CPE 3

Question 1

1. Order

Answer 1

Organisms are highly organized structures that consist of one or more cells. Inside each cell, atoms make up molecules. These in turn make up cell components or organelles. Multicellular organisms, which may consist of millions of individual cells, have an advantage over single-celled organisms in that their cells can be specialized to perform specific functions, and even sacrificed in certain situations for the good of the organism as a whole.

Question 2

2. Sensitivity or Response to Stimuli

Answer 2

Organisms respond to diverse stimuli. For example, plants can bend toward a source of light or respond to touch. Even tiny bacteria can move toward or away from chemicals (a process called chemotaxis) or light (phototaxis). The movement toward a stimulus is considered a positive response, while movement away from a stimulus is considered a negative response.

Question 3

3. Reproduction

Answer 3

Single-celled organisms reproduce by first duplicating their DNA, which is the genetic material, and then dividing it equally as the cell prepares to divide to form two new cells. Many multicellular organisms (those made up of more than one cell) produce specialized reproductive cells that will form new individuals. When reproduction occurs, DNA containing genes are passed along to an organism’s offspring. These genes are the reason that the offspring will belong to the same species and will have characteristics similar to the parent, such as fur color and blood type.

Question 4

4. Adaptation

Answer 4

All living organisms exhibit a “fit” to their environment. Biologists refer to this fit as adaptation and it is a consequence of evolution by natural selection, which operates in every lineage of reproducing organisms. Examples of adaptations are diverse and unique, from heat-resistant Archaea that live in boiling hot springs to the tongue length of a nectar-feeding moth that matches the size of the flower from which it feeds. All adaptations enhance the reproductive potential of the individual exhibiting them, including their ability to survive to reproduce. Adaptations are not constant. As an environment changes, natural selection causes the characteristics of the individuals in a population to track those changes.

Question 5

5. Growth and Development

Answer 5

Organisms grow and develop according to specific instructions coded for by their genes. These genes provide instructions that will direct cellular growth and development, ensuring that a species’ young will grow up to exhibit many of the same characteristics as its parents.

Question 6

6. Homeostasis

Answer 6

To function properly, cells require appropriate conditions such as proper temperature, pH, and concentrations of diverse chemicals. These conditions may, however, change from one moment to the next. Organisms are able to maintain internal conditions within a narrow range almost constantly, despite environmental changes, through a process called homeostasis or “steady state”—the ability of an organism to maintain constant internal conditions. For example, many organisms regulate their body temperature in a process known as thermoregulation. Organisms that live in cold climates, such as the polar bear, have body structures that help them withstand low temperatures and conserve body heat. In hot climates, organisms have methods (such as perspiration in humans or panting in dogs) that help them to shed excess body heat.

Question 7

7. Nutrition

Answer 7

All organisms use a source of energy for their metabolic activities. Some organisms capture energy from the sun and convert it into chemical energy in food; others use chemical energy from molecules they take in.

Question 8

Atom

Answer 8

The atom is the smallest and most fundamental unit of matter. It consists of a nucleus surrounded by electrons. Atoms form molecules.

Question 9

Molecules

Answer 9

A molecule is a chemical structure consisting of at least two atoms held together by a chemical bond. Many molecules that are biologically important are macromolecules, large molecules that are typically formed by combining smaller units called monomers. Examples of macromolecules are ribonucleic acid (RNA) and deoxyribonucleic acid (DNA), essential in various biological roles in coding, decoding, regulation, and expression of genes and contain the instructions for the functioning of the organism that contains it.

Question 10

Organelles

Answer 10

Some cells contain aggregates of macromolecules surrounded by membranes; these are called organelles. Organelles are small structures that exist within cells and perform specialized functions. All living things are made of cells; the cell itself is the smallest fundamental unit of structure and function in living organisms. (This requirement is why viruses are not considered living: they are not made of cells. To make new viruses, they have to invade and hijack a living cell; only then can they obtain the materials they need to reproduce.) Some organisms consist of a single cell and others are multicellular.

