Chapter 7Cell Structure and Function (Aligned with 7.1 Intro Sheet and 7.2 Cell Structure Chart)

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7-1 Life is Cellular

A. Cells – basic units of structure and function in living things

** Cell discovery only occurred after the microscope was invented

B. Early scientists that led to the cell theory

❙ Anton van Leeuwenhoek (1600s) – given credit for developing the 1st mini microscope, looked at pond water and made detailed drawings

❙ Robert Hooke – coined the term “cell” when he looked at slices of cork and dead plant cells

❙ Robert Brown (1833) – observed a dark structure near the center of the cell (we now know this is the nucleus)

❙ Matthias Schleiden (1838) – stated all plants are made of cells

❙ Theodore Schwann (1839) – stated all animals are made from cells

❙ Rudolph Virchow (1855) - stated all cells come from the division of preexisting cells

❙ Lorenz Oken – stated all new cells are the result of division of preexisting cells…VIRCHOW STOLE HIS THUNDER

Schleiden

Schwann

Virchow

C. Cell Theory

❙ All living things are composed of cells.

❙ Cells are the basic units of structure and function in living things.

❙ All cells come from preexisting cells.

D. Exploring the Cell: Microscopes* Lenses used to magnify image by focusing beams of light OR

electrons

• Magnification = image size * Resolution = clarity of detail

The light microscope (LM):

• Enables us to shape and structure of a cell

• Magnify cells up to 1,000X

The electron microscope (EM):• Allows greater magnification and reveals cellular details• Magnify cells up to 2 mill X• Limits: no living specimens

SEM

2,000 ×

TEM

2,800 ×

Figure 4.1C Figure 4.1D

Scanning EM: (SEM) surface

structures

Transmission EM: (TEM)

inside details

LM

1,000

×

Figure 4.1B

E. What is in a Cell?ALL ALL cells:

* contain cytoplasm, cell membrane, and DNA

* are either a prokaryotic or a eukaryotic

Prokaryote Eukaryote

•The smallest cells in nature•DNA not contained in a nucleus, free in the cytoplasm•Ribosomes are the ONLY cell organelle•Who are they? Bacteria

•Much larger and more complex•DNA is wrapped with a nuclear membrane (nuclear envelope)•MANY more cell organelles•Who are they? Protists, Fungi, Plants, Animals

7-2 Cell StructuresA. Cellular Control Center

• Nucleus, nucleolus, chromatin/chromosomes, nuclear membrane/pore

B. Organelles that Store, Clean Up and Support

• Vacuoles, vesicles, lysosomes, cytoskeleton (microtubules, microfilaments), centrioles

C. Organelles that Build Proteins

• Ribosomes, endoplasmic reticulum (smooth and rough), golgiapparatus

D. Organelles that Capture and Release Energy

• Chloroplasts, mitochondria

E. Cellular Boundaries

• Cell wall, cell membrane

F. Fluid Portion Outside of Nucleus (Sort of a boundary!)

• Cytoplasm

CELLULAR CONTROL CENTER: NUCLEUS

❚ Function:❙ Information center of the

cell❙ Contains DNA (chromatin

vs. chromosomes)❙ Directs cell activities

❚ 2 categories of organisms

❙ Prokaryotes – organisms whose cells lack nuclei (i.e. bacteria)

❙ Eukaryotes – organism whose cells contain nuclei

Structure:❙ NUCLEOLUS – a small, darkened region in the nucleus

that is made up of RNA and proteins, this is where ribosomes are made

❙ CHROMOSOMES – large structures formed from DNA that contain the genetic info❘ CHROMATIN – uncondensed DNA found in non-dividing

cells

❙ NUCLEAR ENVELOPE – double membrane around the nucleus that contains pores, allows molecules to move in and out of the nucleus, and protects the nucleus❘ NUCLEAR PORES – allows passage of materials into or

out of nucleus (RNA, ribosomes)

Nucleus

Nucleus

ORGANELLES THAT STORE, CLEAN UP, SUPPORT: VACUOLE

❚ Structure:❙ Large, central structure in plants

❙ Many, small, circular structures in animal cells

❙ Filled with liquid

❚ Function:❙ Storage of water, salts, proteins, carbohydrates, waste products

❙ Pressure system for plants, prevents wilting

❙ Special case: contractile vacuole - prevents excess water intake, leading to cell-bursting

❚ Store and move materials between cell organelles and

to/from cell surface

ORGANELLES THAT STORE, CLEANUP, SUPPORT: VESICLE

ORGANELLES THAT STORE, CLEAN

UP, SUPPORT: LYSOSOME

❚ Structure:❙ Small, circular structures

❙ Found only in animal cells

❙ Contain digestive enzymes

❚ Function:❙ Digestion of:

❘ Worn out organelles

❘ Debris

❘ Large ingested particles

❙ Lysosomes are responsible for your hands not being webbed!!

