[qdeck ” bold_text=”false”]
[h] IB DP Biology HL B2.3 Cell specialization Flashcards
[q] B2.3.1—What cell is produced by fertilisation?
How does this cell turn into different cell types in the body?
[a] a zygote is formed;
it is an unspecialized cell, known as a stem cell;
this cell divides and some cells undergo differentiation;
where certain genes are expressed;
in particular cells types;
leading to different cell;
[q] B2.3.2—What are the unique properties of stem cells?
[a] Stem cells have the capacity to divide indefinitely;
and can differentiate into various cell types, following different pathways;
[q] B2.3.3—What is the location and function of stem cell niches in adult humans? 2 examples only
[a] Bone marrow stem cells;
Maintains and promotes the proliferation and differentiation of blood cells;
Hair follicles;
support the growth and regeneration of hair by maintaining and differentiating stem cells;
[q] B2.3.4—What are the differences between totipotent, pluripotent and multipotent stem cells?
[a] Totipotent cells (early-stage embryos) can form any cell type, including extraembryonic tissues like the umbilical cord and placenta;
Pluripotent cells can form almost any cell type but not extraembryonic tissues;
Multipotent cells (like in bone marrow) can form a limited range of cells related to a specific tissue; e.g. only blood cells in the bone marrow;
[q] B2.3.5—How is cell size an aspect of specialization?
[a] The size of a cell is intricately linked to its function;
For instance, small red blood cells are optimally sized for efficient oxygen transport;
while large neurons can transmit signals over long distances;
Similarly, striated muscle fibers are large to allow contraction over a long distance;
[q] B2.3.6—How does surface area-to-volume ratio limit cell size?
[a] The surface area-to-volume ratio is crucial in determining a cell’s efficiency in exchanging materials with its surroundings;
A higher surface are to volume ratio, found in smaller cells, allows for faster nutrient uptake and waste removal relative to the cell’s volume;
This ratio limits cell size, as larger cells cannot exchange materials fast enough;
[q] B2.3.7—What are the adaptations that increase surface area-to-volume ratios of cells?
[a] Cells adapt to increase their surface area through structures like microvilli or flattening;
For example, erythrocytes are flattened and biconcave to maximize surface area for gas exchange;
while cells in the proximal convoluted tubule have microvilli for efficient reabsorption;
[q] B2.3.8—What are the adaptations of type I and type II pneumocytes in alveoli?
[a] Type I pneumocytes are extremely thin, maximizing their surface area for gas exchange;
and reducing diffusion distance;
increasing the rate of exchange;
Type II pneumocytes are specialized for producing and secreting surfactant, which reduces surface tension in the lungs and prevents alveolar collapse.
[q] B2.3.9—What are the adaptations of cardiac muscle cells and striated muscle fibres?
[a] Cardiac muscle cells are branched and interconnected for synchronized contraction;
with a Y shaped structure;
Striated muscle fibers are long and multinucleated, allowing for powerful, coordinated contractions;
Both contain densely packed myofibrils for efficient muscle contraction;
striated muscle could be considered acellular, as it has multiple nuclei without a specific cell membrane separating it from other cells;
[q] B2.3.10—What are the adaptations of sperm and egg cells?
[a] Sperm Cells
Long, streamlined, with a flagellum for mobility;
have an acrosome which contains enzymes that help penetrate the egg.
have mitochondria in the midpiece provide energy for movement
Egg Cells
Largest cell in the human body, providing ample nutrients for the embryo;
Zona pellucida and corona radiata protect and regulate sperm entry;
Cortical Granules prevent polyspermy by altering the zona pellucida after the first sperm enters;
[q] Differentiation
[a] The process where cells become more specialized and distinct from one another.
[q] All cells have an identical _________.
[a] Genome
[q] Each cell contains the entire set of ______________ for that organism.
[a] Genetic instructions
[q] Different genes are activated by __________.
[a] Chemical signals
[q] Cell differentiation is caused by gene regulating chemicals called _________.
[a] Morphogens
[q] Cells closer to the morphogen source receive ________ concentrations of morphogen, resulting in the activation of MORE genes.
[a] Higher
[q] Cells further away from the morphogen source receive ___________ concentrations of morphogen, resulting in the expression of FEWER genes.
[a] Lower
[q] Morphogen gradients control the ___________________ of genes within an early-stage embryo.
[a] differential expression
[q] Stem cells are unspecialized cells that can do two things:
[a] 1. Self-renewal (They name continually divide and replicate.)
