Quarter 1 Week 1 Flashcards
(96 cards)
1
Q
a dutch eyeglass maker who invented the very first microscopes (specify the date as well)
A
Zacharias Janssen, 1590s
2
Q
While looking out a piece of cork under the microscope, he saw box-shaped structures that he called “cells”
A
Robert Hooke, 1665
3
Q
While looking at pond water under the microscope, he observed what he called “animalcules”
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Anton Van Leeuwenhoek, 1674
4
Q
He is the FATHER OF MICROBIOLOGY
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Anton Van Leeuwenhoek, 1674
5
Q
He stated that cells came from pre-existing cells through cell division»_space; a process in which 1 cell divides into 2 or more cells
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Rudolf Virchow, 1835
6
Q
a german botanist, stated that plants are made up of cells
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Matthias Schleiden, 1838
7
Q
a british zoologist, discovered that all animals are made up of cells
A
Theodor Schwann, 1839
8
Q
Cell Theory is first proposed in the mid-19th century. What are its 3 components?
A
~ All living things are made up of cells (based on the observation of Scheleiden
and Schwann stating that plants and animals are made up of cells)
~ Cells are the basic unit of structure and function in an organism
~ Cells come from pre-existing cells (based from Rudolf Virchow’s famous
statement “Omnis cellula e cellula” – Latin translation of “cells from cells”)
9
Q
3 Components of the Modern Cell Theory
A
~ Cells carry genetic material which is passed from cell to cell during
cell division
~ All cells are basically the same in structure and chemical composition
~ Energy flow (biochemical processes) occurs within cells (e.g metabolism,
photosynthesis in plants, cellular respiration, etc.)
10
Q
What do we mean by “Organelles”?
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- Literally means “little organs”
- Specialized structures found within the cell which performs
specific functions vital to cellular life
11
Q
a thin, double layer of protein and fat
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cell membrane
12
Q
two layers of phospholipids with cholesterol in between the bilayer of phospholipids
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Cell Membrane
13
Q
mainly composed of lipids, proteins, and carbohydrates
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cell membrane
14
Q
separates the interior of the cell from the outside environment
A
cell membrane
15
Q
regulates the passage of materials in and out of the cell (also aids in communication and structural support)
A
cell membrane
16
Q
Is SEMI-PERMEABLE
which pertains to its ability to allow certain molecules or ions to pass through it while blocking the others
A
cell membrane
17
Q
pertains to the ability to allow certain molecules or ions to pass through it while blocking the others
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semi-permeability
18
Q
a rigid membrane that gives the cell protection, support, and structure
A
cell wall
19
Q
it makes plants stiff and upright
- maintains the shape of the cell
- aids for additional structural support
A
cell wall
20
Q
cell wall of plants
A
cellulose
21
Q
cell wall of fungi
A
chitin
22
Q
cell wall of bacteria
A
peptidoglycan
23
Q
cell wall of archaea
A
pseudopeptidoglycan
24
Q
cell wall of protists
A
vary widely;
e.g Algae: cellulose
Diatoms: silica
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what is the structure of nucleus
- double phospholipid bilayer
(inner and outer membranes) with an outer membrane that is continuous with the endoplasmic reticulum
- contains nuclear pores for regulated transport of materials between the nucleus and cytoplasm
- supported by nuclear lamina and interacts with chromatin
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Function of Nucleus
- It aids with compartmentalization or enclosing the genetic material (DNA) and separates it from the cytoplasm, providing a distinct environment for replication, transcription, and translation
- controls and regulates cell activities
- controls the synthesis of ribosomes and proteins
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SITE FOR DNA REPLICATION AND TRANSCRIPTION.
Nucleus
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A complex of DNA and proteins (mainly histones and the DNA is wrapped around these histones). Less tightly packed than chromosomes
chromatin
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2 states of chromatin
euchromatin and heterochromatin
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the state of chromatin that is less condensed and transcriptionally active
euchromatin
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the state of chromatin that is more condensed and usually transcriptionally inactive
heterochromatin
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Function of Chromatin
Chromatin allows DNA to be packaged in a way that fits inside the nucleus while remaining accesible for processes such as transcription and DNA replication, and repair.
