cell surface membrane or plasma membrane
● thin layer outside of every cell
● partially permeable
● works as a barrier between the environment & the cell
● thickness of about 7nm
● trilaminar appearance; consists of 3 layers, 2 dark lines & a pale interior
partially permeable
used to describe a membrane which is a successful barrier but also allows
controlled traffic of materials in both directions
organelle
● small structure found in the cytoplasm
● has been likened to a small organ, hence the name
● can be defined as a functionally & structurally distinct part of the cell
● often surrounded by membranes so its activity can be separated from the
surrounding cytoplasm
● shows division of labour
division of labour
each type of organelle has its own function, sharing the work between different
specialised organelles
compartmentalisation
the activities of each organelle are separated from the cytoplasm
nucleus
● largest organelle
, ● stains intensely
● contains chromatin
● consists of the nuclear envelope & the nucleolus
nucleolus
● an even more deeply staining area of the nucleus
● number of them in each cell is variable (usually 1-5 in mammals)
● made of loops of DNA from several chromosomes
● makes ribosomes using the information in its own DNA
nuclear envelope
● two membranes surrounding the nucleus
● the outer membrane is continuous with the endoplasmic reticulum
● full of many nuclear pores
nuclear pores
● small pores on the nuclear envelope
● they allow & control the exchange between the nucleus & the cytoplasm
○ entering into the nucleus through them eg proteins making ribosomes,
nucleotides, ATP, some hormones
○ exiting the nucleus through these; mRNA, ribosomes for protein
synthesis
chromatin
● loosely coiled state in which the chromosomes are in (except during nuclear
division)
● contain DNA & proteins
genes
● the functional units in which the DNA is organised
● control the activities of the cells
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