CHAPTER #2 - CELLS AND TISSUES - nutleyschools.org Biology... · Introduction To The Cell A cell is the smallest unit of life that can ... Robert Hooke English scientist ... Cell

CHAPTER #2 - CELLS AND TISSUES

Bania

Anatomy/Physiology

Structure And Function Of The Cell

Lily Cell

7,210X TEM

Liver Cell

9,400X

Introduction To The Cell

A cell is the smallest unit of life that can carry out all of the processes of life.

The cell is the simplest collection of matter that can live.

The study of cell structure is cytology

Discovery of the cell

To view most cells, a microscope is needed.

One of the largest cells is an egg.

Microscopy aided in the learning of cell.

In the 1600’s, scientists were first able to view up to 2000X.

Today we can view objects over 2,000,000X

Robert Hooke

English scientist - Mid 1600’s cut a piece of cork and viewed it under lenses

Coined the term cell.

No Pictures exist of Robert

Hooke. This is his first

Microscope

Anton van Leeuwenhoek

Dutch microscope maker – observed the first living cells from pond water in 1675.

Cell Theory

Schleiden, Schwann, and Virchow observed and concluded three basic facts about cells:

1. ALL LIVING THINGS ARE COMPOSED OF ONE OR MORE CELLS.

2. CELLS ARE AN ORGANISMS BASIC UNIT OF STRUCTURE AND FUNCTION

3. CELLS COME FROM OTHER CELLS

CELL DIVERSITY

Cells range from 2 meters long to .2 micrometers. Most are 10 to 50 micrometers.

Most are cuboidal or spherical.

The size is limited by ratio between surface area and volume. Supplies to support the volume must be able to enter and exit through the surface area of the cell membrane

Cell Membrane (plasma membrane) It is a barrier that keeps out some molecules, but allows others to enter – SELECTIVELY PERMEABLE MEMBRANE

It is about 7.5 to 10 nanometers thick

It is a combination of lipids (double layer)and proteins .

The lipids and proteins are free to move about – FLUID MOSAIC MODEL

CYTOPLASM AND ORGANELLES Organelles – “little organ”, part of a cell that performs a specific function

Cytoplasm is the jelly-like material found within the cell that surrounds organelles – it contains water, salt and organic molecules

Cytoplasm is in constant motion – called cytoplamic streaming

Ribosomes

Most numerous and smallest organelle

Composed of nucleic acid and proteins

Ribosomes are the site of protein synthesis

Ribosome’s in kidney cell’s

Endoplasmic Reticulum (ER) System of sacs and tunnels that transports materials around the cell.

Sometimes ribosomes are found on the ER – rough ER

ER without ribosomes is called smooth ER

Golgi Apparatus

Processes, packages and secretes proteins in a vesicle.

The vesicles move to the outside of the cell and its contents are discharged

Golgi Apparatus magnified with TEM

145,000X

Mitochondria

These organelles can grow and divide on their own.The site for cellular respiration.

The inner membrane has many folds – cristae – more space for respiration reaction.

They produce ATP. They have their own DNA

Mitochondria in

muscle cell

Lysosomes

Lysosomes contain digestive enzymes (40)

They digest food particles, disease causing bacteria, and worn out parts of cells.

Microtubules and Microfilaments

Microtubules are protein tubes

Microfilaments are protein threads

Both form the cytoskelaton or framework of cells

Specialized microtubules called spindle fibers move chromosomes apart during cellular division

Cilia and Flagella

Structures that extend from cell for locomotion

Cilia are short hair like extensions – numerous – patterned movement

Flagella are longer and whip like

Made up by microtubules in a “9 + 2” format

CELL NUCLEUS

Where DNA is kept. Control Center

Surrounded by nuclear envelope

Filled with nucleoplasm – protein rich substance; ribosomes are made in the nucleolus.

Molecules Always Moving

Molecules are always moving

This is called Brownian Motion

The more molecules there are in a certain area, the more of a chance of them “bumping” into each other.

Diffusion Diffusion is the process where molecules move from an area of higher concentration to an area of lower concentration

The difference in concentration of molecules across an area is known as the concentration gradient

Equilibrium

Diffusion will occur until equilibrium is reached, where there is an equal amount of molecules throughout the area.

The random movement of molecules still occurs at equilibrium

More Diffusion

Certain molecules can diffuse across a membrane.

Because of this, the membrane is considered permeable

The ability of molecules to pass through the membrane depends on its size and structure.

Osmosis

Osmosis is the diffusion of water.

Water is the solvent in our cells

The amount of water in our cells is controlled by the amount of solute in water, which is the solvent.

Importance of Osmosis

The amount of solvent (water) dictates much of a cells size.

Passive Transport vs. Active Transport

Passive transport is movement of molecules into/out of a cell without using energy

Active Transport is the movement of particles into the cell using a cell’s energy.

Sodium – Potassium Pump

Carrier molecules and the cells energy (ATP).

