Biology Learning Goals - Cell Structure

Define Eukaryotic cell

Cells with a nucleus and other membrane-bound organelles

Define ultrastructure

Those features which can be seen by using an electron microscope

Draw and label diagrams of typical plant and animal cells

Nucleus

Contains coded genetic information in the form of DNA. Directs protein synthesis - controls metabolic activities of the cell

Nucleolus

Area within the nucleus responsible for producing ribosomes. Composed of proteins and RNA

Nuclear envelope

Double membrane surrounding nucleus protects it from damage. Has nuclear pores allowing molecules to move in and out of the nucleus

R.E.R.

Ribosomes bound to surface. Responsible for synthesis + transport of proteins

S.E.R.

Responsible for lipid + carbohydrate synthesis and storage

Golgi apparatus

Compact structure formed of cisternae, no ribosomes. Modifies + packages proteins into vesicles

Ribosomes

Free floating or on R.E.R., not surrounded by membrane. Constructed of RNA. Site of protein synthesis

Mitochondria

Site of final stages of respiration producing ATP.

Chloroplasts

Responsible for photosynthesis

Lysosomes

Specialised vesicles containing hydrolytic enzymes - responsible for breaking down waste material

Plasma membrane

Controls entry + exit to cell etc.

Centrioles

Composed of microtubules, 2 together from a centrosome involved in assembly + organisation of spindle fibres during cell division

Cell wall

Rigid - holds shape. Supports cell and plant as a whole and acts as defense against pathogens

Flagella/cilia

Move cell, move mucus/eggs etc. Outside cell can be sensory

State similarities and differences between plant and animal cells

Both have nucleus, golgi, mitochondria, membrane etc.

Only plant: Chloroplasts, permanent vacuole, cell wall

Mitochondria - diagram and labels

Chloroplast - diagram and labels

Process of protein synthesis (step by step)

RNA leaves nucleus through nuclear pore

Proteins synthesised on ribosomes on R.E.R.

Pass into cisternae and packaged into vesicles

Vesicles move to golgi apparatus using cytoskeleton

Vesicles fuse with cis face of golgi (proteins enter)

Proteins structurally modified. Leave in vesicles from trans face.

Secretory vesicles carry proteins to cell membrane

Vesicles fuse with cell surface membrane releasing contents by exocytosis

Outline the structure of the 3 components of the cytoskeleton

Microfilaments - contractile fibres formed form protein actin. Responsible for cell movement + contraction during cytokinesis

Microtubules - globular tubulin proteins polymerise to form tubes that form scaffold-like structure. Determine shape of cell + are tracks for organelle movement e.g. vesicles (Spindle fibres are microtubules)

Intermediate fibres - mechanical strength + help maintain integrity

Describe the functions of the cytoskeleton in a cell

Strength, Shape, Movement

Describe importance of the cytoskeleton in movements of cilia

Cilia/Flagella - 9+2 arrangement

2 central microtubules + 9 pairs

Pairs of parallel microtubules slide over one another - beating motion

Describe the importance of the cytoskeleton in the shape and behaviour of neutrophils

Neutrophils have multilobed nucleus and are very flexible to squeeze though small gaps to get to site of infection

Define Prokaryotic cell

Cells with no membrane-bound nucleus or organelles

Examples of both eukaryotic and prokaryotic cells

Eukaryotic - Plant, Animal, Fungi

Prokaryotic - Bacteria

Prokaryotic cell - diagram and lables

Cell wall (P)

Made of peptidoglycan/murein

Maintains structure

Ribosomes (P)

Smaller - 70s

Protein synthesis

Bacterial flagellum

Thinner, no 9+2, Rotates with whip like movement to propel cell along

Plasma membrane (P)

Controls entry/exit of cell

Plasmid (P)

Rings of DNA in cytoplasm

Bacterial Chromosome

Supercoiled to make it compact. Genes are grouped into operons so turned on/off together

Pili

Organelles of adhesion allowing bacteria to colonize environmental surfaces or cells and resist flushing

Slime capsule

Defense, Moisture

Comparison of Eukaryotic and Prokaryotic

Nucleus

DNA

DNA organisation

Extra chromosomal DNA

Organelles

Cell wall

Ribosomes

Cytoskeleton

Reproduction

Cell type

Cell surface membrane

	Prokaryotic	Eukaryotic
Nucleus	Present	Not present
DNA	Circular	Linear
DNA organisation	Proteins fold and condense DNA	Associated with proteins called histones
Extra chromosomal DNA	Circular	Only present in certain chloroplasts and mitochondria
Organelles	Non-membrane bound	Both with/without membranes
Cell wall	Peptidoglycan	Fungi = chitin  Plant = cellulose
Ribosomes	70S	80S
Cytoskeleton	Present	More complex
Reproduction	Binary fission	Asexual or sexual
Cell type	Unicellular	multicellular
Cell surface membrane	Present	Present

Describe endosymbiotic theory

There is compelling evidence that mitochondria and chloroplasts were once primitive bacterial cells.

Symbiosis occurs when two different species benefit from living and working together. When one organism actually lives inside the other it's called endosymbiosis. The endosymbiotic theory describes how a large host cell and ingested bacteria could easily become dependent on one another for survival, resulting in a permanent relationship. Over millions of years of evolution, mitochondria and chloroplasts have become more specialized and today they cannot live outside the cell.