IQ2 - Module 1: Cells As A Basis Of Life

Question 1

what are transport processes?

Answer 1

The various transport processes that control the movement of molecules in and out of cells occurs by either:
▪ Passive transport
▪ Active transport

Question 2

what is passive transport?

Answer 2

Passive transport is the movement of molecules across the cell membrane without the input of cellular energy.

Molecules move from areas of high concentration to areas of low concentration going along the concentration gradient.
Passive transport includes:
▪ Diffusion
▪ Osmosis

Question 3

what is diffusion?

Answer 3

Diffusion is a process where molecules move across the cell membrane from an area of high concentration to an area of low concentration until equilibrium is reached.

Note: equilibrium means a balance has been reached on both sides of the cell membrane where molecules move equally in each direction.

There are two types of diffusion:
▪ Simple diffusion
▪ Facilitated diffusion

Question 4

what is simple diffusion?

Answer 4

Simple diffusion is the movement of small, uncharged molecules (e.g. O2, CO2) easily through the phospholipid bilayer.

Question 5

what is facilitated diffusion?

Answer 5

Facilitated diffusion involves the aid of transport proteins to allow the movement of large molecules and small charged molecules across the cell membrane.

The two main types of transport proteins involved are:
▪ Channel proteins – control the movement of specific ions (e.g. Na+, Cl-)
▪ Carrier proteins – control the movement of larger molecules (e.g. glucose, amino acids) by binding to the molecules and changing shape

Question 6

what is osmosis?

Answer 6

Osmosis is the movement of water across the cell membrane through special tiny protein channels called aquaporins.
Water moves across the cell membrane to balance out the solute (salt) concentration.

It is the process by which water moves from an area of high concentration of water (dilute solution, less salt) to an area of low concentration of water (concentrated solution, more salt).

Question 7

what is active transport?

Answer 7

Active transport is the movement of molecules across the cell membrane with the input of cellular energy. Energy known as ATP (adenosine triphosphate) is required for these processes to be performed.

Molecules move from areas of low concentration to areas of high concentration going against the concentration gradient.
Active transport includes:
▪ Vesicular transport
▪Carrier proteins

Question 8

What are carrier proteins?

Answer 8

Carrier proteins known as protein pumps are used to transport small charged molecules (e.g. ions like the Na+/K+ pump) or large molecules (e.g. glucose, amino acids) across the membrane.

Question 9

what is vesicular transport?

Answer 9

Large molecules are transported across the membrane by vesicular transport.
The 2 ways are: ▪ Endocytosis
− Endo = enter cytosis = cell
− process of the cell membrane changing shape to enclose an extracellular molecule forming a membrane bound vesicle that enters the cell
− e.g. phagocytosis
Exocytosis
− Exo = exit cytosis = cell
− process by which a membrane bound vesicle fuses with the cell membrane and releases the molecules to the outside of the cell
− e.g. removal of cell wastes

Question 10

factors that affect the movement of molecules?

Answer 10

The movement of materials is critical to a cells function and survival. Different factors can affect the movement across the cell membrane including:
▪ Properties of materials
▪ Concentration gradient
▪ SA:V ratio

Question 11

what are properties of molecules

Answer 11

Many different types of molecules can move across and do so in different ways depending on their characteristics:
▪ Size (small vs large)
▪ Electrical charge (charged vs neutral)
▪ Solubility (water vs lipid)

Question 12

what are physical properties?

Answer 12

Size has the biggest impact
▪ Small size meaning it can easily pass through the phospholipid bilayer.
▪ Large size meaning it can’t pass through and needs the aid of transport
proteins and energy to cross the membrane.
▪ Very large size needs vesicular transport.

Question 13

what are chemical properties?

Answer 13

Polarity & Charged molecules have the biggest impact
▪ Non-polar & uncharged (neutral) molecules can easily pass through the phospholipid bilayer
▪ Polar & charged molecules can’t either pass through and need to use transport or channel proteins

Question 14

what is permeability?