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highly condensed chromatin fibers, forming distinct structures.
chromosome
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mostly visible and structured during cell division (mitosis and meiosis)
chromosome
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What is the function of Chromosome?
The condensation into chromosomes ensures the accurate separation of DNA during cell division
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Under a microscope during cell division, ________ appear as X-shaped structures (sister chromatids connected by a centromere)
chromosomes
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Summarize the difference of chromatin and chromosomes
In summary, chromatin is the less condensed form of genetic material that is functional during most of the cell cycle, whereas chromosomes are the highly condensed form that appears during cell division to ensure DNA is accurately replicated and distributed.
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What is Gene Expression?
Is the the process by which a gene's information is transcribed into RNA and translated into proteins, resulting in the gene's functional product being produced.
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What is Gene Repression?
the process by which a gene's expression is inhibited, preventing the transcription of its DNA into RNA and subsequent production of its protein product
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Correlation of the Positioning of the Chromatin Within the Nucleus to Gene Expression and Repression
Chromatin Near the Nuclear Lamina - tends to be transcriptionally inactive because it is tightly condensed (Heterochromatin). This region is more condensed and typically gene-poor or contains genes that are not actively transcribed. Genes locaated in these lamina-associated domains (LADs) are often repressed.
Chromatin Far from the Nuclear Lamina (in the interior of the Nucleus) - Genes located in the nuclear interior are more likely to be in euchromatin regions, which are less condensed and more transcriptionally active.
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What is a gene?
Gene is a specific sequence of nucleotides in DNA that encodes the instructions for the synthesis of proteins, which in turn determine the traits and functions of an organism.
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Correlation of the States of Chromatin to Gene Expression and Repression
The degree of packing of chromatin does affect its activity and inactivity.
Heterochromatin - Tightly packed chromatin, known as heterochromatin, is generally inactive. Meaning that the genes within these regions are not actively transcribed.
- Often found near the nuclear lamina and contains repetitive sequences and gene-poor regions.
Euchromatin - In contrast, loosely packed chromatin, known as euchromatin, is usually active, allowing genes within these regions to be more easily accessed by the transcriptional machinery and thus actively transcribed.
- Found in the nuclear interior and contains gene-rich regions that are accessible to transcription factors and RNA polymerase.
VERY IMPORTANT SUMMARY: This difference in packing allows the cell to regulate gene expression dynamically, turning genes on or off as needed by modifying the chromatin structureeeee.
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What the "Turning off and on" of a Gene Really Means
Turned on - it means that the gene is being expressed, which involves the trascription of its DNA into RNA and the subsequent translation of that RNA into a functional protein product. This is the process by which the gene's information is used to produce its intended protein, thereby carrying out its function within the cell.
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TWO MAJOR CATEGORIES OF ORGANISMS BASED ON CELLULAR STRUCTURE
Eukaryotes and Prokaryotes
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Organisms whose cells have a true nucleus enclosed by a nuclear membrane.
Eukaryotes
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Organisms whose cells lack a true nucleus and membrane-bound organelles.
Prokaryotes
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Cell Structure of Prokaryotes
Prokaryotic cells do not have a nuclear membrane. Instead, their genetic material is located in a region called the nucleoid
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DNA of Prokaryotes
Generally a single circular chromosome located in the nucleoid.
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DNA of Prokaryotes
Generally a single circular chromosome located in the nucleoid.
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DNA (deoxyribonucleic acid) is made of molecules called nucleotides. Each nucleotide consists of three components:
1. Deoxyribose Sugar: A five-carbon sugar molecule.
2. Phosphate Group: A phosphorus atom bonded to four oxygen atoms.
3. Nitrogenous Base: One of four types of bases:
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
These nucleotides are linked together in a chain through covalent bonds between the sugar of one nucleotide and the phosphate of the next, forming the backbone of the DNA strand. The nitrogenous bases pair with each other through hydrogen bonds to form the double-stranded structure of DNA: adenine pairs with thymine, and cytosine pairs with guanine.