Question 11

Cells

Answer 11

Cells are classified as prokaryotic or eukaryotic. Prokaryotes are single-celled organisms that lack organelles surrounded by a membrane and do not have nuclei surrounded by nuclear membranes; in contrast, the cells of eukaryotes do have membrane-bound organelles and nuclei.

Question 12

Tissues

Answer 12

In most multicellular organisms, cells combine to make tissues, which are groups of similar cells carrying out the same function.

Question 13

Organs

Answer 13

Organs are collections of tissues grouped together based on a common function. Organs are present not only in animals but also in plants.

Question 14

Organ Systems

Answer 14

An organ system is a higher level of organization that consists of functionally related organs. For example, vertebrate animals have many organ systems, such as the circulatory system that transports blood throughout the body and to and from the lungs; it includes organs such as the heart and blood vessels.

Question 15

Organisms

Answer 15

Organisms are individual living entities. For example, each tree in a forest is an organism. Single-celled prokaryotes and single-celled eukaryotes are also considered organisms and are typically referred to as microorganisms.

Question 16

Microscope

Answer 16

A microscope is an instrument that is used to magnify small objects. Some microscopes can even be used to observe an object at the cellular level, allowing scientists to see the shape of a cell, its nucleus, mitochondria, and other organelles. It is through the microscope’s lenses that the image of an object can be magnified and observed in detail. A simple light microscope manipulates how light enters the eye using a convex lens, where both sides of the lens are curved outwards. When light reflects off of an object being viewed under the microscope and passes through the lens, it bends towards the eye. This makes the object look bigger than it actually is.

Question 17

History of the Microscope

Answer 17

Before the invention of the microscope was invented, the Romans had already invented and experimented with glasses during the first century (year 100). One of these glass samples involved a piece that had thick middle and thin edges. They discovered that small objects become larger when viewed through this glass sample. This became the earliest form of a lens.

Question 18

Inventors of the Microscope

Answer 18

The first compound microscope, which consists of at least two lenses, was invented in 1590 by Dutch spectacle-makers Zacharias and Hans Jansen.

In 1665, Robert Hooke (1635-1703) examined a thin slice of cork under the microscope that he built. He was able to see and observe small compartments of the cork. He initially named the small compartments “cellulae” because they reminded him of the little rooms in the monastery. These eventually became known as cells.

Some of the earliest microscopes were also made by a Dutchman named Antoine Van Leeuwenhoek (1632-1723). Leeuwenhoek’s microscopes consisted of a small glass ball set inside a metal frame. He became known for using his microscopes to observe freshwater, single-celled microorganisms that he called “animalcules.”

Question 19

Unicellular

Answer 19

1. Made up of a single cell
2. Single cell performs all life functions (eat, reproduce, rid waste, move)
3. Example: amoeba, bacteria

Question 20

Multicellular

Answer 20

1. Made up of more than one cell.
2. Specialized cells perform different functions (nerve cells)
3. Example: humans

Question 21

Cell Theory

Answer 21

In 1838, a German botanist named Mathias Schleiden proposed as a result of his experiments that all plants are made up of cells. A year later, a German physiologist, Theodor Schwann, observed and proposed that all animals are, likewise, made up of cells. In 1858 a German pathologist, Rudolf Virchow, concluded that cells reproduce by forming new cells.

The discoveries of Schleiden, Schwann, and Virchow are summarized into a guiding principle now called the cell theory. The cell theory states that:

All organisms are composed of one or more cells
The cell is the basic unit structure and function of all organisms.
All cells arise from pre-existing cells.
The three statements that comprise the cell theory tell us that the cell is the basic structural, functional, and reproductive unit of all organisms. It also provides us with an operational definition of “life”.

Question 22

Spontaneous Generation

Answer 22

Spontaneous generation is an incorrect and obsolete hypothesis about the possibility of life forms being able to emerge from non-living things.

