Cell Biology Overview

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Questions and Answers

What is the primary characteristic of simple diffusion?

It involves movement from high concentration to low concentration. (correct)

It moves molecules against the concentration gradient.

It can only occur with large particles.

It requires energy to move molecules.

Which factor does NOT influence the rate of diffusion?

Membrane surface area

Molecular weight of solids (correct)

Temperature

Concentration gradient

Which is an example of diffusion across a plasma membrane?

Vesicle-mediated endocytosis of proteins

Exchange of O2 and CO2 between blood and cells (correct)

Movement of large glucose molecules into the cell

Active transport of ions out of the cell

What role do membrane pores play in diffusion?

They facilitate the diffusion of certain molecules. Signup and view all the answers

Which statement correctly describes osmosis?

It is a type of simple diffusion involving water molecules. Signup and view all the answers

What is the primary function of the plasma membrane in a cell?

To serve as a selective barrier for cell communication. Signup and view all the answers

Which type of human cells reproduce through meiosis?

Germ cells Signup and view all the answers

What constitutes the cytoplasm of a cell?

Cytosol and organelles. Signup and view all the answers

What is the significance of the cell life cycle stage known as cytokinesis?

It separates the cell into two daughter cells. Signup and view all the answers

Which of the following elements primarily form the basic structure of cells?

Carbon, oxygen, hydrogen, and nitrogen. Signup and view all the answers

In what way do somatic cells differ from germ cells?

Somatic cells are all body cells except sex cells. Signup and view all the answers

What is the primary control center of the cell?

Nucleus Signup and view all the answers

Which of the following correctly describes the function of cellular metabolism?

It encompasses processes for energy production and material synthesis. Signup and view all the answers

What is the main function of connective tissue?

Supports and binds structures together Signup and view all the answers

Which type of membrane is dry and acts as the largest membrane in the body?

Cutaneous Membrane Signup and view all the answers

Which of the following is a characteristic of loose connective tissues?

Fills up space between organs and acts as a cushion Signup and view all the answers

Which of the following is NOT a type of serous membrane?

Dermis Signup and view all the answers

What function do dense connective tissues mostly serve?

Provide strength and support Signup and view all the answers

What is the primary function of mitochondria in a cell?

Generation of ATP through aerobic respiration Signup and view all the answers

Which type of endocytosis is characterized by the selective uptake of molecules?

Receptor-mediated endocytosis Signup and view all the answers

What is the function of rough endoplasmic reticulum (ER)?

Protein synthesis and modification Signup and view all the answers

What is the role of lysosomes in a cell?

Breakdown of molecules and recycling cell structures Signup and view all the answers

Which organelle is involved in detoxifying drugs and synthesizing lipids?

Smooth ER Signup and view all the answers

What structure forms the mitotic spindle during cell division?

Centrosome Signup and view all the answers

What is the main function of the Golgi apparatus?

Modification and packaging of proteins Signup and view all the answers

What type of cellular transport involves the engulfing of large particles?

Phagocytosis Signup and view all the answers

Which organelle would be most abundant in cells that detoxify harmful substances?

Peroxisomes Signup and view all the answers

What distinguishes cilia from flagella?

Flagella generate forward motion of the entire cell Signup and view all the answers

What do microvilli primarily aid in?

Increase surface area for absorption Signup and view all the answers

What is the composition of the cytoplasm?

Organelles suspended in cytosol Signup and view all the answers

Which of the following best describes a function of ribosomes?

Synthesis of proteins Signup and view all the answers

What is produced as a result of somatic cell division?

Two genetically identical diploid cells Signup and view all the answers

During which phase of the cell cycle does DNA replication occur?

S Phase Signup and view all the answers

Which phase of mitosis is characterized by chromosomes aligning at the cell's center?

Metaphase Signup and view all the answers

What type of cell division reduces the number of chromosomes in the nucleus by half?

Meiosis Signup and view all the answers

What is the main function of epithelial tissue?

Cover surfaces and line cavities Signup and view all the answers

Which phase involves the cell checking its DNA for errors?

G2 Phase Signup and view all the answers

What functions do exocrine glands serve?

Transporting substances via ducts to an epithelial surface Signup and view all the answers

What is a common effect of gene mutations?

Most mutations are neutral Signup and view all the answers

Which epithelial tissue type would you expect to find lining the nasal cavity to trap foreign particles?

Ciliated Columnar Epithelium Signup and view all the answers

What does the G0 Phase of the cell cycle signify?