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Summary of Understanding Why Different Cells Express Different Genes
So, in a wider perspective. DNA is the genetic blueprint of life. Every individual has distinct/unique DNA sequence (every individual has a unique genetic profile). In a single human, all of its cells contain the same genetic sequence, meaning the genetic information is nearly identical across different types of cells, it's just that, DIFFERENT CELLS CAN EXPRESS DIFFERENT GENES, leading to diversity of cell types (such as muscle cell, nerve cell).
This happens because the structure of chromatin can vary between cells.
Cells can dynamically alter their chromatin structure in response to external signals, allowing for rapid activation or repression of genes as needed for processes like immune responses or stress adaptation.
When it comes to gene expression, various factors can affect it. Like chromatin positioning or chromatin state, DNA methylation, and histone modifications (acetylation which is associated with adding acetyl groups to histones tails to reduce the positive charge on histones, decreasing the affinity for negatively charged DNA resulting in more open chromatin structure (euchromatin). DNA methylation has something to do with DNA silencing)
Chromatin remodelling can also affect gene expression. These protein complexes use energy from ATP to reposition, eject, or restructure nucleosomes (the basic units of chromatin). By doing so, they can make specific regions of DNA more or less accessible to the transcriptional machinery.
In simple terms, each cell in the human body has the same genetic material or DNA but they differ in which genes to express. This gene expression is regulated due to some factors uncluding the arrangement of chromatin in the nucleus, state of chromatin, and depending on the need they can dynamically rearrange or send in acetyl groups (acetylation, DNA methylation)
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Summary of Understanding Why Different Cells Express Different Genes
So, in a wider perspective. DNA is the genetic blueprint of life. Every individual has distinct/unique DNA sequence (every individual has a unique genetic profile). In a single human, all of its cells contain the same genetic sequence, meaning the genetic information is nearly identical across different types of cells, it's just that, DIFFERENT CELLS CAN EXPRESS DIFFERENT GENES, leading to diversity of cell types (such as muscle cell, nerve cell).
This happens because the structure of chromatin can vary between cells.
Cells can dynamically alter their chromatin structure in response to external signals, allowing for rapid activation or repression of genes as needed for processes like immune responses or stress adaptation.
When it comes to gene expression, various factors can affect it. Like chromatin positioning or chromatin state, DNA methylation, and histone modifications (acetylation which is associated with adding acetyl groups to histones tails to reduce the positive charge on histones, decreasing the affinity for negatively charged DNA resulting in more open chromatin structure (euchromatin). DNA methylation has something to do with DNA silencing)
Chromatin remodelling can also affect gene expression. These protein complexes use energy from ATP to reposition, eject, or restructure nucleosomes (the basic units of chromatin). By doing so, they can make specific regions of DNA more or less accessible to the transcriptional machinery.
In simple terms, each cell in the human body has the same genetic material or DNA but they differ in which genes to express. This gene expression is regulated due to some factors uncluding the arrangement of chromatin in the nucleus, state of chromatin, and depending on the need they can dynamically rearrange or send in acetyl groups (acetylation, DNA methylation)
53
Can a cell have more than one nucleolus?
A cell can have more than one nucleolus. Multiple nucleoli are often seen in cells that are very active in protein synthesis, as these structures are involved in the production and assembly of ribosomes. The number and size of nucleoli can vary depending on the cell type and its physiological state.
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Its main function is for ribosomal subunit contruction
Nucleolus
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Its main function is for ribosomal subunit contruction
Nucleolus
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Is the DNA inside the nucleus continuous with the rDNA in the nucleolus?
The nucleus is where the cell's DNA is located, including ribosomal DNA (rDNA). The nucleolus is a distinct, dense region within the nucleus, but it is not membrane-bound, meaning it is not separated from the rest of the nuclear contents by a membrane.
Ribosomal DNA is part of the chromosomal DNA and is found in specific regions of certain chromosomes (nucleolar organizing regions, or NORs). These regions are located within the nucleus and are associated with the nucleolus during the cell cycle. Therefore, the rDNA is indeed continuous with the rest of the DNA in the nucleus. The nucleolus forms around these NORs and is the site of rRNA transcription and ribosome assembly.
