Chapter 4

Cell Structure and Function

Cell Theory

All living things are composed of one or more cells.

Cells are the basic units of structure and function in an organism.

Cells come only from the reproduction of existing cells.

Cell Diversity

Cells vary in shape, size and internal organization.

All cells have a specific job to do and look and function the best for that job.

White blood cells

Stem cells

Nerve Cells

Heart cells

Skin cells

Plant cells

Important Vocabulary

Many cells have a variety of internal structures called organelles or mini organs.

Most cells are surrounded by a cell membrane. Many cells have a large organelle called the

nucleus. Cells that contain organelles and a nucleus are

called eukaryotic cells. Cells that DO NOT contain organelles and a

nucleus are called prokaryotic cells.

What’s the difference here?

Let’s compare three items: a eukaryotic cell, a prokaryotic cell and a virus.

What are the similarities? What are the differences?

Flu virus

T4 Bacteriophage

HIV

Prokaryotes Vs. Eukaryotes Vs. Viruses

No membrane bound nucleus

Has a cell wall Only a few

organelles or none at all.

Has a capsule surrounding it

Three main types.

Nucleus with membrane

Only plants have cell wall

Contains many organelles

Has a lipid bi-layer membrane surrounding it.

Specialized by thousands of different sizes and shapes.

• No nucleus• No membranes• No organelles• Cannot

reproduce on its own

• Generally not considered alive by most standards

Parts of the Eukaryotic Cell

Cell Membrane Cytoplasm (cytosol) Mitochondria Ribosome Endoplasmic reticulum (rough and smooth) Golgi apparatus Lysosome Cytoskeleton Cilia and Flagella Nucleus Nucleolus Cell wall Vacuole Chloroplast

Plant Cells Vs. Animal Cells Contain chloroplasts for

photosynthesis Have a cell wall to maintain

structure and rigidity Usually do not contain

lysosomes and peroxisomes Cells are square and rigid or

geometric shaped Limited movement Have one large central

vacuole

No cell wall No chloroplasts Contain lysosomes and

peroxisomes Contain cilia and/or

flagella Cells are fluid and flexible,

many shapes Cells can move around. Has small vacuoles

Parts of Eukaryotic Cell

You are required to know the parts, what they look like and their function for the

test!

Cell Membrane

The cell membrane is selectively permeable which means some substances can cross and others cannot cross.

Cell membranes are made of primarily lipids and proteins.

Cell membranes are made of a lipid bi-layer. A cell membrane is called a fluid mosaic because

it behaves more like a liquid than a solid. It is flexible and provides an effective barrier and

transport function.

DRAW THIS!

Cytoplasm

This lies between the cell membrane inside of the cell.

It is a fluid that all the organelles float in.

It is sometimes called the cytosol.

Mitochondria

Mitochondria are the powerhouses of the cell.

Mitochondria create ATP for the cell to use as energy.

One cell many have thousands of mitochondria depending on its function.

Mitochondria have two membranes and have their own DNA which only comes from the mother.

Ribosomes Ribosomes are the most

numerous of the cell’s organelles.

Ribosomes are made of proteins and RNA.

Ribosomes are responsible for creating proteins.

Ribosomes are found free in the cytoplasm and also attached to the rough ER. (endoplasmic reticulum)

Endoplasmic Reticulum

The ER comes in two varieties, the rough ER and the smooth ER.

The rough ER contains ribosomes and makes proteins.

The smooth ER does not contain ribosomes and makes lipids such as steroids.

The rough and smooth ER are sometimes attach to each other.

Both ER are involved in cell product transport of proteins and lipids.

Ribosomes

Nucleus

Golgi Apparatus

The golgi is the processing, packaging and transport system.

It is a system of membranes that work closely with the ER.

The golgi modifies the products for transport throughout the cell.

Lysosomes

Lysosomes contain enzymes that help digest proteins, carbohydrates, lipids, DNA and RNA.

These enzymes can also digest old organelles, viruses and bacteria.

Lysosomes are rare in plant cells.

Cytoskeleton

Cytoskeleton’s are made of two parts: the microtubules and the microfilaments.

The microtubules assist in cell division by moving the cells apart.

Microfilaments are made of protein and help with muscle contractions.

Both help support the cell and give structure but do allow for movement.

Cilia and Flagella

Some cells have flagella. They usually only have one.

Many cells have cilia which can number in the thousands.

A flagella is like a whip. Cilia are like tiny

paddles. Cilia and flagella are

made of microtubules.

Cilia

Flagella

Nucleus The nucleus is

surrounded by a membrane called the nuclear envelope.

The nucleus contains all the DNA for the cell.

It directs all the activities of the cell.

The nuclear envelope contains pores so that RNA can pass into the cytoplasm during protein synthesis.

Nucleolus

The nucleolus is found inside the nucleus.

It is responsible for making the ribosomes.

There is usually only one.

Cell Wall Found in plant cells

and bacteria only. Not found in animal

cells. Helps maintain

structure and protection.

Does contain small pores to move water and oxygen and carbon dioxide in and out.

Vacuoles

These are fluid filled and store many different things such as water, waste, enzymes and poisons.

In plants vacuoles take up 90% of the space.

Vacuoles are small in animal cells.

Chloroplast

This also called a plastid. Chloroplasts have their

own membrane and their own DNA.

Chloroplasts are found only in plant cells and some protists. (little animals)

Chloroplasts do photosynthesis and contain chlorophyll which make them green.

Photosynthesis creates sugar from sunlight for the plant to use.