Bio module 3-cells

Cytology

the study of cellular function and structure

Plasma membrane

forms a cells surface boundary sh. forms cells shape

Cytoplasm

the material between the plasma membrane and nucleus

parts:

• cytoskeleton

• organelles

• inclusions

• cytosol

Cytoskeleton

network of protein filaments and tubules in cytoplasm that structurally support cell

What are the main components of the cytoskeleton?

• microfilaments

• intermediate filaments

• microtubules

What function does the cytoskeleton serve?

• determines cell shape

• contributes to cell movements

• gives cell structural support

• organizes content

Organelles

diverse structures that perform tasks for the cell

Inclusions

A nonessential cell component with no membrane that contains accumulated cell products like fats and pigments as well as viruses and bacteria

Cytosol

clear gel containing enzymes and other proteins that embeds the cell components sh. the fluid in the cell

What are the functions of the plasma membrane?

• governs interactions with other cells

• defines the boundary of the cell

• maintains chemical difference between ECF and ICF

• contributes to movement of cell components

What is the plasma membrane made up of?

a two layered lipid film with embedded proteins

Phospholipids

make up 75% of membrane lipids

Cholesterol

make up 20% of membrane lipids

Functions of membrane proteins

• receptor

• channel

• enzyme

• gated channel

• cell identifier marker

• cell adhesion molecule

Glycocalyz

a fuzzy carbohydrate coat covering cells that is made up of the sugar chains glycolipids and glycoproteins

What are the functions of the glycocalyx?

• cell adhesive

• determines blood types

• protects plasma membrane

• identifies self-cells from foreign cells

• identifies healthy cells from diseased cells

What are the four cell surface extension types?

• microvili

• cilia

• flagellum

• pseudopods

Microvilli

extension with finger shaped projections of the plasma membrane

functions: increases surface area for absorption and secretion

sometimes called a brush border

Cilia

hairlike extensions of the plasma membrane that are found in the mucous membranes of respiratory tract and uterine tubes

functions: helps move things like mucus

ex. move mucus from lungs up to throat

Flagellum

extensions that resemble a long and solitary cilium

sh. essentially a tail attached to a cell

function: helps cell move

Pseudopods

cytoplasm filled extensions of a cell that change shape continually

function: form fake arms that play a role in movement and help cells to eat

What are the functions of extensions?

• absorption

• movement

• sensory processes

• phagocytosis

Macrophages

white blood cells that use pseudopods to engulf bacteria

What are the functions of cell junctions?

• link cells together

• attach cells to extracellular material

Tight junctions

these junctions fully encircle epithelial cells near upper end and join them securely to adjacent cells making it difficult for substances to leak between

ex. ensures absorbed nutrients pass through digestive system cells and not around them

Desmosomes

holds cells together at a specific point and keeps them from pulling apart. enables tissues to resist mechanical stress.

ex. common in skin and cardiac muscles

Gap junctions

formed by ring of proteins that surround a channel and is used for the diffusion of ions, glucose, and other solutes.

Filteration

A process in which external pressure forces fluid through a selectively permeable barrier and holds back large particles while allowing water and small particles to pass through.

sh. the passage of fluid

Simple diffusion

the net movement of particles from high to low concentration with random motion of molecules providing energy for diffusion.

ex. simple diffusion seeks to achieve balance

ex. how oxygen and steroid hormones reach cells

Osmosis

the net movement of water from lower to higher solute concentration (water follows solutes)

Tonicity

the ability of a solution to change intracellular pressure and the volume and shape of a cell

Isotonic

• extracellular fluid has an equal concentration of solutes as the intracellular fluid

• cells gain and lose water by an equal rate sh. cell does not change shape

Hypertonic

• extracellular has a higher concentration of solutes than intracellular fluid

• draws water out of cell and cell shrinks

Hypotonic

• extracellular fluid has a lower concentration of solutes than intracellular

• water enters cell and cell swells

Active transport

like facilitated diffusion, is a carrier mediated transport

What is the difference between active and passive transport?

