W8 Ch.31 & 33

Question 1

Plasma Membrane

Answer 1

The plasma membrane, also known as the cell membrane, is a semi-permeable lipid bilayer that surrounds the cytoplasm of a cell. It serves as a boundary between the cell’s internal environment and the external environment, controlling the passage of substances in and out of the cell

Question 2

Selectively Permeable

Answer 2

Selectively permeable refers to a property of membranes that allows only certain substances to pass through while restricting the passage of others. The plasma membrane is selectively permeable, allowing some molecules and ions to pass through freely while blocking others

Question 3

Semipermeable

Answer 3

Semipermeable is a term used interchangeably with selectively permeable. It describes membranes that permit the passage of some substances but not others based on factors such as size, charge, and solubility

Question 4

Cell Wall

Answer 4

The cell wall is a rigid, structural layer that surrounds the plasma membrane of plant cells, fungi, bacteria, and some protists. It provides support, protection, and shape to the cell, and it is primarily composed of cellulose in plant cells and peptidoglycan in bacterial cells

Question 5

Diffusion

Answer 5

Diffusion is the passive movement of molecules or ions from an area of higher concentration to an area of lower concentration, driven by the random motion of particles. It occurs until equilibrium is reached, where there is an equal distribution of molecules throughout the space

Question 6

Facilitated diffusion

Answer 6

Facilitated diffusion is a type of passive transport in which molecules or ions move across the plasma membrane with the assistance of transport proteins. Unlike simple diffusion, facilitated diffusion involves specific carrier proteins or channel proteins that facilitate the movement of substances down their concentration gradient

Question 7

Osmosis

Answer 7

Osmosis is the diffusion of water molecules across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration. It is driven by the concentration gradient of solutes and serves to equalize the concentration of solutes on both sides of the membrane

Question 8

Channel

Answer 8

A channel, in the context of cell biology, refers to a type of membrane protein that forms a pore or channel through which specific ions or molecules can pass across the membrane. Channels facilitate the movement of substances down their electrochemical gradient, typically without requiring energy input

Question 9

Aquaporin

Answer 9

Aquaporins are a specific type of channel protein found in cell membranes, particularly in the plasma membrane of plant and animal cells. They facilitate the rapid movement of water molecules across the membrane, allowing cells to regulate water balance and osmotic pressure

Question 10

Active Transport

Answer 10

Active transport is the movement of molecules or ions across a membrane against their concentration gradient, from an area of lower concentration to an area of higher concentration. This process requires the input of energy, usually in the form of ATP, to drive the transport of substances against their natural gradient

Question 11

Electrochemical Gradient

Answer 11

An electrochemical gradient is a combined gradient of concentration and electrical charge that drives the movement of ions across a membrane. It consists of both a concentration gradient (due to differences in ion concentration) and an electrical gradient (due to differences in charge), which together determine the direction and rate of ion movement

Question 12

Turgor Pressure

Answer 12

This refers to the pressure exerted by the fluid (usually water) inside the central vacuole of plant cells against the cell wall. It plays a crucial role in maintaining the rigidity and shape of plant cells, supporting structures, and aiding in processes such as cell expansion

Question 13

Desiccation

Answer 13

Desiccation is the process of extreme drying or dehydration. In plants, it often refers to the loss of water from tissues, leading to wilting, cellular damage, and sometimes death, particularly in drought conditions

Question 14

Transpiration

Answer 14

Transpiration is the process by which water is lost from plant tissues, primarily through the stomata (tiny pores on the surface of leaves). It occurs as water evaporates from the leaf surface into the atmosphere. Transpiration plays a vital role in plant cooling, nutrient uptake, and water movement within the plant

Question 15

Endodermis

Answer 15

The endodermis is a specialized layer of cells in plant roots. It surrounds the vascular tissue (xylem and phloem) and serves as a selective barrier, regulating the movement of water, minerals, and other substances from the soil into the vascular system of the plant

Question 16

Casparian Strip

Answer 16

This is a band of impermeable, waterproof material found in the cell walls of the endodermis in plant roots. It forces water and solutes to pass through the selectively permeable plasma membrane of endodermal cells, ensuring regulated uptake of water and nutrients into the plant

Question 17

Nitrogen Fixation

Answer 17

Nitrogen fixation is the biological process by which certain microorganisms, primarily bacteria and archaea, convert atmospheric nitrogen (N2) into ammonia (NH3) or other nitrogen-containing compounds that plants can utilize for growth and development. This process is crucial for maintaining soil fertility and the nitrogen cycle

Question 18

Stomata

Answer 18

Stomata (singular: stoma) are small pores present on the surfaces of plant leaves and stems. They regulate gas exchange, allowing for the uptake of carbon dioxide (CO2) needed for photosynthesis and the release of oxygen (O2) produced during photosynthesis. Stomata also play a role in transpiration and water regulation in plants