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Is the entirety of DNA in the nucleus composed of rDNA? Or are there only specific regions?
The overall DNA inside the nucleus is not composed entirely of rDNA. rDNA sequences are specific regions within the chromatin. In eukaryotic cells, these rDNA regions are typically found in the nucleolar organizer regions (NORs) of certain chromosomes. The majority of nuclear DNA consists of other genes and regulatory sequences that are part of the organism's genome, encoding a wide variety of proteins and regulatory elements necessary for cellular functions.
Thus, the chromatin within the nucleus includes both rDNA regions and non-rDNA regions, with the rDNA regions specifically involved in ribosomal RNA synthesis and nucleolus formation.
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Are DNA parts chopped?
Chromatin within the nucleus is a continuous chain of DNA and associated proteins. The DNA itself is a long, linear molecule that is packaged into chromatin by being wound around histone proteins, forming a structure known as nucleosomes. These nucleosomes further fold and coil to create higher-order structures, ultimately forming chromosomes.
Although chromatin is a continuous chain, the DNA is organized into discrete segments called chromosomes. Each chromosome is a single, continuous DNA molecule that contains many genes, regulatory elements, and other nucleotide sequences. Chromatin is dynamic and can undergo structural changes to facilitate processes like transcription, replication, and repair, but the underlying DNA remains an unbroken linear sequence within each chromosome.
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Is ribosomal DNA found only in chromosomes
Yes, ribosomal DNA (rDNA) is found specifically in the chromosomes. In eukaryotic cells, rDNA is located within the nucleolar organizer regions (NORs) of certain chromosomes. These regions contain the genes that encode ribosomal RNA (rRNA), which is essential for ribosome assembly and protein synthesis.
In humans, for example, the rDNA is located on the short arms of the five acrocentric chromosomes (chromosomes 13, 14, 15, 21, and 22). These regions are transcribed to produce rRNA, which then assembles into ribosomes within the nucleolus. Thus, rDNA is an integral part of the chromosomal DNA within the nucleus.
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Is ribosomal DNA found only in chromosomes
Yes, ribosomal DNA (rDNA) is found specifically in the chromosomes. In eukaryotic cells, rDNA is located within the nucleolar organizer regions (NORs) of certain chromosomes. These regions contain the genes that encode ribosomal RNA (rRNA), which is essential for ribosome assembly and protein synthesis.
In humans, for example, the rDNA is located on the short arms of the five acrocentric chromosomes (chromosomes 13, 14, 15, 21, and 22). These regions are transcribed to produce rRNA, which then assembles into ribosomes within the nucleolus. Thus, rDNA is an integral part of the chromosomal DNA within the nucleus.
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The correct process of ribosomal subunit production
Ribosomal RNA (rRNA) Synthesis: The rRNA is transcribed from ribosomal DNA (rDNA) within the nucleolus.
Protein Synthesis: Ribosomal proteins are synthesized in the cytoplasm.
Import into Nucleolus: These ribosomal proteins are imported into the nucleus and then into the nucleolus.
Ribosomal Subunit Assembly: In the nucleolus, the ribosomal proteins combine with the rRNA to form the large and small ribosomal subunits.
Export to Cytoplasm: These subunits are then exported from the nucleus to the cytoplasm.
Ribosome Assembly: In the cytoplasm, the large and small subunits combine to form functional ribosomes during the initiation of protein synthesis.
So, the ribosomal subunits are assembled in the nucleolus, not fully outside the nucleus as suggested by the video you mentioned.
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structure of nucleolus
- dense non-membrane-bound structure which forms a specialized subdomain of the nucleus that is responsible for the synthesis of ribosomal subunits.
- composed of RNA and proteins
- Trivia#1 RNA converts the genetic information contained within DNA to a format used to build proteins, and then moves it to ribosomal protein factories.
to question specificity*
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Nucleolus contains a significant amount of RNA, and that RNA is involved in synthesizing and assembling ribosomal subunits. Ribosomal subunits get sent into the cytoplasm and they assemble into a functional ribosome. The process using these ribosomes to synthesize proteins according to the instructions encoded in the mRNA is called __________
Protein Synthesis
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Primary site of Protein Synthesis
Ribosome
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Primary site of Protein Synthesis
Ribosome
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Primary site of Protein Synthesis
Ribosome
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Presence of Ribosome in prokaryotes and eukaryotes
Although ribosomes are present in both prokaryotic and eukaryotic cells, they live in slightly different locations.
