Chapter 4

Cell Structure and Function

1. What is a cell?

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

2. 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

Theodor Schwann (1839) – discovered all animals are made of cells

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

3. 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.

4. 8 Characteristics that all living things share

Consist of organized parts (cells) Obtain energy from their surroundings Perform chemical reactions Change with time (evolution) Respond to their environments Reproduce Maintain constant internal environment

(homeostasis) Share a common history

5. Relationship between a cell’s shape and it’s function

Diversity of shape reflects diversity of functions

Can be simple or complex depending on its function

Cell shape evolved to allow the cell to perform its function effectively

Nerve cells: communication

Skin cells: protection

Blood cells: transport

6. What factor limits the size that most cells are able to obtain?

Limited by the relationship of the cell’s outer surface area to its volume

Most cells range from 10 -100µm

7. What is the problem with cells getting too large?

As a cell grows, it’s volume increases much faster than its surface area

The surface area (the membrane) would not allow materials to enter or leave the cell quickly enough to meet the cell’s needs.

Therefore, most cells are microscopic in size.

8. Three Basic Parts of the Cell:

Plasma Membrane – regulates what enters and leaves the cell

Cytoplasm – site of many chemical reactions of the cell

Material between the cell membrane and the nucleus Contains the organelles of the cell

Control Center – controls all of the cells activities

Either free-floating DNA in center of the cell (Prokaryotes) OR a membrane bound organelle called a nucleus (Eukaryotes)

Prokaryotes – organisms whose cells lack nuclei and other organelles (i.e. bacteria)

Eukaryotes – organism whose cells contain nuclei and other organelles

Pro- = beforeEu- = true-karyon = kernel/nucleus

9. Two basic types of cells

10. What is an organelle?

A well-defined, intracellular body that performs specific functions for the cell. Ex/mitochondrion produces energy

(in the form of ATP) for the cell

Prokaryote vs. Eukaryote

Typical Prokaryote (a bacterium):

11. Prokaryote vs. Eukaryote

Characteristic Prokaryotic Eukaryotic

Cell membrane Cytoplasm

Genetic Material Nucleus

Organelles (only ribosomes) Archaea

Bacteria

Plants, animals, fungi, & protists

11. Units of Organization

CELLS TISSUE ORGANS ORGAN SYSTEM ORGANISM

12. PROKARYOTIC CELL DIAGRAM

DNA – controls all cells activities

PILI – used for attachment to surfaces

RIBOSOME – makes proteins

FLAGELLA – moves the cell

CELL WALL – protection

CELL MEMBRANE – Regulates what enters and leaves

Animal Cell

Cell (Plasma) membrane

mitochondria

Smooth ER

(dots)

Rough ER

lysosome

Golgi apparatus

ribosomes

Nuclear envelope

cytoplasmNucleolus Nucleus

Plant Cell

Nuclear envelope

Smooth ER

Rough ER

NucleolusNucleus

Golgi Apparatus

* Chloroplast *

Cytoplasm

Mitochondria

* Central Vacuole *

* Cell Wall *

Cell (Plasma) membrane

*’s = organelles only found in plant cells, NOT animal cells

Cell Membrane – outer boundary

In plants & animals

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

In plants and animals

Structure: Genetic material

called chromatin (DNA + proteins)

Function: Information center

of the cell Protects DNA Directs/controls

cell activities

Nucleus - control center

In plants & animals

Structure: Made of RNA +

proteins Small, darkened

region inside of nucleus

Function: where ribosomes

are made

Nucleolus -

Mitochondria

In plants & animals

Structure: Double membrane

Cristae - inner folds, increase surface areaOuter membrane for protection of organelle

Function: “Powerhouse” of the cell – produces ATP’s (cell energy) Able to self-replicate ( # in cells with high energy need) Releases energy from food for the organism to use in the

process of cellular respiration

Ribosomes

In plants & animals

Structure: Little “dots” 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)

In plants & animals

Structure: Network of flattened sacs Can be rough (w/ ribosomes) or

smooth (w/o ribosomes)

Function: Transport materials within or out of

cell – intracellular highway Synthesis of macromolecules

Rough - proteins, lipids, carbsSmooth - lipids

Endoplasmic Reticulum

Lysosome In animals only

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!!

Golgi Apparatus

In plants & animals

Structure: Flattened stacks of membranes that are not

connected Vesicles fuse with Golgi and get released

from Golgi

Function: Collection, modification, packaging of

proteins and other substances Vesicles attach, deposit materials Golgi modifies materials based on needs Vesicles attach to membrane and

distribute modified substances

Vacuole In plants - 1 large, central In animals – several small

Function: Storage of water, salts, proteins,

carbohydrates, waste products Pressure system for plants, prevents

wilting Special vacuole: contractile vacuole

- prevents excess water intake, leading to cell-bursting found in freshwater PROTISTS like a paramecium

Cell Wall – Only in plants, bacteria,

fungi

Structure - Lies outside the cell

membrane Made of fibers of cellulose

(plants) Very porous

Function Helps to protect and support

the cell Gives rectangular shape to

plant cells

Chloroplasts

Only in plants Structure:

Inner membranes (thylakoids) surrounded by an outer membrane

Function: Conversion of light energy

(sun) into chemical energy (glucose/food) during the process of PHOTOSYNTHESIS

Other Plastids: Chromoplasts – Store pigments (ex.

carrot root cells, flower petals) Amyloplasts - Store food/starch

Cytoskeleton - framework

In plants – microtubules, intermediate filaments, microfilaments

In animals – all

Function: maintains cell shape and provides internal support Microtubules - hollow tubes of proteins, hold

organelles in place, maintain shape, act as tracks that guide organelle movement

Intermediate filaments – rods that anchor organelles in place

Microfilaments – long & threadlike, used for cell movement

Cilia – short, hairlike projections used for cell movement

Flagella – long, taillike projections used for movement Centrioles – organize microtubules during cell division

Who Am I? (quick review)

I stated all plants are made of cellsI stated all cells come from the division of

preexisting cells I coined the term “cell” when I looked at

slices of cork and dead plant cells I am given credit for developing the 1st

mini microscope and I looked at pond water and made detailed drawings

I discovered all animals are made of cells

List 3 organelles you learned about today.

Describe the function of each of the organelles you listed.

Yes, you should write your name on the paper