cells Flashcards
(63 cards)
1
Q
What are the functions of lysosomes?
A
- hydrolyse phagocytic cells
- exocytosis - releases enzymes to the outside of the cell to destroy material
- completely break down dead cells (autolysis)
2
Q
What are the functions of Golgi Apparatus?
A
- secrete carbohydrates
- form lysosomes
- transport, modify and store lipids
- add carbohydrates to form glycoproteins
- produce secretory enzymes
- molecules are ‘labelled’ with their destination
3
Q
What are the functions of mitochondria?
A
- site of ATP production
- site of aerobic respiration
- has the DNA that codes for the enzymes needed for respiration
4
Q
What are the functions of a nucleus?
A
- site of DNA replication and transcription (making mRNA)
- contains the genetic code for each cell
5
Q
What are the functions of the SER?
A
- synthesis
- stores lipids and carbohydrates
6
Q
What are the two types of electron microscopes?
A
- scanning electron microscope (SEM)
- transmitting electron microscope (TEM)
7
Q
What is the formula for magnification?
A
magnification = size of image / size of object
8
Q
What are the features of an SEM?
A
- SEMs knock electrons off the specimen and these electrons come together to form an image
- SEM images can be three-dimensional
- Specimens do NOT have to be thin like when using a TEM
- Resolution is lower than that produced by a TEM
9
Q
What are the features of a TEM?
A
- TEMs use electromagnets to focus the electron beam
- TEMs are high resolution microscopes
- in thin specimens, you can see the internal structures of organelles such as chloroplasts
10
Q
What is meant by ‘membrane-bound organelle’?
A
an organelle that is surrounded by a phospholipid layer
11
Q
Examples of membrane bound organelles
A
- mitochondria
- endoplasmic reticulum (SER and RER)
- chloroplasts
- lysosomes
- nucleoli & nuclei
12
Q
Examples of non-membrane bound organelles
A
- ribosomes
- cytoskeleton
- centrioles
13
Q
What is meant by magnification?
A
how many times bigger the image is compared to the object
14
Q
What is meant by resolution?
A
the minimum distance that objects can be in order for them to appear as separate things
15
Q
Why is a solution cold in homogenisation?
A
so the the rate of enzyme (lysosyme) activity is decreased
16
Q
Why is a solution buffered in homogenisation?
A
it maintains a constant pH so it does not denature proteins
17
Q
Why is a solution isotonic in homogenisation?
A
has the same water potential as the tissue so no net movement of water by osmosis, so this prevents cell lysis
18
Q
What are ribosomes made of?
A
- ribosomal RNA and proteins
19
Q
What is the maximum resolution of an optical microscope?
A
0.2um
20
Q
What is the maximum magnification of an optical microscope?
A
x1,500
21
Q
What is the maximum magnification of a TEM?
A
x500,000
22
Q
What is the maximum resolution of a TEM?
A
0.0001um
23
Q
Limitations of EMs (in general)
A
- can’t view live specimens/process due to the interior of the microscope being in a vacuum
- specimen has to be sliced very thinly
- requires an extensive staining process that can lead to artefacts
24
Q
What is the maximum resolution of an SEM?
A
0.0001um
25
What is the maximum magnification of an SEM?
x100,000
26
What are the 3 stages of interphase?
- G1
- S
- G2
27
What happens in the G1 phase?
the cell grows and makes a new set of organelles and proteins for the daughter cells
28
What happens in the S
phase?
- the DNA in the cell is replicated, so that the two daughter cells can each get one set of DNA
- also a checking of genetic material in this phase
- summary: synthesis of new DNA
29
What happens in the G2 phase?
- cell growth continues
- synthesis of special proteins in preparation for mitosis
30
What is mitosis necessary for?
- growth
- replacing/repairing cells
- asexual reproduction
31
What are the stages of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
32
What happens during prophase?
- chromosomes condense and are now visible when stained
- nuclear envelope breaks down
- nucleolus disappears
33
What happens during metaphase?
- chromosomes line up at the equator of the cell
- spindle fibres reach the chromosomes and attach to the centromeres
- each sister chromatid is attached to a spindle fibre
34
What happens during anaphase?
- the sister chromatids separate at the centromere
- spindle fibres begin to shorten
- the separated sister chromatids (now called chromosomes) are pulled to opposite poles by the spindle fibres
35
What do prokaryotes have instead of mitochondria?
mesosomes - attach to cell membrane
36
What are the functions of glycoproteins?
- acts as recognition sites
- help cells attach to one another + form tissues
37
why are phospholipids present in cell membranes
they form a stable barrier that regulates what enters and exits the cell
38
why are proteins present in cell membranes
- cell-cell recognition
- selective transport
- structural support
39
why are glycoproteins present in cell membranes a level biology
- cell-cell recognition (helps recognise antigens from pathogens)
- cell adhesion (helps form tissues and provide structural integrity)
- cell signalling (act as receptors that receive signals from hormones and neurotransmitters, and relay these signals to the inside of the cell)
40
what is facilitated diffusion
net movement of large polar molecules or ions moving from area of high conc. to area low conc. using carrier proteins and protein channels
41
what is simple diffusion
Simple Diffusion is the net movement of particles down a concentration gradient, from a high concentration to low concentration.
42
the two types of diffusion are?
- simple
- facilitated
43
what is osmosis
the passage of water from a region where it has a higher water potential to a region where it has lower water potential down the water potential gradient through a selectively permeable membrane
44
what does cholesterol do for the cell surface membrane?
- restricts lateral movement of other molecules
- makes membrane less fluid at high temperatures
- prevents leakage of water and dissolved ions from the cell
45
what are the type of molecules that can't pass through the membrane
- water soluble
- large molecules
46
what is meant by water potential
the pressure caused by water molecules
47
Which cell is involved in the humoral immunity?
B-lymphocyte
48
What is an antigen
a protein that is part of the cell-surface membrane of invading microbes or diseased cells
49
Which cell is involved in the cell-mediated response?
T-lymphocyte
50
Where do B-lymphocytes mature in?
Bone marrow
51
Where do T-lymphocytes mature in?
Thymus gland
52
What are T-lymphocytes activated by?
antigen presenting cells
53
What are examples of antigen presenting cells?
- body cells (host cells) invaded by a virus
- transplanted cells
- cancer cells
- phagocytes
54
What cells release antibodies?
plasma cells
55
what is a monoclonal antibody?
an artificially produced antibody that binds and neutralises one specific antigen
56
what are the uses of monoclonal antibodies
- medical testing
- medical diagnosis
- pregnancy tests
57
what is a benefit of using monoclonal antibodies when treating cancer?
reduces harmful side effects of chemotherapy/radiotherapy
58
what type of diseases can monoclonal antibodies be used to diagnose?
- prostate cancer
- hepatitis
- covid-19
- chlamydia
59
how many antibodies does the ELISA test use?
2
60
what activates b-lymphocytes
t-lymphocytes
61
what to b-lymphocytes divide into?
plasma cells
62
list the steps involved in the immune response
1. phagocytosis
2. activation of t-lymphocytes
3. activation of b-lymphocytes
4. production of antibodies
63
what activates t cytotoxic cells
t helper cells
