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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