section 2 - Cell structure

magnification

how many times larger an image is when compared to the object

magnification = image / actual

resolution

the smallest distance between two objects under the microscope that they are distinguisable

cell fractionation

* before place cells in a buffer with same water potential, same pH and a cool temperature
* then blend cells in step called homogentation, remove large pieces of debris
* then slowly spin cells in centrifuge in step called ultracentrifugation
* collect the heaviest collected organelle (nucleus). collect supernatant and then repeat spinning supernatant until all the organelles are collected

order for cell fractionation

→nucleus and whole cells

→lysosomes and mitochondria

→microsomes

→ribosomes and viruses

the nucleus

* nuclear envelope

→double membrane surrounding the nucleus controlling the entry and exit of substances. often extension of the rough endoplasmic reticulum, with ribosomes
* nuclear pores

→around 3000 in a nuclear envelope, control the entry and exit of very large molecules (messenger RNA)
* nucleoplasm

→ jelly like substance which occupies majority of the nucleus
* chromosomes

→linear DNA
* nucleolus

→small sphere where the manufacture of messenger RNA is synthesised

mitochondrion

* surrounded by a double membrane to control entry and exit of the material. folded into cristae
* cristae is an extension of membrane to provide large surface area for the use of enzymes
* matrix makes up remainder of mitochondria. contains enzymes, DNA, proteins ,lipids
* mitochondria are used to produce energy aerobically. they produce ATP which is used in metabolic reactions and other important processes around the body

chloroplasts

* chloroplast double membrane which is highly selective of which substances it will allow in and out.
* chloroplasts contains stacks of thylakoids called grana. these contain the chlorophyll and have bridges connecting the stacks. first stage of photosynthesis takes place here (light absorption)
* stroma is the matrix filled fluid which is where second stage of photosynthesis occurs (synthesis of sugars)
* has DNA and RNA to quickly make proteins for photosynthesis
* large surface area in grana so lots of light can be absorbed

Endoplasmic reticulum

* 3D sheet continuous from the nuclear envelope
* smooth endoplasmic reticulum
* no ribosomes
* synthesise store and transport lipids
* synthesise store and transport carbohydrates
* rough endoplasmic reticulum
* has ribosomes
* large surface area for glycoprotein synthesis and protein synthesis

Golgi appartatus

* occurs in all eukaryotic cells
* functions
* add carbs to proteins to form glycoproteins
* produce secretory enzymes such as enzymes secreted by the pancreas
* transport modify and store lipids
* form lysosomes


* structure
* stack of membranes that make up flattened stacks
* small round hollow vesicles

lysosomes

* hydrolysis material ingested by the phagocytic cells
* releases enzymes
* completely breaks down cells once they’ve been destroyed

ribosomes

* free or connected to the RER
* 80s in eukaryotes
* 70s in prokaryotes

cell wall

* consist of polysaccharides such as cellulose
* thin layer called lamella which marks the boundary between adjacent cells
* provide strength to cell and plant as a whole
* allow water to pass in through cell wall

vacuole

* fluid filled sack bounded by a single membrane
* sugar and amino acid storage
* pigments are attractive to pollenating insects

cell specialisation

* tissues
* group of similar cells working together to perform a similar
* epithelial tissues are in animals and they line surfaces of organs.
* organs
* group of similar tissues together to form an organ to perform a specific function
* examples:
* muscles to turn food
* spongy mesophyll for gaseous diffusion
* xylem to transport water an ions
* phloem to transport organic material
* organ systems
* organs that work together as a single unit
* examples:
* digestive systems to digest and process food
* respiratory system for breathing and gas exchange
* circulatory system to circulate blood

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prokaryotic cells

* cell wall and capsule are made up of mixture of polypeptides and polysaccharides
* cell wall is a physical barrier that excludes certain substances from entry
* capsule protects bacteria from other cells and sticks other bacteria cells together in order to gain more protection
* cell surface membrane controls the entry and exit of substances from between cell and external environment
* circular DNA contains genetic information for replication and cells and coding for proteins
* plasmids are small circular sections of DNA containing gene that aid bacteria to survive in certain conditions
* flagella for species in need to move. some species may have more than one.

virus structure drawing

main features of virus molecule

* capsid - protective protein coat to provide protection for genetic material
* genetic material - virus consists of a core which contains RNA and DNA. has a reduced genome and only produces the proteins which it cannot obtain for host cells
* attachment proteins - allows the virus to attach to the host cell