Cell Structure and Function

The Discovery of Cells• All living things are made up of one or more cells –

from the tiniest bacterium to the largest whale. A _____ is the smallest unit that can carry on all of the processes of _____.

• Before the seventeenth century, no one knew that cells existed.

• Most cells are too _____ to be seen with the unaided _____.

• Cells were not discovered until after the invention of the _____ in the early seventeenth century.

• Cell Video (2:55)

The First Discoveries• One of the first microscopes was made by the

Dutch drapery store owner _____ _____ _____.  • With his hand-held microscope, Leeuwenhoek

became the first person to observe and describe microscopic _____ and living _____.

The First Discoveries• In 1665, the English scientist _____ _____ used a

microscope to examine a thin slice of _____ and described it as consisting of "a great many little boxes.” 

• They reminded him of the small rooms in which _____ lived, so he called them "Cells.” He was the FIRST person to actually see ____.

The First Discoveries• In 1838, German botanist _____ _____ concluded

that all _____ are composed of _____.• The next year, German zoologist _____ _____

reported that _____ are also made of _____.

The First Discoveries• In 1855, German physician

_____ _____ stated that "THE ANIMAL ARISES ONLY FROM AN ANIMAL AND THE PLANT ONLY FROM A PLANT" or “_____ ONLY COME FROM OTHER _____.”

•  His statement contradicted the idea that life could arise from nonliving matter, a.k.a., _____ _____.

The Cell Theory• The combined work of Schleiden, Schwann, and Virchow

make up what is now known as the modern _____ _____.• The Cell Theory consists of THREE Principles: • A. All living organisms are composed of one or more _____.• B. Cells are the basic units of _____ and _____ in an organism. • C. Cells come only from reproduction of _____ _____.

• Cell Overview (3:35)

Review of Cell Theory (6:12)

Cell Diversity• Not all cells are alike.  Even cells within the same

organism show enormous diversity in size, shape, and internal organization.  Your body contains over _____ different cell types.

Cell Shape• Cells come in a variety of specific

shapes. • THE _____ OF A CELL DEPENDS

ON ITS _____.• Notice how cells of the nervous

system that carry information from your toes to your brain are long and threadlike.

• Notice how blood cells are biconcave disks that can carry the optimum amount of _____. They are also flexible allowing them to squeeze through microscopic _____ _____.

Cell Size• A few types of cells are large enough to be seen

by the unaided eye.  The female _____ _____is the largest cell in the human body and can be seen without the aid of a microscope. The male _____ _____ is the smallest.

•  Most cells are visible only with a _____.• Cell Size and Scale

Why are cells so small??• Cells are limited in size by the RATIO between their

outer _____ _____ and their _____.  • A SMALL CELL HAS MORE SURFACE AREA THAN A

LARGE CELL FOR A GIVEN VOLUME OF CYTOPLASM.  This is important because the nutrients, oxygen, and other materials a cell requires must enter through its _____.  As a cell grows larger, at some point its surface area to volume _____ becomes too small to allow these materials to enter the cell quickly enough to meet the cell's need.

• In other words, THE CELL'S _____ CAN ONLY CONTROL A CERTAIN AMOUNT OF LIVING, ACTIVE _____.

Prokaryotes and Eukaryotes

• Cells fall into two broad categories depending whether or not they have a _____.

• _____ - a large membrane-enclosed structure that contains the cell’s genetic material in the form of _____.

Prokaryotes• Generally smaller and less _____ than eukaryotic

cells • Have genetic material not contained in a _____.• Carry out every activity associated with living

things.

Eukaryotes• _____ and more complex than prokaryotic cells.• Contain dozens of structures and internal _____,

many of which are highly specialized.

The Plasma or Cell Membrane (City Gate)

• This _____ _____ membrane regulates what passes into and out of the cell.

• All cells, from all organisms, are surrounded by a plasma membrane.

• The cell membrane is a thin layer of _____, proteins, carbohydrates, and _____ groups that separate the cell's content from the world around it.

• The cell membrane functions like a _____, controlling what enters and exits the cell.

The Plasma or Cell Membrane (City Gate)

• Cell membranes are made mostly of _____ molecules. (phosphate + lipid)

• A phospholipid is a molecule that consists of two _____ (tails), and a _____ group (heads).

• The phosphate head is _____ meaning "water-loving".   The phosphates will turn themselves toward _____ molecules.

• The lipid tails are _____ meaning "water-fearing". The tails will turn themselves away from _____.

The Plasma or Cell Membrane (City Gate)

• Cells are bathed in an _____, or watery, environment.  Since the inside of a cell is also an aqueous environment, both sides of the cell membrane are surrounded by _____ molecules.  These water molecules cause the phospholipids of the cell membrane to form two layers.

