Structure flashcards

How does surface area affect diffusion

The larger the area over which diffusion can occur, the greater the rate of diffusion. This is due to there being more space for the molecules to diffuse across the membrane.

How does concentration gradient affect diffusion

The steeper the concentration gradient, the greater the rate of diffusion.

How does the thickness of the exchange surface affect diffusion

The shorter the diffusion pathway, the more molecules that can diffuse in a given time period.

How does temperature affect diffusion

The higher the temperature, the higher the kinetic energy of particles; the higher the rate of diffusion.

How does the size of molecules affect diffusion

The smaller the molecule, the faster it will diffuse.

How does lipid solubility affect diffusion

Fat-soluble molecules are non-polar (uncharged) and diffuse more rapidly across a membrane than water-soluble molecules, which are polar (charged).

How do organic solvents affect solubility

non-polar solutes dissolve in non-polar solvents. Therefore, the membrane structure may become altered and the permeability of the membrane can increase.

What type of layer do the phosphate heads and fatty acid tails form

The phospholipid bilayer.

Why do the phosphate heads face the outside of the membrane

They are hydrophilic so they interact with water in the cytoplasm and extra-cellular space.

Why do the fatty acid tails face the inside of the membrane

They are hydrophobic so they repel water and want to be protected from the fluid in the cytoplasm and extra-cellular space.

What type of protein are the channel, carrier and intrinsic proteins

Globular.

What are the roles of intrinsic proteins in the cell membrane

Transporting molecules/ions cross the membrane

What are the roles of the extrinsic proteins in the cell membrane

Add structural support, help enzymes to function, be involved in cell recognition or provide receptor sites that hormones can bind to.

What is a glycolipid calyx in a cell membrane

A calyx attached to a phospholipid.

What is a glycoprotein calyx in a cell membrane

A calyx attached to a protein.

What are the roles of glycolipids and glycoproteins

Cell-to-cell recognition or functioning as hormone receptors.

All the carbohydrates on the outer surface of a cell membrane are called the..

glycocalyx

What is the role of cholesterol in a cell membrane

Makes the cell membrane more rigid and stable.

Why is the arrangement of a cell membrane referred to as a ‘fluid mosaic’

The components are not joined or bound to each other and relatively different sizes.

How do molecules pass through the membrane

By crossing the intrinsic channels or carrier proteins.

Simple diffusion

The movement of molecules or ions from a region of high concentration to a region of low concentration until they are equally distributed.

Active transport

An energy-requiring process in which ions and molecules are moved across membranes against a concentration gradient.

Facilitated diffusion

Movement of larger ions and molecules across a membrane. Transport proteins allow these molecules to diffuse because they open up their pores.

Co-transport

A type of facilitated diffusion that brings molecules and ions into cells together on the same transport protein molecule.

Endocytosis

When material is engulfed by extensions of the plasma membrane and cytoplasm, surrounding it, making a vesicle. The two types are phagocytosis and pinocytosis.

Exocytosis

The process where substances may leave the cell, having been transported through the cytoplasm in a vesicle, which fuses with the cell membrane.

Fick’s law (use this sign ∝)

Rate of diffusion ∝ surface area x (difference in concentration/thickness of gas exchange surface)

Polar

charged

Non-polar

uncharged

hydrophobic

repels water molecules

hydrophilic

attracts water molecules