Answer 14

The permeability of a cell membrane depends on the molecule.
High permeability
▪ Molecules that are small, uncharged and lipid soluble can move freely across the lipid bilayer.
Low permeability
▪ Molecules that are large, charged and water soluble are impermeable. These molecules need to pass through using proteins or vesicles.

Question 15

what is concentration gradient?

Answer 15

Concentration gradient is the difference in concentration of a solute between one region to the next. Substances move naturally from high to low. The rate of diffusion changes, depending on the concentration gradient.

▪ Concentrated solution – high amount of solute, low amount of water
▪ Dilute solution – low amount of solute, high amount of water

Question 16

how does the concentration gradient affect movement?

Answer 16

If there is a greater difference in the concentration of substances, the concentration gradient will be steeper and diffusion will occur faster.

If there is a lower difference in the concentration of substances, the concentration gradient will be less steep and diffusion will occur slower.

It is an advantage for cells to maintain steep diffusion gradients if rapid transport is required.

Question 17

Surface Area to Volume Ratio

Answer 17

The surface area to volume ratio (SA:V) of cells determines the efficiency of transport and exchange of materials across the cell membrane.

Question 18

Surface Area

Answer 18

The surface area in terms of a cell is the total area of the cell membrane surrounding a cell.

Question 19

Volume

Answer 19

The volume in terms of a cell is the space taken up by the internal contents of the cell.

Question 20

Large SA:V ratio

Answer 20

Small cells have a large surface area relative to volume. This means there is a smaller distance between the centre of the cell and the outside environment creating a faster exchange rate. Smaller cells perform at optimum level of functioning meaning they are more efficient.

Question 21

Small SA:V ratio

Answer 21

Large cells have a small surface area relative to volume. This means there is a larger distance between the centre of the cell and the outside environment creating a slower exchange rate. Larger cells have more energy needs, but not enough surface areas to meet those needs meaning they are less efficient. This could lead to the death of the cell or they will divide.

Question 22

Cell Requirements

Answer 22

Cells require the following to be able to exist:
- A source of energy
- Supply of matter
- Removal of wastes

Question 23

Cell Energy Requirements

Answer 23

All organisms require energy to maintain their metabolic processes. ATP (adenosine triphosphate) is the universal carrier of energy in all living organisms and is the cell’s store of immediately useable energy.

Question 24

Matter

Answer 24

Nutrients are obtained through organic compounds and inorganic compounds.

Question 25

Inorganic Compounds

Answer 25

Inorganic compounds include:
- Water
- Gases
- Salts

Charged particles like minerals, nitrogen, sodium chloride, etc.
Used for chemical reactions, water balance, synthesis of organic molecules and tissues

Question 26

Organic Substances

Answer 26

Cells require large organic molecules as part of their structure and to maintain biochemical processes involved in effective functioning.

Question 27

Nucleic Acids

Answer 27

Nucleic acids are made up of carbon (C), hydrogen (H), oxygen (O), phosphorous (P) and nitrogen (N). They carry genetic information.

Question 28

Removal of Wastes

Answer 28

The removal of wastes is called excretion. For example:
- carbon dioxide
- nitrogenous waste
- water

Question 29

Photosynthesis

Answer 29

A complex biochemical process in which plants utilise light energy in the presence of chlorophyll to break down CO2 and H2O molecules to produce their own food (glucose) and O2.

Question 30

What is photosynthesis?

Answer 30

A complex biochemical process in which plants utilise light energy in the presence of chlorophyll to break down CO2 and H2O molecules to produce their own food (glucose) and O2.

The process involves trapping light energy and converting it to chemical energy. It occurs in 2 stages, each consisting of a series of chemical reactions that take place in the chloroplasts of plants.

Question 31

What are the two stages of photosynthesis?

Answer 31

Light dependent phase and Light independent phase.

Light Dependent Phase (Photolysis) occurs in the grana of chloroplasts, while Light Independent Phase (Carbon Fixation) occurs in the stroma of chloroplasts.

Question 32

What are the main factors that affect the rate of photosynthesis?

Answer 32

Light intensity, carbon dioxide concentrations, temperature.

Question 33

What is cellular respiration?

