Introduction to Cells

Question 1

Explain the 3 claims of Cell Theory

Answer 1

1. All living things are composed of cells
2. All cells come from pre-existing cells
3. Cells are the smallest unit of life

Question 2

Explain 4 Exceptions to Cell Theory

Answer 2

1. Skeletal muscles — made up of muscle fibers each containing hundreds of nuclei but have no nucleus
   (shows not all cells have one nucleus — )
2. Fungi (e.g Aseptate Fungi) —– consists of thread-like structures called hyphae — hyphae contain many nuclei but have no nucleus
   (shows not all cells have one nucleus — )
3. Giant algae (e.g Acetabularia) —– are giant cell structures as large as 100mm.
   (shows cells are not always small)
4. Red blood, just like Fungi and Skeletal muscles, have many nuclei but have no nucleus
   (shows not all cells have one nucleus — )
   (– makes the cell look concaved – pinched in)

Question 3

Explain cell theory is still accepted despite there being exceptions to the theory?

Answer 3

there is still a strong overall trend of living organisms that follow cell theory, so cell theory cannot be abandoned.

Question 4

What are the Kingdoms of Life?

Answer 4

Animals
Plants
Fungi
Bacteria
Protists

Animals, plants & fungi —- are multicellular

Bacteria & Protists —– are unicellular

Question 5

State the three parts that make up a cell?

Answer 5

1. Plasma membrane
2. Cytoplasm
3. Organelles

Question 6

Describe how the surface area to volume ratio relates to Cell size?

Answer 6

The size of a cell is determined by a cells by its need to exchange resources with its environment. The volume of a cell determines its need (e.g its need to produce heat or waste). The surface area of a cell determines the cell ability to meets its need (e.g its ability to release heat or waste).

Keynote:
production of heat or waste – relates to volume
release of heat or waste from the cell — relates to surface area

Question 7

Why is a cell’s size limited?

Answer 7

As the cell size increases, there is an increase in the cell’s volume to surface area ratio, and the volume of the cell increase much faster than its surface area, decreasing the cell ability to meets its needs (cell is now less ineffiecnt in exchange of material and energy — (e.g slower rate of releasing heat and waste)

Question 8

Why are viruses considered non living?

Answer 8

Viruses are made of
— a capsid (protein)

1. Viruses lack cell structure
2. Cant ingest nutrients
3. Cannot grow or maintain a stable environment
4. Do not self reproduce (depend on a host)

Question 9

Explain functions of (Life) in living organisms?

Answer 9

Have to:

1. Have a metabolism
   (chemical reaction inside a cell/cells)
   (e.g cell respiration & photosynthesis)
2. Display Sensitivity
   (Have to be sensitive to things)
   (Perceive and respond to changes in the environment)
   (e.g respond to sound, light, etc)
3. Display Homeostasis
   (ability to maintain a stable internal environment)
   (e.g in humans — a homeostasis example —- is regulating body temperature)
4. Growth & develop
   (an irreversible increase in size)
5. Reproduce
   (either by asexual or sexual means)
6. Obtain nutrients (nutrition)
   (feeding on food to provide energy, sustain health, and enable growth)
7. Undergo Excretion
   (expelling on metabolic. waste)
   (e.g elimination after digestion)

Question 10

Describe how the Paramecium, a unicellular organism, shows the functions of life?