Question 19

Source

Answer 19

In the context of plant physiology, “source” refers to any plant organ or tissue that produces and releases organic compounds (such as sugars) through photosynthesis or other metabolic processes. Typically, leaves are the primary sources of organic compounds in plants, while sinks, such as roots and developing fruits, consume these compounds for growth and energy

Question 20

Sink

Answer 20

a “sink” refers to a location or organism that absorbs or consumes resources, energy, or materials from its surroundings. This term is often used in the context of nutrient cycling or energy flow within ecosystems

Question 21

Xerophyte

Answer 21

A xerophyte is a type of plant that is adapted to survive in environments with limited water availability. These plants have various adaptations, such as deep root systems, thick cuticles, reduced leaf surface area, or succulent tissues, to conserve water and thrive in arid or semi-arid conditions

Question 22

Translocation

Answer 22

In biology, translocation refers to the movement of substances, such as nutrients or organic compounds, within a living organism. For example, in plants, translocation typically refers to the movement of sugars produced during photosynthesis from the leaves to other parts of the plant, such as roots, stems, or developing fruits

Question 23

Macronutrient

Answer 23

Macronutrients are essential nutrients that are required by organisms in relatively large quantities to sustain life and promote growth, development, and metabolism. In the context of human nutrition, macronutrients include carbohydrates, proteins, and fats

Question 24

Micronutrient

Answer 24

Micronutrients are essential nutrients that are required by organisms in relatively small quantities but are nevertheless crucial for various physiological functions and overall health. Examples of micronutrients include vitamins, minerals, and trace elements

Question 25

Essential Element

Answer 25

An essential element is a chemical element that is necessary for the growth, development, and survival of an organism. These elements are required in specific quantities for various physiological functions and biochemical processes. In plants, essential elements include carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, zinc, copper, molybdenum, boron, and chlorine

Question 26

Epiphyte

Answer 26

An epiphyte is a type of plant that grows harmlessly upon another plant (such as a tree) and derives its nutrients and moisture from the air, rain, and debris accumulating around it, rather than from the host plant itself. Epiphytes are commonly found in tropical rainforests, where they often grow on the branches or trunks of large trees

Question 27

Symplast

Answer 27

The symplast refers to the interconnected network of living plant cells connected by plasmodesmata, allowing for the movement of water, ions, and small molecules between cells

Question 28

Apoplast

Answer 28

The apoplast refers to the extracellular space in plant tissues, including cell walls and intercellular spaces, through which water and solutes can pass freely without crossing a cell membrane

Question 29

Turgid

Answer 29

Turgid describes a plant cell when it is fully swollen with water due to osmotic pressure. In this state, the cell is firm and rigid, providing structural support to the plant

Question 30

Flaccid

Answer 30

Flaccid describes a plant cell when it lacks turgor pressure due to a loss of water. In this state, the cell becomes limp and may wilt

Question 31

Water Potential

Answer 31

Water potential is a measure of the potential energy of water in a system compared to pure water. It includes both pressure potential (physical pressure exerted on water) and solute potential (effect of dissolved solutes on water potential)

Question 32

Solute Potential

Answer 32

Solute potential, also known as osmotic potential, is a component of water potential determined by the concentration of solutes in a solution. More solutes result in a lower solute potential, causing water to move into the solution

Question 33

Membrane Potential

Answer 33

Membrane potential is the electrical potential difference across a cell membrane, resulting from the unequal distribution of ions across the membrane. It is essential for various cellular processes, including the transmission of nerve impulses and muscle contractions

Question 34

Guttation

Answer 34

Guttation is the process by which water droplets are exuded from the tips or edges of leaves of some plants, particularly in the morning or at night, due to root pressure forcing water up from the roots

Question 35

Root Pressure

Answer 35

Root pressure is the upward force exerted on water in the roots of plants, primarily due to active transport of minerals into the root xylem, resulting in the movement of water into the xylem by osmosis

Question 36

Leaching

Answer 36

Leaching is the process by which water-soluble nutrients or minerals are washed out of the soil by the action of water moving downwards through the soil profile

Question 37

Ammonification

Answer 37

Ammonification is the conversion of organic nitrogen compounds into ammonia (NH3) or ammonium ions (NH4+) by decomposer organisms such as bacteria and fungi during the decay of organic matter

Question 38

Nitrification

Answer 38

Nitrification is the biological oxidation of ammonia (NH3) or ammonium ions (NH4+) into nitrite (NO2-) and then into nitrate (NO3-) by specialized bacteria in the soil, primarily Nitrosomonas and Nitrobacter species