Chapter 3 - Cell Structure Flashcards
Cell
The smallest biological entity that still retains the characteristics of life
Two main types of cells
1) Prokaryotic Cells
2) Eukaryotic Cells
What are Prokaryotic Cells?
- Small cells that don’t have a nucleus or membrane-enclosed organelles
- Eg. Bacteria
What are eukaryotic cells?
- Large cells that have a nucleus and cell organelles, which are both enclosed by membranes
- eg. Animal cells
Where are the DNA of eukaryotic cells located?
In the chromosomes
Cell ultrastructure
The structure of a cell as seen with an electron microscope
Cell membrane
- a.k.a. Plasma membrane
- a very thin boundary around the cell
3 functions of a cell membrane
1) Control what enters and leaves the cell
2) Gives support/ holds in contents of the cell
3) Recognise the molecules that touch them
Cell membrane is composed of
Phospholipids and proteins
List the 6 labels in a cell membrane diagram
1) Pore
2) Proteins
3) Phospholipid
4) Phosphate Head
5) Lipid Tail
6) Phospholipid Bilayer
Selectively permeable
Allows the free passage of some molecules and prevents the passage of others
Cytoplasm
The watery solution that fills the cell, which is 90% H2O
Functions of the cytoplasm
1) Acts as a storage are for nutrients
2) To support and separate the organelles
3) Medium in which most metabolic reactions occur
Cytosol
Th liquid part of the cytoplasm (cytoplasm without organelles)
Nucleus
- A spherical structure surrounded by the nuclear membrane with contains DNA and the nucleolus
- Largest organelle in the cell
DNA in the nucleus
In the form of chromosomes or chromatin
Nucleolus
An area in the nucleus where ribosomes are made
Functions of the nucleus
1) Directs the activity of the cell
2) DNS replication and nuclear division
3) Controls the formation of mRNA (transcription)
Nuclear membrane
- A double membrane which contains numerous pores
Functions of the nuclear membrane
1) To retain nuclear contents
2) Has pores to allow materials in and out of the nucleus
Give the labels four labels of the nucleus
1) Nucleolus
2) Nuclear pore
3) Chromatin
4) Double Nuclear Membrane
Ribosomes
-Small organelle shaped like a burger bun which is made of RNA and protein
Function of the ribosome
-Site of protein synthesis, a process called translation
Mitochondrion
- A rod shaped organelle which has its own DNA and ribosomes which is surrounded by a double membrane
- Has inner membrane containing unfolding a which increase the surface area
Function of the mitochondrion
1) Powerhouse of the cell
2) Site of respiration, (release of energy from food)
Cell Wall
- Made from cellulose(a carbohydrate)
- Fully permeable ie. Cannot control what leaves and enters the cell)
Two functions of the cell wall
1) Provides support and mechanical straight to the cell and the whole plant
2) Stops cell membrane bursting when the cell is full of water
Large Vacuole
- Membrane filled with fluid called cell sap
- Fills the centre of the cell pushes content to the edge of the cell
Two functions of the large vacuole
1) Stores sugar and salt dissolved in the water
2) Stores excretory products
Chloroplast
An organelles with internal membrane stacks which contain the green pigment called chlorophyll , surrounded by a double membrane and has its own DNA and ribosomes
Chloroplast Function
Trap sunlight during photosynthesis which allows plants to make their own food in the form of glucose
Simple microscopes
Microscopes composed of a single lens just like a magnifying glass
Compound microscopes
Microscope with two lenses
Electron microscope
Electrons pass through a vacuum so not to be deflected by air molecules
(Provide a much higher magnification but the samples are placed in a vacuum and therefore cannot be living)
T.E.M.
Transmission Electron Microscope
-Sends a beam of electrons through a thin section of the specimen allowing the internal structure to be viewed in great detail
S.E.M.
Scanning Electron Microscope
-Uses beams of electrons to provide a surface view of the specimen
Magnification formula
Magnification= objective x eyepiece
Stage
The stage holds the slide which contains the specimen to be viewed
Diaphragm (microscope)
The diaphragm controls the amount of light reaching the specimen
Fine focus
The fine focus sharpens the image under high and low power. It moves the stage by small amounts
Coarse focus
The coarse focus focuses the image under low power
Objective lens
A lens attached to the nosepiece which magnifies the specimen
Eyepiece lens
The eye piece lens magnifies the image, usually 10 times
