Cell Biology Flashcards
Introduction to cells, Ultrastructure of cells, Membrane structure, Membrane transport, The origin of cells
State three parts of the cell theory
- Living organisms are composed of cells
- Cells are the smallest units of life
- Cells come from pre-existing cells
Outline evidence that supports the cell theory
- Subcellular components have never been seen to perform the functions of life
- Biologists examined tissues from both plants and animals, and saw that every specimen contained at least one or more cell
- We have observed cells coming from other cells, but never observed spontaneous generation
Compare the use of the word theory in daily language and scientific language.
Daily language: a theory is a guess where there is doubt
Scientific language: a theory is something that has been shown to be true through repeated observations and experiments
Outline the functional characteristics of life
Metabolism - organisms carry out chemical reactions such as the synthesis of ATP during cellular respiration
Response - organisms respond and adapt to external stimuli
Growth - organisms increase in size until the cell is too large to function efficiently
Homeostasis - organisms maintain a stable environment within the cell
Reproduction - organisms are able to reproduce (prokaryotes: binary fission, eukaryotes: asexually or sexually)
Nutrition - organisms create or synthesize their own or consumes organic molecules
Excretion - organisms remove waste products
Outline the activities occurring in the volume and at the surface of the cell
Volume: many metabolic reactions which require gases and chemical nutrients and produce waste
Surface area: regulates transport of molecules in and out of the cell
Calculate the surface area, volume, and SA:V ratio of a cell
SA: length * width
Volume: length * width * height
SA:V ratio: SA / volume
Explain the benefits and limitations of using cubes to model the surface area and volume of a cell
Benefits: cubes can be manipulated, visualized, and easily measured
Limitation: most cells are not cubic in shape
Describe the relationship between cell size and the SA:V ratio of the cell
As the cell grows bigger, its volume increases and the cell membrane surface expands. However, the volume increases faster than the SA. Therefore, the amount of surface area relative to the volume (SA:V) decreases.
Explain why cells are often limited in size by the SA:V ratio
Smaller volume requires fewer metabolic nutrients and waste to be transported through the cell membrane.
Relatively more cell membrane for transporting materials into/out of the cell.
Molecules have shorter distance to diffuse within the cell.
List three adaptations of cells that maximize the SA:V ratio
Branching
Microvilli
Folded membranes
Define and provide an example of a multicellular organism
An organism that consists of more than one cell. An example is Homo sapien.
Define and provide an example of a unicellular organism
An organism that consists of only one cell. An example is paramecium.
Define “emergent property”
Properties that arise from the interaction of cellular components.
Provide and example of emergent properties at different hierarchical levels of life
1) Cells grouped together to form tissues
2) Organs are then formed from the functional grouping of multiple tissues
3) Organs that interact may form organ systems capable of carrying out specific body functions
4) Organs systems collectively carry out the life functions of the complete organism
Define “tissue”
A group or collection of similar cells that work together to perform a specific function within an organism
Outline the benefits of cell specialization in a multicellular organism
1) Efficiency in function - specialized cells are more efficient at performing specific tasks compared to generalized cells. For example, red blood cells are specialized for oxygen transport, possessing a unique shape and lacking a nucleus to maximize their capacity for oxygen binding and circulation.
2) Division of labor - cell specialization allows for the division of labor within an organism. This division enables multicellular organisms to perform complex functions more efficiently than single-celled organisms.
3) Formation of tissues and organs - specialized cells organize into tissues with specific functions. In turn, tissues assemble into organs that work together to carry out essential physiological processes.