Lysosome

ORGANELLES THAT STORE, CLEAN UP, SUPPORT: CYTOSKELETON

❚ Structure:❙ Hollow tubes of proteins

❙ Examples: cilia, flagella, centrioles

❚ Function:❙ Framework

❙ Provide cell with support, structure and shape

❙ Movement (cilia, flagella)❘ Microfilaments - allow movement of cytoplasm within the cell (cytoplasmic streaming)

❘ Microtubules - Maintain cell shape, make up cilia, flagella and centrioles

ORGANELLES THAT STORE, CLEAN UP, SUPPORT: CENTRIOLES

❚ Organize cell division

ORGANELLES THAT STORE, CLEAN UP, SUPPORT:PLASTID

❚ Structure:❙ Differ based on type of plastid (chloroplast is one example)

❙ Found only in plants

❚ Function:❙ Store food/starch ❙ Store pigments (give color to fruits & veggies)

ORGANELLES THAT BUILD PROTEINS: RIBOSOMES

❚ Structure:❙ Small (25 nm) ball-like

structures

❙ Found free-floating in cytoplasm or attached to rough endoplasmic reticulum

❙ Composed of RNA and protein

❚ Function:❙ Synthesis of proteins (where

proteins are made)

❚ Structure:❙ Network of flattened sacs❙ Can be rough (w/ ribosomes) or smooth (w/o)

❚ Function:❙ Transport materials within or out of cell

❙ Synthesis of macromolecules

❘ Rough - proteins, lipids, carbs

❘ Smooth - lipids

ORGANELLES THAT BUILD PROTEINS: ENDOPLASMIC RETICULUM

ORGANELLES THAT BUILD PROTEINS: GOLGI APPARATUS

❚ Structure:❙ Flattened stacks of membranes

❙ Vesicles attached to top and bottom

❚ Function:❙ Collection, modification, packaging of proteins and other substances

❘ Vesicles attach, deposit materials

❘ GA modifies materials based on needs

❘ Vesicles attach to membrane and distribute modified substances

ORGANELLES THAT CAPTURE/RELEASE ENERGY:

CHLOROPLAST

❚ Structure:❙ Double membrane

❙ Elaborate structure inside

❚ Function:❙ Another power station

❙ Found in plant cells only

❙ Conversion of light energy (sun) into chemical energy (glucose)

ORGANELLES THAT CAPTURE/RELEASE ENERGY:

MITOCHONDRIA❚ Structure:

❙ Double membrane❘ Cristae - inner folds, increase surface area

❘ Outer membrane for protection of cell

❚ Function:❙ “Powerhouse” of the cell

❙ Able to self-replicate (↑ # in cells with high energy need)

❙ Converts sugars into energy for cells

CELLULAR BOUNDRIES: CELL WALL

❚ Only in plants, algae, and some bacteria❚ Lies outside the cell membrane❚ Function

❙ Helps to protect and support the cell ❙ Very porous (water, oxygen, carbon dioxide, etc. can pass

through easily)❙ Gives rectangular shape to plant cells

❚ Layers❙ 1st layer – contains pectin (gluey substance that helps

hold the cells together)❙ 2nd layer – primary cell wall (made of cellulose)❙ 3rd layer (in woody stems) – secondary cell wall

(composed of cellulose and lignin to make cellulose more rigid)

CELLULAR BOUNDRIES:CELL MEMBRANE – outer boundary

❙ Structure:❘ Phospholipid bilayer

• hydrophilic heads, hydrophobic tails

❘ Contains lipids (bilayer), proteins (channels), and carbohydrate chains (identification cards)

❙ Function:❘ Regulates what enters and leaves the cell❘ Semi-permeable membrane❘ Protection and support

Cell/Plasma Membrane

CELLULAR BOUNDRIES:CYTOPLASM

❚ Material between the cell membrane and the nucleus

❚ Contains the organelles of the cell

QUESTIONS:❚ Describe the steps involved in the synthesis, packaging, and exporting of a

protein from a cell. ❙ Proteins assembled on ribosomes (if targeted for export to cm or to

specialized locations w/in cell, complete their assembly on RER���� protein in vesicle ���� Golgi apparatus (further modifies, proteins before sorting and packaging them in membrane bound vesicles ���� vesicle ���� final destination

❚ What are the two major parts of the cell? ❙ Cytoplasm with organelles, and nucleus

❚ How do contractive vacuoles help maintain water balance? ❙ Pump out excess water

❚ What is the difference between rough and smooth ER? ❙ Rough has ribosomes, smooth does not

❚ Why is the cell membrane sometimes referred to as a fluid mosaic? What part of the cell membrane acts like a fluid? And what makes it like a mosaic? ❙ It is made of many parts (like a mosaic) that can float around in the

fluid phospholipid bilayer❚ How do the properties of lipids help explain the structure of the cell

membrane? ❙ Hydrophilic lipid heads are attracted to water, hydrophobic fatty acid

tails turn away from water. A bilayer forms when heads turn outward towards water inside and outside a cell

❚ Why do you think it’s important that cell membranes are selectively permeable? ❙ Allows needed substances to enter and wastes to leave, while keeping

molecules that are not needed out

Plant vs. Animal Cell

Animal Cell

Plan

t Cell