The theory of spontaneous generation, first comprehensively posited by Aristotle in his book” On the Generation of Animals” around 350 B.C., aims to explain the seemingly sudden emergence of organisms such as rats, flies, and maggots within rotting meat and other decomposable items. The theory suggests that organisms do not descend from other organisms or from a parent, and only require that certain conditions in their environment be fulfilled in order for creation to occur.

Aristotle theorized that non-living matter contained a “vital heat” called pneuma—the concept of a “breath of life” and a combination of the four elements believed to make up all life: earth, air, fire, and water.

He suggested that animals and plants could arise from earth and liquid because there was “vital heat” within all air, there is air in water, and there is water in the earth, meaning there is “vital heat” or “soul” within everything.

Example:
Wet soil after a flood was believed to create amphibians such as frogs and toads.
Garbage in the streets was thought to create rats.
Salamanders were thought to be borne within fire (they often hide inside logs and were probably trying to escape the blaze!).
Oyster shells were believed to form as the earth solidified around them and the “vital heat” grew the creature within.
Crocodiles in Egypt were thought to have emerged from the mud with the sunshine as a catalyst

Question 23

Disproving of Spontaneous Generation Theory

Answer 23

Francesco Redi was an Italian physician and the first scientist to suspect that the theory of spontaneous generation may be flawed, so he set up a simple experiment. He placed fresh meat into two different jars, one with a muslin cloth over the top, and the other left open. A few days later, the open jar contained maggots, while the covered container did not. He saw this as proof that maggots had to come from fly eggs and could not spontaneously generate

Over 100 years later, John Needham, an English naturalist and an avid supporter of spontaneous generation theory, performed an experiment in which he boiled up a broth and poured it into a covered flask—at this time, people were aware that the process of boiling removed the microorganisms that they called “animalcules”. After a short while, the broth was filled with microorganisms, a revelation to Needham who claimed these had arisen through spontaneous generation. His experiment was contested for the fact he did not heat the broth for long enough and his animalcules were heat resistant.

Another Italian scientist, Lazzaro Spallanzani, performed a similar experiment to Needham and found that if the broth was heated after the flask was sealed rather than before, the organisms did not generate. He decided that Needham’s broths had been contaminated between the boiling pan and the flask.

Needham’s response claimed that air was necessary for the spontaneous generation and that the “vital heat” in the air had been destroyed during Spallanzani’s experiment.

Finally, in 1859, a French scientist named Louis Pasteur designed a series of flasks with the necks bent into an S shape. The necks were fashioned so that fresh air could reach the flasks but were bent in such a way that any air-borne microbes would be trapped at the bottom of the curves.

He boiled the broth inside the flask and did not see any microbes in the broth for many months. When he eventually removed the top from the flask and left it off, he found the liquid to be teaming with microorganisms within a few days. Therefore, he had proved that the microbes from which life arises are present within the air and are not spontaneously generated.

Conclusion: Cells can only arise from pre-existing cells.

Question 24

Introduction to Prokaryotic Cells

Answer 24

Prokaryotic cells lack a nuclear envelope and membrane -bound organelles, an example of which is the bacterial cell. Bacterial cells are small, about 0.2 to 5μm (micrometer), less complex, usually exist in unicellular forms and have limited capabilities compared to eukaryotic cells

Question 25

Introduction to Eukaryotic Cells

Answer 25

Eukaryotic cells are generally larger and have very distinct nuclei that are clearly surrounded by nuclear membranes. They also have numerous membrane-bound organelles found in the cytoplasm. Protists, plants, fungi and animals have eukaryotic cells.

Question 26

PROKARYOTIC CELL

Answer 26

The absence of a membrane-bound nucleus mainly distinguishes prokaryotic cells from eukaryotic cells. Also, prokaryotic cells lack membrane-bound organelles that are found in eukaryotic cells. The following structures are found in prokaryotic cells.

