LIFE’S HOME:Lesson # 11

The Cell

Atoms Molecules Cells

OrgansTissues Organisms

Organelles Atoms combine to form molecules

Small molecules: water Macromolecules: DNA, proteins

Highly organized structures with one special function. Ex: mitochondria, ribosomes

Each cell contains hundred of organelles. They can do all things listed previously. Life actually occurs in cells

A collection of cells that serve a common function. Ex: muscle tissue.

A functioning unit formed by several kinds of tissues. Ex: The heart, a blood vessel, the brain

Organisms can be formed by only one cell ( bacteria) or trillions of cells organized in organ systems (human).

Organ SystemsDifferent organs that work together closely. Ex: Cardio- vascular system, respiratory system, nervous system

Community BiospherePopulationMembers of a single type of living thing (species), living in one area.

All the kind of living things in a given area (several species).

EcosystemThe community of organisms plus all the non-living elements

The interactive collections of all the Earth’s ecosystems

All Cells Are Either Prokaryotic or Eukaryotic

Cells

-They have no nucleus.

-They have a membrane-bound nucleus.

- Usually are smaller

- Usually are larger

- Single-celled organisms

- Often multicellular organisms

- No membranous organelles

- Membranous organelles

Prokaryotic cells (bacteria and archaea)

Eukaryotic cells (plants, animals and fungi)

Prokaryotic cells Eukaryotic cells

DNA

Size

Organization

Organelles

in “nucleoid” region within membrane-bound nucleus

much smaller much larger

always single-celled often multicellular

only one type of organelle many types of organelles

  Prokaryotic and Eukaryotic Cells Compared

The human body has 50 to 100 trillion cellsThe trillions of cells in the human body include over 200 different cell types

The Eukaryotic Cell

Nucleus

Organelles

Cytosol

Plasma membrane

Cytoskeleton

Proteins are assembled in the ribosomes, which are in the cytoplasmThe instructions for the assembling are in the nucleus

Along the Protein Production Path

Nucleus

Ribosomes

Rough endoplasmic reticulum

Golgi complex

Plasma membrane

Nuclear envelope

THE NUCLEUS

Functions1- It contains the DNA, which contains all the information for protein synthesis

2- It is the place where the DNA duplicates

3- It contains the nucleolus where the ribosomes are produced

THE NUCLEOLUSIt is the area within the nucleus where the ribosomes are produced

Nucleolus

1- They are the organelles that serve as the site of protein synthesis in the cell

THE RIBOSOMES

2- Ribosomes are not lined by a membrane

3- Ribosomes are made of ribosomal RNA ( rRNA ) and proteins

4- Ribosomes are produced in the nucleolus

Types of RNA

Ribosomal RNA ( rRNA )Messenger RNA ( mRNA )Transference RNA ( tRNA )

1- Ribosomal RNA ( rRNA ): it is structural part of the ribosomes

rRNA + proteins

2- Messenger RNA ( mRNA ): It carries the instructions from the DNA to the cytoplasm for the synthesis of proteins

mRNA

3- Transfer RNA ( tRNA ): Select and transport the aminoacids to be incorporated in the polypeptide chain

tRNA

mRNA

tRNAAminoacids

The Rough Endoplasmic Reticulum It is a network of membranes that collect the proteins assembled in the ribosomes and transfer them to the Golgi complex

Golgi Complex

Rough Endoplasmic Reticulum

The Golgi ComplexIt is a network of membranes that process and distribute proteins that come to it from the rough endoplasmic reticulum

The Smooth Endoplasmic Reticulum It is a network of membranes that is the site of synthesis of various lipids and where harmful substances are detoxified within the cells.

Smooth endoplasmic

reticulum

The Smooth Endoplasmic Reticulum

1- It is farther form the nucleus

2- It does not contain ribosomes

3- It is the site where lipids are synthesized ( triglycerides, steroid hormones, etc)

4- It is the site where harmful substances are detoxified within the cells

The Lysosomes

They are organelles that digest worn-out cellular materials and foreign materials that enter the cell.

The lysosomes contain about 40 different enzymes, in an acidic medium, that can break larger molecules into their component parts.

The lysosomes digest bacteria that enter the cells and also damaged organelles that exist inside the cells.

The MitochondriaThey are the site of the cell where energy from food is converted to ATP

ATP

ATP

The Cytoskeleton

It is a network of protein filaments, which has the following functions:

1- Maintain the cell structure ( scaffolding)

2- It is involved in cell movement

3- Transport of materials within the cell

Common Structures in Animal and Plant Cells

Cell wall

Central vacuole

Plastids

Differences Between Plant and Animal Cells

Cell wall Limit water uptake, maintain cell membrane shape, protect from outside influences

Central vacuole

Cell metabolism, pH balance, digestion, water maintenance

PlastidsNutrient storage, pigmentation, photosynthesis

( chloroplasts )