ap chap 3

cells

• determine the form and functions of the human body

• is the basic living unit of all organisms

trillions

The human body is composed of — of cells and acts as a host to countless other organisms

one-fifth

An average-sized cell is — the size of the smallest dot you can make on a sheet of paper with a sharp pencil

organelles

• Each cell is a highly organized unit. Within cells, specialized structures called — perform specific functions

• little organs

nucleus

The — is an organelle containing the cell’s genetic material.

cytoplasm

the living material surrounding the nucleus is called — and it contains many types of organelles.

cell membrane or plasma membrane

The cytoplasm is enclosed by the —

“the smallest units of life”

Cells are commonly defined as

1. Cell metabolism and energy use

2. synthesis of molecules

3. communication

4. reproduction and inheritance

four main functions of a cell

cell metabolism

The chemical reactions that occur within cells are collectively called

cell membrane (2)

• is the outermost component of a cell.

• encloses the cytoplasm and forms the boundary between material inside the cell and material outside

extracellular substance

Substances outside the cell are called

cytoplasmic substance

Substances inside the cell are called

1. supporting the cell contents

2. acting as a selective barrier that determines what moves into and out of the cell

3. playing a role in communication between cells.

Besides enclosing the cell, the cell membrane has other functions, including :

phospholipids and protein

cell membrane is primarily made up of two major types of molecules:

cholesterol and carbohydrates

the membrane contains other molecules, such as

fluid-mosaic model

Studies of the arrangement of molecules in the cell membrane have given rise to a model of its structure called the

selectively permeable

Cell membranes are —, meaning that they allow some substances, but not others, to pass into or out of the cells

enzymes, glycogen, and potassium ions (K +)

Substances such as —are found in greater concentrations inside the cell

Na + , Ca 2+ , and Cl −

whereas— are found in greater concentrations in the extracellular fluid.

passive or active

Movement through the cell membrane may be

Passive membrane transport

— does not require the cell to expend energy

Active membrane transport

— does require the cell to expend energy, usually in the form of ATP.

1. diffusion

2. osmosis

3. facilitated diffusion

Passive membrane transport mechanisms include

1. active transport

2. secondary active transport

3. endocytosis

4. exocytosis

Active membrane transport mechanisms include

solution

is generally composed of two major parts, solutes and the solvent

solutes

are substances dissolved in a predominant liquid or gas

solvent

• Liquid that holds another substance in solution.

• solutes are dissolved in a liquid or gas called —

constant motion

Solutes, such as ions or molecules, are in —

diffusion

• Each solute tends to move from an area where it is in higher concentration to an area where it is in lower concentration in solution.

• This process is called —

• — results from the natural, constant random motion of all solutes in a solution.

osmosis

• When water is the solvent of a solution, we use a specific term to refer to its movement.

• is the diffusion of water across a selectively permeable membrane, such as the cell membrane, from a region of higher water concentration to one of lower water concentration

osmotic pressure

• is the force required to prevent the movement of water across a selectively permeable membrane.

• is a measure of the tendency of water to move by osmosis across a selectively permeable membrane

hydrostatic pressure

As the solution rises, the weight of the solution produces —- which pushes water out of the tube back into the distilled water surrounding the tube

hypotonic

When placed into a solution, a cell may swell, remain unchanged, or shrink, depending on the concentration gradient between the solution and the cell’s cytoplasm. A — solution

isotonic

When a cell is immersed in an —solution, the concentrations of various solutes and water are the same on both sides of the cell membrane.

hypertonic

a — solution has a higher concentration of solutes and a lower concentration of water relative to the cytoplasm of the cell.

crenation

When a cell is immersed in a hypertonic solution, water moves by osmosis from the cell into the hypertonic solution, resulting in cell shrinkage, or —

cell membrane channel or carrier molecules

Other water-soluble substances, such as ions, diffuse across the cell membrane by passing through —

facilitated diffusion

• is a mediated transport process, involving membrane proteins such as channels or carrier proteins, to move substance across the cell membrane.

