1. IB SL Biology
Midterm Review

2. Science is a process of inquiry that includes repeatable observations and testable hypotheses

3. Designing a Controlled Experiment
Controlled experiment: tests the effect of a single variable.
Variable: any factor that can be changed
Dependent variable is the measured effect caused by the
Independent variable which is the factor being studied
Controlled Factors: all other variables must be held constant.
Hypothesis: "If , then . . ."

4. Observations may lead to questions and hypothesis
Warning coloration: Why is this frog so colorful and visible?
Why does this fly look so much like a bee?

5. Data: is the measured results of the experiments
Data of Height vs. Age of a child’s growth.
Independent Variable:
Dependent Variable:
Age
Height

6. Components of a Controlled Experiment
State the Purpose of the Experiment
State a hypothesis
Identify the independent variable
Control all other factors
Identify the dependent variable
Identify or make a control group
Collect and record data
Make data table and graphs
Verify results with repeats
Design an experiment to test the effectiveness of a particular cough drop.
Design an experiment to test if a new fertilizer increases plants to growth.

7. Level of Organization
Atoms
Molecules
Organelles
Cells
Tissues
Organs
Organ systems
Whole Organism

8. Characteristics of Life
Respiration Reproduction
Repair and Growth
Regulation
Transport
Excretion
Nutrition
Synthesis
All Living things show these 8 Life Functions, even unicellular organisms.

9. Cell Theory Cells are the basic units of living organisms.
The cell theory states that:
All living things are made of one or more cells.
Cells are the basic unit of structure and function in living things.
All cells come from other cells.

10. Cell Types Two categories: 1. Cell that have membrane-bound organelles
Called Eukaryotic Cells
2. Cells that do not have membrane-bound organelles
called prokaryotic cells
Unicellular organisms such as bacteria are examples of prokaryotes.

11. Cell Types Eukaryotic cells-
Cells that contain organelles which are held together by membranes
Examples include plant and animal cells.

12. 1). Prokaryotic and eukaryotic cells differ in size and complexity
Similarities
All cells are surrounded by a plasma membrane.
The semi-fluid substance within the cell is called “cytosol”, containing the cell organelles.
All cells contain chromosomes which have genes in the form of DNA.
All cells have tiny organelles called “Ribosomes” that make proteins.

13. 1). Prokaryotic and eukaryotic cells differ in size and complexity
Differences
A major difference between prokaryotic and eukaryotic cells is the location of chromosomes.
In an eukaryotic cell, chromosomes are contained in a true nucleus ).
In a prokaryotic cell, the DNA is concentrated in the nucleoid) without a membrane separating it from the rest of the cell.
In prokaryotic cell, DNA is a single strand or double strand DNA. But in eukaryotic cell, DNA is double strand.

14. Stem Cell – Definition
A cell that has the ability to continuously divide and differentiate (develop) into various other kind(s) of cells/tissues
Stem cells are different from other cells of the body in that they have the ability to differentiate into other cell/tissue types. This ability allows them to replace cells that have died. With this ability, they have been used to replace defective cells/tissues in patients who have certain diseases or defects. 14

15. Stem Cell Characteristics
‘Blank cells’ (unspecialized)
Capable of dividing and renewing themselves for long periods of time (proliferation and renewal)
Have the potential to give rise to specialized cell types (differentiation)
Common variants, called polymorphisms, occur at greater than 1% frequency
I have given some examples of how exposure induced risk is modified in various ways
Typically the effects are modest in magnitude.
We are interested in how genetics modifies Exposure and exposure-related diseases Because….. 15

16. Kinds of Stem Cells Stem cell type Description Examples Totipotent
Each cell can develop into a new individual
Cells from early (1-3 days) embryos
Pluripotent
Cells can form any (over 200) cell types
Some cells of blastocyst (5 to 14 days)
Multipotent
Cells differentiated, but can form a number of other tissues
Fetal tissue, cord blood, and adult stem cells
Stem cells can be classified into three broad categories, based on their ability to differentiate. Totipotent stem cells are found only in early embryos. Each cell can form a complete organism (e.g., identical twins). Pluripotent stem cells exist in the undifferentiated inner cell mass of the blastocyst and can form any of the over 200 different cell types found in the body. Multipotent stem cells are derived from fetal tissue, cord blood and adult stem cells. Although their ability to differentiate is more limited than pluripotent stem cells, they already have a track record of success in cell-based therapies. Here is a current list of the sources of stem cells:
Embryonic stem cells - are harvested from the inner cell mass of the blastocyst seven to ten days after fertilization.
Fetal stem cells - are taken from the germline tissues that will make up the gonads of aborted fetuses.
Umbilical cord stem cells - Umbilical cord blood contains stem cells similar to those found in bone marrow.
Placenta derived stem cells - up to ten times as many stem cells can be harvested from a placenta as from cord blood.
Adult stem cells - Many adult tissues contain stem cells that can be isolated. 16

