MODULE 1 CELLS/MEMBRANE/TRANSPORT

All matter is composed of one or more ___ such as hydrogen, oxygen, carbon, nitrogen, calcium, and iron

Elements

Elements are ___ substances composed of one or more pure substances (e.g. hydrogen, oxygen, carbon)

Pure. When atoms of elements bond together, they form molecules (water, proteins, carbohydrates).

When atoms bond together, they form ___ which include water, proteins, and carbohydrates

Molecules

A ___ is the smallest independently functioning unit of life

Cell. All human anatomical structures contain cells, and nearly all physiological functions occur within or are initiated by cells.

A typical human cell has a flexible ___ that encloses cytoplasm containing functional units called organelles

Membrane

The plasma membrane is also called the ___ membrane

Cell membrane

What is the primary structural component of the plasma membrane

Phospholipid bilayer (two adjacent sheets of phospholipids arranged tail-to-tail)

In the phospholipid bilayer, the ___ tails are hydrophobic and face inward, while the ___ heads are hydrophilic and face outward toward the fluid

Lipid; phosphate

What role does cholesterol play in the plasma membrane

Cholesterol is embedded in the membrane and contributes to membrane fluidity, especially at different temperatures.

The plasma membrane is ___ because only certain substances can pass through it unaided

Selectively permeable (or semipermeable)

Define selective permeability in the context of the plasma membrane

The property that allows only certain substances to pass through the membrane unaided based on their size, polarity, and the presence of transport proteins.

Small, nonpolar molecules like oxygen and carbon dioxide can cross the plasma membrane by ___ without cellular energy

Simple diffusion

What is simple diffusion

Movement of small, nonpolar molecules directly through the lipid bilayer without transport proteins or cellular energy. Examples: oxygen, carbon dioxide.

What is facilitated diffusion

Movement of larger or polar molecules across the membrane via channel or carrier proteins, without using cellular energy (ATP).

Glucose enters cells by ___ because it is too large to cross the lipid bilayer directly

Facilitated diffusion (via glucose transporter protein)

Channel proteins allow molecules to pass in the direction of the ___

Concentration gradient (passive movement; no energy required)

Carrier proteins ___ bind to molecules, change shape, and release them on the other side

Selectively

Pump proteins use ___ to move molecules against their concentration gradient

ATP (adenosine triphosphate; cellular energy)

What is active transport

Movement of substances across the plasma membrane against their concentration gradient (from low to high concentration) USING cellular energy (ATP) and often involving membrane protein pumps.

Define osmosis

The movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.

In osmosis, water molecules move toward the area with ____ solute concentration

Higher

A ___ solution has equal solute concentration inside and outside the cell

Isotonic

A ___ solution has higher solute concentration outside the cell, causing water to leave the cell and the cell to shrink

Hypertonic

A ____ solution has lower solute concentration outside the cell, causing water to enter the cell and the cell to swell or burst

Hypotonic

The sodium-potassium pump is an example of ____

Active transport

The sodium-potassium pump moves ____ sodium ions out and ____ potassium ions in per cycle

3; 2

The Na+/K+ pump maintains an ____ across the cell membrane, especially critical in neurons

Electrical gradient (or membrane potential)

Oxygen diffuses into cells by ___

Simple diffusion

The cytoplasm is a ___ rich in ___ that houses various specialised structures called organelles

Fluid; nutrients

Organelles are ___ structures found within the cytoplasm that perform essential tasks

Specialised (or distinct)

The nucleus is the ___ of the cell

Control centre

The mitochondrion is the ___ of the cell, generating ATP to power cellular processes

Powerhouse (or energy factory)

Cells carry out all vital processes including ____, ____, ____, and ____

Growth; repair; communication; reproduction