• involves the movement of substances from an area of higher concentration to an area of lower concentration

1. size

2. shape

3. charge

Characteristics of an ion or molecule determine whether it can pass through a channel. These characteristics include :

leak channels and gated channels

Two classes of cell membrane channels include:

Leak channels

constantly allow ions to pass through

Gated channels

limit the movement of ions across the membrane by opening and closing

carrier molecules

• which are proteins within the cell membrane, are also involved in facilitated diffusion.

• can move water-soluble molecules or electrically charged ions across the cell membrane,

active transport

is a process that utilizes membrane proteins to move substances across the cell membrane from regions of lower concentration to those of higher concentration, against a concentration gradient

Cystic fibrosis

— is a genetic disorder that affects the active transport of Cl − into cells.

secondary active transport

involves the active transport of one substance, such as Na + , across the cell membrane, establishing a concentration gradient, which then provides the energy for moving a second substances across the membrane

cotransport

the diffusing substance moves in the same direction as the transported substance

countertransport

the diffusing substance moves in a direction opposite to that of the transported substance

vesicles

Large water-soluble molecules that cannot be transported by carrier molecules, small pieces of matter, and even whole cells can be transported across cell membranes in membrane-bound sacs called

endocytosis

is the uptake of material through the cell membrane by the formation of a vesicle

receptor-mediated endocytosis

Endocytosis usually exhibits specificity, through the process of

phagocytosis

• is often used for endocytosis when solid particles are ingested.

• is an important means by which white blood cells take up and destroy harmful substances that have entered the body

pinocytosis

is distinguished from phagocytosis in that much smaller vesicles are formed, and they contain liquid rather than solid particles.

exocytosis

is the release of substances from the cell through the fusion of a vesicle with the cell membrane

transcytosis

• In some cases, such as endothelial cells of blood capillaries, material is moved through the cell by the process of —

• during — , a substance is taken into the cell by endocytosis, the vesicle is moved across the cell, and the substance is then released from the cell by exocytosis

nucleus

• a little nut or the stone of a fruit

• is a large organelle within the cell

nuclear envelope

• contents of the nucleus is separated from the rest of the cytoplasm by a —

• consists of an outer membrane and an inner membrane with a narrow space between them

nuclear pores

At many points on the surface of the nucleus, the inner and outer membranes come together to form —- passageways through which materials can move into or out of the nucleus.

chromosomes

The nucleus contains most of the genetic material of the cell. This genetic material is organized into 23 pairs of — which consist of DNA and proteins.

chromatin

During most of a cell’s life, the chromosomes are loosely coiled and collectively called —

tightly coiled

When a cell prepares to divide, the chromosomes become — and are visible when viewed with a microscope

DNA molecules

The genes that influence the structural and functional features of every individual are portions of —

nucleoli

are diffuse bodies with no surrounding membrane that are found within the nucleus

nucleolus

. The subunits of ribosomes, a type of cytoplasmic organelle, are formed within a —.

ribosomal ribonucleic acid (rRNA)

these proteins are joined to —, produced within the nucleolus, to form large and small ribosomal subunits.

ribosome

are the organelles where proteins are produced

free ribososme

Ribosomes that are not attached to any other organelle are called

endoplasmic reticulum

is a series of membranes forming sacs and tubules that extends from the outer nuclear membrane into the cytoplasm

Rough Er

• is ER with attached ribosomes.

• A large amount of — in a cell indicates that it is synthesizing large amounts of protein for export from the cell.

smooth ER

• ER without attached ribosomes is called

• is a site for lipid synthesis and participates in detoxification of chemicals within cells.

calcium ions

In skeletal muscle cells, the smooth ER stores —-

golgi apparatus

• consists of closely packed stacks of curved, membrane-bound sacs

• It collects, modifies, packages, and distributes proteins and lipids manufactured by the ER.

golgi complex

golgi apparatus is also called the

secrotory vesicles

• pinch off from the Golgi apparatus and move to the cell membrane

• accumulate in the cytoplasm and are released to the exterior when the cell receives a signal

lysosomes

• are membrane-bound vesicles formed from the Golgi apparatus

• They contain a variety of enzymes that function as intracellular digestive systems.

