A Tour of the Cell

Microscopic view

Membrane structure

Nucleus and ribosomes

The Endomembrane System

Chloroplasts, Mitochondria

Cytoskeleton

Cilia and flagella

A Prokaryote

Measured in microns ~ 0.5 m

Example? Bacteria

Name some structures:

Flagella

Pili

Ribosomes (blue ‘dots’)

Capsule

Cell wall

Plasma membrane

orange

green

yellow

Nucleoid region (DNA)

Functions?1. Surface appendages that allow a bacterium to stick to a surface

2. Where are proteins synthesized?

3. The sticky, jellylike protective layer outside the cell wall

4. The rigid structure that surrounds, supports, and protects the cell

5. Which structure is a selective barrier, allows passage of oxygen, nutrients, and wastes?

6. Where is the cell's DNA, containing the genes that control the cell

7. The structure that propels the cell

Flagella

Plasma membrane

Ribosomes

Pili

Cell wall

Capsule

Nucleoid region

Compare cells

1. Which is the animal cell?

2. Which is the plant cell?

3. Which is characteristic of bacteria?

4. Which does not have a nucleus?

5. Which does not have a cell wall?

6. Which does not have organelles?

A

B

C

Eukaryotic cells Plasma membrane

Nucleus

Ribosomes

Endoplasmic Reticulum (rough, smooth)

Cytoskeleton

The Golgi Apparatus

Lysosomes

Mitochondria

DNA

Cilia, flagella

Plasma membraneSeparates living cells from nonliving surroundings

It is known as? the fluid mosaic model

Cholesterol

Lipid bilayer

Cytoskeleton Protein Cytoplasm

Extracellular fluid

Carb

Glycoprotein

Phospholipid bilayer

Hydrophilic ‘head’

Hydrophilic ‘tails’

Hydrophilic ‘head’

Extracellular fluid

Cytoplasm

?

?

?What is the function of this component?

Learning check

Which best describes the structure of the plasma membrane?

a. Proteins sandwiched between 2 layers of phospholipid

b. Proteins embedded in 2 layers of phospholipid

c. A layer of protein coating a layer of phospholipid

d. Phospholipids embedded in 2 layers of protein

The Nucleus Is the ‘manager’ of the cell

What does it contain? • DNA

(Chromatin; chromosomes)

• Nucleolus (Produces parts of ribosomes)

It is bordered by a double membrane

& has pores

What is chromatin?

Long DNA molecules + protein(forms long fibers)

What is the nucleolus?

Ball like mass(of fibers and granules)

Produces part of ribosomes(blue ‘dot’)

What are ribosomes?Organelles responsible for protein synthesis

Where do they go?Move from nucleus to cytoplasm

Why?Protein synthesis occurs in the cytoplasm

Recall protein synthesis?(cf last talk on molecules of life)

DNA

Transfers information

To mRNA

Leaves nucleus

Travels to cytoplasm

Binds to ribosome

Protein synthesized

Learning checkIn eukaryotic cells, the first step in protein synthesis is the ____.

a. translation of an RNA nucleotide sequence into a sequence of amino acids

b. linking of nucleotides to form a polypeptide

c. translation of a DNA nucleotide sequence into a sequence of amino acids

d. transferring of information from DNA to messenger RNA

Endoplasmic reticulum

RER: Makes membrane and secretory proteins

SER: lipid synthesis and detoxification

SER

RERwith

ribosomes

Nuclearmembrane

(blue ‘dots’)

Secretory proteinsAfter the RER synthesizes a molecule, it packages the molecule into transport vesicles

Example?

Saliva with enzymes

Ribosome with

peptide chain

Secretory vesicle

Buds off

SER

• No ribosomes

Structure?

• But, membrane has many enzymes

What are some of the enzyme functions?

Ovaries, testes: Sex hormones enriched

Liver cells: Detoxification of drugs

Learning check

Proteins destined for secretion are made on _____ bound to the _____.

a. lysosomes ... Golgi apparatus

b. ribosomes ... Golgi apparatus

c. ribosomes ... mitochondria

d. mitochondria ... endoplasmic reticulum

e. ribosomes ... endoplasmic reticulum

The Golgi ApparatusRefines ER products and packages

And packages them in transport vesicles

transport to organelles

Flattened sacs

vesicles ‘become’ lysosomes

export from cells

What do transport vesicles do?

Lysosomes Membrane enclosed sac of digestive enzymes

• Food

What do they break down?

• Damaged organelles

Proteins, polysaccharides, fats, nucleic acids

Mitochondria

Lysosome

Learning check

Lysosomes can form by budding directly off _____.

a. the Golgi apparatus

b. the endoplasmic reticulum

c. mitochondria

d. chloroplasts

e. the nucleus

1.

2.

3.

4.

The Endomembrane

System

Transport of ?

Digestive ?

Storage ?

Secreted ?

Chloroplasts & Mitochondria

Think energy!

Site of photosynthesis

Site of cell respiration

Conversion of light (energy) to chemical energy

More to come in Chapter 7

Produces ATP (energy) from food molecules

More to come in Chapter 6

Cytoskeleton Its like an infrastructure:

‘Skeleton’ ‘Muscles’

What is it made up of?

Its a network of fibers(microtubules, filaments)

Microtubules Are straight, hollow tubes

What are they composed of?Globular proteins Tubulin

What are some functions?

• Anchor organelles• Move organelles• Guide movement

of chromosomes• Crawling motion

• Rapid degeneration and rebuilding of microtubules

Crawling motion?

• Allows ‘crawling’ movement like the

amoeba

• And some of our white blood cells

Cilia and flagellaare motile appendages

How do cilia move?• In a coordinated back-and-forth way

Paramecium

Example?

How do flagella move?

• In a whip-like motion

Sperm

Example?

What happens in our respiratory tract?

The human windpipe is lined with cilia on non-motile cells

Function to move fluid over the surface of the tissue

Sweep mucus with trapped debris out of lungs

Learning check

Which one of the following statements about cilia and flagella is true?

a. Cilia and flagella are typically found just inside a cell membrane.

b. Cilia are typically much longer than flagella.

c. Flagella and cilia assist in moving a cell or the cell's surroundings.

d. The inside of flagella and cilia consists of many rows of actin and myosin filaments.

e. Cilia are only found in animals.

Which of these organelles is found within the nucleus?

a. nucleolus b. mitochondrion c. SER d. chloroplast e. ribosome

Which of these organelles carries out cellular respiration?

a. nucleolus b. chromatin c. SER d. mitochondrion e. ribosome

Which organelle plays a role in intracellular digestion?

a. Lysosome b. ribosome c. chloroplast d. Golgi apparatus

Concept CheckThe three domains of life described by biologists today include the bacteria, the archaea and the eukarya (all other forms of life).

A. The prokaryotes do not have a plasma membrane surrounding the cell.

B. The prokaryotes use RNA and not DNA to pass on the genetic message.

C. The eukaryotes have the interior of the cell divided by internal membranes into specialized compartments.

D. The eukaryotes engage in cellular metabolism while the prokaryotes do not.