2.1.1 structure of eukaryotic cells

What are the distinguishing features of eukaryotic cells

• cytoplasm containing membrane-bound organelles

• So DNA enclosed in a nucleus

List the structure of animal cells

• cell surface membrane

• Mitochondrion

• Nucleus

• Ribosomes

• Rough endoplasmic reticulum

• Smooth endoplasmic reticulum

• Golgi apparatus

• Lysosome

List the general structure of plant cells

(Same as animal +)

• chloroplast in plants and algae

• Cell wall in plants, algae and fungi

• Cell vacuole in plants

Describe the structure of the cell surface membrane

• hydrophillic phosphate head. Attracted to water so points towards water

• Hydrophobic fatty acid tail. Repelled by water so points away

Describe the function of the cell surface membrane

• selectively permeable, so controls passage of substances in/out of the cell

• Molecules/ antigens/ receptors on surface which allows cell recognition/ signalling

Describe the structure of the nucleus

• nuclear envelope: double membrane with nuclear pores

• Nucleoplasm

• Nucleolus (dense region)

• Protein/ histone bound, linear DNA: chromatin=condensed. Chromosome=highly condensed

Describe the function of the nucleus

• holds/ stores genetic information which codes for polypeptides (proteins)

• Site of DNA replication

• Site of transcription (proteins synthesis), producing mRNA

• Nucleolus makes ribosomes/ RNA

Describe the structure of a ribosome

• made of ribosomal RNA and protein (two subunits)

• Not a membrane bound organellE

Describe the function of a ribosome

• site of protein synthesis (translation)

Describe the function of the rER

• ribosomes on surface synthesise proteins

• Proteins are processed/ folded/ transported inside rER

• Proteins packaged into vesicles for transport, e.g Golgi apparatus

Describe the function of the sER

• synthesises and processes lipids

• E.g cholesterol and steroid hormones

Describe the structure of the rER and sER

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Describe the structure of the Golgi apparatus and vesicles

• Golgi apparatus - flattened membrane sacs

• Golgi vesicle - small membrane sacs

Describe the function of the Golgi apparatus

• modifies protein and lipids, adds carbohydrates to produce glycoproteins and glycolipids

• Packages proteins/ lipids into Golgi vesicles

• Produces lysosomes

Describe the function of the Golgi vesicles

• transports proteins/ lipids to their required destination

• E.g moves to and fuses with cell membrane

Describe the structure of lysosomes

• membrane

• Hydrolytic enzymes

Describe the function of lysosomes

• release hydrolytic enzymes (lysozymes)

• To break down/ hydrolyse pathogens or worn out cell components

Describe the structure of mitochondria

• outer membrane

• Cristae - inner membrane fold

• Matrix - small (70s) ribosomes, circular DNA

Describe the function of mitochondria

• site of aerobic respiration

• To produced ATP for energy release

• E.g for protein synthesises/ vesicle movement/ active transport

Describe the structure of chloroplasts

• double membrane

• Stroma: thylakoid membrane, small 70s ribosomes, circular DNA, starch granules/ lipids droplets

• Lamellae - thylakoid linking grana

• Grana - stacks of thylakoid

Describe the function of chloroplasts

• absorbs light energy for photosynthesis

• To produce organic substances, e.g carbohydrates/ lipids

Describe the structure of cell walls

• composed of mainly cellulose (a polysaccharide), in plants/ algae

• Composed of chitin (a nitrogen-containing polysaccharide) in fungI

Describe the function of the cell wall

• provides mechanical structure to cell

• So prevents cell changing shape or bursting under pressure due to osmosis

Describe the structure of the cell vacuole

• tonoplast membrane

• Cell sap

Describe the function of the cell vacuole

• maintains turbot pressure in cell (stops plant wilting)

• Contains cell sap which stores sugars, amino acids, pigments and any waste chemicals

How are eukaryotic cells organised in complex multicellular organisms

• become specialised for specific functions

• Organised into tissues, organs and organ systems

What is a tissue

• group of specialised cells with a similar structure

• Work together to perform a specific job/ function, often with the same origin

What is an organ

• aggregations of tissues performing specific functions

What is an organ system

• group of organs working together to perform specific functions