UNIT 1 SECTION 2

cell organisation and structure

define eukaryotic cell

a type of cell that contains a true nucleus and membrane bound organelles

what types of organisms can be classed as eukaryotes

animals and plants

what is included in an animal cell

ribosomes, cytoplasm, mitochondria, lysosomes, vacuole, nucleus, rough endoplasmic reticulum, golgi body, cell membrane

what is included in a plant cell

cytoplasm, nucleus, cell membrane, cell wall, mitochondria, vacuole, chloroplast, smooth endoplasmic reticulum, nucleolus, golgi body, rough endoplasmic reticulum

describe the structure of the nucleus

● Surrounded by nuclear envelope, a semi-permeable double membrane.

● Nuclear pores allow substances to enter/exit.

● Dense nucleolus made of RNA & proteins assembles ribosomes.

describe the function of the nucleus

• contains DNA which codes for or controls protein synthesis

• DNA replication takes place here

• and transcription produces mRNA

what is chromatin

a DNA protein complex found in eukaryote cells

what is the function of chromatin

condenses before cell division to form chromosomes

describe the structure of mitochondria

• Double membranes (mitochondrial envelope)

• folded inner membranes form cristae (large surface area)

• fluid matrix contains mitochondrial DNA, respiratory enzymes, lipids and protein

describe the function of the mitochondria

● Site of aerobic respiration

● To produce ATP for energy release

● Eg. for protein synthesis / vesicle movement / active transport

describe the structure of the endoplasmic reticulum

series of flattened membrane bound sacs (cisternae) within the cytoplasm , continuous with the nuclear envelope

• two types, rough and smooth ER

describe the function of the smooth ER

produce, package and transport lipids and steroids (lipid synthesis)

describe the function of the rough ER

packaging and storing proteins, producing transport vesicles which merge to form the Golgi body

describe the structure of ribosomes

Made from rRNA and proteins

Found free in the cytoplasm or associated with the RER

describe the function of ribosomes

site of protein synthesis

primary protein structure is formed at the ribosomes

• large subunits join amino acids

• small subunits read RNA

describe the structure of the Golgi body

• Planar stack of membrane-bound, flattened sacs

• cis face aligns with RER.

• Molecules are processed in cisternae.

• Vesicles bud off trans face via exocytosis

describe the function of the Golgi body

• packaging proteins for secretion from the cell

• modifies proteins, producing lysosmes and digestive enzymes (tertiary structure)

describe the structure of lysosomes

fluid filled vesicles surrounded by a single membrane, contains enzymes

describe the function of lysosomes

• contains powerful digestive enzymes to break down worn out organelles or cells

• role in phagocytosis - to digest unwanted materials in the cytoplasm

describe the structure of centrioles

• Cylindrical structure.

• Organised into microtubules in a 9+0 pattern.

• Found in pairs in centrosomes.

describe the function of centrioles

form the spindle during cell division

describe the structure of the chloroplast

• Disk shaped surrounded by double membrane.

• Thylakoids - flattened discs stacked to form grana.

• Grana - contain photosystems with chlorophyll.

• Intergranal lamellae - tubes attach thylakoids in adjacent grana.

• Stroma - fluid-filled matrix.

describe the function of the chloroplast

site of photosynthesis

describe the structure of the permanent vacuole in plants

• surrounded by a single membrane - tonoplast

• contains cell sap

describe the function of the permanent vacuole in plants

• controls turgor pressure

• water storage

• isolates harmful waste products

• maintains PH

define plasmodesmata

cytoplasm filled canals which pass through cell walls and allows the transport of water through the symplastic pathway

briefly explain how secretion of digestive enzymes in a cell (protein synthesis) is an example of how organelles work together

1. nucleus contains DNA which codes for the production of polypeptides

2. ribosomes leave nucleus via nuclear pore, and join rough ER

3. nuclear pores also allow mRNA molecules to leave the nucleus and attach to ribosomes on rough ER

