Ch7: Cell Structure

Question 1

Name the two types of microscopes

Answer 1

-Compound
-Electron

Question 2

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

Answer 2

1. Used to magnify
2. Eyepiece lens: The one you look through (10x)
   Objective lens: The one directly above the specimen
3. Low power (4x)
   Medium power (10x)
   High power (40x)
4. Eyepiece lens x objective lens
   e.g. 10x x 40x = 400x total magnification

Question 3

Name the parts of the compound microscope and their functions

Answer 3

-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

Question 4

Describe the electron microscope

Answer 4

-Uses a beam of electrons instead of light
-Electrons have a shorter wavelength than light
-Resolution is better and the magnification is higher

Question 5

Name the two types of electron microscopes and how they work

Answer 5

-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

Question 6

How do you prepare a microscope slide?

Answer 6

-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

Question 7

What is protoplasm?

Answer 7

All the living parts of a cell

Question 8

Describe the cell membrane

Answer 8

-Proteins are completely or partially embedded in the phospholipid bilayer
-Some proteins are attached but some are detachable and move throughout the bilayer

Question 9

What is the function of the cell membrane?

Answer 9

-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

Question 10

What is ultrastructure?

Answer 10

-The detail of a structure as seen using an electron microscope

Question 11

What are organelles?

Answer 11

Structures found inside cells
e.g. nucleus, cell membrane, ribosomes

Question 12

What is the function of the nucleus?

Answer 12

Control centre of the cell

Question 13

Describe the structure of a nucleus

Answer 13

-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

Question 14

Describe chromosomes

Answer 14

-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

Question 15

What makes up a nucleus? What are their functions?

Answer 15

-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

Question 16

What is the cytoplasm?

Answer 16

The living material in a cell outside the nucleus (jelly-like liquid in the cell)

Question 17

Function of the cytoplasm?

Answer 17

Organelles are suspended in the cytoplasm

Question 18

Function of mitochondria?

Answer 18

Supply energy to the cell (Cells with fewer mitochondria produce less energy)

Question 19

Describe the structure of a mitochondrion

Answer 19

-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

Question 20

What are chloroplasts?

Answer 20

Green structures in plants in which photosynthesis occurs

Question 21

Describe the structure of chloroplasts

Answer 21

-Surrounded by a double membrane
-They have membrane stacks which contain the green pigment chlorophyll
-They also have a loop of DNA

Question 22

Function of cell wall?

Answer 22

To support and strengthen the cell

Question 23

Describe the structure of the cell wall

Answer 23

-Made of cellulose
-Fully-permeable meaning all molecules can pass through

Question 24

Function of vacuoles?

Answer 24

-Provide structural support
-Storage, waste disposal, protection, growth

Question 25

Describe vacuoles

Answer 25

-Fluid filled space bounded by a membrane
-Fluid is called cell sap, which contains water, food, minerals and pigments

Question 26

Describe the structure of ribosomes

Answer 26

-Tiny, bead-like structures
-Made of RNA and protein
-Combine amino acids to make proteins

Question 27

Function of ribosomes?

Answer 27

To make proteins

Question 28

What are the differences between plant and animal cells?

Answer 28

PLANT
-Have a cell wall
-May have chloroplasts
-Large vacuole

ANIMAL
-No cell wall
-No chloroplasts or chlorophyll
-Small vacuole (if any)

Question 29

What are prokaryotic cells?

Answer 29

Do not have a nucleus or membrane-enclosed organelles
e.g. bacteria

Question 30

Describe prokaryotic cells

Answer 30

-Single-celled
-Circular loop of DNA that is not surrounded by a membrane
-Small cells

Question 31

What are eukaryotic cells?

Answer 31

Have a nucleus and cell organelles, all of which are enclosed by membranes
e.g. animal, plants and fungi

Question 32

Describe eukaryotic cells

Answer 32

-Large cells
-More advanced than prokaryotic cells

Question 33

What stain is used to see animal cells?

Answer 33

Methylene Blue

Question 34

What stain is used to see plant cells?

Answer 34

Iodine