Define “differentiation”
The process during development whereby newly formed cells become more specialized and distinct from one another as they mature
Describe the relationship between cell differentiation and gene expression
During differentiation, a cell only uses the genes that it needs to follow its pathway of development. Other genes are unused (turned off)
Define “zygote”
The fetus at its earliest stage of development following fertilization, characterized as a diploid cell formed by the fusion of two haploid gametes during fertilization
Define “embryo”
A development of the zygote after it has underwent multiple divisions
List 2 key properties of stem cells that have made them on the active areas of research in biology and medicine today
- Unspecialized, which allows scientists to differentiate into any bodily cell (treatment of disease)
- Divides indefinitely
Explain why stem cells are most prevalent in the early embryonic development of a multicellular organism
During early embryonic development, stem cells possess pluripotency, meaning they have the ability to differentiate into many different cell types. They are mostly prominent in the early development of multicellular organisms, as the fetuses require great numbers of tissues to form necessary organs for survival
Contrast the characteristics of embryonic, umbilical cord, and adult somatic stem cells
Embryonic:
- Derives from the inner cell mass of the blastocyst
- Pluripotent: potential to differentiate into any cell type in the body
Umbilical cord:
- Derives from the blood or tissue of the umbilical word following childbirth
- Multipotent: more limited potential to differentiate
Adult somatic:
- Derives from various tissues and organs of the adult organism
- Multipotent: even further limited potential to differentiate
Define “totipotent”, “multipotent”, and “pluripotent”
Totipotent: can differentiate into any type of cell and can give rise to a complete organism
Pluripotent: can differentiate into all body cells, but cannot give rise to a whole organism
Multipotent: can differentiate into a few closely related types of body cells
Describe features of striated muscle fibers that make them a discrepancy from an atypical cell
- Muscle cells fuse to form fibres that may be very long (>300mm)
- Multiple nuclei despite being surrounded by a single, continuous plasma membrane
Describe features of aseptate fungal hyphae that make them a discrepancy from an atypical cell
- No dividing cell walls (septa), which results in a shared cytoplasm and multiple nuclei
Describe features of giant algae that make them a discrepancy from an atypical cell
- A single cell can grow to be 100mm
Describe characteristics of Paramecium that enable it to perform functions of life
- Surrounded by small hairs called cilia which allow it to move (responsiveness)
. Engulf food via a specialized membranous feeding grove called a cytosome (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 vacuoles (excretion)
- Essential gases enter and exit the cell via diffusion (homeostasis)
- Divide asexually via fission, although horizontal gene transfer car occur via conjunction (reproduction)
Describe characteristics of Scenedesmus that enable it to perform the functions of life
- Gases and other essential materials are exchanged 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)
- May exist as unicells or form colonies for protection (responsiveness)
Outline why stem cells are used in medical research and treatment
Stem cells can differentiate into all cells, meaning that they can be used to treat damaged tissue in medical treatment.
Outline the cause and symptoms of Stargardt’s disease
Cause: Gene mutation on gene ABCA4 in fetus
Symptoms: Photoreceptor cells degenerate which leads to a progressive loss of central vision
Explain how stem cells are used in the treatment of Stargardt’s diease
Patients are given retinal cells derived from human embryonic stem cells, which are injected into the retina. These cells then divide, providing the patient with healthy retina cells.
Outline the cause of leukemia
High levels of abnormal white blood cells which lead to a type of cancer in the blood or bone marrow
Explain how stem cells are used in the treatment of leukemia
Hematopoietic stem cells (HSCs) are multipotent stem cells which are harvested from bone marrow, peripheral blood or umbilical cord blood. This may derive from the patient or a suitable donor. Then, the patient undergoes chemotherapy to get rid of the diseased blood cells. Lastly, the HSCs are transplanted back into the bone marrow where they differentiate to form new healthy white blood cells.
Discuss the benefits and drawbacks in using adult stem cells; embryonic stem cells; cord blood stem cells
Benefits
- Adult: Effective for certain conditions
- Embryonic: Greatest yield of stem cells
- Umbilical cord: Effective for multiple conditions
Drawbacks
- Adult: Limited in its scope of application
- Embryonic: Destruction of potential living organisms
- Umbilical cord: Availability and access - storing them are costly
Define “magnificaiton”
The act of enlarging something
State why the magnification of a drawing or micrograph is not the same as the magnification of the microscope
A microscope will always be to scale.
Use a formula to calculate the magnification of a micrograph or drawing
M = I / A
I = M * A
A = M / I
Define “trend” and explain why trends are useful in scientific study
Can predict how something will be over a period of time.
