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Announcements. ● Tutoring Center SCI I, 407 M 12-3, 5:30-6:30; W 8-9, 5:30-6:30, Th 8-12, 6-7; F 8-9 ● MasteringBiology Assignment due Tuesday 4/19 ● Exam I Tuesday 4/19 ● Scantron ABF-10-ID-200A . Review. ● Importance of Carbon ● Biologically Important Molecules

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Announcements

Announcements

● Tutoring Center

SCI I, 407

M 12-3, 5:30-6:30; W 8-9, 5:30-6:30,

Th 8-12, 6-7; F 8-9

● MasteringBiology Assignment due Tuesday 4/19

● Exam I Tuesday 4/19

● Scantron ABF-10-ID-200A


Announcements

Review

● Importance of Carbon

● Biologically Important Molecules

Macromolecules:

Carbohydrates

Proteins

Nucleic Acids

Lipids


Announcements

The Microscopic World of Cells

  • ● Organisms are either:

    • Single-celled, such as most prokaryotes and protists or

    • Multicelled, such as plants, animals, and most fungi


Announcements

The Microscopic World of Cells

How do we study cells?

Light microscopes can be used to explore the structures and functions of cells.


Announcements

The Microscopic World of Cells

● Electron Microscope

10 m

Human height

1 m

Length of some

nerve and

muscle cells

10 cm

Unaided eye

Chicken egg

1 cm

Frog eggs

1 mm

100 mm

Plant and

animal cells

Light microscope

10 mm

Nucleus

Most bacteria

Mitochondrion

1 mm

Smallest bacteria

Electron microscope

100 nm

Viruses

Ribosomes

10 nm

Proteins

Lipids

1 nm

Small molecules

Atoms

0.1 nm

Figure 4.3


Announcements

The Microscopic World of Cells

TYPES OF MICROGRAPHS

Light Micrograph (LM)

(for viewing living cells)

Scanning Electron Micrograph (SEM)

(for viewing surface features)

Transmission Electron Micrograph (TEM)

(for viewing internal structures)

LM

Colorized TEM

Colorized SEM

Light micrograph of a protist, Paramecium

Scanning electron micrograph ofParamecium

Transmission electron micrograph ofParamecium


Announcements

The Two Major Categories of Cells

● The countless cells on earth fall into two categories:

Prokaryotic cells — Bacteria and Archaea

Eukaryotic cells — Eukarya

protists, plants, fungi, and animals

● All cells have several basic features.

1. They are all bound by a thin plasma membrane.

2. All cells have DNA.

3. All cells have ribosomes.

Cytoplasm-the entire contents of a cell


Announcements

Prokaryotic Cells

● Prokaryotes

Are smaller than eukaryotic cells

Lack internal structures surrounded by membranes

Lack a nucleus

Have a rigid cell wall

Plasma membrane

(encloses cytoplasm)

Cell wall (provides

Rigidity)

Capsule (sticky

coating)

Prokaryotic flagellum

(for propulsion)

Ribosomes

(synthesize proteins)

Nucleoid (contains DNA)

Pili (attachment structures)

Colorized TEM


Announcements

Eukaryotic Cells

● Eukaryotic cells are fundamentally similar.

*Generalized plant cell

*Generalized animal cell


Announcements

Membrane Structure

● The plasma membrane separates the living cell from its nonliving surroundings.

Proteins

Outside of cell

Outside of cell

Hydrophilic

region of

protein

Hydrophilic

head

Hydrophobic

tail

Hydrophilic

head

Phospholipid

bilayer

Hydrophobic

tail

Phospholipid

Cytoplasm (inside of cell)

(a) Phospholipid bilayer of

membrane

Hydrophobic

regions of

protein

Cytoplasm (inside of cell)

(b) Fluid mosaic model of

membrane


Announcements

Membrane Structure

● Phospholipid structure

Phospholipids are amphipathic molecules


Announcements

Membrane Structure

● The plasma membrane separates the living cell from its nonliving surroundings.

Proteins

Outside of cell

Outside of cell

Hydrophilic

region of

protein

Hydrophilic

head

Hydrophobic

tail

Hydrophilic

head

Phospholipid

bilayer

Hydrophobic

tail

Phospholipid

Cytoplasm (inside of cell)

(a) Phospholipid bilayer of

membrane

Hydrophobic

regions of

protein

Cytoplasm (inside of cell)

(b) Fluid mosaic model of

membrane


Announcements

Membrane Structure

● Some functions of membrane proteins

Cytoplasm

Fibers of

extracellular

matrix

c

Enzymatic activity

b

Cell signaling

a

Attachment to

cytoskeleton and

extracellular

matrix

e

Intercellular

joining

f

Cell-cell

recognition

d

Transport

Cytoplasm

Cytoskeleton

● Cell surface – Extracellular Matrix


Announcements

Nucleus

● The nucleus is an organelle that houses the genetic material of the cell.

