cell structure and function

What is cell theory?

Cells are the basic structural units of living organisms. Cell theory states that all living cells are made up of cells, cells are the smallest functioning unit of living things and all cells come from pre-existing cells.

Contrast the differences and compare the similarities between Prokaryotes and Eukaryotes?

prokaryotes

  • no nuclear membrane

  • simple internal structure

  • no membrane bound organelle

  • most primitive type of cell

  • unicellular

eukaryotes

  • can be multicellular

  • nuclear membrane surrounding genetic material

  • numerous membrane-bound organelle

  • complex internal structure

  • appeared approximately 1 billion years ago

  • have golgi apparatus

similarities

  • both have ribosomes

  • both have DNA

  • both have cytoplasm

  • both have plasma membrane

  • both unicellular

Why do eukaryotes posses more organelles than prokaryotes?

  • the presence of a nucleus in eukaryotic cells allows for compartmentalisation of cellular functions

  • segregation enables different organelles to perform specific tasks efficiently, leading to increased complexity and specialisation within eukaryotic cells

  • prokaryotic cells lack a nucleus and membrane-bound organelles, resulting in a simpler structure with fewer specialised compartments

What are membrane-bound organelles?

It is a tiny compartment within a cell that is surrounded by a membrane. This organelle is often found in eukaryotes to help protect it and help carry out various tasks efficiently.

Why are cells so small?

Cells are small so they are able to maximise their ratio of surface area to volume (SA:V ratio).

What is the importance of a high SA:V ratio?

A smaller object is said to have a higher SA:V ratio, meaning things can diffuse in and out of it very quickly. Cells have to diffuse things in out of the cell at a rapid rate in order to survive.

Therefore they are small to maximise diffusion rate and not too large (as they will not be able to survive).

Which organelles are unique to plant cells, and which are unique to animal cells?

plant cells

  • has chloroplast

  • has a cell wall

  • large vacuole

animal cells

  • lysosomes

  • flagella

  • small vacuole

organelles in both

  • has a nucleus

  • cell membrane

  • have a vacuole

  • mitochondria

Define types of organelles

plasma membrane

  • forms the boundary between the cells and extracellular environment

  • regulates movement of substances in and out of the cell

  • separates inside and outside of cell

cell wall

  • provides strength and support

  • prevents over-expansion of cell

  • allows passage of water, oxygen and carbon dioxide

cytoplasm

  • holds organelles in place

nucleus

  • controls metabolic activity

  • controls DNA replication during cell division

  • repair of genetic material

rough ER

  • attaching sugar groups to some proteins to form glycoproteins

  • folding proteins into correct functional shape

smooth ER

  • detoxification of harmful products

  • contain enzymes that are involved in phospholipid and steroid production

  • storage and release of substances

golgi apparatus

  • modifications of proteins received from rough ER

  • sorting and packaging proteins into secretory vesicles

  • transports proteins around cell and plasma membranes

mitochondria

  • involved in respiration of ATP, which is the form of energy used by cells

chloroplast

  • site for photosynthesis

lysosomes

  • digestion of some excess macromolecules (carbohydrates, proteins, lipids)

  • breakdown of non-functioning cell organelles

  • breakdown of substances such as bacteria

vacuole

  • contains water enzymes and other molecules

flagella

  • involved in the movement of cells

Origin of mitochondria

  • Mitochondria were probably prokaryotic cells capable of oxidative metabolism (using O2 to create energy)

  • One was eaten by a eukaryotic cell, but not digested

  • Instead it stayed inside the eukaryotic cell, producing energy for it in return for a safe place to live

What is the fluid mosaic model?

The fluid mosaic model is a way to describe the structure of cell membranes. The membrane is made up of a fluid-like phospholipid bilayer with proteins and other molecules floating around in it, kind of like a mosaic. This model helps us understand how the membrane is flexible and can allow certain things to pass through while keeping others out

  • fluid - always moving, not solid

  • mosaic - collection of things stuck together

  • model - representation