The exchange of 3 Na (+) ions and 2 K (+) ions creates an electrical gradient.

It is responsible for the transmission of nerve impulses and muscle contraction

Gated Channels proteins that allow the membrane to be as permeable as needed

Endocytosis

Process by which cells engulf large substances into the cell.

The cell membrane moves around the material and then makes it a vesicle that pinches off into the cell membrane

Types of Endocytosis

Phagocytosis is the movement of large molecules into the cell

Pinocytosis is the movement of smaller molecules into the cell

Exocytosis

Exocytosis is the passage of large particles out of the cell.

The Golgi Aparatus packages particles in vesicles.

The vesicle membrane fuses with the cell membrane and its contents are released.

BASIC MOLECULAR BIO

DNA – Deoxyribonucleic Acid

Blueprints of living organisms – controls the production of protein

Composed of repeating subunits - nucleotides

Nitrogen Bases Purines

Adenine and guanine

Contain a double ring of carbon and nitrogen

Pyridamines

Thymine and cytosine

Contain a single ring of carbon and nitrogen

DOUBLE HELIX

Two strands twisted around a central axis

Discovered by Watson and Crick

Two strands held together by hydrogen bonds

Bonding

Adenine always bonds with thymine

Cytosine always bonds with guanine

Complementary Strands

Replication of DNA DNA helicase breaks hydrogen bonds and DNA unwinds

Each strand reacts with complimentary base floating in the nucleus

DNA polymerase adds the sugar to phosphate bonds or the ladder

Copying occurs at many

- points on DNA

Again, Central Dogma

RNA – Ribonucleic Acid Copies DNA and then moves outside the nucleus to synthesize proteins

Single – Stranded

Has ribose rather than deoxyribose

Places Uracil nitrogen base rather than Thymine

Types of RNA Messenger RNA – template or pattern that is uncoiled – transmits information

Transfer RNA – folded RNA that connects amino acids

Ribosomal RNA – globular RNA - makes up ribosomes

Transcription

RNA polymerase seperated DNA

The enzyme connects RNA bases to the DNA strand.

A certain pattern of nucleotides triggers the release of the newly formed RNA molecule.

Protein Synthesis Proteins are made from polypeptides, which are made from over 20 amino acids

A series of three nucleotides on RNA, or codon, code for one amino acid.

Translation

Complete Process

mRNA moves out of the nucleus

mRNA goes to ribosomes

tRNA moves amino acids in cytosplam to ribosome

tRNA anticodon bases pair with codon and drag amino acid to add to polypeptide

Ribosome enzymes create peptide bonds between amino acids

Amino acids are added until stop codon is reached

Genetic Information

Contained in nucleus

When cell is not dividing, genetic info is kept in uncoiled DNA called chromatin

When a cell begins to divide it coils around proteins called histones to form chromosomes

Chromosomes

Each chromosome has two identical parts– sister chromatids

The point at which they meet is called a centromere

Info about Chromosomes

Entire human genome mapped (all chromosomes)

Above the centromere is the “p” region

Below the centromere is the “q” region

Chromosome Numbers

Every Species has a different number of chromosomes

Humans have 46 (23 pairs)

Paired chromosomes are homologous chromosomes

Mitosis

It is the division of the nucleus that produces an identical cell (genetically)

It does not change the amount of DNA in a cell

For some organisms, it is a means of reproduction.

The Cell Cycle The sequence of events that occurs from one mitosis to another – or birth to division

It includes:

Interphase – growth and development – cellular function

Mitosis – division of the nucleus

Cytokinesis – division of the cytoplasm

Interphase Takes up 80-90% of cells lifespan

Three distinct parts:

G1 (Growth Phase) – cell doubles in size, organelles double in number

S1 (Synthesis Phase) – chromatin replicates

G2 (Growth Phase) rapid growth phase

Mitosis

4 phases:

Prophase, Metaphase, Anaphase, Telophase

Prophase Chromatin coils and forms chromosomes, nucleolus disappears, centrioles and spindle fibers appear, and asters appear

Metaphase

Chromosomes line up at center, or equator of cell

Anaphase

Spindle Fibers pull chromosomes towards poles of cell

Telophase

Centrioles and Spindle fibers disappear

Chromosomes unwind and a nucleus forms around each of the chromatid masses

Cytokinesis

Takes place after mitosis

Cytoplasm splits and forms two daughter cells

Organelles also separate

Cell membrane pinches

LAB #3 TITLE: ANIMAL MITOSIS LAB

MATERIAL: Microscope and whitefish slides

Procedure: Observe, draw, and label each stage of mitosis at 400X

Results: 5 drawings w/labels

Conclusion: What did you learn in this lab?

INTERPHASE (p. 105)

Prophase (p. 106)

Metaphase (p. 106)

Anaphase (p.107)

TELOPHASE (p. 107)

Back to INTERPHASE

TISSUES OF THE BODY