Biology- cells

A-LEVEL biology

What are eukaryotic cells?

Eukaryotic cells are complex cells that contain a nucleus and membrane-bound organelles. They are found in organisms such as animals, plants, fungi, and protists.

what does compartmentalisation mean?

 eukaryotic cells contain different organelles, each adapted to perform particular functions.  This is called compartmentalisation. 

Why is compartmentalisation important?

-different reactions can occur in separate compartments

-organelles provide specific conditions for particular reactions

-enzymes and substrates can be concentrated in particular locations

what does the cell surface membrane do

separate the cytoplasm from the external environment

what model describes the cell surface model

what are the features of the phospholipid bilayer

The membrane consists of two layers of phospholipids 

Each phospholipid contains 

• A hydrophilic phosphate head 

• Two hydrophobic fatty acid tails 

The phospholipids arrange themselves into a bilayer 

The hydrophilic phosphate head face towards the watery environments inside and outside the cell 

Hydrophobic tails face inwards away from tails 

This is important as the hydrophobic interior restricts the movement of many water soluble and charged substances through the membrane. This helps the membrane act as a selectively permeable barrier 

What are membrane proteins

proteins associated or embedded with the phospholipid bilayer

what are Chanel proteins

Proteins that for hydrophilic forms allowing particular charge and polar substances to move through facilitated diffusion

what are carrier proteins

Bind and change shapes of substances to transport them across the membrane

what are receptor proteins

bind signalling cells such as hormones and trigger a response within the cell

what are enzymes

proteins that act as biological catalyst that speed up the rate of reaction by providing an alternative pathway

what are cell-adhesion proteins

help cells attach to other cells or extracellular structures

what are integral proteins

proteins that are on the span of the entire bilayer

what are peripheral proteins

proteins only associate don one surface

Were is cholesterol located

fit between phospholipids

What does cholesterol

• Help regulate membrane fluidity

• restrict excessive movement of phospholipids

• prevent phospholipids from packing too closely together at lower temperatures

• reduce the permeability of the membrane to some small, water soluble molecules

What are glycoproteins

proteins with a carbohydrate chain attached

what are the functions of the glycoprotein

• act as a receptors for signalling molecules

• help cells recognise other cells

• participate in cell signalling

• help cells adhere to one another