Answer 10

1. Metabolism
   …………………………………………………………………………………………………..
   Produce enzymes — Source of many reactions in the cytoplasm
   …………………………………………………………………………………………………..
2. Sensitivity (Response)
   …………………………………………………………………………………………………..
   Reacts to stimuli,
   e.g. reverses its direction of movement when it touches a solid object or if it interacts with light
   …………………………………………………………………………………………………..
3. Homeostasis
   …………………………………………………………………………………………………..
   Limit conditions within the cell
   (e.g Expel excess water through contractile vacuoles)
   …………………………………………………………………………………………………..
4. Nutrition
   …………………………………………………………………………………………………..
   Feeds on smaller organisms by ingesting and digesting them in vesicles (endocytosis)
   …………………………………………………………………………………………………..
5. Excretion
   …………………………………………………………………………………………………..
   Expels waste products of metabolism by plasma membrane
   e.g. CO2 from respiration diffuses out of the cell
   …………………………………………………………………………………………………..
6. Growth
   …………………………………………………………………………………………………..
   Increases in size and dry mass by accumulating organic matter and minerals from its food
   …………………………………………………………………………………………………..
7. Reproduction
   …………………………………………………………………………………………………..
   reproduces asexually using mitosis or sexually using meiosis and gametes
   …………………………………………………………………………………………………..

Question 11

Describe the role of food vacuoles, contractile vacuoles, food vacuole, gullet and cilia of a Paramecium

Answer 11

Contractile vacuoles — get rid of excess water and help a cell maintain turgur pressure (turgur pressure is the pressure in a cell that pushes cell contents outward)

Food Vacuole — encapsulate food consumed by the paramecium, stores it and digests it

Gullet — used for feeding and forms food vacuole

Cilia — used for locomotion (movement)

Question 12

Chlamydomonas have identical functions of life with a Paramecium except for:

Answer 12

1. Nutrition
   …………………………………………………………………………………………………..
   Chlamydomonas Produces their own food by photosynthesis using a chloroplast that occupies much of the cell whilst paramecium feed on smaller organisms
   …………………………………………………………………………………………………..
2. Excretion
   …………………………………………………………………………………………………..
   Expels waste products of metabolism, e.g. oxygen
   from photosynthesis whilst paramecium expels CO2
   …………………………………………………………………………………………………..
3. Growth
   …………………………………………………………………………………………………..
   Increases in size and dry mass due to photosynthesis whilst parameciums need to ingest other organism to obtain carbon compounds and nutrients
   …………………………………………………………………………………………………..

Question 13

Describe how the Scenedesmus shows the functions of life?

Answer 13

1. Metabolism
   …………………………………………………………………………………………………..
   production of organic molecules via photosynthesis
   Also produces enzymes
   …………………………………………………………………………………………………..
2. Sensitivity (Response)
   …………………………………………………………………………………………………..
   Scenedesmus may form colonies for protection from the external environment
   …………………………………………………………………………………………………..
3. Nutrition
   …………………………………………………………………………………………………..
   Produces its own food by photosynthesis
   …………………………………………………………………………………………………..
4. Excretion
   …………………………………………………………………………………………………..
   Expels waste products of metabolism, e.g. oxygen
   from photosynthesis diffuses out of the cell
   …………………………………………………………………………………………………..
5. Growth
   …………………………………………………………………………………………………..
   Increases in size and dry mass by accumulating organic matter and minerals from its food
   …………………………………………………………………………………………………..
6. Reproduction
   …………………………………………………………………………………………………………………
   Daughter cells form as non-motile autospores via the internal asexual division of the parent cell
   …………………………………………………………………………………………………..

Question 14

Describe what Emergent properities are?

Answer 14

Emergent properities are properities that arise when individual components work together to produce new functions

Question 15

Give examples of Emergent Properities

Answer 15

1. Cells in muticellular organisms coming together to form tissues (muscle cells forming cardiac tissue)
2. Mutliple tissue working collectively to produce organs (cardiac tissues forming the heart)
3. Organs interacting with other parts of the body to form systems (Heart working with blood and blood vessels to form vascular system)
4. Systems working together to carry out the functions of life in an organisms (body systems working together to form humans and make us living)

Question 16

Explain the process of differentiation

Answer 16

involves the expression of some genes and not others in a

cell’s genome. (some gene are activated while others are turned off)

Question 17

Stems are unspecialized cells that can give rise to many types of cells in multicellular organisms. State two characteristics of stem cells