Capsule - a sticky outer layer that provides protection
Cell wall - a structure that confers rigidity and shape to the cell
Plasma membrane - a structure that serves as a permeability barrier
Plasmid - a genetic structure in a cell that can replicate independently of the chromosomes, typically a small circular DNA strand in the cytoplasm of a bacterium.
Nucleoid - a DNA-containing region with cytoplasm
Cytoplasm - the region where all cytoplasmic organelles are found
Ribosome - the site where protein is synthesized
Pilus (Plural, Pili) - a hair-like appendage that functions in adhesion
Flagellum - facilitates movement of bacteria.

Question 27

Cell Membrane

Answer 27

The cell membrane (also known as the plasma membrane or plasmalemma) is a double-layered membrane that encloses the cell. It is made up of two layers of phospholipids with proteins and carbohydrates scattered outside, within, and inside the bilipid layer like a mosaic

The cell membrane or plasma membrane functions as:

the boundary between the cell and its external environment; and
as a structure that controls the movement of substances in and out of the cell (because it is a semipermeable membrane, it allows the entry of some substances, such as water, and prevents the entry of others).
The cell membrane is a very flexible membrane, allowing the cell to change its shape when needed. The proteins found in a cell membrane are important for the cell to communicate with its neighbors (cell to cell interaction).

Question 28

Cytoplasm

Answer 28

Inside the cell membrane and surrounding the nucleus is a part of the protoplasm called cytoplasm. The cytoplasm forms the largest part of the cell where most life processes occur. It is made up of a fluid-like substance where membrane-bound organelles (small structures inside the cell that carry specific functions) are located.

Question 29

Cytoplasmic Organelles: 1. Mitochondria

Answer 29

Mitochondria (singular: mitochondrion) are small, double-membrane, spherical, or sausage-shaped organelles involved in the production of energy. The mitochondrion is popularly known as the powerhouse of the cell. The energy produced by the mitochondria is important for the vital activities of cells, such as growth and reproduction. Cells that need more energy, like muscles cells, contain more mitochondria. Recent findings show that this organelle also contains its own DNA and RNA and is capable of producing its protein. It is, therefore, capable of division to produce more mitochondria.

Question 30

Cytoplasmic Organelles: 2. Endoplasmic Reticulum

Answer 30

The endoplasmic reticulum (ER) is a network of intercommunicating channels in the cytoplasm. It is composed of membrane-enclosed sacs and tubules. The two types of endoplasmic reticulum are the rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER).

The more common type is the RER, described as such due to the presence of ribosomes (the structure where protein is synthesized) on its
membrane surface, giving it a “rough” appearance.
The RER plays a role in the production of protein,
as well as in its folding, quality control and dispatch.

On the other hand, the SER is a more tubular non-granular structure due to the absence of ribosomes. It plays a role in the manufacture and metabolism of lipids. It also plays a role in the biosynthesis of steroid
hormones in endocrine cells.

Question 31

3. Golgi Apparatus

Answer 31

The ( Golgi Body or Golgi Complex) is composed of sets of cisternae and numerous vesicles filled with fluid and suspended substances. It is responsible for the processing, packaging, and sorting of secretory materials for use within and outside the cell. For example, after protein is synthesized by the ribosomes, it passes into the channels of the endoplasmic reticulum and moves into the fluid-filled sacs of the Golgi apparatus-a membranous pouch, that buds off from the smooth ER, then migrates and fuses

Question 32

Lysosomes

Answer 32

Lysosomes are small, spherical, membrane-bound organelles that contain a number of enzymes for intracellular digestion. A lysosome is bounded by a single-layered membrane. It contains around 40 kinds of enzymes that help digest food, disease-causing bacteria engulfed by white blood cells, and worn-out and broken parts of the cell.

Question 33

Cytoplasmic Inclusion

Answer 33

Cytoplasmic Inclusions are non-membranous substances and structures suspended in the cytoplasm with varying functions. Their presence or absence depends on the cell type (although ribosomes are present in all cells.)