17. Totipotent Pluripotent Multi- potent
CLICK! This diagram will eventually show the entire range of development, from fertilized egg to mature cell types in the body.
Each cell in the 8-cell embryo, here in red, can generate every cell in the embryo as well as the placenta and extra-embryonic tissues. These cells are called CLICK! TOTIPOTENT stem cells. Why are they called totipotent? (wait for answers) Because one red cell can potentially make all necessary tissues for development. CLICK!
During In Vitro Fertilization, can parents choose whether their baby is going to be a boy or a girl? (wait) Yes, there is a widely-practiced procedure called pre-implantation genetic diagnosis, where one cell is removed from the 8-cell embryo and its DNA is examined. What might you look for when trying to identify the embryo’s sex? (wait) If there’s an X and Y chromosome it’s a boy and if there are two X’s it’s a girl. The parents can decide whether to implant it. Also parents with a genetic disease might want to see if their baby has any identifiable genetic disorders and decide whether to implant based on this information. Pre-implantation genetic diagnosis doesn’t destroy the embryo. Scientists are attempting to adapt this pre-implantation genetic diagnosis procedure and use it to create a stem cell line from one single TOTIPOTENT cell, without destroying the embryo.
The embryonic stem cells inside the blastocyst, here in purple, can generate every cell in the body except placenta and extra-embryonic tissues. These are called CLICK! PLURIPOTENT stem cells…why? (wait for answers) Because they can differentiate into all the 200+ cell types in the body, but they do not form the placenta. CLICK! Pluripotent stem cells can be isolated and grown in culture, or left to develop into more specialized cells in the body.
CLICK! Adult stem cells or tissue-specific stem cells have restricted lineages. Adult stem cells show up when the three distinct layers form in the 14-day-old embryo, and are present in the fetus, baby, child, and so forth. Adult just means they’ve gone further down their lineage pathway than the initial stem cells in the embryo. They are called CLICK! MULTIPOTENT stem cells because they will only become mature cells from the tissue in which they reside. Adult stem cells are present throughout your life and replace fully mature CLICK!, yet damaged and dying cells.
So to review (if time): TOTIPOTENT stem cells come from embryos that are less than 3 days old. These cells can make the TOTAL human being because they can form the placenta and all other tissues. PLURIPOTENT stem cells come from embryos that are 5-14 days old. Embryos and fetuses that are older than 14 days DO NOT contain pluripotent cells. These cells can form every cell type in the body but not the placenta. MULTIPOTENT stem cells are also called adult stem cells and these appear in the 14 day old embryo and beyond. At this point these stem cells will continue down certain lineages and CANNOT naturally turn back into pluripotent cells or switch lineages.
Totipotent
This cell
Can form the
Embryo and placenta
Pluripotent
This cell
Can just form the
embryo
Multi-
potent
Fully mature 17

18. Prokaryotic and eukaryotic cells differ in size and complexity
All cells are surrounded by a plasma membrane.
The semifluid substance within the membrane is the cytosol, containing the organelles.
All cells contain chromosomes which have genes in the form of DNA.
All cells also have ribosomes, tiny organelles that make proteins using the instructions contained in genes.

19. Differentiation causes cells to specialize.
All genes are present in every type of cell.
Only specific genes are actually expressed in each type of cell.