Resting state with no division Signup and view all the answers

Which type of tissue is responsible for producing hormones?

Glandular epithelium Signup and view all the answers

What is the result of meiosis in terms of chromosome number?

Cells become haploid containing half the chromosomes Signup and view all the answers

Which phase of mitosis is characterized by the separation of sister chromatids?

Anaphase Signup and view all the answers

What happens during the S Phase of the cell cycle?

DNA replication occurs Signup and view all the answers

Study Notes

Cells

Basic structural and functional units of all living organisms
Primary formed by carbon, oxygen, hydrogen, and nitrogen
All cells are created by cell division. After division, they differentiate into different cell types for their purpose
Classified by size, shape and function
Each cell maintains homeostasis at the cellular level
2 main types of cells in the human body
- Sex Cells (Germ Cells)
  - Reproductive cells, reproduce by meiosis
  - Examples: Male sperm, Female oocyte
- Somatic Cells
  - All body cells except sex cells, reproduce by mitosis

Cell Structure

Consists of 3 main parts
- Plasma membrane
  - Sturdy yet flexible outer surface
  - Selective barrier, important in cell communication
- Cytoplasm
  - Cytosol
  - Organelles
- Nucleus
  - Cell control center
  - Contains heredity information

Plasma Membrane

A semipermeable lipid bilayer found outside the cytoplasm of a cell and surround the inner contents
Transport mechanisms:
- Simple diffusion
- Facilitated diffusion
- Osmosis

Passive Transport

Simple Diffusion
- Movement of molecules from a region of high concentration to a low concentration region, down the concentration gradient
- Membrane may not be needed
- Factors that speed up the diffusion rate:
  - Increased temperature, light, and small particles
  - Increase in membrane surface area
  - Steeper the concentration gradient

Diffusion Across the Plasma Membrane

In the body, diffusion occurs across the lipid bilayer
- Exchange of O2 and CO2 between blood and cells, between blood and air within lungs
- Absorption of lipid-soluble molecules
- Release waste from body cells
Diffusion occurs through pores of channels
- Examples:
  - Pinocytosis (Cell drinking)
  - Phagocytosis (Cell eating)
  - Receptor-mediated endocytosis
  - Exocytosis

Vesicular Transport

Endocytosis
- Tiny droplets of extracellular fluid are taken up
- The cell engulfs large solid molecules, like bacteria, dust
- Vesicle is called phagosome
Receptor-mediated endocytosis
- A more selective form of phagocytosis or pinocytosis
- Minimum unnecessary matter is taken
Exocytosis
- Materials move out of a cell by fusion with the plasma membrane of vesicular inside the cell
- Essential in:
  - Secretory cells that secrete digestive enzymes, hormones, mucus or other secretions
  - Nerve cells that release neurotransmitters

Cytoplasm

Consists of all cellular contents between the plasma membrane and the nucleus
Components:
- Cytosol (Intracellular fluid)
  - Site of many chemical reactions
- Organelles (tiny structures that perform different functions in the cell)

Organelles

Organelles with Membrane
- Endoplasmic reticulum
- Golgi apparatus
- Mitochondria
- Lysosomes
- Peroxisomes
Non-membranous organelles
- Centrosome & Centrioles
- Cytoskeleton
- Cilia & Flagella
- Microvilli
- Ribosome

Endoplasmic Reticulum (ER)

System of interconnected channels
Extends from the nuclear membrane throughout the cytoplasm, more than half of membrane surface within the cytoplasm of the cell
2 forms of endoplasmic reticulum (ER)
- Rough ER
  - Covered with ribosomes
  - Functions:
    - Involved in protein synthesis
    - Attach sugar groups to proteins
    - Proteins are bound in vesicles for transport to Golgi apparatus
    - External face synthesizes phospholipids
- Smooth ER
  - No ribosomes
  - Functions:
    - Involved in the synthesis of fatty acid and steroid
    - Detoxification of drugs/toxic
    - Calcium storage

Mitochondria

Rod-like organelle surrounded by a double membrane
The powerhouse of a cell
Generate ATP to provide energy through aerobic respiration
A cell may have thousands of mitochondria, depending on its activity

Golgi Apparatus/Complex

Small flattened membrane and associated vesicles close to the nucleus
Cupcake shape
Functions:
- Synthesis of carbohydrates
- Package, modifies, and segregates proteins for secretion from the cell, inclusion of lysosomes, and incorporation into the plasma membrane

