrion –

converts the energy stored in food into usable energy for the cell (the “powerhouse”) - cellular respiration

• Ribosome – manufacture proteins, the building blocks for structures in the cell.

• Endoplasmic reticulum – network of flattened tubes that transport proteins within the cell.

• Golgi Body – sorts and packages proteins in membrane-wrapped structures called vesicles.

• Vesicles - small packages containing proteins, nutrients and water into, out of, and around the cell.

• Vacuole – temporary storage areas; assist in regulating water (usually bigger in plant cells)

• Lysosomes – contain digestive chemicals that break down food particles, cell wastes, and worn-out cell parts.

Additional Plant Cell Structures

• Cell Wall - rigid outer wall that provides protection, support and shape. Contains pores to allow substances to pass.

• Chloroplast - captures light to synthesize food energy. Contains green pigment chlorophyll.

Energy for CellsPhotosynthesis

• Process where plants manufacture their own food

• Occurs in the chloroplast, which contains the pigment chlorophyll

• chlorophyll absorbs light and converts it into chemical energy.

Photosynthesis

light energycarbon dioxide + water ---> glucose + oxygen

chlorophyll

• The glucose (sugar) is then stored for use later

Cellular Respiration

• cellular respiration takes place in the mitochondria

• occurs in both plants and animalsglucose + oxygen ---> carbon dioxide + water + energy

• the energy released can then be used by the cell

Diffusion, Osmosis, and the Cell Membrane

I. Membrane Permeability

• Permeable – lets everything througho Cheesecloth is permeable to water

• Semi- permeable – lets only some things througho A sieve is selectively permeable to pasta and water

• Impermeable – lets nothing througho A plastic bag is impermeable to water

II. Concentration• amount of substance in a given volume.– The more you have in a given space, the higher

the concentration.

III. Diffusion• movement of molecules from an area of high

concentration to an area of low concentration.

• Equilibrium is reached when there is an equal number of particles on either side of a membrane

• particles will still move back and forth, but the numberof particles on each side stays the same

Movement of Substances In and Out of the Cell

• Nutrients and waste materials must be able to move into and out of the cell.

• Cell membrane regulates the passage of substances in and out of the cell.

• “Selectively permeable” – permits only certain molecules to enter or leave (semi-permeable).

IV. Osmosis• process by which water moves across a membrane.

• Water moves across the cell membrane, depending on the relative concentration of water inside and outside the cell.

• Water moves from high water concentration to lowwater concentration (special type of diffusion).

Diffusion OsmosisWhat type of material(s) is/are transported?

Nutrients and waste products

water

How is it used by the cell?

To bring in food, to export wastes

To maintain a balance of water

within the cellWhich direction is the flow of the material?

High concentration to low

concentration

High concentration to low

concentration