cell structure Flashcards
1
Q
basic cell theory
A
- all living organisms are made of one or more cells
- the cell is the most basic unit of life
- all cells arise only from pre existing cells by divison
2
Q
What common features do cells share?
A
- every living cell is surrounded by a membrane, which separates the cell contents from everything else outside
- Dna
- ribosomes
- cytoplasm
- cells contain genetic material which stores all of the instructions needed for the cell’s activities
- many of these activities are chemical reactions, catalysed by enzymes produced inside the cell
- cells have their own energy release system that powers all of the cell’s activities
3
Q
What are the three levels of magnification on a typical high school microscope?
A
- x40 (low power)
- x100 (medium power)
- x400 (high power)
4
Q
What is the formula to calculate magnification?
A
size of image/actual size of specimen
image size/ actual size = magnification
5
Q
Explain striated muscle as an atypical example which questions the cell theory
Hello
A
- building blocks of striated muscle are muscle fibres (similar to cells)
- they have an average length of 30mm in humans, whereas other cells typically have a size of less than 0.03mm
- have multiple nuclei
6
Q
Explain fungi as an atypical example of a cell which questions the cell theory
A
- fungi consists of narrow thread-like structures called hyphae
- hyphae have a cell membrane and a cell wall
- in some types of fungi, the hyphae are divided up into small cell-like sections by cross walls called septa
- in other types of fungi, however, there are no septa and each hypha is an uninterrupted tube-like structure with many nuclei spread along it
7
Q
Explain algae as an atypical example of a cell which questions the cell theory
A
- algae are organisms that feed themselves by photosynthesis and store their genes inside nuclei
- many algae consist of one microscopic cell
- giant algae can grow to a length as much as 100mm despite only having one nucleus
8
Q
Outline the seven functions of life: MR H GREN
A
- Nutrition: obtaining food, to provide energy and the materials needed for growth
- Metabolism: chemical reactions inside the cell, including cell respiration to release energy
- Growth: an irreversible increase in size
- Response: the ability to react to changes in the environment
- Excretion: getting rid of the waste products of metabolism
- Homeostasis: keeping conditions inside the organism within tolerable limits
- Reproduction: producing offspring either sexually or asexually
Note: Unicellular organisms must carry out all functions of life in the one cell
9
Q
Unicellular organisms must carry out all functions of life in the one cell
true of false
A
true
10
Q
Limitations on cell size
A
- surface area to volume ratio is important in the limitation of cell size
- large numbers of chemical reactions take place in the cytoplasm of the cells (metabolism)
- the rate of the reactions (metabolic rate) is proportional to the volume of the cell
- substances used for the reactions must be absorbed by the cell and the waste products must be removed; the rate at which substances cross this membrane depends on its surface area
- surface area:volume ratio is also important for heat production and loss
11
Q
Outline the ways in which Paramecium demonstrates the functions of life
A
- Paramecia are surrounded by small hairs called cilia which allow it to move (responsiveness)
- Paramecia engulf food via a specialised membranous feeding groove called a cytostome (nutrition)
- Food particles are enclosed within small vacuoles that contain enzymes for digestion (metabolism)
- Solid wastes are removed via an anal pore, while liquid wastes are pumped out via contractile vacoules (excretion)
- Essential gases enter (e.g. O2) and exit (e.g. CO2) the cell via diffusion (homeostasis)
- Paramecia divide asexually (fission) although horizontal gene transfer can occur via conjugation (reproduction)
12
Q
Outline the ways in which Scenedesmus demonstrates the functions of life
A
- Scenedesmus exchange gases and other essential materials via diffusion (nutrition / excretion)
- Chlorophyll pigments allow organic molecules to be produced via photosynthesis (metabolism)
- Daughter cells form as non-motile autospores via the internal asexual division of the parent cell (reproduction)
- Scenedesmus may exist as unicells or form colonies for protection (responsiveness)
13
Q
Emergent properties
A
- multicellular organisms have properties that emerge from the interaction of their cellular components
- multicellular organisms can be regarded as cooperative groups
- the characteristics of the whole organism, including the fact that it is alive, are known as emergent properties
- emergent properties arise from the interaction of the component parts of a complex structure
14
Q
Cell differentiation
A
- specialized tissues can develop by cell differentiation in multicellular organisms
- different cells perform different functions
- often a group of cells specialize in the same way to perform the same function (tissue)
- the development of cells in different ways to carry out specific functions is called differentiation
- involves the expression of some genes and not others in a cell’s genome (cells have all genes needed to specialize in every possible way but only expresses certain ones)
15
Q
Stem cell
A
- can divide again and again to produce copious quantities of new cells; good for the growth of tissues or the replacement of cells that have been lost/damaged
- not fully differentiated; can differentiate in different ways to produce different cell types
- essential in embryonic development for the above reasons
16
Q
What is an example of a non-therapeutic use for embryonic stem cells
A
- produce large quantities of striated muscle fibres/meat for human consumption
17
Q
Use of stem cells to treat Stargardt’s disease
A
- usually caused by a genetic mutation, the membrane protein used for active transport in the retina cells malfunction
- as a result, photoreceptive cells in the retina degenerate; vision becomes progressively worse
- can be treated by injecting retina cells derived from embryonic stem cells into the patient’s eyes
- the cells attach themselves to the retina and improve the vision of the patient
18
Q
Use of stem cells to treat leukemia
A
- leukemia is a type of cancer caused by mutations involving the production of abnormally large numbers of white blood cells, which are produced in the bone marrow
- to cure leukemia, the cancer cells in the bone marrow that are producing excessive white blood cells must be destroyed
- this can be done via chemotherapy (using chemicals that kill dividing cells) but to remain healthy in the long term, the patient must be able to produce white blood cells needed to fight disease
- stem cells that can produce blood cells must be present, but they are killed by chemotherapy
- therefore, they extract stem cells from the patient by sticking a large needle into a large bone (ie. pelvis) and remove the fluid from the bone marrow; they perform chemotherapy, killing the cancer cells but also causing the bone marrow to lose its ability to produce blood cells; the stem cells that were extracted are returned to the patient’s body and they reproduce/re-establish themselves in the bone marrow
19
Q
Outline the three sources of stem cells and the ethics of using them
A
- embryos –> embryonic stem cells
- almost unlimited growth potential/can differentiate into any type of cell
- less chance of genetic damage due to accumulation of mutations than with adult stem cells
- more risk of becoming tumour cells than with adult stem cells
- likely to be genetically different from an adult patient receiving the tissue
- ethical controversy because removal of cells from the embyro is likely to kill it - umbilical cord –> cord blood stem cells
- easily obtained/stored
- fully compatible with the adult individual that it comes from; no rejection issues
- limited capacity to differentiate into different cell types (naturally develops into blood cells)
- limited quantities of stem cells from one baby’s cord
- ethical because umbilical cord is discarded whether or not stem cells are taken from it. - bone marrow –> adult stem cells
- difficult to obtain; very few and buried deep in tissues
- limited capacity to differentiate/less growth potential than embryonic stem cells
- less chance of malignant tumours developing
- fully compatible with the individual it comes from; no rejection issues
- ethical because removal of stem cells does not kill the adult it comes from
20
Q
Electron microscopes
A
- much higher resolution than light microscopes
- reveal the ultrastructure of cells
- needed to see viruses with diameter of 0.1 micrometres