Answer 17

1. Have self-renewal (ability to divide many times)

2. Have Potency (ability to differentiate into specialized cells)

Question 18

State the 4 types of Stem cells

Answer 18

1. Totipotent
   - these stem cells can differentiate into all cells in an organism
   (Example: can give rise to a zygote as well as meristematic tissue in plants)
2. Pluripotent
   - these stem cells give rise to many cell of the body most notably embryonic cells
   (Example: Embryonic stem cells)
3. Multipotent
   - these stem cells can give rise to a limited number of cell types
   (Example: Bone Marrow stem cells)
   (all blood types develop from multipotent stem cells)
4. Unipotent
   - these stem cells cannot differentiate but are capable of self renewal (Example: Muscle stem cells)

Question 19

Define Stem cells?

Answer 19

Stem cells are cells that have the capacity to divide

and to differentiate along different pathways.

Question 20

Describe why stem cells are used therapeutically

Answer 20

Stem cells are used therapeutically to help regenerate, repair, and or replace damaged and diseased cells. Embryonic stem cells in particular have been known to help improve the health of patients suffering from incurable diseases.

Question 21

State 2 instances in which stem cells have been used effectively as form of medical (therapeutic) treatment.

Answer 21

1. Stargardt’s disease
   - a genetic disorder that is caused by a mutation in the gene ABCA4. Common amongst children aged 6 - 12 years old, this disorder causes progressive vision loss and blindness.

Treatment:
Can be treated by replacing dead cells in the retina with functioning ones derived from embryonic stem cells. For example, in 2010, a woman in her 50’s was treated by having 50,000 embryonic stem cells injected into her eyes. The stem cells attached to the women’s retina and remained there for 4 months. This treatment improved her sight with no harmful side effect. Though more studies need to be conducted, there is strong evidence supporting the effectiveness of embryonic stem cells in treating Stargardt’s disease

2. Leukemia
   - types of cancer that leads to an abnormal production rate of white blood cells, causing a person to have an extremely abnormal white blood cell count.
   (Normal white blood cell count: 4,000 to 11,000 white blood cells — a person with leukemia may have as many as 100,000 white blood cells)

Treatment:
Fluid is extracted from the bone marrow of a patient. The adult stem cells in the fluid are stored and frozen. The patient is then given a high dosage of chemotherapy to kill cancer cells in the bone marrow until the bone marrow loses its ability to produce blood cells. The adult stem cells are then re-added to the patient’s body and begin to re-establish themselves in the bone marrow, causing the production of new red and white blood cells

Question 22

What are the ethical concerns associated with the use of embryonic stem cells as therapeutic treatment?

Answer 22

Concerns stem from the source of embryonic stems cells, namely embryos. Embryoes are produced in ivitro fertislation (IV) clinics. A large number of embryos produced at IV clinics are never implanted but rather destroyed and or used for research. Some argue the use of embryonic stem cells is unethical because it involves the deliberate production and destruction of embryos, human life in its very early stages.

However, some also argue that are only balls and lack the essential features of a human life. Others also say that embryoes lack a nervous system, so the don’t feel pain or suffering during the procedure.

The ethical tension that exists around the use of embryonic stem cells make them forces scientists to question the ethics behinds their actions. Thus, adult stem cells are more often used in comparison to embryonic stem cells due the less ethical controversy that exists around them.

Question 23

Stated and Differentiate between the different types of Microscopes

Answer 23

1. light microscope
   - can observe true color of speciemen as well as the entire unicellular organism or cell
   - Sample preparation is easy
   - living material may be used
2. Electron Microscopes
   First one:
   TEM (Transmission electron microscope)
   - used to observe ultrastructure of cell

SEM (Scanning electron microscope)
- used to observe external features of organism or cell

Both TEM & SEM have a high resolution and magnification relative to the light microscope
- however, sample preparation isn’t as easy