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 was

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 ____. However, he had no idea what he was observing. WHY? We don’t know

what Robert Hooke looked like because Sir Isaac Newton destroyed the only portrait ever made of Hooke.

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 _____ 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 _____ 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 _____ _____ THAN A LARGE

CELL FOR A GIVEN _____ 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 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 ______ 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 contains 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.    • 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 (under the control of the nucleus).

Mitochondria (Power Plants)

Ribosomes (Factories)

• Unlike the 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 (exocytosis). The circular

structures are vesicles that have been released from the Golgi.

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

_____ enzymes. • They 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 _____.• Lysosomes digest worn-out

_____ and are also responsible for dissolving _____ when it is time for them to die (apoptosis)

• 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.

• 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 are primarily made 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.• However, vacuoles are filled mainly with _____, which

provides the _____ needed to help support the plant.• 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, roots, 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