Pompe disease

• Some diseases result from nonfunctional lysosomal enzymes.

• For example, — is caused by the inability of lysosomal enzymes to break down the carbohydrate glycogen produced in certain cells.

• Glycogen accumulates in large amounts in the heart, liver, and skeletal muscle cells; the accumulation in heart muscle cells often leads to heart failure

peroxisomes

are small, membrane-bound vesicles containing enzymes that break down fatty acids, amino acids, and hydrogen peroxide

hydrogen peroxide

is a by-product of fatty acid and amino acid breakdown and can be toxic to a cell

mitochondria

• are small organelles with inner and outer membranes separated by a space

• are the major sites of adenosine triphosphate (ATP) production within cells.

• carry out aerobic respiration, a series of chemical reactions that require to break down food molecules to produce ATP

cristae

The outer membranes have a smooth contour, but the inner membranes have numerous folds, called — which project into the interior of the mitochondria

mitochondrial matrix

The material within the inner membrane is the —

enzymes and mitochondrial DNA (mtDNA)

The material within the inner membrane contains

cytoskeleton

is the internal framework of the cell. It consists of protein structures that support the cell, hold organelles in place, and enable the cell to change shape

1. microtubules

2. microfilament

3. intermediate filaments

these protein structures in cytoskeleton are

microtubules

are hollow structures formed from protein subunits. The — perform a variety of roles:

• including helping to support the cytoplasm of cells, assisting in cell division, and forming essential components of certain organelles, such as cilia and flagella.

microfilaments

• are small fibrils formed from protein subunits that structurally support the cytoplasm, determining cell shape.

• Some — are involved with cell movement.

intermediate filaments

• are fibrils formed from protein subunits that are smaller in diameter than microtubules but larger in diameter than microfilaments.

• They provide mechanical support to the cell

keratin

A specific type of intermediate filament is — a protein associated with skin cells

centrosome

is a specialized area of cytoplasm close to the nucleus where microtubule formation occurs

centriole

• centrosome contains 2 — which are normally oriented perpendicular to each other.

• Each — is a small, cylindrical organelle composed of microtubules organized into nine triplets; each triplet consists of three parallel microtubules joined together

cilia

• project from the surface of cells

• They vary in number from none to thousands per cell and are capable of moving

• are composed of microtubules, organized in a pattern similar to that of centrioles, which are enclosed by the cell membrane.

flagella

• have a structure similar to that of cilia but are much longer, and they usually occur only one per cell.

• Sperm cells each have one—, which propels the sperm cell.

microvilli

• are specialized extensions of the cell membrane that are supported by microfilaments but they do not actively move as cilia and flagella do.

• are numerous on cells that have them and they increase the surface area of those cells

gene expression

is the process by which information stored in the genes of DNA molecules directs the manufacture of the various proteins of our cells

gene

• The two strands are connected and resemble a ladder that is twisted around its long axis.

• Sections of these DNA strands are called—, which are sequences of nucleotides that provide a chemical set of instructions for making specific proteins

transcription

• occurs in the nucleus.

• During this process information stored in a region of the DNA is used to produce a complementary RNA molecule

messenger RNA (mRNA)

transcription produces a complementary molecule called —

translation

• The mRNA molecule moves to ribosomes in the cytoplasm where — occurs.

• During this process, the nucleotide sequence of the molecule is used to determine the composition of a polypeptide chain, a precursor to a protein

transfer RNAs (tRNAs)

• The ingredients necessary to synthesize a protein are amino acids.

• Specialized molecules, called —-, carry the amino acids to the ribosome