Cell Structure and Function
Separates the cytoplasm from the extracellular fluid, provides physical isolation, regulates exchange with the environment, monitors the environment, and provides structural support.
What is the plasma membrane?
A cell is placed in a solution and begins to swell until it bursts.
a) What type of solution was the cell placed in?
b) Explain the osmotic mechanism that caused this outcome.
a) Hypotonic solution
b) The cell's semipermeable membrane allows water to move across. Since there is a higher concentration of water outside the cell (due to the lower solute concentration of the hypotonic solution), water moves into the cell, causing it to swell and burst.
During which phase of mitosis do chromosomes align in the center of the cell?
Prophase? Metaphase? Anaphase? Telophase?
Metaphase
Prophase: nucleoli disappear and centriole pairs move to cell poles. nuclear envelope disappears too.
Anaphase: microtubules pull chromosomes apart and daughter chromosmes group near centrioles
Telophase: has two complete nuclei and is ready to separate into 2 daughter cells.
Explain epithelial tissue and connective tissue. Name characteristics and functions of each.
Epithelial Charactertics: Cellularity, polarity (apical: projections such as microvilli to increase surface for absorption and cilia for movement; basal: attachment), attachment, avascularity, regeneration.
Functions of Epithelial: physical protection (movement of fluids over the epithelium), controls permeability (movement of fluids through the epithelium), provides sensation, and produces specialized secretions (glandular epithelium).
Connective Characteristics: specialized cells, solid extracellular protein fibers, and fluid extracellular ground substance. Last two make up the matrix.
Connective Tissue Function: Connect eptihelium to the rest of the body (basal lamina), provide structure (bone), store energy (fat), transport materials (blood), highly vascular, no contact with environment, and are the most abundant tissue type.
List the three types of muscle tissue and describe one structural or functional feature that distinguishes each.
Skeletal muscle: long, cylindrical, multinucleated fibers with striations that controls voluntary body movement.
Cardiac muscle: branched fibers with striations and intercalated discs, found only in the heart and has involuntary contractions regulated by pacemaker cells.
Smooth muscle: small, spindle-shaped, non-striated cells with a single nucleus responsible for involuntary contractions in walls of hollow organs.
Contrast nonmembranous and membranous organelles, give examples of each and their function.
Nonmembranous: have direct contact with cytosol; cytoskeleton (shape and structure, microfilaments, intermediate filaments, and microtubules), microvilli (increase area for absorption), centrioles (form spindle apparatus during cell division), cilia (move fluids across the cell surface), ribosomes (build polypeptides in protein synthesis), and proteasomes (disassemble damaged proteins for recycling).
Membranous: ER (syntheis of proteins, carbs, and lipids, storage of synthesized molecules and materials, transport of materials in ER, and detoxification of drugs and toxins), Golgi apparatus (vesicles enter forming face and exit maturing face), Lysosomes (clean up inside cells, break down large molecules, attack bacteria, recycle damaged organelles, eject wastes by exocytosis), peroxisomes (break down fatty acids, produce hydrogen peroxide, replicate by division), and mitochondria (takes chemical energy from food produces ATP).
Differentiate between pinocytosis, phagocytosis, exocytosis, and endocytosis.
Endocytosis (vesicular transport): transports substances into a cell through vesicle formation (absorbs nutrients, takes in signaling molecules, or engulfs pathogens and waste).
Pinocytosis: endosomes "drink" extracellular fluid (cell drinking)
Phagocytosis: engulfs large objects in phagosomes (cell eating)
Exocytosis (vesicular transport): release of substances out of the cell, such as hormones, neurotransmitters, and waste (membrane recycling).
Transcription (nucleus): copies instructions from DNA to mRNA in 3 steps: gene activation, DNA to mRNA, and RNA processing. (Initiation, Elongation, and Termination). RNA polymerase binds to a promoter on DNA and synthesizes an RNA strand.
Translation (cytoplasm): synthesize a protein using the instructions encoded in the mRNA molecule, essentially translating into a new language. mRNA molecule moves from the nucleus and a ribosome reads the codons and finds the correct tRNA molecules carrying amino acids to form a polypeptide chain and create a protein.
What is one major difference between loose and dense connective tissue? What is one example where each is found?
Loose connective tissue has less fibers and more ground substance, while dense connective tissue has more fibers and less ground substance.
Loose connective: fat/adipose tissue
Dense connective: tendons
Ground substance is a clear, colorless, and viscous substance that fills spaces between cells and slows pathogen movement.