Lysosome & Peroxisomes

Lysosome
- Membrane-enclosed vesicles
- Form from the Golgi apparatus
- Contain digestive and hydrolytic enzymes
- Break down a wide variety of molecules
- Help recycle worn-out cell structures
- Removal of pathogens
Peroxisomes / Microbodies
- Structurally similar to lysosomes but smaller
- Contain oxidases- enzymes that can break down fats and other organic compounds
- Neutralize toxic compounds
- Abundant in liver and kidney
- In mitochondria, peroxisomes decompose fatty acids to generate energy for ATP synthesis

Centrosome & Centrioles

Centrosome
- Consists of 2 hollow cylinders called centrioles
- Located near the Golgi apparatus and nucleus
- Contain a pair of centrioles at the right angle
- Form mitotic spindle- essential for the movement of chromosomes during cell division
- Form the basal bodies found at the base of cilia and flagella
Centrioles
- Located near the Golgi apparatus and nucleus
- Contain a pair of centrioles at the right angle
- Form mitotic spindle- essential for the movement of chromosomes during cell division
- Form the basal bodies found at the base of cilia and flagella

Microvilli, Cilia & Flagella

Microvilli
- Finger-like projections that increase the cell's surface area
- Found in cells that absorb nutrients
Cilia
- Short, hair-like projections
- Move in a coordinated way to move fluids or particles across the cell's surface
- Found in cells that line the respiratory tract
- Help move mucus and trapped debris out of the lungs
Flagella
- Similar structure with cilia but much longer
- Generate forward motion of the entire cell
- Example: Sperm cells

Gene Mutation

A permanent alteration in the DNA sequence that makes up a gene
May occur due to:
- Errors in DNA replication
- Exposure to mutagens (e.g., radiation, chemicals)
Types of gene mutation:
- Deletion: One or more bases are deleted from the DNA sequence
- Insertion: One or more bases are added to the DNA sequence
- Substitution: One base is replaced by another base
Effects of gene mutation
- Proteins produced may be beneficial or harmful, or may have no effect at all
- The effect can be positive, negative or neutral

Protein Package, Processing, & Secretion

Ribosomes translate mRNA into a polypeptide chain
The polypeptide chain is then transported to the endoplasmic reticulum (ER)
- Modification occurs:
  - Folding
  - Attachment of sugar groups
The modified polypeptide chain is then transported to the Golgi apparatus
- Further processing occurs:
  - Packing into vesicles
  - Sorting and packaging
The vesicles containing the protein are then transported to the plasma membrane and released from the cell (Exocytosis)

Cell Cycle

A cell's life from it forms until it divides consists of a series of phases called cell cycle
Phases:
- Interphase
- Mitosis
- Cytokinesis (Cytoplasmic division)

Types of Cell Division

Somatic Cell Division
- Any cell of the body except sex cells
- Undergo nuclear division (Mitosis) and cytoplasmic division (Cytokinesis)
- Produce 2 genetically identically cells- same number and kind of chromosomes as the original cell, i.e. 23 pairs of chromosomes cell (n=46) called Diploid cells
Reproductive Cell Division
- Reproductive Cell Division
- Undergo 2-step division called Meiosis
- The number of chromosomes in the nucleus is reduced by half (n=23) to become Haploid cells
- Called Haploid cells

Cell Cycle- Interphase

Interphase consists of 4 phases:
- G0 Phase: Resting phase
- G1 Phase: Organelle duplication and protein synthesis occur
- S Phase: Cell duplicate centrioles and conduct DNA replication
- G2 Phase: Cell continues growing to:
  - Makes more organelles
  - Finishes replicating centrioles
  - Synthesis enzymes for cell division
  - Checks DNA and repairs any errors

DNA Replication

Occurs in S phase
DNA helix unwound by helicases into single template strand and expose the nitrogenous bases, ATP required
DNA polymerase read the exposed short segments of nitrogenous bases and assemble the sequence of the new strand with complementary nitrogenous bases with the RNA primers
DNA ligase joins the short segments together

Mitosis (M Phase)

Happens in the nucleus
Functions: Growth, repair, replace, wore out cells
The replicated chromatin becomes tightly coiled and easier to see under the microscope
Consists of 4 sub-phases:
- Prophase
- Metaphase
- Anaphase
- Telophase
Sub-phases:
- Early Prophase: Chromatin fibers condense and shorten into chromosomes, centrioles get pushed apart to each pole of the cell by spindle fibers, spindle fibers attached to the centromere on the chromosomes
- Late Prophase: Nucleoli disappear and the nuclear envelope breaks down
- Metaphase: The chromatids align on the center of the spindle fibers, attached by their centromeres
- Anaphase: Centromeres split by enzyme, sister chromatids separated and move toward opposite poles of the cell, chromatids become chromosomes after separated
- Telophase: Chromosomes are in opposite ends, uncoil and revert to chromatin form, nuclear envelope reform, nucleoli reappear in the identical nuclei, mitotic spindle breaks up
Following telophase, cytokinesis occurs- the cytosol, intracellular organelles and plasma membrane split to form 2 identical daughter cells

