Ch7: Cell Structure Flashcards
Name the two types of microscopes
-Compound
-Electron
Lenses
1. Function
2. 2 types of lenses + description
3. Names and Magnification of the different powers of the lenses
4. How to calculate magnification
- Used to magnify
- Eyepiece lens: The one you look through (10x)
Objective lens: The one directly above the specimen - Low power (4x)
Medium power (10x)
High power (40x) - Eyepiece lens x objective lens
e.g. 10x x 40x = 400x total magnification
Name the parts of the compound microscope and their functions
-Lenses
-Stage: to place the slide on
-Clips: holds the slide in place
-Diaphragm: adjusts the amount of light reaching the slide
-Coarse focus: approximate focusing
-Fine focus: precise focusing
-Light source: illuminates the slide
-Nosepiece: rotates to move the desired lens in place
-Condenser: focuses light on the slide
-Arm
Describe the electron microscope
-Uses a beam of electrons instead of light
-Electrons have a shorter wavelength than light
-Resolution is better and the magnification is higher
Name the two types of electron microscopes and how they work
-Transmission Electron Microscope: sends a beam of electrons through a thin section of the specimen to show the internal structure
-Scanning electron microscope: Uses a beam of electrons to provide a surface view of the specimen
How do you prepare a microscope slide?
-Cover slip is held at a 40 degree angle to the slide and lowered slowly using a mounted needle to prevent air bubbles being trapped
-Cover slip is used to prevent the sample from drying out and to protect the lens from the stain
What is protoplasm?
All the living parts of a cell
Describe the cell membrane
-Proteins are completely or partially embedded in the phospholipid bilayer
-Some proteins are attached but some are detachable and move throughout the bilayer
What is the function of the cell membrane?
-Retain the cell contents
-Selectively permeable to control what enters and leaves the cell
-Recognise molecules that tough them (to recognise what is/isnt allowed in the cell)
-Give some support to the cell
What is ultrastructure?
-The detail of a structure as seen using an electron microscope
What are organelles?
Structures found inside cells
e.g. nucleus, cell membrane, ribosomes
What is the function of the nucleus?
Control centre of the cell
Describe the structure of a nucleus
-Surrounded by a double membrane with several nuclear pores
-The nucleolus stains darkly when using the microscope
-Contains strands of DNA which are arranged into chromosomes
Describe chromosomes
-Every organism has a definite number of chromosomes, e.g. humans have 46 chromosomes
-Genes are located on chromosomes
-When a cell is not dividing, chromosomes are called chromatin in this form
What makes up a nucleus? What are their functions?
-Double membrane
-Nuclear pores: controls the movement of substances (like mRNA) in and out of the nucleus
-DNA (deoxyribonucleic acid)
-Chromatin: Name given to chromosomes when they are elongated and not dividing (tangle of DNA in the nucleus)
-Chromosomes: individual strands of DNA
-Nucleolus: Contains RNA, DNA, and proteins and makes ribosomes
What is the cytoplasm?
The living material in a cell outside the nucleus (jelly-like liquid in the cell)
Function of the cytoplasm?
Organelles are suspended in the cytoplasm
Function of mitochondria?
Supply energy to the cell (Cells with fewer mitochondria produce less energy)
Describe the structure of a mitochondrion
-Surrounded by a double membrane
-Energy is released on the inner membrane, more infoldings allows more energy to be produced
-Each mitochondrion has its own loops of DNA
-Active mitochondria convert to inactive mitochondria if the cell rests for too long
What are chloroplasts?
Green structures in plants in which photosynthesis occurs
Describe the structure of chloroplasts
-Surrounded by a double membrane
-They have membrane stacks which contain the green pigment chlorophyll
-They also have a loop of DNA
Function of cell wall?
To support and strengthen the cell
Describe the structure of the cell wall
-Made of cellulose
-Fully-permeable meaning all molecules can pass through
Function of vacuoles?
-Provide structural support
-Storage, waste disposal, protection, growth
Describe vacuoles
-Fluid filled space bounded by a membrane
-Fluid is called cell sap, which contains water, food, minerals and pigments
Describe the structure of ribosomes
-Tiny, bead-like structures
-Made of RNA and protein
-Combine amino acids to make proteins
Function of ribosomes?
To make proteins
What are the differences between plant and animal cells?
PLANT
-Have a cell wall
-May have chloroplasts
-Large vacuole
ANIMAL
-No cell wall
-No chloroplasts or chlorophyll
-Small vacuole (if any)
What are prokaryotic cells?
Do not have a nucleus or membrane-enclosed organelles
e.g. bacteria
Describe prokaryotic cells
-Single-celled
-Circular loop of DNA that is not surrounded by a membrane
-Small cells
What are eukaryotic cells?
Have a nucleus and cell organelles, all of which are enclosed by membranes
e.g. animal, plants and fungi
Describe eukaryotic cells
-Large cells
-More advanced than prokaryotic cells
What stain is used to see animal cells?
Methylene Blue
What stain is used to see plant cells?
Iodine
