1. Cells Chapter 3

2. Early studies led to the development of the cell theory
The Cell theory has three principles.
All organisms are made of cells.
All existing cells are produced by other living cells.
The cell is the most basic unit of life.

3. All cells share certain characteristics.
Cells tend to be microscopic.
All cells are enclosed by a membrane.
All cells are filled with cytoplasm.
All cells contain DNA
cell membrane
Bacterium
(colored SEM; magnification 8800x)
cytoplasm

4. There are two cell types: eukaryotic cells and prokaryotic cells
Eukaryotic cells do
have a nucleus
have membrane-
bound organelles
Prokaryotic cells
do not have a nucleus.
nucleus
organelles
cell membrane
cytoplasm

5. The Cell Membrane

6. The cell membrane has two major functions
forms a boundary between inside and outside of the cell
controls passage of materials

7. Cell membranes are composed of two phospholipid layers
The cell membrane is made of a phospholipid
bi-layer.
There are other molecules embedded in the membrane.
cell membrane

8. The fluid mosaic model describes the membrane
Fluid = moving within the structure
ex: water molecules moving in a body of water
Mosaic = looks like a patchwork pattern
ex: patchwork art

9. Cell Structure

10. Prokaryotes Prokaryote:
A single-celled organism that lacks a nucleus and other internal compartments
Can not carry out many specialized functions
Ex: Modern day bacteria

11. Bacteria Characteristics
Cell Wall:
Surrounding the cell membrane that provides structure and support.
Flagella:
Long threadlike structures that stick out from the cell’s surface and enable movement.

12. Eukaryotic cells have organelles
Eukaryotic cells have a membrane bound nucleus and other organelles
Organelles:
Are membrane-bound structures inside the cell
Have specific functions

13. Cell Boundaries Cell Membrane Cell Wall
Separates the inside of the cell from the outer environment
Found in all cells
Cell Wall
Provides protection and rigid support
Found in plant cells

14. Several organelles are involved in making and processing proteins
The nucleus
stores genetic information = chromatin
Is the control center of the cell

15. The nucleolus
Organelle where ribosomes are made

16. The ribosomes link amino acids to form proteins
Are found on the surface of rough endoplasmic reticulum or floating freely in the cytoplasm

17. Organelles that assemble, transport and store proteins
The endoplasmic reticulum (ER)
Series of highly folded membranes

18. Two types of endoplasmic reticulum
rough endoplasmic reticulum
Surface has ribosomes
attached to it
Transports proteins
smooth endoplasmic reticulum
Surface is smooth
Aids in the production
and storage of lipids

19. Golgi Apparatus – process, sort, deliver proteins

20. Vesicles are membrane-bound sacs that hold materials

21. Other organelles have various functions
Mitochondria are the site of cellular respiration = ATP production

22. Lysosomes contain enzymes to digest material

23. Peroxisomes contain enzymes that catalyze biochemical reactions

24. Cells have an internal structure
The cytoskeleton has many functions.
Made of microtubules and microfilaments
supports and shapes cell
helps position and transport organelles
provides strength
assists in cell division
aids in cell movement

25. Centrioles are tubes found in cells of animals and most protists
Made up of microtubules
Aid in division of DNA.

26. Organelles of locomotion
Cilia
Short hair-like projections
Many work together
Flagella
Long projections
Usually one or two per cell
Move with a whip-like motion

27. Specialized cells perform specific functions
Cells develop into their mature forms through the process of cell differentiation.
Cells differ because different combinations of genes are expressed.
A cell’s location in an embryo helps determine how it will differentiate.
Outer: skin cells
Middle: bone cells
Inner: intestines

28. Stem cells are unique body cells
Stem cells have the ability to
divide and renew themselves
remain undifferentiated in form
develop into a variety of specialized cell types

29. Stem cells are classified into three types
Totipotent = growing into any other cell type
Pluripotent = growing into any cell type but a totipotent cell
Multipotent = growing into cells of a closely related cell family

30. Stem cells come from adults and embryos
Adult stem cells can be hard to isolate and grow.
The use of adult stem cells may prevent transplant rejection.
The use of embryonic stem cells raises ethical issues
Embryonic stem cells are pluripotent and can be grown indefinitely in culture.
First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules.