2. Potency (They can differentiate into specific cell types.)
[q] Stem Cell Niches
[a] Sites where adult stem cells hang out in preparation for future proliferation and differentiation.
[q] Examples of stem cell niches:
[a] Bone marrow, hair follicles, heart, intestines, and brain.
[q] Hemopoietic stem cells are located in the bone marrow and give rise to different type of _______ ______. (E.G, erythrocytes ((red)), leucocytes ((white)), and thrombocytes ((platelets)).)
[a] Blood cells
[q] Hair follicles contain epidermal _____ cells that are involved in hair growth, skin innervation, vascularization, and wound repair.
[a] Stem
[q] Three Main Types of Stem Cells
[a] 1. Totipotent- Can form any cell type. (Zygote)
2. Pluripotent- Can form any cell type arising from the three germ layers. (Inner mass of blastocyst.)
3. Multipotent- Can only form a number of closely related cell types.
[q] The ____ of cells can vary significantly to optimize specific functions
[a] size
[q] Red blood cells need to squeeze through narrow capillaries and have a diameter of only ______.
[a] 7-8 μm
[q] Neurons need to transmit signals throughout the body and can be over _____ in length (but with a width only ~10 μm.)
[a] 1 m
[q] Striated muscle fibers consist of fused muscle cells- they can have a width of 20-100 μm and a length of up to _____.
[a] 12 cm
[q] A human ovum (female egg) is one of the largest cells with a diameter of (A), while the male sperm is extremely small (B).
[a] (A)- 120 μm
(B)- ~5 μm
[q] Cells need energy (via metabolism), which requires a ___________.
[a] Gas exchange
[q] The rate of material exchange is a function of its _____________ (large membrane surface equates to more material movement.)
[a] Surface area
[q] As a cell grows, volume (units^3) increases faster than the surface area (units^2), leading to a ________ SA:Vol ratio.
[a] decreased
[q] Growing cells tend to divide and remain small in order to maintain a ______ SA:Vol ratio suitable for survival.
[a] High
[q] Red blood cells are ______ ______ (large SA:Vol ratio)
[a] Very small
[q] Proximal Convoluted Tubule Cells (Kidney) Facts:
[a] 1. They reabsorb a lot of the filtrate that was produced earlier, i.e.- glucose.
2. Structure: one cell thick, cells have two membranes, one touching the filtrate, the others close to blood capillaries.
3. Substances must diffuse through these cells to get back into the blood stream.
4. Apical side: microvilli
5. Basal membrane: infolds
6. Both the apical side and the basal membrane increase SA.
[q] Alveoli
[a] Structures in the lung (type I and type II pneumocytes.)
[q] Adaptations of Type I Pneumocytes
[a] 1. Adapted for gas exchange (O2 and CO2)
2. Very thin cells (0.15 μm)
3. Wall of adjacent blood vessels is also very thin.
The distance these gasses have to diffuse is very small.
[q] Adaptations of Type II Pneumocytes
[a] 1. Smaller, more numerous, occupy only 5% of alveolus.
2. Synthesizes a lot of phospholipids which hare secreted to form a very thin film of moisture (gasses diffuse easier through moisture and the alveoli don’t collapse during breathing.)
[q] Adaptations of Cardiac Muscle Cells:
[a] 1. Branched, faster signal propagation and contraction in three dimensions.
2. Not fused together but are connected by gap junctions at intercalated discs.
3. More mitochondria, as they are more reliant on aerobic respiration than skeletal muscle.
[q] Adaptations of Striated (skeletal muscle):
[a] 1. Attached to the skeleton and is responsible for the voluntary movement of bones (needs nerve input to contract.)
2. Run in parallel tracts and are multinucleated and heavily striated.
[q] Egg cells have structures that allow ________ sperm to fertilize it.
[a] Only one
[q] Egg cells also have structures that provide resources for the (A) and (B).
[a] (A)- Zygote
(B)- Early Embryo
[q] Sperm cells have the following structures that allow them to insert their nucleus:
[a] 1. Receptors for the binding proteins in the egg cell zona pellucida.
2. Acrosome- A sac of enzymes that digest the zona pellucida.
3. Binding proteins in the acrosome, which mediate fusion of the two membranes.
[q] Only the _______ of the sperm cell makes it in the egg.
Everything else falls away.
That’s why we only have maternal mitochondrial DNA.
[a] Nucleus
[x] Exit text
[/qdeck]