Week 2: Cells Flashcards

Question

Describe Cell Growth and Reproduction (6 points)

Answer 1

- Cell division = cellular reproduction; A single cell divides by duplicating its nucleus and then dividing into 2 new identical cells - A general rule to be applied to cell reproduction: The simpler a cell, the more power it has to regenerate. Cells with greater regenerative power have shorter life spans than those with less regenerative power. Cells which regenerate quickly include the cells that line our hollow structures, cover more delicate cells and tissues to protect them from the harsh external environment and bone marrow cells. More specialised cells, such as nerve and muscle cells, have weaker regenerative potential. - Some cells divide often, others divide if required, whilst others rarely or never divide in a lifetime. In each cycle, the original parent cell grows, and divides to form daughter cells which in turn grow and function until they themselves divide or maybe even die from wear and tear or by design (called apoptosis). - Chemical messages are constantly changing the chemical environment in which a cell and its nucleus exist. This change may result from chemicals being produced by nerve signals, hormones, the cells themselves or neighbouring cells, or degraded by enzymatic action. It is the dynamic chemical environment that is responsible for switching on the cell’s genes for cell division or the synthesis of the required protein. This process is often referred to as gene expression. - There are many chemical factors that interact to control cellular activities: these chemicals are sometimes called growth factors. Tumours and cancers occur when cells lose their controls on growth and division. Scientists need to study the cell cycle to gain an appreciation the unique cell cycles for different cell types, and factors which may adversely affect these cycles. - If a cell needs to divide, it will undergo additional growth, and begin to replicate the strands of DNA molecules (chromosomes) in the nucleus. The actual division of the nucleus into 2 identical nuclei is known as mitosis.

Answer 2

- A series of changes a cell goes through from the time it is formed until it has reproduced itself - Cell cycle is divided into two major periods: interphase and mitotic phase - Interphase is further divided into three phases, from beginning to end: 1. G1 phase 2. S phase 3. G2 phase - Mitotic (M) phase is further divided into four phases, from beginning to end: 1. Prophase: where chromosomes become visible, the nuclear envelope breaks down and a spindle forms 2. Metaphase 3. Anaphase: where chromosomes move toward each pole of a cell 4. Telophase - Non-dividing cells do not experience this cycle. Instead, they have their own phase known as G0

Answer 3

- One of the two major periods in the cel life cycle in which the cell grows and carries on its usual activities - the period from cell formation to cell division. - In addition to carrying on its life-sustaining activities, an interphase cell prepares for the next cell division. - Interphase is divided into G1, S, and G2 subphases - the Gs stand for gaps before and after the S phase, and S is for synthetic. - In all three subphases, the cell grows by producing proteins and organelles, but chromatin is reproduced only during the S subphase

Answer 4

- First phase of interphase - Cell metabolically active, synthesizing proteins rapidly and growing vigorously - Duplicates organelles and cytosolic components - As it ends, the centrioles start to replicate in preparation for cell division. - This is the most variable phase in terms of length. typically lasts several minutes to hours, but it may last for days or even years.

Answer 5

- Second phase of interphase - DNA is replicated, ensuring that the two future cells being created will receive identical copies of the genetic material - New histones are made and assembled into chromatin. - Duration = approximately 6-8 hours

Answer 6

- Third and final phase of interphase - Cell growth continues - Enzymes and other proteins needed for division are synthesized and moved to their proper sites - Replication of centrosomes is completed - At the end of phase, the cell is ready to divide - Duration = approximately 4-6 hours

Answer 7

- A type of cell membrane that separates the intercellular fluid within the cell and the extracellular fluid outside the cell - Flexible in nature - The main component of the membrane is a specialised molecule called a phospholipid. - The lipid molecules of the membrane naturally assemble into a double layer, known as a phospholipid bilayer - Also is composed of cholesterol (approximately 20%), which helps maintain the structural integrity and fluidity - Embedded in the phospholipid bilayer is: 1. Carbohydrates: These are often attached to proteins (forming glycoproteins) or lipids (forming glycolipids). The carbohydrate chains protrude from the extracellular surface of the membrane and are involved in cell recognition, signaling, and interactions with the environment 2. Proteins: found on membrane outer surfaces and helps in cell to cell recognition, interaction, communication and immunity. Some membrane proteins drift freely along the surface while others are “tethered” and are restricted in their movement - Different protein types provide different purpose

Answer 8

1. Tranport of nutrients and certain molecules 2. Receptors for signal transduction 3. Enzymatic activity 4. Cell to cell recongnition 5. Attachment to the cytoskeleton and extracellular matrix (ECM) 6. Cell to cell joining

Answer 9

- The phospholipid bilayer forms the bulk of the plasma membrane for all cells. - The phospholipid molecule consists of 2 parts joined together by a glycerol molecule: 1. the rounded red phosphate entities are the water-loving or hydrophilic (water attracting) heads, and 2. the attached orange/pink lines are the water-hating or hydrophobic (water repellent) tails. - The tails, being attracted to each other, form a bilayer with the heads facing the external and internal environments. - The lipid layer does not mix with water, hence the hydrophobic molecules line up inside the membrane “sandwich”, whereas the attached phosphate groups being water-loving or hydrophilic line up on both surfaces. - This ‘picket fence’ arrangement is the basis of the fluid-mosaic model of the plasma membrane. - The fluid describes the ability of the molecules within the bilayer to move: the mosaic refers to the many other large molecules embedded within the layer. - These molecules include proteins, carbohydrates and other lipids: the components vary from cell to cell, but all have a role to play in the function of that cell.