Active transport requires ATP (energy) while passive transport does not

Vesicular transport

substances move through membranes in vesicles (resemble bubbles or sacs)

Endocytosis

brings matter into cell

Phagocytosis

A type of endocytosis that is “cell eating” and uses pseudopods to reach out and surround particles, enzymatically degrading it

occurs especially in macrophages (white blood cells)

Pinocytosis

A type of endocytosis that is “cell drinking” that starts off with the formation of dimples that cave in and pinch off as vesicles

Receptor mediated

This type of endocytosis is more selective, and the cell can take in specific molecules from the ECF through receptor proteins on plasma membrane

ex. absorption of insulin from blood

Exocytosis

exports matter from cell

How does exocytosis occur?

cell vesicle migrates to surface, fuses with plasma membrane and ruptures, releasing products from the cell

Facilitated diffusion

a carrier mediated transport that employs carrier proteins to move solutes down a concentration gradient

Nucleus

the largest and most important organelle that stores chromosomes and DNA and gives out orders to maintain organization within the cell

Nuclear envelope

two parallel membranes, perforated by nuclear pores, that surround the nucleus

Nucleoli

dense masses within the nucleus where subunits of ribosomes are made

Endoplasmic reticulum (ER)

a system of interconnected channels called cisternae that is enclosed by a membrane

functions: synthesizes steroids and other lipids, manufactures cell membranes, and produces proteins

Rough ER (RER)

• cisternae is covered with ribosomes

• abundant in cells producing proteins

• function: the synthesis of proteins

Smooth ER (SER)

• lack ribosomes

• continuous with rough ER

• abundant in cells that synthesize steroid hormones like testes, ovaries

• function: helps with detoxification and stores calcium

Ribosomes

small granules of protein and ribonucleic acid (RNA) that read the genetic code from the nucleus and assemble amino acids into proteins

function: the synthesis of proteins

location: nuclear envelope, rough ER, and free in cytoplasm

Golgi complex

A small cluster of cisterns that synthesize carbohydrates and put the finishing touches on protein and glycoprotein synthesis

sh. reshapes or changes proteins sent from ER

Golgi vesicle

• membranous sacs

• filled with secretory product

• some become part of plasma membrane

• others become secretory vesicles that store products released by exocytosis

  sh. allow cisternae to receive and release proteins

Lysosomes

packages or sacs of enzymes enclosed within a membrane that store “good” products and help carry out apoptosis (programmed cell death)

Mitochondria

A double membrane organelle that synthesizes ATP and has its own DNA while its inner membranes cristae (folds) synthesize enzymes

Centrioles

an organelle with a short cylindrical assembly of microtubles

function: plays a key role in cell division

What are the two types of cells?

• somatic cells

• sex cells

Mitochondrial matrix

the space between the cristae that contain enzymes, ribosomes, and mitochondrial DNA

Centrosome

area of cytoplasm near nucleus that contains a pair of centrioles

True or false: all cells arise from existing cells and divide giving us new cells

true

What are the four phases and functions of processes within the life cycle?

• G₁ first gap phase

interval between cell division and DNA replication that prepares for new division by synthesizing proteins and packing itself with nutrients for DNA replication

• Synthesis phase

where DNA replication occurs

• G₂ second gap phase

interval between cell division and DNA replication where centriole replication finishes along with the synthesis of enzymes that control cell division

• Mitotic (M) phase

where the nucleus replicates and mitosis occurs

What are the four phases of the Mitosis?

• prophase

• metaphase

• anaphase

• telophase

Cytokinesis

when the cytoplasm divides and the cell divides forming two genetically identical daughter cells

ex. occurs during telophase

telophase:

• chromosomes gather at each pole of cell

• chromatin decondenses

• new nuclear envelope appears at each pole

• new nucleoli appear in each nucleus

• mitotic spindle vanishes

What is mitosis cell division used for?

growth

• fertilized egg into individual'

• continues growth of organs after birth

• repairs damaged tissues