Cells Flashcards
(49 cards)
1
Q
Magnification equation
A
Magnification = image size / real object size
2
Q
What is resolution?
A
- Minimum distance apart that two objects can be distinguished as separate objects in an image.
- The greater the resolution the more clear the image will be
3
Q
Properties of optical microscopes
A
- Use light
- Cannot see small internal organelles eg, ribosomes
- Low resolution and magnification
4
Q
Properties of SEM (scanning electron microscope)
A
- Can use thick specimen
- Lower resolution than TEM
- 3D image
5
Q
Properties of TEM (transmission electron microscope)
A
- High resolution, so you can see internal organelles
- Only used on thin specimens
- No living specimens
6
Q
Why should a solution be kept ice cold?
A
To reduce enzyme activity that breaks up organelles
7
Q
Why should the solution be isotonic?
A
To prevent the osmotic pressure of the cell changing and destroying the organelles
8
Q
Why is a buffer solution used?
A
To maintain the pH
9
Q
What do eukaryotic cells have?
A
A nucleus and membrane bound organelles
10
Q
Function of the nucleus
A
- Controls the cell’s activity
- The nuclear pores allow substances to pass in and out of the nucleus
- The nucleolus makes ribosomes
11
Q
Function of RER (rough endoplasmic reticulum)
A
- Folds and processes proteins
12
Q
Function of SER (smooth endoplasmic reticulum)
A
- Synthesises and processes lipids
13
Q
Function of Golgi apparatus
A
- Processes and packages new lipids and proteins
- Also makes lysosomes
14
Q
Function of Golgi vesicles
A
- Stores lipids and proteins
- Transports it out of the cell
15
Q
Function of Mitochondria
A
- Site of aerobic respiration where ATP is produced
16
Q
Function of Ribosomes
A
- Site where proteins are made
17
Q
Function of lysosomes
A
- Contain lysozymes which are digestive enzymes
18
Q
Function of cell membrane
A
- Regulates the movement of substances in and out the cell
- Also has receptor molecules
19
Q
Function of the cell wall
A
- Supports cell
20
Q
Function of chloroplasts
A
- Site where photosynthesis takes place
21
Q
Function of cell vacuole
A
- Helps maintain pressure and keep cell rigid
- Involved in isolation of unwanted chemicals
22
Q
Function of capsule
A
- Protect bacteria from attacks from the cells of the immune system
23
Q
What are viruses?
A
- Non living structures which contain nucleic acid enclosed in a capsid
24
Q
The role of mitosis?
A
To produce identical daughter cells for growth and asexual reproduction
25
Stages of cell cycle
- Mitosis
- Interphase
- Cytokinesis
26
What is mitosis?
- A form of cell division that produces identical cells,
| - There are four stages of mitosis: prophase, metaphase, anaphase and telophase
27
What happens in interphase?
- The cell grows & then prepares to divide
- Chromosomes & some organelles are replicated
- Chromosomes also begin to condense
28
What happens in cytokinesis?
- The parent & replicated organelles move to opposite sides of the cell
- The cytoplasm divides thus producing two daughter cells
29
Why is mitosis important?
- Growth: all cells produced are identical so organisms can grow using mitosis.
- Repair: all cells produced are identical so organisms can replace dead tissues using mitosis.
- Reproduction: some single-celled organisms, like yeast, reproduce by dividing into two identical daughter cells by mitosis.
30
What occurs in prophase?
- Chromosomes condense
- Centrioles move to opposite ends of the cell forming spindles
- Nuclear envelope breaks down
31
What occurs in metaphase?
- Chromosomes line up along the middle of the cell
| - They become attached to the spindle by the centromeres
32
What occurs in anaphase?
- Centromeres divide, separating each pair of sister chromatids
- Spindles contract, pulling chromatids to opposite poles of the spindle
33
What occurs in telophase?
- Chromatids reach the opposite ends on the spindle
- They uncoil and become chromosomes
- Nuclear envelope forms around each group of chromosomes creating 2 nuclei
- Cytokinesis finishes leaving two genetically identical daughter cells
34
Steps of Required Practical 2- Mount slide
- Cut 2 cm tip of the root and place in HCl for about 15 minutes
- Rinse the tip with distilled water
- Cut off 1 mm of the tip and place on a slide
- Cover the sample with toluidene blue and macerate with amounted needle
- Add cover slip and squash the material gently and place under a microscope
- Calculate the mitotic index
35
How to calculate the mitotic index
Number of cells undergoing mitosis / total number of cells observed
36
How do you calculate the size of cells?
- Using a eyepiece graticule
| - Or the IAM equation
37
What happens in G1?
- Cell growth and protein production
38
What happens in the S phase?
DNA replication
39
What is binary fission?
- The process at which prokaryotic cells divide
40
The stages of binary fission
- The circular DNA in the cells replicates & both copies attach to the cell membrane. Plasmids replicate.
- The cell membrane begins to grow between the two DNA molecules & begins to pinch inwards, dividing the cytoplasm in two.
- A new cell wall forms between the two DNA molecules dividing the original cell.
41
What is a cell membrane made up of?
- Phospholipids with proteins in between
| - Also contains receptors
42
Why are cell membranes described as fluid mosaic?
- The phospholipids are constantly moving
| - The proteins are scattered
43
The role of cholesterol
- Make the membrane more rigid and reduce the lateral movement of the phospholipids.
- It also prevents the leakage of water and dissolved ions from the cell as it is very hydrophobic.
44
The role of glycolipids
- Acts as cell surface receptors for certain molecules.
| - They also allow cells to adhere(stick) to one another to form tissues
45
The role of glycoproteins
- Acts as cell surface receptors and neurotransmitters.
| - These allow cells to recognise one another as well as attach to form tissues
46
What is diffusion?
- Passive movement of small, non-polar, lipid soluble molecules such as carbon dioxide and oxygen from an area of high concentration to an area of low concentration
47
What is osmosis?
- Diffusion of water molecules from an area of high water potential to an area to low water potential through a partially permeable membrane
48
Active transport
- Can transport all types of molecules through carrier proteins from an area of low concentration to an area of high concentration.
- However, this process requires energy in the form of ATP
49
Factors that increase the rate of diffusion
- Large surface area
- Short diffusion pathway
- Steep diffusion gradient
- An increase in temperature