Meiosis

Sex cells are produced through Meiosis
Involves 2 cell division instead of one, and produces four genetically unique cells rather than two identical cells
Sex cells are haploid cells that contain only half of the full set of 46 chromosomes
Because of haploid and genetically unique, it can combine with another sex cell during fertilization to create offspring with genetic variation
Detailed process discussed in the reproductive system

Cell Differentiation

All cells in the human body comes from stem cells, through the processes of mitosis and differentiation- process enables cells to specialize and become mature cells

Tissues

Groups of similar cells working together to perform a particular function
8 types of tissues:
- Blood
- Bone
- Epithelial tissue
- Cartilage tissue
- Adipose tissue
- Connective tissue
- Muscle tissue
- Nervous tissue

Epithelial Tissue

Cover body surface
Line hollow organs, body cavities and ducts
Form glands and membranes

Classification of Epithelial Tissue

Classified by:
- Number of cell layers
- Cell shape

Simple Epithelial Tissue

Location:
- Found in heart, blood and lymphatic vessels linings
- Epithelial layer of peritoneum, pleura and pericardium
- Located at glands, ducts, kidney tubules
- Makes up secreting portion of thyroid gland and ducts of pancreas
- Lining of stomach, guts, gall bladder, uterine tubes, collecting ducts of kidney
- Ciliated: Lining of nasal cavity, trachea and bronchi
- Non-ciliated: Lining of large ducts, epididymis, and part of male urethra
Function:
- Reduce friction
- Control vessels permeability
- Perform diffusion
- Perform secretion
- Secretion and absorption
- Secretion, absorption, protection
- Secrete mucus to trap foreign particles, cilia sweep away mucus for elimination from the body
- Absorption and protection

Stratified & Transitional Epithelial Tissue

Location:
- Found in skin surface, linings of mouth, throat, oesophagus, rectum and vagina, covers tongue
- Ducts of sweat glands and oesophageal glands
- Part of male urethra
- Part of urethra, large excretory ducts
- Lines several parts of the urinary tract, including bladder
Function:
- Protect against abrasion, water loss, ultraviolet radiation, and foreign invasion
- Form the first line of defense against microbes
- Protection
- Limited secretion and absorption
- Protection and secretion
- Variable appearance, subject to expansion

Glandular Epithelium

Found in cells or organs that secret substances for use in other body parts
Include Endocrine and Exocrine glands
Endocrine
- No ducts
- Secrete directly into blood
- Secretions are known as hormones
Exocrine
- Contact with the surface by means of duct- an epithelial tube that brings secretion to the surface,
- Example:

Secretions

Secretions are substances released to the body's surface or into the cavity or lumen of another organ
Examples include sweat, tears, saliva and digestive enzymes

Membranes in the Body

Line body cavities and cover the viscera (internal organs)

Cutaneous Membrane (Skin)

The largest membrane in the body
Dry

Mucous Membrane (Mucosa)

Line all body cavities that open to the outside of the body
Examples include the digestive tract, respiratory tract, and urogenital tract

Serous Membrane (Serosa)

Internal membrane that covers organs and lines walls of body cavities
Examples include the pleura, pericardium, and peritoneum

Connective Tissue

Most abundant tissue and widely distributed
Found between cells
Functions:
- Support and binds structures together
- Store energy
- Provide immunity to disease

Loose Connective Tissues

Fill up space between organs
Act as cushion and stabilize cells
Surround and support blood vessels and nerves
Store lipids
Provide a route for diffusion of materials
Examples include areolar, adipose tissue, finely woven reticular fibers

Dense Connective Tissues

Contain elastic fibers
Can tolerate cycles of extension and recoil
Examples include:
- Lung
- Vessels
Connects, provides strength and support
Examples include:
- Ligament
- Tendon

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Explore the essential concepts of cell biology with this quiz. Learn about the different types of cells, their structures, and the functions of each component. Test your knowledge on how cells maintain homeostasis and reproduce through mitosis and meiosis.