• Cell membranes consist of two phospholipid layers called a _____ _____.

• _____ phosphate heads face the watery fluids inside and outside the cell; _____ lipid tails are sandwiched inside the bilayer.

The Plasma or Cell Membrane (City Gate)

Membrane Proteins• A variety of _____ are embedded in the lipid

bilayer. • Some proteins are attached to the surface of the

cell membrane; these are called _____ _____, and are located on both internal and external surfaces.

•  The proteins that are embedded in the lipid bilayer are called _____ _____.

•  Some integral proteins extend across the entire cell membrane and are exposed to both the inside of the cell and the exterior environment (_____ _____).

Membrane Proteins• These proteins help to _____ material into and out

of the cell. • Integral proteins exposed to the cell's external

environment often have _____ attached to them that serve as _____ badges that allow cells to recognize each other and may act as sites where viruses or chemical messengers such as hormones can _____. Membrane Video

(1:26)Another One (1:23)

Desmosomes (Bridges)• They are cellular _____ that extend from the

plasma _____.• They function in _____ cells together and are

especially important in cells where shearing forces would easily tear them apart (muscle tissue, intestinal walls, epidermis).

Fluid Mosaic Model• Membranes are _____ and have the consistency of

vegetable oil. • The lipids and proteins of the cell membrane are

always in _____. • Proteins in and on the membrane form patterns,

or _____.  • Because the membrane is FLUID with a MOSAIC of

proteins, scientists call the modern view of membrane structure the _____ _____ model.

Nucleus (City Hall)• The nucleus is often the most prominent structure

within a eukaryotic cell. • The nucleus is the _____ _____ (brain) of the cell. • Most cells have a single nucleus; some cells have

more than one. • The nucleus is surrounded by a double-layered

membrane called the _____ _____.• The nuclear envelope is covered with many small

_____ through which proteins and chemicals from the nucleus can pass.  

Nucleus (City Hall)• The nucleus contains _____.• The DNA is in the form of long strands called

_____, which is a matrix of protein and DNA. • During _____ _____, chromatin strands coil and

condense into thick structures called _____.• Most nuclei contain at least one _____ (plural,

nucleoli). • The nucleolus synthesizes _____, WHICH BUILD

PROTEINS. • When a cell prepares to reproduce, the nucleolus

_____.

Nucleus (City Hall)

Centrioles• They are organelles that exist in

pairs and are made of a _____ called tubulin.

• They are usually located near the nucleus, which makes sense because they seem to assist in organizing cell division by moving _____ to opposite ends of the cell via fibers they produce called _____ fibers.

• However, their main function is to produce the cell’s _____, cilia, and flagella.

• They are not found in _____ cells.

Mitochondria (Power Plants)• Mitochondria are the sites of _____ reactions that

transfer ____ from organic compounds to ATP.  Energy contained in food is released and converted to _____.  ATP is the molecule that nearly all cells use as their main source of _____.

• Nickname: THE “_____” OF THE CELL. • Mitochondria are usually more numerous in cells

that have a high _____ requirement like _____ cells.

Mitochondria (Power Plants)• Mitochondria are surrounded by TWO _____. • The outer membrane serves as a _____ between the

mitochondria and the cytosol. • The inner membrane has many long folds, known as cristae (KRIS-tee).   The cristae greatly increase the _____ _____ of the inner membrane, providing more space for chemical reactions to occur, making the mitochondria more _____.

• Mitochondria have their own _____ (from the ovum), and new mitochondria arise only when existing ones grow and divide.

Mitochondria (Power Plants)

Ribosomes (Factories)• Unlike most other

organelles, ribosomes are NOT surrounded by a _____.

• Ribosomes are the sites of _____ _____ in a cell.

• They are the most numerous organelle in almost all cells.

• Some are free in the cytoplasm; others line the membranes of _____ _____ _____.

Endoplasmic Reticulum (Streets)• The ER is a system of membranous tubules and

sacs. • The ER functions primarily as an intracellular

_____, a path along which _____ move from one part of the cell to another.

• The amount of ER inside a cell varies, depending on the cell's activity.

• Poisons, wastes, and other toxic chemicals are made harmless (detoxification).

• ER is an extensive network of membranes that connect the nuclear envelope to the _____ _____.

Endoplasmic Reticulum (Streets)

• Can be ROUGH or SMOOTH. • Rough ER is studded with

_____ and it processes PROTEINS to be exported from the cell. • Smooth ER IS NOT covered

with _____ and processes LIPIDS and CARBOHYDRATES. • The Smooth ER is involved in

the synthesis of steroids in gland cells, the regulation of calcium levels in muscle cells, and the breakdown of toxic substances within _____ cells.