What are the cardinal signs of inflammation, and what physiological changes cause each one?
Heat: increased blood flow brings warm blood to the area
Redness: Vasodilation and increased capillary permeability cause local redness
Swelling: fluid leaks from capillaries into tissue, also known as edema
Pain: release of chemicals like bradykinin and prostaglandins stimulate pain receptors.
These changes help isolate the injury, bring immune cells to the site, and begin tissue repair.
Describe how the rough ER, Golgi apparatus, and lysosomes work together to synthesize, modify, and transport proteins.
Ribosomes on the RER synthesize proteins, which are then folded and modified inside the RER. From there, transport vesicles move the proteins to the Golgi apparatus for further processing, sorting, and packaging. Finally, vesicles bud off from the Golgi and deliver the processed proteins to their destinations, including lysosomes for breakdown or other cellular functions.
Distance the particle has to move
Molecule Size: smaller is faster
Temperature: more heat, faster motion
Gradient size: the difference between high and low concentrations
Electrical forces: opposites attract and like charges repel
Which of the following correctly lists the stages of somatic cell division in order?
a) Mitosis -> DNA Replication -> Cytokinesis
b) DNA Replication -> Cytokinesis -> Mitosis
c) DNA Replication -> Mitosis -> Cytokinesis
d) Cytokinesis -> Mitosis ->DNA Replication
c) DNA Replication -> Mitosis -> Cytokinesis
Explain how areolar, adipose, and reticular tissues each provide different kinds of support in the body.
Each of these tissues are classifed as loose connective tissues.
Areolar: least specialized, has an open framework, viscous ground substance, and elastic fibers. It's main contribution is to hold blood vessels and capillary beds, provides a site for immune responses due to amount of immune cells present, and connects tissues and provides support.
Adipose: contains adipocytes (fat cells) and has two types: white fat (most common, stores fat, absorbs shock, and provides insulation) and brown fat (more vascularized, is able to be broken down to provide energy to the body).
Reticular: mainly provides support, has supportive fibers (stroma) and supports functional cells. (spleen, liver, lymph nodes, and bone marrow).Explain why neuroglia are essential even though they do not transmit electrical impulses.
Neuroglia (glial cells) support and maintain the neurons and act as the support team for the nervous system. Neurons would not survive or function properly without neuroglia thats why damage to them can be detrimental.
Functions: Supplying nutrients and oxygen to neurons, removing waste products, protecting neurons from pathogens (immunity and repair), forming myelin sheaths for faster signal transmission, and regulating the extracellular environment around neurons.
Explain the difference between chromatin and chromosomes, and when each form appears.
Chromatin is the decondensed, "unwound" form of DNA and proteins found in a non-dividing cell, while chromosomes are the highly condensed and visible structures that form when chromatin coils tightly for cell division.
A researcher is studying transport across a cell membrane and observes the following:
1. Calcium ions move out of the cell using a pump that requires ATP.
2. Glucose and sodium enter the cell together through the same carrier protein.
3. Sodium and hydrogen ions move in opposite directions across the membrane through a single transporter.
4. Potassium ions diffuse out of the cell through a channel that moves only one substance at a time.
Q: Identify which of the following terms applies to each example above (cotransport, uniport, symport, antiport or countertransport) and explain the difference between symport and antiport in terms of the direction of solute movement.
1. Uniport (also Active Transport): one substance moving out of the cell.
2. Symport/Cotransport: two substances move in the same direction at the same time.
3. Antiport/Countertransport: one substance moves in while another moves out.
4. Uniport: one substance moving out of the cell.
Which phase of the cell cycle is considered a non-dividing state where more cells spend the majority of their time performing specialized functions?
a) G1 phase
b) S phase
c) G2 phase
d) G0 phase
d) G0 phase
Why is cartilage slower to heal after injury than other connective tissues? What are the different types of cartilage and how does their structure and function differ from bone?
Cartilage heals slower due to its avascularity. It's limited access to blood vessels prevents quick healing. It will recieve oxygen and nutrients through diffusion.
Cartilage vs. bone: cartilage is gel-type gorund substance and provides shock absorption and protection while bone is calcified and provides weight support.
Hyaline cartilage: stiff, flexible support that reduces friction between the bones. Found mainly in synovial joins, rib tips, sternum, and trachea.
Elastic cartilage: supportive but bends easily (external ear and epiglottis).
