Cell MEMBRANE

CELL MEMBRANE MEMBRANE CELL

Where does metabolism take place in the cell?

the MITOCHONDRIA

What does it mean when the cell membrane is “semipermeable”?

Semipermeable = it lets some things through while preventing other things

What is the cell membrane structure similar to?

Micelles: it has molecules which arrange themselves, and have a hydrophilic head facing the outside whilst their hydrophobic tails face the inside

What is the phospholipid bilayer?

The cell membrane itself.

Bilayer refers to its 2 layers of phospholipids.

One layer = faces outwards to the aqueous environment OUTSIDE of cell

Second layer = faces inwards to the aqueous environment INSIDE of cell

What makes the membrane semipermeable?

The nonpolar, hydrophobic tails of the phospholipids

What does the “fluid mosaic model” refer to?

The movement of phospholipids that make up the cell membrane.

The phospholipids are constantly changing places, think of a CRAMPED, BUSY CROWD

What is the purpose of the cholesterol in the cell membrane?

It gives the cell membrane RIGIDITY

What are “channel proteins”?

Specialised proteins found on the cell membrane that facilitate movements of molecules across or into the membrane

What kind of molecules can pass through the membrane without channel proteins?

Small, nonpolar molecules

(e.g. CO₂ and O₂)

What is passive transport?

When molecules pass through the cell membrane WITH OR WITHOUT the need for channel proteins. This includes normal diffusion and FACILITATED DIFFUSION

TRUE OR FALSE: Facilitated diffusion does require energy

FALSE. Facilitated diffusion does not require energy as it lets larger molecules diffuse from a high to low concentration

What is facilitated diffusion?

When larger molecules need to go through the membrane with the support of channel proteins.

The transport does not need energy, as the molecules are diffused across the natural gradient of high to low concentration

Molecules in question: water, glucose, or some ions

What is active transport?

When channel proteins move ions AGAINST the concentration gradient.

As in, in order to move them from low to high concentration, they need ATP from CELLULAR RESPIRATION in order to go against the natural gradient

TRUE OR FALSE: Osmosis does not occur with cell membranes

FALSE. Osmosis by definition involves the movement of water often through a SEMIPERMEABLE membrane

What is “amphiphilic”?

When a molecule is both hydrophilic and hydrophobic.

LITERALLY PHOSPHOLIPIDS. As their head is hydrophilic whilst their tail is hydrophobic

What does cholesterol do for the membrane again?

It provides structure (for when phospholipids are too fluid),

AND

Act as a spacer (for when phospholipids are too cramped)

In what temperatures would phospholipids start to drift and become too fluid?

Hotter temperatures (think of it like its melting)

In what temperatures would phospholipids become cramped and too packed against each other?

Colder temperatures (think of it like its freezing)

What are peripheral proteins?

Proteins that are normally external (found outside of the cell) and can act as enzymes or shaping the cell itself.

When attached to carbohydrates, they become glycoproteins

When attached to phospholipids, they become glycolipids

What does a peripheral protein become when they are attached to carbohydrates?

Glycoproteins

What does a peripheral protein become when it is attached to phospholipids?

Glycolipids

What is one major purpose both glycoproteins and glycolipids share?

They act as cell-signaling, meaning they are the function of the “self vs non-self” recognition amongst cells. This identifies them as a cell to not be mistaken for a harmful bacteria