00. All Unit 1.3 Biology

What is the cell membrane mostly made of?

Phospholipids and proteins

What can phospholipids do?

Form bilayers with 1 sheet of phospholipid forming over another

Describe the phosphate head

Polar molecule (hydrophillic) -> attracted to other polar molecules like water

Describe the fatty acid tails

Non polar (hydrophobic) -> Repel water

What does the phospholipid bilayer form?

Forms basis of the membrane structure

What does the phospholipid component allow?

Allows lipid soluble (non polar) molecules to enter and leave cell -> prevents water soluble (polar) from doing so

How are proteins arranged in the membrane?

Arranged randomly, unlike phospholipids

Where do extrinsic proteins occur?

Occur on surface of bilayer or partly embedded in it

What do extrinsic proteins do?

Provide structural support and form recognition sites by identifying cells

Where do intrinsic proteins occur?

Span through phospholipid bilayer

What do intrinsic proteins do?

Some act as channels / carriers to facilitate diffusion of polar (water soluble) molecules across membranes e.g. ions, others form pumps and carry out active transport against conc. gradient

What does the cell membrane act as?

Boundary separating living cells from non living surrounding

What does cell membrane control?

Which substances pass in and out of cell + uptake of nutrients

What does the cell membrane allow? (cell membrane functions)

Allows waste products to pass out of cell

What is the cell membrane responsible for?

Secreting substances like enzymes and glycoproteins

What is another function of the cell membrane?

Cell recognition

What is simple diffusion? Examples?

Diffusion of non polar molecules (e.g. oxygen and carbon dioxide) across the phospholipid bilayer

What molecules can diffuse by simple diffusion?

Lipid soluble, uncharged, non polar molecules e.g. oxygen

Describe the movement in simple diffusion?

Movement of molecules / ions from high concentration to low concentration until equally distributed

How does diffusion move in relation to the concentration gradient?

Moves down concentration gradient

What kind of process is simple diffusion? Why?

A passive process -> no atp needed

What is the result at the end of simple diffusion?

Equilibrium will be reached unless molecule used by cell

What happens at EQM?

No net movement in a particular direction -> molecules + particles continue to cross membrane in both directions

What does equilibrium mean?

Concentration of molecules equal on either side of membrane

Draw the graph of diffusion

Yes

Describe the simple diffusion graph? Why is it like this?

It’s linear -> conc. of gradient increases = rate of diffusion increases

How does rate of uptake and concentration difference across membrane relate?

They are directly proportional

How does stopping respiration or killing the cell with toxin affect diffusion?

Will not stop diffusion as it does not need ATP

What factors have no affect on diffusion?

Rate of respiration or toxins e.g. respiratory inhibitors like cyanide

What do not pass through the cell membrane in simple diffusion? Why?

Charged particles, ions, large molecules (e.g. glucose) -> bc they’re insoluble in lipid

What do charged particles, ions and large molecules not do?

Pass through the cell membrane

What help such particles diffuse in and out?

Intrinsic proteins

What do intrinsic proteins do?

Help such particles diffuse in and out

What type of intrinsic proteins help facilitate diffusion?

Channels or carriers

What are channels and carriers?

Proteins

How do carrier proteins and channels impact facilitated diffusion?

Increase rate of diffusion along conc. gradient without ATP

Draw the graph of facilitated diffusion

Yes

Describe the beginning of the facilitated diffusion graph?

Initial increased rate of diffusion as increased conc. gradient -> Channel + carrier proteins help

What happens at the end of the graph of facilitated diffusion?

Rate of diffusion levels off at higher conc. -> Channel + carrier proteins saturated -> limits rate of diffusion

How do respiratory inhibitors affect facilitated diffusion?

No affect as ATP not needed

What factor does not impact facilitated diffusion?

Respiratory inhibitors

What do channel proteins have?

Pores lined with polar groups (hydrophilic) allowing charged ions to pass

Describe the types of channel proteins

Each channel protein is specific for one type of ion

How do the channel proteins function?

Open and close depending on needs of cell -> called gated channels

What do carrier proteins allow?

Allow facilitated diffusion across membranes of larger polar molecules e.g. sugars + amino acids

how do carrier proteins function?

Particular molecule attaches to carrier protein at binding site

What does a molecule attaching to carrier protein binding site cause?

Causes carrier protein to change shape / rotate in membrane -> This release molecule onto other side of membrane

What is co transport a form of?

A form of facilitated diffusion

How does co transport work?

Brings molecules + ions into cells together on the same carrier protein

Give an example of co transport?

Sodium glucose co transport absorbs glucose + sodium ions across cell membrane into blood in ileum and kidney nephron

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Who proposed this the fluid mosaic model?

Singer and Nicholson

What does fluid mosaic model describe?

The arrangement of phospholipids and proteins

Why is it called fluid?

Phospholipid layer capable of movement + components of membrane free to move

Why is it called mosaic?

Random placement of proteins -> mosaic arrangement