1. Cell Structure & Function
Chapter 7
Cell Structure & Function

2. Scientists & Discoveries
Early 1600’s (Holland): 1st
microscope was constructed
Anton van Leeuwenhoek (1600’s) used single lens as a microscope to study and very carefully draw tiny living organisms
(1665) English physicist Robert Hooke used light microscope to study thin slices of plants-saw cork had many tiny chambers he called “cells” like monastery cells

3. cells= the basic units for all forms of life
(1838) Matthias Schleiden -concluded all plants made of cells
(1839) Theodor Schwann - animals made of cells
(1855) Rudolf Virchow -studied cell reproduction; 5yrs research concluded with: “Where a cell exists, there must have been a preexisting cell…”

4. The Cell Theory All living things are composed of cells
Cells are the basic units of structure and function in living things
New cells are created from existing cells.

5. Basic Cell Structures Cells usually measure 5-50 micrometers
Smallest: measures 0.2 micrometers
Largest: (amoeba Chaos chaos) 1000 micrometers
All cells have a cell membrane and cytoplasm
Cell membrane: thin flexible barrier around a cell

6. Cytoplasm: material inside the cell membrane
Many cells also have cell wall (strong layer around cell membrane)
Cell membranes & cell walls support & protect cells while allowing them to interact with their environment
Some cells also have a nucleus (a large structure that stores the cells genetic information & controls the cells activities)

7. Prokaryotes vs. Eukaryotes
Cells are divided into 2 categories:
Prokaryotes
Eukaryotes
*divided into these 2 categories to separate cells that contain a nucleus and organelles (eukaryotes) and those that do not (prokaryotes)

9. Prokaryotes Usually smaller & simpler than eukaryotes
Contain cell membranes
& cytoplasm
DO NOT have nuclei
All bacteria are prokaryotes
- examples: Escherichia coli (intestines), Staphylococcus aureus (skin infections)

10. Prokaryotes Carry out all activities that define life (grow,
reproduce,
respond to
their
environment, &
some even
move)

11. Eukaryotes
CONTAIN nuclei, cell membrane, cytoplasm, & dozens of other specialized structures that perform special functions (organelles)
Some are single celled organisms, but most make up multicellular organisms
All plants, animals, fungi, and many microorganisms are eukaryotes

12. Eukaryotes

13. Section 2: Cell Structures
A. Cytoplasm- refers to the region outside the nucleus but inside the cell membrane
B. Cell Membrane
Also called the plasma membrane
Bi-layer phospholipids that regulates what enters and leaves the cell

14. C. Cell Wall
*main function=provide support & protection for the cell
*located outside cell membrane
*found in plants and algae & nearly all eukaryotes (not animal cells)
In plants the cell wall is
composed of cellulose
In fungi the cell wall contains
chitin
In bacteria it contains peptidoglycan

15. C. Nucleus
*controls most of the cell processes & contains hereditary information of DNA
*chromatin-granular material in the nucleus that consists of DNA bound to protein
*chromosomes-condensed chromatin that consists of genetic information that is to be passed on during cell division

16. (Nucleus contd.)
*Nucleolus-small , dense region where assembly of ribosomes begins
*Nuclear envelope- double-membrane layer that surrounds the nucleus. It contains many nuclear pores that allow material to move in/out of the nucleus

17. D. Cytoskeleton
*network of protein
filaments that help
the cell to maintain
its shape, also
involved in cell
movement
*microtubules-hollow tubes of protein, can serve as “tracks” along which organelles move
*microfilaments-long, thin fibers that function in the movement & support of cells

18. E. Organelles in the cytoplasm
Ribosomes -small particles made of RNA & protein
-produce proteins following coded instructions from the nucleus
Endoplasmic Reticulum (ER)- organelle in which components of the cell membrane are assembled & some proteins
are modified (rough
E.R.-have ribosomes
attached to the surface)

19. Golgi Apparatus-enzymes in the
Golgi Apparatus attach
carbohydrates & lipids to proteins
Lysosomes-small organelles filled
with enzymes that break down lipids,
carbohydrates, & proteins
from food into particles
that can be used by the
rest of the cell (also break
down organelles)

21. Vacuoles- sac-like structures that store materials like water, salts, proteins & carbohydrates
Chloroplast-found in plants
-use energy from sunlight to make energy rich molecules in a process known as photosynthesis
-have a double membrane

23. Mitochondria- use energy from food to make high energy compounds that the cell can use to power growth, development, & movement
-have a double
membrane
-found in nearly all
eukaryotic cells

24. F. Organelle DNA
Chloroplasts and mitochondria contain some of their own genetic information in the form of DNA
These small DNA molecules contain information that is essential for them to function
Could be prokaryotic cells that were engulfed by eukaryotic cells & formed a symbiotic relationship

25. CENTRIOLES Appear during cell division to guide chromosomes apart
Made up of microtubules
Only seen in animal cells

26. CENTRIOLES/MITOTIC SPINDLE
Made of MICROTUBULES (Tubulin)
Image from:

27. FLAGELLA & CILIA Made of PROTEINS called MICROTUBULES
(9 + 2 arrangement)
Image from:

28. FLAGELLA
Help in cell movement
Very few and long in length

29. CILIA And substances past the cell. Very many and short in length
Animation from:
Move cell itself
And substances past the cell. Very many and short in length

30. Section 3: Movement through the Membrane
The cell membrane regulates what enters & leaves the cell & also provides protection & support (figure 7-15)
-lipid bilayer–a double layered membrane formed when certain kinds of lipids are dissolved in water
-embedded proteins-forms channels & pumps that help move materials across the membrane
-carbohydrate chains-attach to proteins & aids in chemical identification to allow cells to ID one another

31. Cell Membrane

32. Diffusion: tendency of molecules to move from an area of high concentration to an area of lower concentration to reach equilibrium (figure 7-16)
-causes many substances to move across the cell membrane but does not require the cell to use energy
-concentration=mass of solute/volume of solution

33. Osmosis: diffusion of water through a selectively permeable membrane (fig 7-17)
-selectively permeable= some substances can pass through but others cannot
-isotonic-same strength solution on both sides
-hypertonic-above strength inside (water leaves)
-hypotonic-below strength inside (water enters)

34. Osmosis exerts pressure known as osmotic pressure on the hypertonic side of the selectively permeable membrane.
-osmotic pressure can cause a cell to shrink or burst (figure 7-18)

35. Facilitated Diffusion: the process of protein channels allowing a pathway for certain molecules to cross the membrane (figure 7-19)
-100’s of different protein channels have been found that allow ions, sugars & salts to cross the membrane

36. Active Transport: requires energy to move molecules across a cell membrane against a concentration difference. The materials move from an area of lower concentration to an area of higher concentration (figure 7-20)-often compared to a pump

37. Endocytosis: the process of taking large particles into the cell by
means of infoldings or
pockets of the cell
membrane that form
vacuoles

38. Phagocytosis: process of taking large particles into the cell by endocytosis. Extensions of the cytoplasm surround & engulf the large particles.

39. Exocytosis: membrane of the vacuole surrounding material fuses with the cell membrane, forcing the contents out of the cell

40. Review What processes are made possible by the cell membrane?
How does diffusion affect cells?
Describe how water moves during osmosis.
What is the basic structure of a cell membrane?
How does active transport differ from diffusion?