Chapter 3 - Cell Structures and their Functions

7/27/2019 Chapter 3 - Cell Structures and their Functions

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Cell Structures

Cells highly organized units containing

organelles, which perform specificfunctions

Nucleus contains genetic material

Cytoplasm living material surrounding

the nucleus

Functions of the Cell:

1. Basic unit of life2. Protection and Support3. Movement4. Communication5. Cell Metabolism and Energy Release6. InheritanceCell Membrane (Plasma Membrane)

- outermost component of a cell- encloses the cytoplasm and the cell- forms the boundary between

materials inside and outside the cell

- plays a role in communicationbetween cells

Extracellular Substances substances

outside the cell

Intracellular Substances substances

inside the cell

Phospholipids and Proteins major

molecules that make up cell membraneThe phospholipid forms a double layer

of molecules:

Polar hydrophilic (water loving),face the water inside and outside

the cell

Non-polar hydrophobic (waterfearing) face away from the water

Fluid-mosaic model arrangement ofmolecules in the cell membrane

The double layer of phospholipid

molecules has a liquid quality..

Cholesterol within the phospholipid

membrane gives it added strength andflexibility

Proteins function as membrane

channels, carrier and receptor

molecules , or structural support.

Membrane Channels and Carrier

Molecules are involved with the

movement of substances through the

cell membrane.Receptor Molecules part of

intracellular communication system

that enables cell recognition and

coordination of the activities of cells.

Movement Through the Cell

Membrane

Cell membranes are selectively

permeable, allowing some substances,

but not others, to pass into or out of

the cells.

Enzymes, glycogen and potassium ions

are found at higher concentrations

intracellulary. Na+, Ca2+, Cl- are found

in greater concentrationsextracellularly.

Molecules pass through cell membranes

in 4 ways:

1.) Directly through the phospholipidmembrane

2.) Membrane Channels3.) Carrier Molecules4.) Vesicles

Chapter 3

Cell Structures and their Functions


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Diffusion tendency for solutes, such

as ions or molecules, to move from an

area of higher concentration to an area

of lower concentrations.

- Results from the constant random

motion of all solutes in a solution*More solute particles occur in an area

of higher concentration than in one of

lower concentration.

Ex: Smoke, Perfume, in Oxygen, Carbon

Dioxide, Chloride ions and Urea

Concentration Gradient a measure of

the difference in the concentration of

a solute in a solvent

Osmosis diffusion of water across a

selectively permeable membrane, from

a region of higher water concentration

to a lower concentration.

- occurs only when the cell membrane is

less permeable, selectively permeable

or not permeable to solutes and a

concentration gradient for water

exists across the cell membrane.Osmotic Pressure force required to

prevent the movement of water across

a selectively permeable membrane.

Hydrostatic Pressure produced when

the weight of the solution rises.

Hypotonic Solution low solute

concentration/results to swelling or

bursting of RBC/water enters the cell

by osmosis

Isotonic Solution equal solute

concentration/water moves into and out

of the cell/no net water movement

Hypertonic Solution high solute

concentration/causes shrinkage of the

RBC/water moves out of the cell by

osmosis

Filtration movement of fluid through

a partition containing small holes.

Ex: in kidneys, blood, etc.

Carrier-mediated Transport

Mechanisms function to move large,water soluble molecules or electrically

charged ions across the cell membrane

- exhibit specificity, that is, only

specific molecules are transported by

the carriers

3 Kinds: Facilitated Diffusion, Active

Transport, & Secondary Active

Transport

Facilitated Diffusion carrier-

mediated transport process that moves

substances into or out of cells from a

higher to a lower concentration of that

substance.

*Because movement is with the

concentration gradient, metabolic

energy in the form of ATP is not

requiredEx: Glucose in most cells

Active Transport carrier-mediated

process that moves substances across

the cell membrane from regions of

lower concentrations to those of higher

concentrations against a concentration

agent. ATP is required.

Sodium-Potassium Pump moves Na+

out of cells and K+ into cells.

(3Na2K) Result is higher concentration

of Na+ outside the cell and a higher

concentration of K+ inside the cell.

Cystic Fibrosis genetic disorder that

affects the active transport of

chlorine ions into cells.


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Secondary Active Transport involves

the active transport of one substance,

such as Na+, across the cell membrane,

establishing a concentration gradient

Co-transport diffusing substance

moves in the same direction as thetransported substance

Counter-transport diffusing

substance moves in opposite direction

as the transported substance

Endocytosis uptake of material

through the cell membrane by the

formation of a membrane-bound sac

called a vesiclePhagocytosis term often used for

endocytosis when solid particles are

ingested

Pinocytosiscell drinking

distinguished from phagocytosis in that

much smaller vesicles are formed that

contain liquid rather than particles

Secretory vesicles membrane-bound

sacs that accumulate materials forrelease from the cell

Exocytosis - a process by which the

contents of a cell vacuole are released

to the exterior through fusion of the

vacuole membrane with the cell

membrane

Whole Cell Activity

Cell Metabolism sum of all the

chemical reactions in the cell

Glycolysis breakdown of sugar

glucose, by a series of reactions within

the cytoplasm of the cell

Aerobic Respiration occurs when

oxygen is available

Anaerobic Respiration occurs withoutoxygen and includes the conversion of

pyruvic acid to lactic acid

DNA influences the structural and

functional characteristics of the entire

organism because it directs protein

synthesis

Gene sequence of nucleotides

providing a chemical set of instructionsfor making a specific protein

2 Steps in the Production of Proteins:

Transcription and Translation

Messenger RNA (mRNA) copy of

information in the DNA

Transfer RNA (tRNA) carry amino

acids to the ribosome

Codons groups of 3 nucleotides, code

for specific amino acids.Anticodons series of 3 nucleotides of

each tRNA molecule

Cell Division

Cell Division formation of 2 daughter

cells from a single parent cell.

*Each cell of the human body, except

sex cells, contains 46 chromosomes

*Sex cells have 23 chromosomes

*46 chromosomes are called diploid

*23 chromosomes are called haploid

X Chromosome female

X & Y Chromosome - male

Autosomes remaining 22 pairs of

chromosomes

Mitosis - a type of cell division that

results in two daughter cells each

having the same number and kind of

chromosomes as the parent nucleus

2 Types:

1. Genetic material within the cellis replicated/duplicated

2.

Cell divides to form 2 daughtercells with the same amount and

type of DNA as the parent cell


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Interphase the period between active

cell divisions, during which DNA is

replicated

Chromatin thin threads that dispersethe DNA through the nucleus.

4 Stages in Mitosis:

1.) Prophase chromatin condensesinto chromosomes. Each

chromosome consists of 2

chromatids joined at the

centromere. The centrioles move

to the opposite side of the cell.Nucleolus and nuclear envelope

disappear

2.)Metaphase the chromosomesalign in the center of the cell in

association with the spindle

fibers

3.)Anaphase chromatids separateto form 2 sets of identical

chromosomes. Chromosomesmove toward the centrioles at

each end of the cell

4.)Telophase chromosomesdisperse, nuclear envelopes and

the nucleoli form, cytoplasm

begins to divide to form two

cells.

Differentiation process by which cells

develop with specialized structures and

functions.

Cellular Aspects of Aging:

1.) Cellular clock2.)Death Genes3.)DNA Damage4.)Free radicals5.)Mitochondrial damage

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Chapter 3 - Cell Structures and their Functions