4. protein synthesis takes place at ribosomes

5. the mRNA molecule contains the order of amino acids in a polypeptide chain

6. the rough ER transports the polypeptides via transport vesicles which merge to the Golgi body

7. they are converted into enzymes and packaged into secretory vesicles

8. the vesicles merge to the cell membrane and release enzyme by exocytosis

even BRIEFLYER give the steps to protein synthesis

1. ribosomes leave nucleus

2. mRNA molecules leave nucleus

3. both join onto rough ER

4. polypeptides are transported on transport vesicles

5. taken to the Golgi body

6. enzymes packaged into secretory vesicles

7. released from cell by exocytosis

give 4 similarities of chloroplasts and mitochondria

1. double membrane

2. circle of DNA for self replication

3. have ribosomes

4. produce ATP

give 3 differences of chloroplasts and mitochondria

1. mitochondria = cristae membrane, chloroplast = thylakoid membrane

2. chloroplasts contain photosynthetic pigment

3. mitochondria have an inner matrix, chloroplast have stroma

define prokaryotic cell

A type of cell that does not contain any membrane bound organelles or a true nucleus.

describe the structure and function of the flagella in prokaryotic cells

• long whip like protrusion made of flagellin

• rotates to propel the organism

• sensory organism

how is genetic information stored in prokaryotes

PLASMIDS - small rings of DNA that carry non essential genes

LOOP OF DNA - circular DNA stored in nucleoid

describe the structure and function of pili in prokaryotes

• hair like microfibres that extend through the cell wall

• enable the attachment of bacteria to each other and other surfaces

describe the structure and function of the mesosome

• infolds of the cell membrane

• increase the surface area of the cell

what is the function of the capsule in prokaryotic cells

protective, slimy layer

helps the cell to retain moisture and adhere to other surfaces

how is magnification of an image calculated

magnification = size of image divided by size of specimen

describe cell theory

• All life made up of cells

• All cells come from previously existing cells

• Cell is the basic unit of life

what is a virus

a non - living micro organism that consists of genetic material surrounded by a protein husk

how do viruses differ from eukaryotes and prokaryotes

• viruses are non living

• simple in structure

• genetic material in the form of DNA or RNA

• can reproduce only with a host cell and dont have any ribosomes

why do viruses not fit cell theory

they have no cell membrane, no cytoplasm, no organelles and no chromosomes

what does a virus exist as outside of a living cell

an inert virion

what are viruses that attack bacteria called

bacteriophages

define tissue

group of similar cells that work together to perform a specific function

define organ

A group of tissues working together for specific functions

define organ system

group of organs that work together to perform a specific function

what are the three main types of tissue

muscular, connective, epithelial

what are the main types of epithelial tissue

squamous epithelium, columnar epithelium, cuboidal epithelium

describe epithelium tissue

Covers or lines external and internal body surfaces.

explain cuboidal epithelium

• cube shape

• tissue is one cell thick

• lines kidney and small intestine

explain columnar epithelium

• elongated cells

• line tubes that substances move through (like trachea)

explain squamous epithelium

• consists of flattened cells on basement membranes

• they form walls of the alveoli and line bowman's capsule

what are the three types of muscle tissue

skeletal, cardiac, smooth

explain skeletal muscle

• attached to bone

• has bands of long cells called fibres

• also called voluntary or striated muscle

explain cardiac muscle

• only found in the heart

• cells have stripes but lack long fibres of skeletal muscles

• they contract rhythmically

• don't tire

explain smooth muscle

• contract rhythmically due to spindle shape

• they occur in the skin, walls of blood vessel and digestive/respiratory tracts

• they are involuntary

describe connective tissue

• connects, supports or separates tissues and organs

• contains elastic and collagen fibres in extracellular fluid or matrix

give 4 examples of connective tissue

areolar tissue, collagen, ligaments and adipose