Life Processes At Cellular Level - Explain

List essential life processes (4)

movement, respiration, growth, reproduction

State the 2 types of Cells

Eukaryotic and Prokaryotic cells

Explain Prokaryotic Cells

lack a nucleus and other organelles

Explain Eukaryotic Cells

have a membrane-bound nucleus

what do nuclear pores do

regulate the transport of molecules between the nucleus and cytoplasm

Explain the difference of a shape of an animal cell and a plant cell

Plant cells are rectangular, animal cells are rounded

Explain the difference in a vacuole, in a plant cell and an animal cell

Plant cell are large and central, animal cell are small and multiple

Why are the plant and animal cells different

Cells specialise to perform different roles

Explain the function of a plasma membrane

separates internal environment from external environment,

allows some molecules to pass in and out - semipermeable

important for cell signalling and communication

Explain “fluid” “mosaic” model

The fluid mosaic model describes the structure of cell membranes as a mosaic of diverse protein molecules embedded in a fluid phospholipid bilayer. This model explains how the membrane is flexible and allows for the movement of proteins within the layer, contributing to various cellular functions.

Explain phospholipid bilayer

two layers of phospholipids that forms the fundamental structure of cell membranes, with hydrophilic heads facing outward and hydrophobic tails facing inward, creating a barrier that regulates the movement of substances in and out of the cell.

Explain proteins in cell membrane

Proteins are embedded in the phospholipid bilayer: transport materials across membrane, send and receive cellular signals and provide structure to the membrane

What do transmembrane proteins do

function as channels that allow specific substances to move across the cell membrane

What do surface proteins do

serve as receptors, facilitating communication between the cell and its environment, and may also assist in cell recognition and signaling.

Explain cholesterol in cell membrane

maintains the stability of the cell membrane

prevents phospholipids from packing together too tightly or moving too freely

Explain carbohydrates in cell membrane

involved in cell signalling and communication

Explain Passive Transport

movement across a cell membrane that does not require energy

Explain Simple Diffusion + Example

the process by which small, non-polar molecules pass through the phospholipid bilayer of the cell membrane from an area of high concentration to an area of low concentration, requiring no energy

O2, CO2

What does Non-Polar mean

not charged

Explain facilitated diffusion + Example

the process by which large, polar molecules move across the phospholipid bilayer from high to low concentration, using a specific protein channel, requiring no energy

Glucose, Na+, K+

Explain the impact of the concentration gradient on diffusion

a steeper gradient results in molecules moving more rapidly towards areas of low concentration

while a shallower gradient slows the rate of diffusion.

Explain the impact of temperature on diffusion

higher temperatures increase the rate of diffusion as the molecules gain kinetic energy, resulting in a greater number of collisions

Explain the impact of surface area on diffusion

larger surface area increases rate of diffusion by providing more space for molecules to move across allowing a greater number of particles to diffuse through

Explain the impact of the size of particles on diffusion

smaller particles result in an increased rate of diffusion as the particles are able to pass through the membrane quickly

Molecule Type in Facilitated & Simple Diffusion + Example

Simple: small, non-polar, O2 & CO2

Facilitated: large, polar, Glucose, Na+, K+

Movement across membrane in Facilitated & Simple Diffusion

Simple: directly through phospholipid bilayer

Facilitated: through carrier or channel proteins

Selectivity in Facilitated & Simple Diffusion

Simple: any small, non-polar molecules can diffuse

Facilitated: specific transport proteins can transfer certain molecules

Importance of osmosis

keeps water levels of a cell balanced, which is essential to the overall health of the organism

Explain hypotonic solution (1)

Low solute concentration, high water concentration than that of the cell

Explain movement in hypotonic solution

Water moves into the cell by osmosis as the hypotonic solution has a high water concentration, causing the cell to swell

Hypotonic Solution - Cells

Animal: Burst (Lysis)

Plant: Turgid

Explain Hypertonic Solution (1)

high solute concentration, low water concentration than that of the cell

Explain Hypertonic Solution (2)

water leaves the cell via osmosis, as the hypertonic solution has a low water concentration, causing the cell to shrink

Hypertonic Solution - Cells

Animal: Crenation (shriveled)

Plant: Shriveled (Plasmolysis)

Explain Isotonic Solution (1)

equal solute and water concentration

Explain Isotonic Solution (2)

the solute concentration inside and outside the cell is equal, so water moves in and out at the same rate, causing the cell to maintain its normal shape and size

Isotonic Solution - Cells

Animals: Normal

Plant Cell: Flaccid

What can facilitated diffusion also be used for

move small non-polar molecules quickly through the cell membrane

Explain how carrier proteins are used + example of their usage

to move the molecules from a low concentration to a high concentration

Na+/K+ pump

Explain endocytosis + example

active transport process where the cell membrane folds inward to surround large molecules or particles, forming a vesicle that brings them into the cell.