31. … and raises some controversial issues - ethical objections
The use of stem cells offers many currently realized and potential benefits…
Stem cells are used to treat leukemia and lymphoma.
Stem cells may cure disease or replace damaged organs.
Stem cells may revolutionize the drug development process.
… and raises some controversial issues
- ethical objections
- moral objections

32. Apoptosis is programmed cell death
a normal feature of healthy organisms
caused by a cell’s production of self-destructive enzymes
occurs in development of infants
webbed fingers

33. The Cell Membrane is Selectively Permeable
Selective Permeability:
Same as semi-permeable
Allows some materials to cross
Molecules can cross in a variety of ways
Enables cell to maintain homeostasis

34. Chemical signals are transmitted across the cell membrane.
Receptors bind with molecules and change shape.
There are two types of receptors.
intracellular receptor
Inside cell - bind to
Molecule that can
Cross membrane
membrane receptor
In the membrane
Binds to molecule
Changes it’s shape
Transmits message to
Cell

35. the cell Passive transport does not require energy input from
Molecules can move across the cell membrane via passive transport.
There are two types of passive transport.
Diffusion is the movement of molecules down a concentration gradient.
Osmosis is the diffusion of water molecules across a semi-permeable membrane.

36. Three types of solutions
Isotonic – no net movement of water = osmotic pressure is at equilibrium
Hypertonic – net movement of water is to outside of cell = higher osmotic pressure
Hypotonic – net movement of water is to inside of cell = lower osmotic pressure

37. Facilitated diffusion is diffusion aided by transport proteins
Some molecules cannot easily diffuse across the cell membrane.

38. and enables a cell to move a substance against its
Active transport requires energy input from a cell
and enables a cell to move a substance against its
concentration gradient
Active transport is powered by chemical energy (ATP).
Cells use active transport to maintain homeostasis.
One form of active transport occurs through transport protein pumps.

39. of material in vesicles during the processes of endocytosis
Cells can import and export large materials or large amounts
of material in vesicles during the processes of endocytosis
and exocytosis.
Cells use energy to transport material in vesicles.
Endocytosis is the process of taking material into the cell.
Phagocytosis, “cell eating,” is the process of engulfing and digesting solid material, such as bacteria or cell debris
Pinocytosis , “cell drinking,” is the process of engulfing liquids

40. Receptor-mediated endocytosis- moves specific types of particles into the cell by binding to ligands

41. Exocytosis is the process of expelling material from the cell.

42. Cell Cycle

43. Cell size is limited
Volume increases faster than surface area.

44. Surface area must allow for adequate exchange of materials
Cell growth is coordinated with division.
Cells that must be large have unique shapes.

45. Cell size limitations Too small – might not have all organelles
Too large – exchange across membrane inadequateCell
growth is coordinated with division to maintain suitable size.

46. The cell cycle has four main stages
The cell cycle is a regular pattern of growth, DNA replication, and cell division.

47. The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitosis.
Gap 1 (G1): cell growth and normal functions
DNA synthesis (S): copies DNA
Gap 2 (G2): additional growth
Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)
Mitosis occurs only if the cell is large enough and the DNA undamaged.

48. Cells divide at different rates
The rate of cell division varies with the need for those types of cells.
Some cells are unlikely to divide (G0).

49. Cells divide during mitosis and cytokinesis

50. Chromosomes condense at the start of mitosis
DNA wraps around proteins (histones) that condense it.
DNA double helix
DNA and histones
Chromatin
Supercoiled DNA

51. Interphase prepares the cell to divide.
Mitosis and cytokinesis produce two genetically identical daughter cells
Parent cell
centrioles
spindle fibers
centrosome
nucleus with
DNA
Interphase prepares the cell to divide.
During interphase, the DNA is duplicated.

52. Prophase: chromosomes condense and spindle fibers form

53. Metaphase: chromosomes line up in the middle of the cell

54. Anaphase: sister chromatids separate to opposite sides of the cell

55. Telophase: the new nuclei form and chromosomes begin to uncoil

56. Cytokinesis: the membrane pinches closed to form two new cells

57. Cell cycle regulation is necessary for healthy growth

58. Internal and external factors regulate cell division
External factors include physical and chemical signals.
Growth factors are proteins that stimulate cell division.
Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells.

59. Two of the most important internal factors are kinases and cyclins.
Kinase – enzymes promote increased energy
Cyclins - proteins
External factors trigger internal factors, which affect the cell cycle.
Cell contacts and other physical signals
Chemical signal – growth factors

60. Cell division is uncontrolled in cancer
Cancer cells form disorganized clumps called tumors.
Benign tumors remain clustered and can be removed.
Malignant tumors metastasize, or break away, and can form more tumors.
cancer cell
bloodstream
normal cell

61. Cancer cells do not carry out necessary functions
Cancer cells come from normal cells with damage to genes involved in cell cycle regulation.
Carcinogens are substances known to promote cancer.
Standard cancer treatments typically kill both cancerous and healthy cells.