Ro ugh

Smoo t h

Golgi Apparatus (Post Office)• The Golgi apparatus is the processing, _____, and

secreting organelle of the cell. • The Golgi is a system of _____ made of flattened

sac-like structures.• Working closely with the ER, the Golgi modifies

proteins for _____ by the cell. • Golgi also produces _____, which are transporting

organelles.

Vesicles (UPS Trucks)• Cells contain several types of vesicles, which

perform various roles; especially involved in _____ of materials.

• Vesicles are small, spherically shaped sacs that are surrounded by a single _____ and are classified by their contents.

• Vesicles often migrate to and merge with the _____ _____ to release their contents outside of the cell.

The circular structures are vesicles that have been released from the Golgi.

Lysosomes (Street Cleaners)• Lysosomes are vesicles that contain _____

enzymes. • Lysosomes are vesicles that bud (break off) from

the _____ apparatus.• They are the sites of “food” digestion in the cell.

They can _____ _____ large molecules such as proteins, nucleic acids, carbohydrates, and lipids.

Lysosomes (Street Cleaners)• Some white blood cells use

lysosomes to destroy _____.• Within a cell, lysosomes

digest worn-out _____ and are also responsible for dissolving _____ when it is time for them to die, thereby maintaining an organism’s overall health.

• Lysosomes are common in the cells of animals, fungi, and protists, but they are rare in _____ cells.

Lysosome Video (1:00)

Cytoskeleton (Scaffolding)• Just as your body depends on your _____ to

maintain its shape and size, a cell needs structures to maintain its shape and size.

• In animal cells, an internal protein framework called the _____ maintains the shape of the cell.

• The cytoskeleton (1) maintains the 3-D _____ of the cell, (2) participates in the _____ of organelles within the cytosol, and (3) helps the cell _____.

• The cytoskeleton consists of three types of proteins: microtubules, microfilaments, and intermediate filaments.

Microtubules• Microtubules are HOLLOW TUBES like plumbing

pipes. They are the largest strands of the _____. • Microtubules are made of a PROTEIN called _____.• Microtubules have three functions: • To maintain the _____ of the cell and hold organelles

in place. • To serve as tracks for _____ and molecules to move

along within the cell. • To form the centrioles.  

Microfilaments• Microfilaments are NOT HOLLOW and have a

structure that resembles rope made of two twisted chains of protein called actin.

• Microfilaments can _____, causing movement. • _____ cells are LOADED with microfilaments.

Cytoskeleton (Scaffolding)

Cilia and Flagella• Cilia and flagella are organelles that extend from

the surface of the cell, where they assist in _____ and food acquisition.

• Cilia are short _____ projections, while flagella are long _____ projections.

• Unicellular organisms use cilia and flagella to move through _____.

• In humans, cilia line parts of the upper _____ system, moving dust particles and _____ away from the lungs. This is why you should breathe through your _____, AND NEVER SMOKE! (The chemicals destroy cilia.)

Cilia and Flagella

The ciliary escalator in upper

respiratory tract

Bacterial cell with multiple flagella

Cilia/Flagella Video (3:12)

Plant Cell Organelles• One of the most important differences between

plant and animal cells is the presence of a CELL _____ IN PLANT CELLS.

• _____ such as mushrooms and yeast also have cell walls. 

• A cell wall DOES NOT REPLACE the cell _____; cells with walls also have a cell membrane.  Plant cells are surrounded by a rigid cell wall that lies _____ the cell membrane.

• The rigidity of cell walls helps _____ and _____ the plant.

• Cell walls of plants contain a lot of _____, a complex carbohydrate.

The Cell Wall

Notice that the cell wall is MUCH thicker than the membrane.

Cell wall

Membrane

Vacuole (Warehouse)• The vacuole is a large membrane-bound sac that

takes up a large amount of _____ in most plant cells.

• The vacuole serves as a _____ area, and may contain stored proteins, ions, waste, or other cell products.

• Vacuoles of some plants contain _____. • Cells of animals and other organisms also may

contain vacuoles, but they are much smaller and are usually involved in FOOD _____.

Vacuole (Warehouse)

Plastids• A third distinguishing feature of plant cells is the

presence of structures called plastids that make or store _____.

• They are surrounded by a double membrane and contain their own ______.

• A common kind of plastid is the _____ (greenhouse), an organelle that uses _____ to covert _____ _____ AND _____ into SUGARS.  This process is called _____.

• Chloroplasts are green because they contain _____, a pigment that ABSORBS THE _____ IN SUNLIGHT. 

Plastids• Other plastids called _____ store reddish-orange

pigments that color fruits, vegetables, flowers, and autumn leaves.

• Colorless plastids that store STARCH, LIPIDS, and PROTEINS are called _____ (bakery). They are found in the non-_____ parts of plants (mainly roots).

Leucoplasts in potato cell

Plastids

Chromoplasts in red pepper cell