Module 2.1 - Cell Structure Flashcards
Role of the nucleus
Stores organism’s genome
Controls the cell
Transmits genetic information
Provides instructions for protein synthesis
Role of chloroplasts
Site of photosynthesis
First stage of photosynthesis, light energy is trapped by chlorophyll and used to make ATP (occurs in grana)
Second stage of photosynthesis, hydrogen reduced carbon dioxide using energy from ATP to make carbohydrates (occurs in the stroma)
Main points about light microscopes
Magnification up to x1500 Resolution up to 200nm Stain using methylene blue or acetic orcein for DNA Glass lenses Light as radiation source Dead specimen prepared on slide
Role of smooth endoplasmic reticulum
Contains enzymes that catalyse reactions involved with lipid metabolism (e.g. synthesis of cholesterol, lipids/phospholipids needed by the cell and steroid hormones)
Involved with absorption, synthesis and transport of lipids
Role of ribosomes
Those bound to exterior of RER are manly for synthesising proteins that will be exported outside the cell
Those free in the cytoplasm are mainly the site of assembly of proteins that will be used inside the cell
Main points about TEMs
Magnification up to x500,000 Resolution up to 0.1nm Stain using heavy metal or metal salt Electromagnetic lenses Electrons as radiation source Dead specimen prepared as thin and trained 2D image
Role of lysosomes
Keep powerful hydrologic enzymes separate from rest of the cell
Many of them in phagocytes
Engulf old cell organelles and foreign matter, digest them and return these components to the cell for reuse
Role of centrioles
Spindle forms from centrioles before a cell divides
Involved in formation of cilia and undulipodia
Main points about vacuoles
Large and permanent part of plant cells only
Tonoplast membrane is filled with water and sugars to push against the cell wall to keep the cell turgid
Role of the nuclear envelope
Separates contents o nucleus from rest of the cell
Outer and inner membranes fuse so some dissolved substances and ribosomes can pass through
Pores in membrane allow larger substances (e.g. mRNA) to leave the nucleus or enter the nucleus (e.g. steroid hormones)
Role of nucleolus
Contains RNA
Is where ribosomes are made
Define magnification
The degree to which the size of the image is the larger than the size of the object itself
Main points about actin microfilaments
2 intertwined strands of actin 7nm diameter Maintain cell shape Cause muscle contractions Involved in cell division (cytokinesis) Cause a certain type of movement called pseudopodia seen by amoeba and some white blood cells
Main points about plant cell walls
Made of cellulose (a carbohydrate polymer)
Forms grid of strands which makes the wall strong
Supports the cell because of pressure from liquid in the cell, keeping it rigid and helping to support the plant
Define cytoskeleton
Network of protein fibres within a cell that gives structure and shape to the cell and also moves organelles around the cell
Main points about microtubules
Main part of cytoskeleton
Hollow cylinders of tubulin (protein) about 25nm diameter
Maintain cell shape
Connect organelles to each other to keep them in place
May be used to move microbes through liquid or waft liquid past a cell
Role of mitochondria
Site of ATP (energy currency) production during aerobic respiration
Main points about flagella
Structurally the same in all types of cells
Sticks out of surface
Cylinder with 9 microtubules in a circle and 2 more microtubules in a central bundle
Move using energy from ATP
Role of rough endoplasmic reticulum
Intracellular transport system - cisternae form channels for moving substances between areas of the cell
Provides large surface area for ribosomes
Main points about intermediate filaments
Thick cables made of keratin
10nm diameter
Maintain cell shape
Anchor nucleus and organelles
Main points about vesicles
Membrane bound sacs
Carry substances around
Role of Golgi apparatus
Modify proteins (e.g. add sugar molecules to make glycoproteins; add lipid molecules to make lipoproteins; fold into their 3D shape) Proteins are packaged into vesicles and then either stored in the cell or moved to the plasma membrane
What are the three parts of the cytoskeleton?
Microtubules
Intermediate filaments
Actin microfilaments
Define resolution
The degree to which it is possible to distinguish between two objects that are very close together
Advantages of light microscopes
Relatively cheap
Easy to use
Portable
Can be used to study whole living specimens
Disadvantages of light microscopes
Lower magnification than electron microscopes
Lower resolution than electron microscopes
Main points about SEMs
Magnification up to x100,000 Resolution up to 10nm Stain using metal or metal salt Electromagnetic lenses Electrons as radiation source Dead specimen 3D image
Explain microtubules motors
They are proteins found on microtubules
Use ATP to move organelles or cell contents along the fibres
This is how chromosomes are moved in mitosis as spindle fibres are microtubules made by centrioles
This is how vesicles move from the ER to Golgi apparatus
Main points about cilia
Occur in large numbers on ciliates epithelial tissue
Less than 10 micrometers long
Beat to and fro to move substances across cell surfaces
Move mucus across airway linings
Move egg down oviducts
Rare in plants
Main points about laser scanning microscopes
Also called confocal microscopes
Use laser light to scan an object point by point and assemble the pixel information on the computer screen
Images are high resolution with high contrast
Able to observe whole living specimens
