Topic 3 - Voice of the Genome

Describe prokaryotic cells

- no nuclei or other membrane-bound organelles
- DNA circular, not wrapped around proteins but lies free in cytoplasm
- cell wall is always present
- ribosomes (70s)

structure and function of cell wall in prokaryotic cells

rigid structure made of peptidoglycan
it gives the cell shape and prevents rupture

structure and function of cell surface membrane in prokaryotic and eukaryotic cells

layer of phospholipids and protein that surrounds the cell
controls what enters and leaves the cell

structure and function of cytoplasm in prokaryotic and eukaryotic cells

jelly-like substance filling the cell
site of many chemical reactions

structure and function of capsule in prokaryotic cells

slimy layer outside of the cell wall
protects the cell and prevents dehydration

structure and function of flagella in prokaryotic cells

hollow cylindrical structure (only some bacteria have)
rotate to move the cell

Structure and Function of Pili in prokaryotic cells

hairlike features that form a fringe around the bacteria
used for attaching to surfaces and other bacteria

structure and function of circular chromosome in prokaryotic cells

DNA is located (they lack nucleus)
The circular DNA contains genes that encode proteins

structure and function of plasmids in prokaryotic cells

Small, circular DNA molecules. May many per cell.
Contain additional genes, also encoding proteins

Structure and function of mesosome in prokaryotic cells

An infolding of the cell surface membrane
Site of respiration

Structure and function of ribosomes in a prokaryotic and eukaryotic cells

Very small organelles made of RNA and protein
Site of protein synthesis

Describe eukaryotic cells

Membrane bound organelles, nuclei mitochondria
DNA is inside the nucleus. It is linear and wrapped around proteins
Not all have cell wall
Large ribosomes (80S)
Most are larger than prokaryotic

Structure and function of nucleus in eukaryotic cells

Surrounded by two membranes (the nuclear envelope) containing nuclear pores. Contains chromatid (DNA wrapped around proteins).

DNA contains genes that encode proteins
Nuclear pores allow molecules to enter and leave the nucleus

Structure and function of nucleolus in eukaryotic cells

Darkly staining part of the nucleus, there may be more than one.
Where ribosomes are made

Structure and function of rough endoplasmic reticulum
(rER) in eukaryotic cells

Interconnected of membrane bound sacs covered with ribosomes. Often found near nucleus
It fold proteins that have been made by ribosomes on its surface

Structure and function of Smooth endoplasmic reticulum (sER) in eukaryotic cells

Interconnected system of membrane bound sacks
Makes lipids

Structure and function of mitochondria in eukaryotic cells

Rod shaped organelles surrounded by a double membrane. Inner membrane is folded into cristae
Site of aerobic respiration, make ATP

Structure and function of lysosomes in eukaryotic cells

Small sacs bound by a single membrane containing digestive enzymes
Breakdown unwanted structures in the cell

Structure and function of centrioles in eukaryotic cells

Found as a pair at right angles to each other.
Usually next to or close to nucleus
Each is a cylinder made of microtubules

Involved in forming the spindle which is needed when a cell divides

Structure and function of Golgi apparatus in eukaryotic cells

Stack of curved, flattened, membrane bound scans called cisternae. Vesicles are often seen at the edges.

Modifies proteins received from the ER and packages them into vesicles to be transported through the cell.
Also makes lysosomes.

Feature and adaption: Follicle cells

surround the egg

release chemicals to attract the sperm

Feature and adaption: Zona pellucida

jelly-like layer outside of the cell surface membrane

thickens and hardens to prevent polyspermy

Why is the egg cell large?

increase the chance of fertilisation

Feature and adaption: receptors

receptors for the sperm in the cell surface membrane

allow the sperm to bind

Feature and adaption: haploid nucleus in egg cells and sperm

half the number of chromosomes than a normal body cell
so that the diploid number of chromosomes is restored at fertilisation

Feature and adaption: cytoplasm

containing lipid droplets
provide energy for cell divisions after fertilisation

Feature and adaption: cortical granules

(specialised lysosomes containing digestive enzymes) around the edge of cell near cell surface membrane

release their contents (enzymes) to make the zona pellucida thicken and harden, preventing polyspermy

Feature and adaption: receptors on the sperm

on its cell surface membrane
to detect chemicals released by the egg and to bind to egg cell surface membrane

Feature and adaption: streamlined shape

reduces resistance when swimming

Feature and adaption: lots of mitochondria

provide atp as a source of energy to move the flagellum

Feature and adaption: acrosome

containg digest enzymmes (acrosin)
digest zona pellucida to allow the sperm to reach and fuse with the cell surface membrane of the egg

Feature and adaption: flagellum

propel sperm towards egg

why are gametes haploid

when gametes fuse, the correct (diploid) number of chromosomes is restored. It allows the mixing of alleles from father and mother generating variation

describer homologous pair

same size, same genes in same order, can have different alleles of each gene (versions)