(2.1.1g) Cell Ultrastructure

Cell ultrastructure (animal)

• Nucleus

• Nucleolus

• Nuclear envelope

• SER

• RER

• Golgi apparatus

• Ribosomes

• Mitochondria

• Vesicles (transport and secretory)

• Lysosomes

• Plasma membrane

• Centrioles

Which ones aren’t membrane bound

• nucleolus

• Ribosomes

• Cytoplasm

• Centrioles

Cell ultrastructure (plants additions)

• Vacuole

• Chloroplasts

• Cell wall

Nucleus function

• Stores genetic material

• Site of transcription

• Makes ribosomes in nucleolus

Nucleus ultrastructure

• Nucleolus - composed of proteins and RNA (used to make rRNA) + not membrane bound

• Nuclear pore

• Nuclear envelope - double membrane that contains pres

• Chromatin - DNA wound around histone proteins, condenses and coils tightly into chromosomes before cell division, otherwise more spread out

• Nucleoplasm

Nucleus ultrastructure functions

• Nucleolus - forms ribosomes necessary for protein synthesis

• Nuclear pore - allows molecules to move in/ out of the cell

• Nuclear envelope - protects nucleus from damage in the cytoplasm

• Chromatin - condenses DNA

Nucleus size

10 micrometers

RER function

Synthesis and transport of proteins

• Folds and processes proteins made in ribosomes

• Destroys deformed proteins

• Prepared proteins for transport to Golgi apparatus

RER structure

• System of membranes containing fluid filled cavities (cisternae) that are continuous with the nuclear membrane

• Coated with ribosomes

SER function

Responsible for lipid and carbohydrate synthesis, storage and transport

• Synthesis of cholesterol, steroid hormones

• Helps with detoxification

SER structure

• System of cisternae that are continuous with the nuclear membrane

• NO ribosomes

Golgi apparatus function

• Modifying proteins and packaging them into vesicles (into lysosomes which stay in the cell or secretory vesicles which leave the cell)

• forms lysosomes

• Forms lipoproteins and glycoproteins

Golgi apparatus structure

• Compact structure formed of cisternae

• Contains smaller vesicles

• Kinda looks like the WiFi signal

• NO ribosomes

Ribosomes function

Site of protein synthesis

Ribosomes structure

• Either free floating or attached to the RER

• Made up of proteins and rRNA

• consists of a large and small subunit

• Eukaryotic: 80S ribosomes

• Prokaryotic: 70S ribosomes

Mitochondria function

Site of the final stages of cellular respiration, where ATP is produced

Mitochondria structure

• Matrix - enzyme rich liquid

• MtDNA - own DNA

• Double membrane - inner highly folded to form cristae

• Can produce own ribosomes and reproduce themselves

Lysosomes function

Contains hydrolytic enzymes to break down organelles and pathogens

Lysosomes structure

• Round organelles

• Contain hydrolytic enzymes

• Surrounded by membrane to keep enzymes separate from cytoplasm of cell

Name 3 things that lysosomes engulf

• Old organelles

• Foreign matter

• Bacteria

Vesicle function

Transport and store materials in and around cells

Vesicle structure

• Membranous sacs

• Single membrane that contains fluid inside

How do vesicles move from one organelle to another

• Cytoskeleton provides pathways/ tracks for movement

• Vesicle moves along microfilaments

• Microtubules are broken down

• ATP energy is used

Centrioles function

• Involved in the assembly and organisation of the spindle fibres during cell division (centrosomes)

• In organisms with flagella and cilia, centrioles are thought to play a role in the positioning of those structures

Centrioles structure

• Component of cytoskeleton

• Made of microtubules (hollow)

• 2 centrioles at right angles to each other form the centrosome

What eukaryotic organisms do not have centrioles

Not in flowering plants and most fungi

Cytoplasm function

• Solvent

• Reaction medium

• Stable environment due to high SHC

Cell surface membrane function

• Controls movement of substances into and out of cells

• Cell signalling

Name 5 substances that need to travel through nuclear pores

• mRNA

• tRNA

• Nucleotides

• Steroid hormones

• rRNA

Cell surface membrane structure

• See other topic

• Phospholipid bilayer

Chloroplast function

Site of photosynthesis - reactions to take place in grana and stoma

Chloroplast structure

• Contains own DNA and ribosomes for replication

• Surrounded by double membranes

• Thykaloids - membrane bound containing chlorophyll

• Thykaloids stack up to form grana

• Grana are connected by lamellae (thin thykaloids)

• Stroma - fluid

Where are chloroplasts found

The green part of plants (leaves and stems)

Chloroplast size

2-5 micrometres

Vacuole function

• Storage of water, sugars and salts

• Helps to maintain pressure within cells, which keeps the cells rigid and stops the plant from wilting

Vacuole structure

• contains cell sap

• Surrounded by tonoplast - selectively permeable membrane

Cell wall function

• Support cell

• Prevents cell from bursting

• Allows exchange of substances between cells

Cell wall structure

• Made of cellulose in plants

• Made of peptidoglycan in bacteria

• Made of chitin in fungi

• Freely permeable

Flagella function and structure

• Enable cell motility (movement)

• Made of long microtubules

• E.g. sperm cell

Cilia function

• Moves mucus out of lungs

• Moves eggs into uterus

• Made of microtubules (hair like projections)

Algae cells

• Same as plant cells

• Chloroplasts are different shapes

Fungi cells

• contain most of the organelles found in plant cells

• Do not contain chloroplasts

• Cell wall made of chitin instead of cellulose

Name 3 organelles that have structures to increase surface area

• Mitochondria - cristae on inner membrane

• RER/ SER - cisternae

• Chloroplast - grana

Where is DNA found

• Nucleus

• Mitochondria - mDNA

• Chloroplasts - cpDNA