section 2 - Cell structure

get a hint

hint

magnification

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

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