Pinocytosis

Phagocytosis

Explain exocytosis + example

active transport process where vesicles inside the cell fuse with the cell membrane to release substances out of the cell.

neurotransmitters

Explain pinocytosis

type of endocytosis where the cell takes in fluids by forming small vesicles from the cell membrane. It is an active transport process that requires energy.

Explain phagocytosis

type of endocytosis where the cell takes in large solids by forming vesicles from the cell membrane. It is an active transport process that requires energy

Explain effect of concentration gradient on movement

Passive; high to low

Active; low to high

Explain effect of molecule size on movement

small molecules diffuse easily whereas larger molecules require facilitated diffusion or cytosis

Explain effect of polarity on movement

non-polar molecules can pass easily whereas charged molecules require transport proteins

Explain importance of concentration gradient in transport

oxygen is essential for respiration

neurons use ion gradients for nerve signal

Explain importance of molecule size in transport

amino acids and glucose must enter the cell for protein synthesis and energy

Explain importance of polarity in transport

Ions rely on channel or carrier proteins for transport, important for muscle contraction and nerve impulse

Describe the structure of an enzyme

protein made up of a specific sequence of amino acids linked by peptide bonds, which folds into a unique 3D shape. This shape includes an active site that allows the enzyme to bind to a specific substrate.

How do enzymes work

having a specific active site, shaped by their amino acid sequence, where the substrate binds. This enzyme-substrate complex lowers the activation energy of the reaction, allowing it to proceed faster.

not used in the reaction

What is an advantage of enzymes not being used up by reactants

they can catalyse the same reaction again and again

Explain the Lock & Key Model

The Lock & Key Model suggests that the enzyme’s active site has a specific shape that exactly matches the shape of its substrate, like a key fitting into a lock. This explains the enzyme’s specificity, as only substrates with the correct shape can bind to the active site and undergo the reaction.

Explain the Induced Fit Model

suggests that the enzyme’s active site is not a perfect fit for the substrate but instead the active site molds itself around the substrate when it fits. Once the reaction is complete, the enzyme returns to its original shape.

Why is the active site of the enzyme able to mold itself

The weak hydrogen bonds present in the secondary structure of the enzyme allow the enzyme to alter their shape as they are not rigid

Effect of low temp on enzyme activity

At low temperatures, enzyme and substrate molecules have reduced kinetic energy, so they move more slowly. This leads to fewer collisions between them. Even when collisions do occur, they are less likely to have enough energy to overcome the activation energy barrier needed for the reaction to proceed. As a result, the rate of enzyme activity is low

Effect of high temp on enzyme activity

At high temperatures, the increased kinetic energy causes the bonds holding the enzyme’s structure together to break. This changes the shape of the enzyme, including the active site. As a result, the substrate can no longer bind to the active site because it is no longer complementary in shape. The enzyme is said to be denatured, and this causes the reaction rate to decrease sharply and eventually stop

Effect of extreme pH on enzyme activity

At extreme pH levels, the ionic bonds that maintain the enzyme’s three-dimensional structure are disrupted. This changes the shape of the enzyme, including the active site. As a result, the substrate can no longer bind to the active site because it is no longer complementary in shape. The enzyme is said to be denatured, and this causes the reaction rate to decrease sharply and eventually stop

Effect of enzyme concentration on enzyme activity

Increasing enzyme concentration increases the number of active sites available for substrate molecules to bind to, so the rate of reaction increases. Once all of the substrate molecules are bound to an enzyme, the rate of reaction won’t increase anymore even if more enzymes are added

Effect of substrate concentration on enzyme activity

Increasing substrate concentration increases the number of substrate molecules available to bind to enzyme active sites, so the rate of reaction increases. Once all the enzyme active site’s are occupied , the rate of reaction won’t increase even if more substrate is added

What is a limiting factor

the factor that limits the reaction rate in a process, is least in supply

What are the two types of co-factors

Inorganic and co-enzymes

Example of inorganic molecules

Mg2+

Example of co-enzymes

Organic molecules

Explain inihibitors

Molecules that slow down or stop enzyme activity by interfering with enzyme function

List the two types of inhibitors

Competitive & Non-Competitive

Explain competitive inhibitors

Molecules that bind to the active site, preventing the substrate from doing so

Explain non-competitive inhibitors

Molecules that bind to an alternate site on the enzyme, resulting in a change in the enzyme’s shape, including the active site. As a result, the substrate can no longer bind effectively, and the enzyme’s activity is reduced or inhibited

State the purpose of respiration

release energy from glucose to power essential life processes

How is energy stored in the body

As Adenine Triphosphate

List purpose of respiration in animals

movement, body temperature, nerve impulse transmission

List purpose of respiration in plant

active transport (moving minerals into roots), synthesis of proteins, transports sugar

