A-LEVEL
BIOLOGY
OCR A
___
Notes
CELL ULTRASTRUCTURE (only seen with an electron
microscope)
Organisms are either :
● Prokaryotic : single-celled
E.g. bacteria
● Eukaryotic : made up of many cells
E.g. animal + plant cells
ANIMAL CELL
,PLANT CELL
, FUNCTIONS OF ORGANELLES
PLASMA (CELL SURFACE) MEMBRANE Regulates movement of substances into
and out of the cell
Has receptor molecules that allow it to
respond to chemicals like hormones
CELL WALL of cellulose (plants) Provides mechanical strength
NUCLEUS - Surrounded by double-membrane
nuclear envelope that contains
pores that allow substances to
move btw nucleus + cytoplasm
- Contains chromatin (DNA wound
around histones)
- Controls the cell’s activities (by
controlling transcription of DNA)
- Contains instructions to make
BIOLOGY
OCR A
___
Notes
CELL ULTRASTRUCTURE (only seen with an electron
microscope)
Organisms are either :
● Prokaryotic : single-celled
E.g. bacteria
● Eukaryotic : made up of many cells
E.g. animal + plant cells
ANIMAL CELL
,PLANT CELL
, FUNCTIONS OF ORGANELLES
PLASMA (CELL SURFACE) MEMBRANE Regulates movement of substances into
and out of the cell
Has receptor molecules that allow it to
respond to chemicals like hormones
CELL WALL of cellulose (plants) Provides mechanical strength
NUCLEUS - Surrounded by double-membrane
nuclear envelope that contains
pores that allow substances to
move btw nucleus + cytoplasm
- Contains chromatin (DNA wound
around histones)
- Controls the cell’s activities (by
controlling transcription of DNA)
- Contains instructions to make