Outline the major differences between prokaryotic and eukaryotic cells
Prokaryotic:
- Cell wall
- Naked DNA
- Flagellum
Eukaryotic:
- No cell wall
- DNA contained within nucleus
-No flagellum
List the functions of the following structures of a prokaryotic cell: cell membrane, nucleoid, plasmid, cytoplasm, ribosome, cell wall, pili, capsule, and flagella
Cell membrane:
Nucleoid:
Plasmid:
Cytoplasm:
Ribosome:
Cell wall:
Pili:
Capsule:
Flagella:
Contrast the size of eukaryotic and prokaryotic ribosomes
Eukaryotic:
Prokaryotic:
State the meaning and advantages of eukaryotic cells being “compartmentalized”
Enzymes and substrates used in a process can be concentrated in a small area.
State structural differences between plant and animal cells
Animal cells have only a plasma membrane, whereas plant cells have an additional membrane: the cell wall.
Define “asexual reproduction”
An organism’s ability to reproduce by itself.
Outline the steps of binary fission
Binary fission is how prokaryotes reproduce asexually. It means splitting in two. The bacterial chromosome is replicated so there are two identical copies. These are moved to opposite sides of the organism, and the wall and plasma membrane are pulled inwards so the cell pinches apart to create two identical cells.
Define “resolution”
The ability of the microscope to show two close objects separately in the image.
Compare the functionality of light and electron microscopes
Light microscope:
- Resolution: 0.25μm
- Magnification: x 500
Electron microscope:
- Resolution: 0.25nm
- Magnification: x 500,000
State the function of an exocrine gland cell
To secrete fluids on the exterior of the body (sweat glands, mammary glands).
Describe the following function of the following structures in an exocrine gland cell: plasma membrane, nucleus, mitochondria, Golgi apparatus, lysosomes, vesicles, and endoplasmic reticulum
Plasma membrane:
Nucleus:
Mitochondria:
Golgi apparatus:
Lysosomes:
Vesicles:
Endoplasmic reticulum:
State the function of a palisade mesophyll cell
Draw a labeled diagram of a palisade cell from the leaf mesophyll
Describe the function of the following structures in a palisade mesophyll cell: cell wall, plasma membrane, chloroplasts, vacuole, nucleus, and mitochondria
Cell wall: supports and protects the cell
Plasma membrane: controls entry and exit of substances
Chloroplasts: carries out photosynthesis
Vacuole: transport molecules
Nuclear membrane: protects chromosomes
Mitochondria: synthesizes ATP
Explain why the ultrastructure of prokaryotic cells must be based on electron micrographs
They are too small to be seen well enough with a light microscope.
Draw the ultrastructure of E. coli as seen on an electron micrograph
Draw and label a diagram the ultrastructure of a generic animal cell
Draw and label a diagram of the ultrastructure of a generic plant cell
Explain why cells with different functions will have different structures
Different structures are specialized for cell functions. Muscle cells will for example have more mitochondria, as these synthesize large amounts of ATP.
Identify ultrastructures visible in a micrograph of a eukaryotic cell
Look for rER, mitochondrion, golgi apparatus, nucleus
Given a micrograph of a cell, deduce the function of the cell based on the structure present,
With reference to a specific example, explain how an improvement in apparatus allowed for greater understanding of cell structure
The structure of membranes:
- First, Davson and Danielli proposed that the membrane of cells are composed of phospholipids and proteins in a sandwich-like structure. This was during the 1930s, and in the 1950s, the first high magnification electron micrographs were produced. This led to the Singer-Nicolson model, which proposed that the membrane was more fluid then the first model proposed.
Draw a simplified diagram of the structure of the phospholipid, including a phosphate-glycerol head and two fatty acid tails
Define “hydrophilic” and “hydrophobic”
Hydrophilic: water attracting
Hydrophobic: water repelling
Define “amphipathic” and outline the amphipathic properties of phospholipids
Having both hydrophobic and hydrophilic properties. A phospholipid has a hydrophilic head and hydrophilic tails.
Explain why phospholipids form bilayers in water, with reference to hydrophilic heads and two hydrophobic hydrocarbon tails
Phospholipids form bilayers in water to protect the water-hating tails. The hydrophilic heads are facing outwards, whilst the hydrophobic tails face inwards.
State the primary function of the cell membrane
