Life Processes At Cellular Level - Explain

Define A Cell

basic unit of all living organisms; surrounded by cell surface membrane, contains genetic material, and cytoplasm, containing organelles

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

Define Cell (Plasma Membrane)

semi-permeable membrane, composed primarily of phospholipids, which separates the internal environment of a cell from the external environment

Define Nucleus + Pores

organelle found in eukaryotic cell that contains DNA

contains nuclear pores which allow materials in/out of the cell

Define Mitochondrion

membrane-bound organelle which is the site of aerobic respiration

Define Cell Wall + composition

rigid, external structure which provides support to the cells, which is composed of cellulose

Define Vacuole

Define Chloroplast

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

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

Define Organelle

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

Define diffusion

net movement of particles from a region of high concentration to a region of low concentration (down the concentration gradient) as a result of their random movement until the concentration is equal, requiring no energy

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

Define the term osmosis

diffusion of water from a high concentration to a low concentration through a semi-permeable membrane

Importance of osmosis

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

Define tonicity

concentration of solutes in a solution

Explain hypotonic solution (1)

Low solute concentration, high water concentration

Explain hypotonic solution (2)

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

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

Define active transport + example

movement of molecules from a low concentration to a high concentration, requiring energy

Na+/K+ Pump

Root hair cells uptaking ions

Explain how carrier proteins are used

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

Explain cytosis

form of active transport where molecules are transported into or out of a cell by the folding of the cell membrane into vesicles

Explain endocytosis

molecules move into the cell

Explain exocytosis + example

molecules move out of the cell

neurotransmitters

Explain pinocytosis

endocytosis of fluids

Explain phagocytosis

endocytosis of solids

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