20. Cells have organelles for specific jobs.
Just as body systems are coordinated, cell parts work together

22. Some Cell Organelles
Organelle Function
Nucleus control center of the cell contains DNA which directs the synthesis of proteins by the cell
Mitochondrion carries on the process of cell respiration converting glucose to ATP energy the cell can use
endoplasmic reticulum transport channels within the cell
Ribosome found on the endoplasmic reticulum and free within the cell  responsible for the synthesis of proteins for the cell
cell membrane selectively regulates the materials moving to and from the cell
food vacuole stores and digests food
contractile vacuole pumps out wastes and excess water from the cell
Chloroplast found in plant cells and algae  carries on the process of photosynthesis
cell wall surrounds and supports plant cells

23. Cell Membranes have several functions
Separation from outside environment
Control transport in/out of cell
Recognition of chemical signals

24. Membrane Transport
Passive transport doesn’t require cell input of energy (ATP) Movement is from H  L

25. Active Transport
Molecules transport from lower to higher transportation with the use of cellular energy (uses ATP)
Special proteins transport molecules help transport

26. How can you determine which is passive or active transport?
Diffusion may use special proteins moves from high to low
Active transport may use special proteins moves from low to high

27. Receptor molecules are important for cell communication
The receptors are specific in shape (they are proteins) and to the individual organism

28. Nerves and hormones use specific chemical signals to communicate.
What happens if the signals are blocked?

29. Biochemical Nature of Life
Biochemical processes and molecules are essential fro maintaining Homeostasis (dynamic equilibrium).

30. Metabolism is the sum of the processes in an organism
Metabolism describes ALL chemical reactions

31. Carbon is the main ingredient of organic molecules
Organic compounds are carbon based and contain carbon and hydrogen.
Inorganic compounds are not carbon based. (Water, salt, minerals…)

32. Large and Small Organic Molecules
Small molecular units that are the building block of a larger molecules
Polymer: long chain of small molecular units (monomers)
Living things must both synthesize (build) large molecules and break them down.
Can you think of examples when this is done?- Dehydration synthesis and Hydrolysis

33. Organic chemistry is the study of carbon compounds
Carbohydrates, Proteins, Fats, Nucleic Acids

34. Carbohydrates provide fuel and building material
Carbohydrates are organic compounds made of sugar molecules.
Sugars are combined to synthesize starch.
Starches are broken down (digested) to make sugars.

35. Fats are important for stored energy and membrane structure

36. Proteins are long folded chains made of 20 different kinds of amino acids
Specific shape determines its function.

37. Proteins are synthesized at the ribosomes and folded into specific shapes
Protein shape is essential to function

38. Protein Synthesis
Review the process and outline the steps.
DNA template – used to form mRNA
mRNA binds with ribosome
tRNA bind with mRNA
Amino acids form a polypeptide chain

39. Protein shape determines function

40. Denaturation occurs at high temperatures or various chemical treatments. Shape maybe permanently changed.
How will denaturation effect the functioning of the protein?

41. Structure of DNA (Nucliec Acids) Building Blocks are Nucleotides
Nitrogen Bases
Adenine
Thymine
Guanine
Cytosine

42. Enzymes specialized protein that catalyzes the chemical reactions of a cell
Enzyme shape fits the shape of only particular reactant molecules called the substrate.
Enzymes are specific to the substrate.
The substrate fits the enzyme at the active site.
Identify the enzyme, substrate, and active site

43. Catalytic cycle of a enzyme

44. Enzymes are substrate specific due to the “fit” at the active site of the enzyme.
Enzyme sucrase will catalyze this reaction

45. Factors influence rate of enzyme reactions
Do all enzymes require the same condition?
What happens when enzymes are heated beyond optimal temperatures?

46. Principles of Energy Harvest
Energy flow occurs through the ecosystem
The products of photosynthesis are used in cellular respiration.
The products of cellular respiration are the ingredients for photosynthesis.
What is needed to keep it all going?

47. Photosynthesis: Use light energy from the sun to make sugar from carbon dioxide and water.

48. Chloroplasts are the sites of photosynthesis in plants
The leaf is the organ of photosynthesis.
Photosynthesis takes place in cellular organelles called chloroplasts.

49. Photosynthesis
Two stages of photosynthesis: light independent and light dependent
Different sets of reactions used in each stage
Light dependent produces ATP and allows photolysis to occur (O2 is a waste product)
Light independent allows for carbon fixation

50. Photosynthesis-rates
Photosynthesis does not occur at such a steady rate
Greatly affected by intensity of light, temperature, and CO2 levels
Can be measured directly via CO2 intake and O2 production amounts IF adjusted to account for respiration
Biomass (amount of plant/size) is an indirect method of measuring rate of photosynthesis—indirect b/c a lot of other potential factors

51. Cell Respiration
Energy stored in organic molecules is released as and temporarily stored as ATP

52. Respiration Glycolysis is the first step in respiration
Controlled release of energy from organic compounds in cells to form adenosine triphosphate (ATP)
Glycolysis is the first step in respiration
Two types of respiration: Aerobic (uses oxygen) and anaerobic (without oxygen)
Two types of anaerobic respiration: Lactic acid fermentation (humans) and alcoholic fermentation (yeast)

