Topic 3 - The Voice of the Genome

Structure of eukaryotic cell

have nucleus (contains DNA), mitochondria and chloroplasts (which are all membrane bound organelles)

Nucleus

Structure:

• surrounded by a double membrane called the envelope. which contains pores enabling molecules to enter and leave the nucleus

Function:

• stores the nucleolus and the DNA

Nucleolus

Structure:

• located in the middle of the nucleus

Function:

• site of ribosome production

Mitochondrion

Structure:

• oval shaped membrane bound by a double membrane (envelope)

• The inner membrane is folded to form projections called cristae with a fluid matric on the inside containing enzymes for cellular respiration

Function:

• site for aerobic respiration

Centrioles

Structure:

• hollow tubes made up of 9 proteins, 9 protein microtubes

• globular protein chains

• always come in a pair

Function:

• spindle

• help transport in cytoplasm

Lysosome

Structure:

• vesicles containing digestive enzymes, bound by a single membrane.

• protein

Function:

• intracellular digestion

• Autolytic function (killing of cells)

Gogli apparatus

Structure:

• a series of fluid-filled, flattened and curved sacs with vesicles surrounding the edges.

Function:

• transport of proteins and lipids

• produces lysosomes

Smooth endoplasmic reticulum (SER)

Structure:

• system of interconnected membrane bound flattened sacs

Function:

• produces and processes lipids +steroids

Cell surface membrane

Structure:

• found on the outside of the cytoplasm

• two rows of phospholipids

• in the phospholipid bilayer you find channel and carrier proteins

• glycolipids and glycoproteins

• cholesterol

Function:

• control what exits and enters the cell

• Phospholipid - hydrophilic head, hydrophobic tails for small and non-polar molecules to go through

• Channel & carrier proteins - facilitated diffusion of large and charged molecules

• Glycoproteins & glycolipids - cell adhesion

• Cholesterol - controls fluidity

Ribosomes

Structure:

• made up of RNA & proteins

Function:

• site of protein synthesis

Rough endoplasmic reticulum (RER)

Structure:

• system of interconnected membrane bound flattened sacs that have ribosomes attatched to them on the surface.

Function:

• folds and processes proteins made on the ribosomes; often located close to the nucleus.

Explain the role of the rER and the Golgi apparatus in protein transport within cells + their role in the formation of extracellular enzymes

• Rough Endoplasmic Reticulum (rER):

  • Protein Synthesis: Ribosomes on the rER synthesize proteins, including enzymes.

  • Folding and Modification: Newly synthesized proteins enter the rER lumen, where they are folded and undergo initial modifications (e.g., glycosylation).

• Golgi Apparatus:

  • Further Modification: Proteins from the rER are transported to the Golgi apparatus in vesicles. Here, they undergo further modifications, such as additional glycosylation and sulfation.

  • Sorting and Packaging: The Golgi apparatus sorts and packages proteins into vesicles based on their final destinations. Extracellular enzymes are packaged into secretory vesicles.

• Formation of Extracellular Enzymes:

  • Transport to Cell Membrane: Secretory vesicles containing extracellular enzymes move to the cell membrane.

  • Exocytosis: Vesicles fuse with the cell membrane, releasing the enzymes outside the cell to perform their functions.

Structure of a prokaryotic cell

nucleoid, cell wall, cell membrane, plasmids, flagella, pili, capsule, ribosomes, cytoplasm

Cell wall

Structure:

• The cells rigid outer layer made out of peptidoglycan

Function:

• provides strength and support

Capsule

Structure:

• Protective slimy layer

Function:

• Helps the cell to retain moisture and adhere to surfaces

Plasmid

Structure:

• Circular

Function:

• DNA

flagellum

Structure:

• A tail-like structure

Function:

• rotates to move the cell

pili

Structure:

• hair-like structures

Function:

• attach to other bacterial cells to allow the exchange of plasmids

ribosomes

Structure:

• Composed of 2 subunits

Function:

• site of protein synthesis

mesosomes

Structure:

• infoldings of the inner membrane

Function:

• May contain enzymes required for respiration

• May just be artefacts from the preparation process for microscopy

Ovum structure

Nucleus, cytoplasm, cortical granules, zona pellucida. follicle cells, lipid droplets

Nucleus function

Contains the genetic material (haploid no. Of chromosomes)

Cytoplasm function

Contains nutrients and organelles needed for embryo development

cortical granules function

Releases enzymes after fertilisation to harden the zona pellucida and prevent polyspermy

zona pellucida function

A jelly-like layer that protects the ovum and regulates interactions with sperm during fertilisation

follicle cells function

Form a protective coating around the egg

lipid droplets function

Store energy for early development stages

Sperm structure

nucleus, acrosome, head, mid-section, flagellum

Nucleus function

Contains the genetic material (haploid no. Of chromosomes)

Acrosome function

Contains digestive enzymes which break down the zona pellucida an allow sperm to penetrate the egg

Head function

Contains the nucleus and acrosome

Mid-section function

Contains mitochondrion which provides energy for the rotation of the flagellum which allows the cell to move

flagellum function

For movement to swim to the egg

Describe the process of fertilisation

• The sperm head meets the zona pellucida and the acrosome reaction occurs - enzymes digest the zona pellucida.

• The sperm head fuses with the cell membrane of the egg allowing the sperm nucleus to enter the egg cell.

• The cortical reaction occurs which causes the zona pellucida to harden and prevents polyspermy.

• The nuclei fuse and a full set of chromosomes is restored, forming a diploid zygote.