Question 34

1. Ribosomes

Answer 34

Ribosomes are small granular structures made up of RNA and proteins. The RNA found in ribosomes is produced in the nucleus and enters the cytoplasm through the nuclear pores. Ribosomes are involved in the production of proteins in a process called protein synthesis. Each ribosome is composed of large and small subunits that are tightly bound to each other.

Question 35

2. Centriole

Answer 35

The centriole has a central role in cell division where it participates in the formation of the mitotic spindle. It is usually adjacent to the nucleus. Its wall is composed of nine groups of parallel subunits arranged in a longitudinal fashion. Each of the nine groups consists of three microtubules aligned and fused together so that they appear as 3 circles in a row.

Question 36

3. Cytoskeleton

Answer 36

The cytoskeleton is a structure that helps cells maintain their shape and internal organization, and it also provides mechanical support that enables cells to carry out essential functions like division and movement.

Question 37

Adaptation and Modification

Answer 37

Cell specialization has contributed greatly to the adaptation of organisms. Specialized cellular modifications are alterations in cells that distinguish them from one another: Cellular modifications are commonly found in eukaryotic cells, where there is a need for cell specialization.

For instance, cells that absorb nutrients in the small intestine have microvilli. These are extensions on the cell membranes that help increase the surface area of the cell, thus, facilitating increased absorption of nutrients.

Question 38

Red blood cells (RBCs)

Answer 38

have a biconcave disc shape and are highly deformable. This allows for easy movement through blood vessels, which can be as small as 2 to 3 (micrometer) in diameter. The red blood cells and platelets lose their nucleus as they mature. In the case of RBCs, losing the nucleus increases the surface area for gas exchange, thus, enabling optimal oxygenation of tissues in the body.

Question 39

Sperm Cell

Answer 39

Sperm cells have a tail, the flagellum, which propels it toward the egg cell for fertilization. Likewise, sperm cells have plenty of mitochondria along with their middle piece, which powers the flagellum to move the sperm cells toward the egg cell.

Question 40

Root hair cells

Answer 40

The function of the root hair cell is to obtain water from the ground and transport this to the Xylem. Plants absorb water from the soil by osmosis. Root hair cells are adapted for this by having a large surface area to speed up osmosis. Another adaptation that they have is root hair cells have a large permanent vacuole. This speeds up the movement of water by osmosis.
The water which enters the root hair cell then travels up the Xylem and travels to the leaves.

Question 41

Nerve Cells

Answer 41

Nerve Cells, which are mostly elongated, facilitate the transmission of impulses from the brain and the spinal cord to the different parts of the body.

Question 42

Tracheal cells

Answer 42

Tracheal cells have cilia that beat and drive air impurities or foreign particles and mucus secretion up the trachea to the mouth where they can be coughed out.

Question 43

Cell-cell junctions

Answer 43

Another specialized modification observed in multicellular cells is the cell-cell junctions, the points where two cells come together. Through the cell junctions, the cells are joined in long-term associations, forming tissues and organs.

Question 44

What is Fluid Mosaic Model?

Answer 44

The fluid mosaic model was first proposed by Seymour Jonathan Singer and Garth L. Nicolson in 1972 to describe the structure of cell membranes.

The model is “fluid” because the various functional macromolecules embedded in the phospholipid matrix of the cell membrane can move about the surface of the cell. Also, the membrane, according to this model, is made up of various parts (ie., proteins, carbohydrates, and cholesterol) that pave the surface of the matrix just like individual tiles, hence the “mosaic” appearance.

Question 45

Major Components of Plasma Membrane

Answer 45

Phospholipids: make up the majority of the cell membrane
Cholesterol: found in between the phospholipids and acts as a fluidity buffer
Proteins: can be found on the surface or embedded across the cell membrane and involved in the transport of materials in and out of the cell membrane.
Carbohydrates: generally attached to proteins and lipids on the surface of the cell membrane

Question 46

Phospholipids

Answer 46

This phospholipid molecule is composed of a hydrophilic head and two hydrophobic tails. The hydrophilic head group consists of a phosphate-containing group attached to a glycerol molecule. The hydrophobic tails, each containing either a saturated or an unsaturated fatty acid, are long hydrocarbon chains.