Nuclear

envelope

Nucleolus

Chromatin

Pore

Chromatin

Nuclear envelope

Nucleolus

Nuclear Pore

TEM

TEM

Surface of nuclear

envelope

Nuclear pores


Announcements

Chromatin

DNA molecule

Proteins

Chromatin

fiber

Chromosome

Figure 4.9


Announcements

Ribosomes

● Ribosomes build all the cell’s proteins (protein synthesis)

Composed of proteins and Ribosomal RNA

Free: proteins for cytosol

Membrane-bound: proteins for

cell membranes and export


Announcements

How DNA Directs Protein Synthesis

● DNA controls the cell by transferring its coded information into RNA

DNA

1

Synthesis of

mRNA in the

nucleus

mRNA

  • The information in the RNA is used to make proteins

Nucleus

Cytoplasm

mRNA

2

Movement of

mRNA into

cytoplasm via

nuclear pore

Ribosome

3

Synthesis of

protein in the

cytoplasm

Protein


Announcements

The Endomembrane System

  • ● Many of the membranous organelles in the cell belong to the endomembrane system


The endoplasmic reticulum

The Endoplasmic Reticulum

  • Produces an enormous variety of molecules

  • Is composed of smooth and rough ER

Nuclear

envelope

Ribosomes

Rough ER

Smooth ER


The endoplasmic reticulum1

The Endoplasmic Reticulum

After the rough ER synthesizes a molecule it packages the molecule into transport vesicles

4

Transport vesicle

buds off

Secretory

protein inside

transport

vesicle

Ribosome

3

Protein

1

Rough ER

2

Polypeptide


The golgi apparatus

The Golgi Apparatus

  • Works in partnership with the ER

  • Refines, stores, and distributes the products of cells

Transport

vesicle

from ER

“Receiving” side of

Golgi apparatus

Golgi apparatus

New vesicle forming

Transport vesicle

from the Golgi

“Shipping” side of

Golgi apparatus

Plasma membrane


Lysosomes

Lysosomes

  • It contains digestive enzymes

  • The enzymes break down macromolecules

  • A lysosome is a membrane-enclosed sac

  • They break down damaged organelles

Lysosome

Digestion

Damaged

organelle

(b) Lysosome breaking down damaged organelle


Announcements

The Endomembrane System

Rough ER

Transport

vesicle from ER

Golgi

apparatus

Secretory

vesicle from Golgi

Vacuole

Lysosome

Secretory

protein

Plasma membrane


Announcements

Cellular energy conversion

Mitochondria are the sites of cellular respiration, which involves the production of ATP from food molecules

Outer

membrane

Inner

membrane

Cristae

Matrix

Space between

membranes

Figure 4.18


Announcements

Cytoskeleton

  • ● Provides mechanical support to the cell and maintain its shape


Announcements

Cytoskeleton

The cytoskeleton can change the shape of a cell

  • This allows cells like amoebae to move


Cilia and flagella

Cilia and Flagella

Cilia and flagella are motile appendages

  • Flagella propel the cell in a whiplike motion

  • Cilia move in a coordinated back-and-forth motion


Vacuoles

Vacuoles

  • Two types are the contractile vacuoles of protists and the central vacuoles of plants

Vacuoles are membranous sacs

Central

vacuole

Contractile

vacuoles

(a) Contractile vacuoles in a protist

(b) Central vacuole in a plant cell


Plant cells

Plant Cells

Not in animal cells

Cytoskeleton

Mitochondrion

Central

vacuole

Nucleus

Cell wall

Rough endoplamsicreticulum (ER)

Chloroplast

Ribosomes

Plasma

membrane

Smooth

endoplasmic

reticulum (ER)

Plasmodesmata

Golgi apparatus


Announcements

Plant Cells

Walls of two adjacent

plant cells

Plant cells are encased by cell walls

Vacuole

Plasmodesmata

(channels between cells)


Chloroplasts

Chloroplasts

Inner and outer

membranes of

envelope

Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy

Granum

Space between

membranes

Stroma (fluid in

chloroplast)


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