Chapter 3 The Cellular Level of Organization€¦ · Terms of importance 1. Diffusion 2. Osmosis 3. Hypertonic 4. Hypotonic 5. Active Transport 6. Endocytosis 7. Cytoplasm 8. Plasma

Copyright 2009 John Wiley & Sons, Inc.

Chapter 3

The Cellular Level of

Organization

Warm Up

In this process carrier proteins help molecules

across membranes, but the cell does not input

any energy for this process to occur.

a. active transport

b. facilitated diffusion

c. osmosis

d. diffusion


Warm Up

All of the following molecules are part of the cell

membrane except

a. lipids.

b. proteins.

c. cholesterol.

d. nucleic acids.


Terms of importance

1. Diffusion

2. Osmosis

3. Hypertonic

4. Hypotonic

5. Active Transport

6. Endocytosis

7. Cytoplasm

8. Plasma membrane

9. Mitosis

10. Ribosomes

11. Endoplasmic

reticulum

12. Golgi Complex

13. Lysosomes

14. Mitochondria

15. Nucleus



A Generalized Cell

Plasma membrane

- separates the cell’s

internal environment

from the outside

environment

- is a selective

barrier

- plays a role in

communication

Structure of a Membrane

Consists of a lipid bilayer - made up of

phospholipids, cholesterol and glycolipids

Transmembrane proteins – extend through the

entire lipid bilayer (aka integral proteins)

Peripheral proteins - attached to the inner or

outer surface of the membrane, do not extend

through it


Fig. 3.1 Generalized Body Cell


A Generalized Cell

Cytoplasm

- all the cellular contents between the plasma

membrane and the nucleus

- cytosol - the fluid portion, mostly water

- organelles - subcellular structures


A Generalized Cell

Nucleus

- large organelle that contains DNA

- contains chromosomes, each of which

consists of a single molecule of DNA

- a chromosome contains thousands of

hereditary units called genes


Membrane Permeability

The cell is either permeable or impermeable

to certain substances

The lipid bilayer is permeable to oxygen,

carbon dioxide, water and steroids, but

impermeable to glucose

Transmembrane proteins act as channels

and transporters to assist the entrance of

certain substances, for example, glucose and

ions


Passive vs. Active Processes

Passive processes - substances move across

cell membranes without the input of any

energy; use the kinetic energy of individual

molecules or ions

Active processes - a cell uses energy,

primarily from the breakdown of ATP, to

move a substance across the membrane, i.e.,

against a concentration gradient



Osmosis

Net movement of water through a selectively permeable membrane from an area of high concentration of water (lower concentration of solutes) to one of lower concentration of water

Water can pass through plasma membrane in 2 ways:

1. through lipid bilayer by simple diffusion

2. through aquaporins, integral membrane proteins


An isotonic solution is one in which the concentration of solutes is the same both inside and outside of the cell.

A hypotonic solution is one in which the concentration of solutes is greater inside the cell than outside of it.

A hypertonic solution is one where the concentration of solutes is greater outside the cell than inside it.


Tonicity and its effect on RBCS


• Simple Diffusion

Channel-mediated Facilitated Diffusion

Carrier-mediated Facilitated Diffusion


Transport in Vesicles

Vesicle - a small spherical sac formed by budding off from a membrane

Endocytosis - materials move into a cell in a vesicleformed from the plasma membrane

three types: receptor-mediated endocytosis

phagocytosis

bulk-phase endocytosis (pinocytosis)

Exocytosis - vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid

Transcytosis - a combination of endocytosis and exocytosis



Cytoplasm - 2 components

1. Cytosol - intracellular fluid, surrounds the organelles

- the site of many chemical reactions

- energy is usually released by these reactions

- reactions provide the building blocks for cell maintenance, structure, function and growth

2. Organelles

Specialized structures within the cell

The cytoskeleton - network of protein filaments throughout the cytosol

-provides structural support for the cell

-three types according to increasing size: microfilaments, intermediate filaments, and microtubules

The Cytoskeleton


Organelles

Centrosome -

located near the

nucleus, consists of

two centrioles

Cilia - short, hair-

like projections

from the cell

surface

Flagella - longer

than cilia, move an

entire cell


Organelles

Ribosomes - sites

of protein

synthesis

Endoplasmic

reticulum -

network of

membranes in the

shape of flattened

sacs or tubules

Rough ER - connected to

the nucleus, surface is

studded with ribosomes,

produces proteins

Smooth ER - a network of

membrane tubules, does

not have ribosomes,

synthesizes fatty acids

and steroids, detoxifies

certain drugs


Golgi complex – modify and

package proteins for transport

Lysosomes - vesicles that contain

powerful digestive enzymes

Peroxisomes

- smaller than

lysosomes,

detoxify

several toxic

substances

Proteasomes

- destroy

unneeded or

faulty proteins,


Organelles

Mitochondria - the

“powerhouses” of the

cell

Generate ATP


Nuclear envelope - a double membrane that separates the nucleus from the cytoplasm

Nuclear pores - openings in the nuclear envelope

Nucleolus - spherical body that produces ribosomes


Genes - are the cell’s hereditary units, control activities and structure of the cell

Chromosomes - long molecules of DNA combined with protein molecules

Packing of DNA

into a

Chromosome of

a Dividing Cell


Overview of Gene Expression

Transcription

Process of creating

single stranded RNA

by using DNA as a

template.

The RNA is then

used as a template

to create proteins.

RNA uses Uracil

instead of Thymine

when created.


Translation

A ribosome uses

mRNA as a template

to create a chain of

amino acids.

This chain is called a

polypeptide.

What will this

polypeptide become?

A protein!


Videos of the processes

Transcription: http://youtu.be/5MfSYnItYvg

Translation: http://youtu.be/8dsTvBaUMvw


http://youtu.be/5MfSYnItYvg

http://youtu.be/8dsTvBaUMvw


Nuclear Division: Mitosis

Prophase - the chromatin fibers change into

chromosomes

Metaphase - microtubules align the centromeres of

the chromatid pairs at the metaphase plate

Anaphase - the chromatid pairs split at the

centromere and move to opposite poles of the cell;

the chromatids are now called chromosomes

Telophase - two identical nuclei are formed around

the identical sets of chromosomes now in their

chromatin form


Cytoplasmic Division: Cytokinesis

Division of a cell’s cytoplasm to form two identical cells

Usually begins in late anaphase

The plasma membrane constricts at its middle forming a cleavage furrow

The cell eventually splits into two daughter cells

Interphase begins when cytokinesis is complete

Documents

Chapter 3 The Cellular Level of Organization€¦ · Terms of importance 1. Diffusion 2. Osmosis 3. Hypertonic 4. Hypotonic 5. Active Transport 6. Endocytosis 7. Cytoplasm 8. Plasma