Life and Cells 1 & 2

Week 1 content

List the major Elements of Life

Carbon, Hydrogen, Nitrogen, Phosphorus(sulphur found in amino acids) and Oxygen.

What are hydrogen bonds

The between water molecules due to uneven charge distribution.

Detailed: Water consists of two hydrogen atoms bonded covalently to an oxygen which results in a polar molecule as electrons are unequally shared across the atoms.

What is water cohesion

The attraction of water molecules to EACH OTHER. eg. creates a column of water where plant xylem cells allow water to move via transpiration

What is water adhesion

The attraction of water molecules to polar surfaces such as glass

What is water/ surface Tension

A property of water due to strong hydrogen bonding at the surface.

eg. some insects can “walk” on the surface

Why is water a universal solvent?

Water dissolves more substances than any other liquid due to the water molecule’s uneven charde, allowing it to interact with other polar molecules and charged substances which distributes them evenly throughout the liquid.

Wha is pH?

A measure of the concentration of protons (hydrogen ions) in a solution.

How does Water and pH affect living organisms?

eg1. Carbonic acid is formed when carbon dioxide dissolves in water, which is important for maintaining pH balance in blood.

eg2. Water acidification may result in an excess of CO2 being dissolved into oceans. The carbonate is then not available to form calcium (CaCO3 at the bottom) to provide the compound needed for marine organisms to survive.

How is the diversity of life classified?

Living organisms are classified into three domains of life through rRNA.

Bacteria: are prokaryotic where most has a cell well that can be classified as either gram positive or negative.

Archaea: Similar in size to bacteria but can vary in shape and share some traits of eukaryotes (eg. composition of the cell membrane)

Eukaryotes:Cells that contain membrane-bound organelles and a nucleus. (eg. plants, fungi, and animals)

Define what a cell is

A cell is the smallest unit of organisation that can perform all the activities essential for life.

note: All cells have a membrane

List some characteristics of life

• reproduce

• grow and develop

• respond to environment

• metabolise to use energy

Explain the differences between prokaryotes and eukaryotes

Eukaryotic cells	Similarities	Prokaryotic cells
Eukaryotic cells have membrane-bound organelles. The largest of these is usually the nucleus. Eukaryotes are typically 10- 100 μm in diameter.	Prokaryotic and eukaryotic cells share some features: a plasma membrane, DNA and ribosomes.	Prokaryotic cells are simpler, typically smaller, the DNA is not contained within a nucleus and they do not carry membrane bound organelles. Prokaryotic cells are typically smaller than eukaryotic cells. Bacteria are typically 1-5 μm in diameter.

Explain the concept of endosymbiosis

Endosymbiosis states that ancestors of eukaryotes took up oxygen using non-photosynthetic prokaryrotic cells.

identify characteristic structures of bacterial cells

Prokaryotes: bacteria and archaea —>

• fimbriae which is the surface of some prokaryotes

• nucleoid where the cell’s Dna is located

• Ribosomes that synthesises proteins

• cell wall

• plasma membrane (membrane enclosing cytoplasm

• Flagella

identify characteristic structures of eukaryotic cells

Eukaryotic cells contain membrane bound organelles. Compartmentalisation of eukaryotic cells allows for diverse local environments where different functions can be carried out

Plant and animal cells differ in key structures: plant cells have a cell wall, chloroplasts for photosynthesis, and a large central vacuole, while animal cells lack these and instead possess centrosomes and lysosomes

Describe the endomembrane system and its features

The endomembrane system regulates protein traffic and performs metabolic functions

• endoplasmic reticulum

  • Smooth ER lacks ribosomes and plays a role in metabolic processes

  • rough ER is used to secrete proteins. They are segregated and transported via vesicles

• Golgi apparatus: vesicles may travel to the golgi apparatus where proteins are modified, stored, and transported onwards.

• Lysosomes: removes “junk and clutter” in the cell as well as segregates an acidic environment that contains enzymes

• Vacuoles: vesicles derived from the ER and golgi apparatus —> may remove water to maintain ion concentrations

List the main components of the cytoskeleton

A network of fibers that provides support and mobility in cells.

• microtubules (tubulin polymers)

  • Maintenance of cell shape (compression-resisting “girders”) and provides ‘tracks’ for organelles; cell motility (as in cilia or flagella);chromosome movements in cell division; organelle movements.

• Microfilaments (actin filaments)

  • Maintenance of cell shape (tension bearing elements) and also provide ‘pulling’ forces; changes in cell shape; muscle contraction; cytoplasmic streaming in plant cell; cell motility (as in amoeboid movement); division of animal cells.

• Intermediate filaments

  • Maintenance of cell shape (tension bearing elements); anchorage of nucleus and certain other organelles; formation of nuclear lamina