The main fabric of the membrane is composed of amphiphilic or dual-loving, phospholipid molecules. The hydrophilic or water-loving areas of these molecules are in contact with the aqueous fluid both inside and outside the cell. Hydrophobic, or water-hating molecules, tend to be non-polar. A phospholipid molecule consists of a three-carbon glycerol backbone with two fatty acid molecules attached to carbons 1 and 2, and a phosphate-containing group attached to the third carbon. This arrangement gives the overall molecule an area described as its head (the phosphate-containing group), which has a polar character or negative charge, and an area called the tail (the fatty acids), which has no charge. They interact with other non-polar molecules in chemical reactions, but generally do not interact with polar molecules. When placed in water, hydrophobic molecules tend to form a ball or cluster.

The hydrophilic regions of the phospholipids tend to form hydrogen bonds with water and other polar molecules on both the exterior and interior of the cell. Thus, the membrane surfaces that face the interior and exterior of the cell are hydrophilic. In contrast, the middle of the cell membrane is hydrophobic and will not interact with water. Therefore, phospholipids form an excellent lipid bilayer cell membrane that separates fluid within the cell from the fluid outside of the cell.

Question 47

Cholesterol

Answer 47

Cholesterol helps maintain the fluidity of cell membranes and by adding firmness to the plasma membrane also prevents it from becoming overly fluid, so cholesterol generally helps the plasma membrane maintain its structure.

Question 48

Proteins

Answer 48

Proteins make up the second major component of plasma membranes, which are two types. Proteins found only on the surface of the cell are called peripheral proteins, whereas those that cross the bilayer are called integral proteins.

Question 49

Function of Proteins

Answer 49

Peripheral Proteins: loosely bound to the surface of the membrane. cell surface identity marker (antigen)

Integral Proteins: penetrate lipid bilayer. transport proteins

Question 50

Carbohydrates

Answer 50

Carbohydrates are the third major component of the cell membrane
The extracellular surface of the cell membrane is decorated with carbohydrates groups attached to lipids and proteins
play a key role in cell-cell recognition

Question 51

Two Types of Carbohydrate in Membrane
1. Glycolipid

Answer 51

a lipid molecule that has one or more carbohydrate units covalently bonded to it and an essential part of the cell membrane.
acts as receptors at the surface of the red blood cell and also helps determine the blood group of an individual
some microorganisms use glycolipids on their cell surface as well. This helps the immune system destroy pathogens from the body.

Question 52

Two Types of Carbohydrate in Membrane
2. Glycoprotein

Answer 52

a protein molecule that has one or more carbohydrate units covalently bonded to it.
identifies the cell type and allows it to bind with other cells of the same type.
repel other cell types and other particles.

Question 53

Characteristics of Living Things

Answer 53

Movement: An action by an organism or part of an organism causing a change of position or place

Cellular Respiration: The chemical reactions in cells that break down nutrient molecules and release energy for metabolism.

Sensitivity: The ability to detect or sense stimuli in the internal or external environment and to make appropriate responses.

Growth: A permanent increase in size and dry mass by an increase in cell number or cell size or both.

Reproduction: The processes that make more fo the same type of organism.

Excretion: Removal from organisms of the waste products of metabolism (chemical reactions in cells including respiration), toxic materials and substances in excess of requirements.

Nutrition: Taking in of materials for energy, growth and development: plants require light, carbon dioxide, water and ions; animals need organic compounds and ions and usually need water.

Question 54

Levels of Organization

Answer 54

— subatomic particles
— atoms
— molecules
— macro molecules
— cells
— tissue
— organs
— organ systems
— organism
— population
— community
— ecosystem
— biome
— biosphere

Question 55

Modern Cell Theory

Answer 55

1. The cell is the smallest living unit in all organisms.
2. All living things are made of cells.
3. All cells come from other pre-existing cells