Word Equation for Aerobic Respiration

Glucose + Oxygen > Carbon Dioxide + ATP + Water

Symbol Equation for Aerobic Respiration

C6H12O6 + 6O2 > 6H20 + 6CO2 + ATP

Explain the matrix of the mitochondrion

Fluid-filled space containing enzymes

Explain the Cristae of the mitochondrion

the folds of the inner membrane

Explain the inner membrane of the mitochondrion

Semi-permeable and has lots of folds

List the 3 stages of respiration

Glycolysis

Krebs Cycle

Electron Transport Chain

State the location of glycolysis

Cytoplasm

State the reactants in glycolysis

Glucose

State the products in glycolysis

2 Pyruvate, 4ATP (Net gain of 2ATP), H+, electrons

Explain the process of glycolysis

one molecule of glucose is broken down into two pyruvate molecules in the cytoplasm, two ATP are used in the process, 4ATP molecules are produced, H+ and electrons are produced

Does glycolysis require oxygen

No

Where do the products of glycolysis go if there is oxygen present

To the mitochondrion

State the location of Krebs Cycle

Mitochondrial Matrix

State the reactants of Krebs Cycle

Pyruvate Molecule

State the products of Krebs Cycle

CO2 and ATP

Explain the process of Krebs Cycle

One pyruvate molecule is converted into acetyl CoenzymeA. CoenzymeA goes through the Krebs Cycle. 2ATP are produced. CO2 is produced as a waste product. H+ and electrons are produced.

What is required in the Krebs Cycle

Enzymes

State the location of the Electron Transport Chain

Inner Membrane/Cristae

State the reactants in the Electron Transport Chain

H+ and electrons

State the products of Electron Transport Chain

Around 34ATP molecules

State the process of Electron Transport Chain

H+ and electrons undergo a series of reactions. Around 34ATP molecules are produced. H2O is produced as a waste product

What is required for the Electron Transport Chain

Oxygen

Discuss mitochondrial adaptations (elongated oval shape)

The elongated oval shape of mitochondria increases their surface area to volume ratio, which allows more efficient diffusion of oxygen into the mitochondria and carbon dioxide out. This is important because oxygen is required for aerobic respiration, which occurs in the mitochondria and produces ATP. The greater surface area ensures a higher rate of gas exchange, supporting high rates of ATP production needed for energy-demanding processes in the cell.

Discuss mitochondrial adaptations (enzymes)

Mitochondria contain specific enzymes in their matrix that act as biological catalysts for the reactions of the Krebs Cycle. These enzymes speed up the breakdown of pyruvate into carbon dioxide, hydrogen ions, and high-energy electrons. By increasing the rate of these reactions, more ATP is being produced during aerobic respiration, providing energy for the cell’s activities.

Discuss mitochondrial adaptations (Cristae)

The inner membrane of the mitochondrion is highly folded into structures called cristae. These folds increase the surface area available for the electron transport chain, which is the final stage of aerobic respiration. A larger surface area allows more electron transport proteins and ATP synthase enzymes to be embedded in the membrane. This means more electrons can pass through the chain at once, allowing more ATP to be produced per unit of time. This adaptation enables the mitochondria to supply large amounts of energy efficiently to the cell.

Effect of temperature on respiration rate

Temperature affects the rate of respiration because enzymes control the reactions involved. At low temperatures, enzymes and substrate molecules have less kinetic energy, resulting in fewer successful collisions, so the rate of respiration is slower. As the temperature increases, the kinetic energy of the molecules increases, leading to more frequent successful collisions and a faster rate of respiration. However, if the temperature becomes too high, the enzyme’s active site begins to denature — its shape changes, so substrates can no longer bind. This reduces or stops the rate of enzyme-controlled reactions, and therefore the rate of ATP production in respiration drops sharply.

Effect of energy requirement on respiration rate

When a cell or organism becomes more active, such as during exercise, it requires more energy in the form of ATP to power muscle contractions and other processes. This increased energy demand causes the rate of cellular respiration to rise. To meet this demand, the body increases its supply of glucose and oxygen to the cells by increasing breathing and heart rate. This allows aerobic respiration to occur more rapidly, producing more ATP to match the energy requirements of the cell. If the demand exceeds the oxygen supply, cells may also switch to anaerobic respiration, which is less efficient and produces lactic acid. Overall, higher energy requirements lead to an increased rate of respiration to maintain adequate ATP production.

Effect of oxygen availability on respiration rate

Oxygen is the final electron acceptor in the electron transport chain, the last stage of aerobic respiration. If oxygen is unavailable or limited, the ETC cannot operate because electrons cannot be passed along the chain. This causes ATP production to drops significantly. Cells may then rely on anaerobic respiration, which produces much less ATP and leads to the buildup of lactic acid. Therefore, limited oxygen availability reduces the efficiency of respiration and the energy supply to the cell.