What is a Cell?Cell – a membrane-bound

structure that is the basic unit of life.

What is required to be a cell?

*All cells MUST have the following:

1) Cell Membrane – a double-layer of phospholipids that regulate what comes into and out of the cell.

2) Organelles – tiny structures within the cell that serve a specific function.

3) Cytoplasm –jelly-like material inside the cell where the organelles are located.

4) Nucleic Acid – must have DNA to control cell activities and to code for the production of proteins.

Categories of Cells

*Cells come in a variety of shapes and sizes; in most cases, a cell’s shape will determine its function.

*Regardless of the many varieties of cells, all cells will fall in one of two categories:

Eukaryotic CellsProkaryotic Cells

Prokaryotic CellsProkaryote – are simple cells

with no true membrane-bound nucleus or organelles; aka “prokaryotic cells”.

Characteristics:

1) Usually belong to single-celled organisms, such as bacteria.

2) Oldest type of cell; thought to be the first forms of life.

3) Though they do contain few organelles, prokaryotic cells do not have any membranes that surround their organelles or nuclei.

4) DNA is not contained in a true nucleus, but rather a nuclear “region” called a nucleoid.

Eukaryotic CellsEukaryote – type of complex

cell that contains a true, membrane-bound nucleus and organelles; aka “eukaryotic cells”

Characteristics:

1) More complex; containing more organelles.

2) All eukaryotic cells are specialized, meaning that they belong to a multicellular organism and that each cell serves a specific function within that organism. Plant and animal cells are eukaryotic.

3) Contain a double-membrane bound nucleus in which the DNA is separated from the rest of the cell.

Eukaryotic Cell vs. Prokaryotic Cell

Cell Structure *Cells are often compared to a

factory – their tiny organelles work together, instructed by DNA, to produce proteins.

*Cytologists (cell biologists) divide the cell into three general areas:

1) Nuclear Region – nucleus or nucleoid.

2) Cytoplasm – contains most of the organelles.

3) Cell Membrane – made up of a double-layer of phospholipids.

Cell Diagrams

*You will draw, color, and label the parts and functions of the following cells:

Prokaryotic Cell (Bacteria)Eukaryotic Cell (Animal)Eukaryotic Cell (Plant)

*Diagrams will be collected and graded based upon completion and neatness.

Discovery of the Cell

*In 1665, English scientist Robert Hooke was the first person to view a true cell.

*He observed cork tissue using a crude microscope and saw hundreds of chambers, which he called a “cell”.

*Years after Hooke’s and other scientists’ discoveries regarding the cell, unified theory was developed, known as the Cell Theory:

The Cell Theory

1) All living organisms are made up of at least one or more

cells.2) Cells are the basic

unit of structure and function of living

organisms.3) Cells can only come

from preexisting cells.

Important Structures of

Eukaryotic Cells

Organelles or Structures To Know….

Cell MembraneCytoplasm

MitochondriaChloroplast

Cell Membrane

1) Function:

*Regulates what comes into and out of cell.*Cell membrane is sometimes described as selectively permeable (or semi-permeable) because it lets some things in and out of cell, but not others.*Being selectively permeable is important to the homeostasis of a cell.

2) Structure:

*Three main ingredients:

PhospholipidsProteins

Carbohydrates

*Phospholipids are the most abundant ingredient of the cell membrane…the cell membrane is also called a lipid bilayer because it is made up of TWO layers of phospholipids

*The structure of the cell membrane is also described as the Fluid Mosaic Model, meaning that the cell membrane is NOT rigid (its very flexible….”fluid”) and its made up of a mixture of ingredients (lipids, carbs, and proteins……a “mosaic” of macromolecules).

Cell Membrane Structure

What Purpose Do the Cell Membrane Structures Serve?

Phospholipids – protective barrier; allows very small substances (oxygen, water, etc.) to easily pass through.

Proteins – serve as either gatekeepers or channels to allow larger molecules into or out of cell.

Carbohydrates – receives signals from other cells or from other substances that want into or out of cell; cell’s “antennae”.

Cytoplasm*Jelly-like substance that

includes all of the area between the cell membrane and the nuclear membrane.

*Three ingredients that make up the cytoplasm:

1) Cytosol jelly-like substance.2) Organelles cell organelles are found embedded in the cytosol of the cytoplasm.3) Cytoskeleton network of fibers that support the cell and give it shape; microfilaments and microtubules make up the cytoskeleton

*Makes up 54% of cell’s total volume.

Functions of Cytoplasm

1) Holds organelles in their place.

2) Gives cell additional internal shape and support (cytoskeleton).

3) Chemical reactions take place here.

*Glycolysis is a chemical reaction that takes place in the cytoplasm. It is a process where glucose is broken down during cellular respiration.

Cytoskeleton Structure

*These are the structures that make up a network of fibers inside the cytoplasm, called the cytoskeleton.

Cytoplasm Structure

Mitochondria- “powerhouse” of cell;

produces cellular energy from chemical reactions of organic compounds; this chemical reaction is known as cellular respiration.

- energy produced = ATP (adenosine triphosphate).

- the amount of mitochondria vary from one cell to another, depending on the cell’s activities.

ex: A heart cell contains thousands of mitochondria compared to a skin cell (which would only contain just a few mitochondria, because the heart cell requires more energy to function than skin cell.

Microscopic View of the Mitochondria

Mitochondria Diagram

Functions of Mitochondrial PartsInner and Outer

Membranes – regulate what comes into / out of mitochondria.

Cristae – “folds” of the inner membrane; majority of cellular respiration takes place here; the inner membrane is folded to allow more surface area for chemical reactions to take place (more surface area = more ATP that can be made = more power to cell).

Mitochondrial Matrix – liquid center of mitochondria; some reactions of cellular respiration take place here.

Chloroplast*The chloroplast is a type of

plastid that contains the green pigment “chlorophyll” used in photosynthesis.

*A plastid is a type of organelle with any colored pigment used in photosynthesis; the chloroplast happens to be the most common type of plastid since most plants are green (duh?).

*The purpose of the chloroplast is to convert sun’s energy, water, and carbon dioxide into organic compounds, such as glucose. This is called photosynthesis. The waste product that comes out of the chloroplast during photosynthesis is the oxygen that we breathe.

*Since photosynthesis takes place in the chloroplast, only the green parts of the plant will have chloroplasts.....the roots of plants are not photosynthetic and will not have chloroplasts (plant roots undergo cellular respiration).

*The chloroplast is very similar to the mitochondria.....

1) Similar shape2) Double-membraned3) Contains its own DNA

*Like the mitochondria, the chloroplast was thought to be a pre-existing cell due to it having a double membrane and its own DNA.

*Scientists believe that the chloroplast is the ancestor of photosynthetic organisms. They believed that the chloroplast merged with other prokaryotic cells to give rise to photosynthetic organisms.

Functions of Chloroplast Structures

Inner/Outer Membrane – regulates what comes into/out of chloroplast.

Thylakoid – round disc that captures sunlight during photosynthesis.

Lumen – inside of thylakoid where pigment is stored.

Granum (Grana) – stacks of thylakoids

Stroma – liquid area of chloroplast; some reactions of photosynthesis take place here.