Answer 33

A complex biochemical process in which plants and animals breakdown glucose to release energy (ATP). This is the energy used for all cellular processes.

The process involves transforming stored chemical energy into more usable form of chemical energy.

Question 34

What are the two forms of cellular respiration?

Answer 34

Aerobic and Anaerobic.

Aerobic respiration occurs in the presence of O2, while Anaerobic respiration occurs in the presence of no O2 and occurs in the cytosol.

Question 35

What are the two main stages of Aerobic Respiration?

Answer 35

Glycolysis and Krebs Cycle.

Glycolysis occurs in the cytosol and does not require oxygen, while Krebs Cycle occurs in the mitochondria and requires oxygen.

Question 36

What are the two pathways of fermentation in Anaerobic Respiration?

Answer 36

Alcohol fermentation and lactic acid fermentation.

Alcohol fermentation occurs when yeast and bacteria break down glucose to form carbon dioxide and ethanol, while lactic acid fermentation occurs when cells are deprived of oxygen and break down glucose to form lactic acid.

Question 37

What are the main wastes that need to be removed at the cellular level?

Answer 37

CO2, urea, water.

CO2 lowers pH in cells, urea is toxic to cells, and water helps maintain osmotic pressure within cells.

Question 38

What are the main organs involved in the removal of waste products?

Answer 38

Lungs, sweat glands, liver & intestines, kidneys.

Lungs remove carbon dioxide, sweat glands excrete water and salts, liver & intestines break down old blood cells to form bile, and kidneys remove nitrogenous wastes.

Question 39

What are enzymes?

Answer 39

Enzymes are biological catalysts that control the rate at which metabolic reactions take place in cells. They make reactions more efficient.

Catalysts are chemical substances that can accelerate chemical reactions. They are unchanged at the end of the reaction and can be reused many times.

Question 40

What is the structure of enzymes?

Answer 40

Enzymes are protein molecules that are highly folded to create a specific shape which is related to its function.

The surface of the enzyme with a specific shape is called the active site. It is here that the substrate binds forming a substrate-enzyme complex. The reaction proceeds and the products are released from the active site.

Question 41

What is the specificity of enzymes?

Answer 41

Enzymes are highly specific - one enzyme for each substrate. This is because the shape of the active site of the enzyme matches the shape of the substrate material.

Enzymes can either build complex molecules from simpler molecules (anabolic reaction) or break down complex molecules into simpler molecules (catabolic reaction).

Question 42

What are the two models developed to describe how enzymes and their substrates interact?

Answer 42

Lock & Key Model and Induced Fit Model.

The Lock & Key Model is an older version and thought to be less accurate, believed that the active site was rigid, and only a specific substrate can exactly fit into the active site. The Induced Fit Model is a newer model that suggests the active site is flexible and can change shape to accommodate the substrate.

Question 43

What is the function of enzymes in relation to substrates?

Answer 43

Enzymes can either build complex molecules from simpler molecules (anabolic reaction) or break down complex molecules into simpler molecules (catabolic reaction)

Example: Enzymes help in the digestion of food by breaking down complex molecules into simpler molecules.

Question 44

What are the two models developed to describe how enzymes and their substrates interact?

Answer 44

Lock & Key Model and Induced Fit Model

The Lock & Key Model is the older version and thought to be less accurate, while the Induced Fit Model is a more recent modification and the currently accepted model.

Question 45

What are the factors affecting enzyme activity?

Answer 45

Temperature, pH, and substrate concentration

Enzymes require specific environmental conditions to function at their optimal efficiency.

Question 46

What is the optimal temperature range for enzyme function in humans?

Answer 46

37°C

Enzymes function most efficiently at this temperature in humans.

Question 47

What happens to enzyme reactions at low temperatures?

Answer 47

Enzyme reactions are slow as the molecules have low kinetic energy and collisions between the enzyme and substrate are infrequent

Low temperatures result in slower enzyme reactions.

Question 48

What is denaturation in relation to enzymes?

Answer 48

Denaturation is the irreversible change in the active site of an enzyme due to high temperatures and changes in pH

Denaturation means the substrate can no longer fit in the active site because it has been permanently changed.