53. Glycolysis- in the cytoplasm
Glucose enters the cell via the cell membrane and stays in the cytoplasm
After a few modifications and a handful of reactions glucose eventually cleaved into 2 pyruvate (3-C)
2 ATP molecules needed to start, 4 ATP molecules produced, net gain of 2 ATPs

54. Anaerobic Respiration-cytoplasm
Breakdown of organic molecules for ATP WITHOUT using oxygen
Organisms that do this only are called anaerobes
Fermentation is another word for this
Two main pathways: Alcoholic Fermentation and Lactic acid fermentation
ONLY ATP comes from glycolysis

55. The ATP Cycle
ATP is constantly recycled in your cells. A working muscle cell recycles all of its ATP molecules about once each minute. That's 10 million ATP molecules spent and regenerated per second!

56. Cell Respiration takes place in the mitochondria in eukaryotic cells (cell with organelles bound by membrane)
Plants and Animals perform cell respiration. O2
food
ATP

57. Aerobic Respiration-mitochondria
Most efficient pathway to produce ATP
Begins with glycolysis just like anaerobic…pyruvate enters a mitochondrion to finish pathway though
Pyruvate loses a C as CO2, becomes acetyl-CoA
Acetyl-CoA enters Kreb’s cycle where two more CO2 molecules are produced, as well as some ATP
Byproducts of Kreb’s cycle move onto electron transport chain where most ATPs are produced

58. Genetic Nature of Life
DNA is the language of life

59. Nucleotides: The building blocks of DNA
Nitrogen Bases

60. Structure of DNA
Nucleotides of sugar, phosphate, nitrogen bases
The bases pair forming the a double helix A:T and G:C.

61. DNA Replication occurs when cells divide
Occurs before cells divide in mitosis and meiosis
The original parent DNA molecule serves as a template for making a new strand.
Results in two daughter DNA molecules, each consisting of one original strand and one new strand.

62. DNA regulates cell processes with its specific code to synthesize proteins.
DNA to RNA to Protein
Information flows from gene to protein.

63. Step 1: DNA to RNA The DNA template is used to make a single stranded RNA.

64. Step 4: Amino Acids are carried to ribosome and joins according to the genetic code

65. Step 5: The protein chain is created

66. The DNA is wrapped around proteins to form Chromosomes
The Gene is a unit of information within a chromosome
Many genes or on a chromosome

67. Humans have 46 chromosomes in a “normal” body cell.
Chromosomes in a body cell are paired (diploid), so we have two of each one.
Sex chromosomes: Males are XY and Females are XX

68. Chromosomes replicate and separate so body cell have the same chromosomes
Daughter cells are genetically identical!

69. Meiosis makes Sex Cells (gametes)
Meiosis reduces chromosome number from (2n) diploid to (1n) Haploid
Chromosomes replicate and there is a double division in meiosis.
Gametes have one of each set of chromosomes

70. Why do children look like their parents?
Why are they different?
Gametes carry ½ the chromosomes of body cells and are genetically different.
Recombination - when gametes form and at fertilization.

71. How does Mitosis and Meiosis compare?
No Genetic Variation
Genetic Variations

72. Mutations that result in an abnormal number of chromosomes
Nondisjunction occurs when chromosome fail to separate during meiosis.

73. Extra chromosome 21 Human Disorders Due to Chromosomal Alterations
One condition, Down syndrome, affects approximately one out of every 700 children born in the United States – Use a Karyotype to diagnose
Extra chromosome 21

74. Damaged Chromosomes Changes in chromosome structure may also cause disorders. For example, a chromosome may break, leading to a variety of new arrangements that affect its genes.

75. Cloning makes identical genetic copies
Nuclear Transplant Technology

76. What is the source of Variation?
Mutations: Changes in the DNA
Sexual Reproduction: Recombination of chromosomes

77. Damaged Chromosomes Changes in chromosome structure may also cause disorders. For example, a chromosome may break, leading to a variety of new arrangements that affect its genes.

78. Alters the gene product: Altered Protein produced
Mutations of a gene A gene mutation is a change in the nucleotide sequence of DNA.
What could this do to the code?
Alters the gene product: Altered Protein produced

79. A single amino acid substitution in hemoglobin causes sickle-cell disease. How does an individual get this disorder?