Cells: The Basic Units of Life

Ms. Samuelian 2011

Cells: Starting out small• Most cells are too small to be seen

• Not all of your cells look and act the same

• Each type is specialized to do a particular job (e.g. bone cells, blood cells, skin cells)

The first cell of a chicken is one of the largest cells in the world.

Tissues: Cells Working in Teams

When you look closely at your clothes, you can see that threads have been grouped together (woven) to make cloth that has a function

Cells are the basic units of life. They are grouped together to make a tissue that has a function

A tissue is a group of cells that work together to perform a specific job in the body.

Organs: Teams Working Together

When two or more tissues work together to perform a specific job, the group of tissues is called an organ

Examples: stomach, intestines, heart, lungs, and skin

The skin is the body’s largest organ.

Organ Systems: A Great Combination

Organs work together in groups, called organ systems, to perform particular jobs.

The organs in an organ system depend on each other – If any part of the system fails, the whole system is affected.

Your body has several organ systems (e.g. nervous system, digestive system)

Did you know…?

Your digestive system’s job is to break down food into very small particles so it can be used by all of your body’s cells.

Your nervous system’s job is to transmit information back and forth between your brain and the other parts of your body.

There are 11 main organ systems.

Organisms: Independent Living

Anything that can live on its own is called an organism

All organisms are made up of at least one cell

If a single cell is living on its own, it is called a unicellular organism

You are a multicellular organism because you can exist only as a group of cells and most of your body cells can survive only is they remain a part of your body

The Big PictureA group of organisms that are of the same kind and that live in the same area make up a population

Two or more different populations living in the same area make up a community

The community and all of the nonliving things that affect it (water, soil, rocks, temperature, light) make up an ecosystem

The Cell TheoryAll living things are composed of one or more cells

The cell is the basic unit of life in all living things

New cells are produced from existing cells

Cell SimilaritiesAll cells are surrounded by a cell membrane, which acts as a barrier between the inside of the cell and the cell’s environment.

All cells have organelles, which are chemicals and structures that enable the cell to live, grow, and reproduce.

Two Types of CellsProkaryotic cells (also called bacteria) are the world’s smallest cells and they do not have a nucleus or any other membrane-covered organelles.

Eukaryotic cells are 10 times larger than prokaryotic cells. They have a nucleus and many other membrane-covered organelles. All living things that are not bacteria are made of one or more eukaryotic cells. This includes plants, animals, and fungi.

Prokaryotic Cells Eukaryotic Cells

No nucleus Nucleus

No membrane-covered organelles

Membrane-covered organelles

Circular DNA Linear DNA

Bacteria All other cells (not bacteria)

Eukaryotic Cells- Cell membraneAll cells are covered by a cell membrane. The job

of the cell membrane is to keep the cytoplasm inside, to allow nutrients in and waste products out, and to interact with things outside the cell.

Cell WallThe cell wall provides strength to support the cell membrane

For example, the strength of billions of cell walls in plants enables a tree to stand tall and its limbs to defy gravity

Nucleus: The Cell’s Library

The largest and most visible organelle in a eukaryotic cell is the nucleus

It is the control center of the cell

It stores the DNA

ProteinProteins are the building blocks of all cells

They are made of chemicals known as amino acids

These amino acids are hooked together to make proteins at very small organelles called ribosomes

All cells have ribosomes because all cells need protein to live

Cells need energy, too!Cells need energy to function and live

Where do they get it from?

Mitochondria Chloroplasts

MitochondriaInside all cells, food molecules are “burned” (broken down) to release energy

The energy is transferred to ATP (a special molecule that the cell uses to get work done)

ATP is mostly made in a bean-shaped organelle called mitochondria

Mitochondria need oxygen to work

The reason you breathe air is to make sure your mitochondria have the oxygen they need to make ATP

ChloroplastsPlants and algae have an additional kind of energy-converting organelle called a chloroplast

The word chloroplast means “green structure”

They contain an important chemical called chlorophyll

Chlorophyll is what makes chloroplasts green and also what makes a chloroplast a power plant for the cell

The energy of sunlight is trapped by chlorophyll and used to make sugar (photosynthesis)

The sugar produced is used

by mitochondria to make ATP

The Cell’s Packaging Center

When proteins and other materials need to be processed and shipped out of a eukaryotic cell, the job goes on to an organelle called the Golgi complex

The Golgi complex processes, packages, and transports material

Organelles and Their Functions

Nucleus Contains the cell’s DNA and is the control center of the cell

Ribosome The site where amino acids are hooked together to make proteins

Mitochondria Break down food molecules to make ATP

Chloroplast Make food using the energy of sunlight

Golgi complex Processes and transports materials out of the cell

Plant or Animal?

They both have a cell membrane, nuclei, ribosomes, mitochondria, endoplasmic reticula, Golgi complexes, and lysosomes

But plant cells have things that animal cells don’t have: a cell wall, chloroplasts, and a large vacuole

Review

How does the nucleus control the cell’s activities?

Which of the following would not be found in an animal cell: mitochondria, cell wall, chloroplast, ribosome, endoplasmic reticulum, Golgi complex, vacuole, DNA, chlorophyll?

Use the following words in a sentence: oxygen, ATP, breathing, and mitochondria.

Discussion Questions

What is the structure of the nucleus? What is the function of the nucleus?

Why do cells divide?

Describe the process of mitosis.

What is cytokinesis?

What is the role of mitochondria?

What is the role of chloroplasts?

Describe the process of photosynthesis.