Fibrocartilage: limits movement, prevents bone-bone contact, pads knee joins, and is also found between pubic bones and intervetebral discs.
What are intercalated discs, and why are they essential for cardiac muscle function?
Intercalated discs are specialized junctions that connect cardiac muscle cells end to end. They contain gap junctions for electrical communication and desmosomes for mechanical strength.
Importance: permit rapid electrical impulses to spread between cells which leads to coordinated heart contractions and provides strong physical connections to prevent separation during pumping of the heart.
Explain how the structure of the plasma membrane and the presence of receptor proteins enable cells to respond to hormones.
The plasma membrane is a selectively permeable phospholipid bilayer that separates the inside of the cell (cytoplasm) from the outside environment.
Because many hormones (especially large or polar ones like peptide hormones) cannot cross the lipid bilayer, the cell relies on receptor proteins embedded in the membrane to detect and respond to them. Receptor proteins have specific binding sites to recognize certain hormones.
During nerve cell activity, sodium and potassium ions are moved across the plasma membrane in opposite directions, both against their concentration gradients. What type of transport is this, and what specific membrane protein facilitates it? Explain the type of transport and how it differs from others.
The sodium-potassium exchange pump is a form of active transport and is carrier mediated. One ATP molecule moves 3 Sodium out (Na) and 2 Potassium in (K).
Active transport moves substrates against a concentration gradient and requires energy (ATP).
Passive transport moves along a concentration gradient and does not require energy. Ex: osmosis, diffusion, facilitated diffusion (carrier proteins transport molecules too large to fit through channel proteins; molecule binds to receptor site on carrier protein, protein changes shape and molecules pass through, or receptor site is specific to certain molecules).
What distinguishes a malignant tumor from a benign tumor?
a) Malignant tumors are smaller in size
b) Malignant tumors are non-cancerous
c) Malignant tumors invade surrounding tissues and can metastasize
D) Malignant tumors do not divide
c) Malignant tumors invade surrounding tissues and can metastasize
Connective tissues contain 3 main types of protein fibers: collagen, reticular, and elastic fibers.
Match each fiber type with its correct description and give an example for each:
1. _______Strong, flexible fibers that resist force in one direction
2. _______Branched fibers that form supportive networks around organs
3. _______Stretchy fibers that return to their original length after being stretched
1. Collagen fibers (tendons and ligaments)
2. Reticular fibers (sheaths around organs)
3. Elastic fibers (elastic ligaments of vertebrae)
A pathologist is analyzing tissue samples from several patients and notes the following findings:
The cells in one tissue show disorganized growth with abnormal shapes and sizes, but the changes are still limited to the epithelial layer.
Another tissue shows a complete loss of normal cell differentiation, and the cells appear immature and vary greatly in shape — a sign of malignancy.
In a third sample, one mature cell type has been replaced by a different mature cell type, usually as an adaptive response to chronic irritation.
Another tissue exhibits an abnormal, uncontrolled proliferation of cells, forming a mass.
A muscle biopsy shows shrinkage of muscle fibers after prolonged limb immobilization in a cast.
A glandular tissue shows an increase in the number of cells, causing the organ to enlarge.
Finally, a cardiac muscle sample shows enlarged individual cells, resulting in a thicker heart wall.
a. Identify the process described in each case (use: dysplasia, anaplasia, metaplasia, neoplasia, atrophy, hyperplasia, hypertrophy).
b. Briefly explain whether each change is reversible or irreversible, and which could indicate a precancerous or malignant condition.
1) Dysplasia: disorganized growth; cells vary in shape, size, arrangement, but remain within the tissue boundary. Reversible if stimulus is removed, is precancerous and may lead to cancer if left unchecked.
2) Anaplasia: complete loss of normal cell structure and differentiation; cells appear immature and abnormal. Irreversible (malignant).
3) Metaplasia: one mature cell type replaces another. Reversible if irritant is removed. Prolonged metaplasia can lead to dysplasia.
4) Neoplasia: abnormal, uncontrolled cell growth forming a mass that may be benign or malignant. Irreversible once established and malignancy is invasive and may metastasize.
5) Atrophy: decrease in cell size or number. Reversible if normal functions is restored.
6) Hyperplasia: increase in the number of cells in a tissue, leading to enlargement. Reversible.
7) Hypertrophy: increase in the size of individual cells, rather than number. Reversible in early stages and may become pathologic if stimulus persists.