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Where are the ribosomes of prokaryotic cells?
In prokaryotic cells, ribosomes can roam freely in the cytoplasm and they're called 70S ribosomes. The "S" refers to a Svedberg unit, measuring sedimention coefficient.
For biological macromolecules and cell organelles, the sedimentation rate is typically measured as the rate of travel in a centrifuge tube subjected to high g-force.
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Where are the ribosomes of Eukaryotic Cells?
In eukaryotic cells, their ribosomes, which are called 80S ribosomes, can roam free or also hang out on the endoplasmic reticulum.
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Main Function of Ribosome
The ribosome's duty is simple: help the cell make proteins it needs to function. The location of the ribosome within the cell helps dictate what kind of protein it makes. For example, ribosomes can attach to the endoplasmic reticulum, making it what we now call a rough endoplasmic reticulum. Ribosomes on a rough endoplasmic reticulum are versatile, and can make proteins that can be used inside or outside the cell
Main Function: Help make protein.
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What is a Ribosome made of?
2/3 Ribonucleic Acid (RNA), 1/3 protein to make up the difference. Using this proportion of RNA and protein, ribosomes are made in the nucleolus of the nucleus and released to fulfil their ribosomal duties.
A ribosome's structure is composed of two main RNA protein complexes called subunits. There is a larger and a smaller subunit, both with a similar shape and both composed of ribosomal RNA and ribosomal proteins. Both subunits exist separately, and stay separated until they get a cell phone call that they're needed for protein production.
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It is double-membraned and
rod-shaped
- has its own DNA
Mitochondria
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produces chemical energy in the form of ATP to power the cell (adenosine triphosphate)
Mitochondria
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- a series of interconnected membranous sacs and tubules
- It has two types; rough ER and smooth ER
[They differ in function]
Endoplasmic Reticulum
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An Endoplasmic Reticulum with ribosomes attached to its surface
Rough Endoplasmic Reticulum
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modifies proteins synthesized by ribosomes [makes phospholipids for cellular membranes
Rough Endoplasmic Reticulum
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An Endoplasmic Reticulum no attached ribosomes
Smooth Endoplasmic Reticulum
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function of Smooth Endoplasmic Reticulum
- responsible for the production of carbohydrates, lipids, steroids
- detoxification of drugs and toxins
- storage of calcium ions
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structure of Golgi Apparatus
a series of flattened sac-like membranes that resembles a stack of pancakes
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An organelle that sorts, tags, packages, and ditributes lipids and proteins
Golgi Apparatus
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what is the structure of lysosome
Spherical bodies containing digestive enzymes
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What is the function of Lysosome?
- digests cellular nutrients
- breaks down worn-out or damaged organelles
- aids in apoptosis (programmed cell death)
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Structure of Chloroplast
- a long disc-shaped organelle containing the pigment chlorophyll
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Site of Photosynthesis
Chloroplast
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structure of Vacuole
a large space within the cell that is enclosed in a membrane and filled with fluid
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Function of Vacuole
- maintains water balance
- maintains cell shape
- stores nutrients and waste poducts
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- a network of protein filaments or fibers
- Types: microfilaments, microtubules, and intermediate filaments
Cytoskeleton
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Function of Cytoskeleton
- provides shape and structure of the cell
- aids with movement
- involved in spindle formation during cell division
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Brain of the Cell
Nucleus
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Subway System of the Cell
Endoplasmic Reticulum
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Garbage Collector of the Cell
Lysosome
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Security Guard of the Cell
Cell Membrane
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Protein Factory of the Cell
Ribosome
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Powerhouse of the Cell
Mitochondria
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Mailman of the Cell
Golgi Body
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Cafeteria of the Cell
Chloroplast