Answer 10

- The structure of the plasma membrane ensures that it acts as the gatekeeper of the cell. - A bilayer of phospholipids ensure few molecules can move freely through this medium. - To do this molecules must be lipophilic and relatively small: carbon dioxide and oxygen are examples of molecules that can do this with ease. - Some other molecules can move more slowly, and other not at all. - This ability gives rise to the description of the plasma membrane as being semi-permeable. - many protein structures embedded with the phospholipid bilayer. Proteins can vary considerably in structure and behavior: in fact many can change their shape on command! - Some proteins are integral to the full thickness of the membrane, whilst the peripheral proteins are bound to one surface and may be easily separated from it. - In addition there are other molecular types which may also have a role in membrane function. - There are proteins embedded in the membrane that can act as channels that allow some molecules to move through (similar to a door or windows). - Other embedded proteins act as carriers, binding to specific molecules and changing its confirmation to allow the molecule to move through the membrane (similar to a revolving door) - In addition other cellular processes may be required to move special or bulk materials in and out of cells. - There are 2 main types of transport: passive transport and active transport.

Answer 11

- The type of transportation requires no input energy to perform - Three main kinds of passive transport: 1. Simple diffusion 2. Facilitated diffusion 3. Osmosis - All of these are various types of diffusion

Answer 12

- In diffusion, substances move from an area of higher concentration to an area of lower concentration. This is called a moving down or along the concentration gradient. - The concentration gradient is the difference in the concentration of a particular substance between two different areas. - The movement continues until distribution is uniform. - This can happen in air, liquid or even solids. - This process is occurring constantly within the body, ensuring materials are mixing, and across the membrane if the permeability allows it to occur. - There are only 2 ways a molecule can move across the membrane. 1. simple diffusion - molecules diffuse across the lipid portion (the 'picket' fence) of the plasma membrane, 2. channel-mediated diffusion - molecules diffuse through a membrane channel.

Answer 13

- The unassisted transports across a plasma membrane of a lipid-soluble or very small particle - In simple diffusion, substances diffuse directly through the lipid bilayer - Two factors determine whether a molecule can move freely through the membrane. The molecule must meet all three factors to move easily through. They are: 1. Size: must be relatively small 2. Polarity: must be non-polar - These include: 1. Gases such as oxygen and carbon dioxide 2. Steroid hormones 3. Fatty acids

Answer 14

- Passive transport process used by certain large (such as glucose) or charged (Na+) molecules that are unable to pass through the plasma membrane unaided - Involves movement through channels or movement facilitated by a membrane carrier - Transported substance either: 1. binds to carrier proteins in the membrane and is ferried across. This is known as carrier-mediated facilitated diffusion 2. moves through water-filled channel proteins. This is known as channel-mediated facilitated diffusion

Answer 15

- Carriers are transmembrane proteins that are specific for transporting certain polar molecules or classes of molecules, such as sugars and amino acids, that are too large to pass through membrane channels. - Within the carrier protein is a specific area termed the receptor. Upon contact of this area by the substance (or another messenger chemical), the carrier protein simply changes its shape to facilitate the movement of the substance through its channel. - Alterations in the shape of the carrier allow it to first envelop and then release the transported substance, allowing it to bypass the nonpolar regions of the membrane. - A carrier protein is always specific for a particular substance. - This process is important for the movement of nutrients, such as glucose and amino acids into a cell. - The principles of passive transportation still exist: there must be concentration gradient and energy is not required. - These carrier proteins are also called transporters. - Carrier-mediated transport is limited by the number of protein carriers that are available. For example, when all the glucose carriers are “engaged,” they are said to be saturated, and glucose transport is occurring at its maximum rate.

Answer 16

- Channels are transmembrane proteins that transport substances, usually ions or water, through aqueous channels from one side of the membrane to the other. - Channels are selective due to pore size and the charges of the amino acids lining the pore. - Leakage channels are always open and simply allow ions or water to move according to concentration gradients. - Gated channels are controlled (opened or closed), usually by chemical or electrical signals. - Like carriers, many channels can be inhibited by certain molecules, show saturation, and tend to be specific. - Substances moving through them also follow the concentration gradient (always moving down the gradient).

Answer 17

- Osmosis is the passive transport of water across a membrane, from an area of lower solute concentration into an area of higher solute concentration - Alternatively water can transport from an area of higher water concentration into an area of lower water concentration. This is a special case of diffusion where only water moves rather than the solutes. - Osmosis has many consequences for fluid movement within the body. - Large solutes that cannot move across the membrane often govern how much water enters or leaves the cell in an attempt to reach equilibrium. - This movement of only water can create an osmotic pressure between compartments within the body.

Answer 18

- the ability of a solution to cause a cell to gain or lose water, thus changing the shape of the cell - Three types of solutions: 1. An isotonic solution does not result in the flow of water into or out of the cell. Using the principles of osmosis, the particle concentration inside the cell is similar to the particle concentration outside the cell, resulting in no net movement of water. 2. A hypotonic solution is lower in solute concentration, resulting a net movement of water into the cell. Cells placed in a hypotonic solution plump up rapidly as water rushes into them. In some cases, primarily in distilled water as it contains no solutes, water continues to enter cells until they finally burst, or lyse. 3. A hypertonic solution is higher in concentration, resulting in a net movement of water out of the cell. Cells immersed in hypertonic solutions lose water and shrivel, or crenate

Answer 19

- This type of transportation does require input energy to perform - Substances moved actively across the plasma membrane are usually unable to pass in the necessary direction by passive transport processes. - The substance may be too large to pass through the channels, incapable of dissolving in the lipid bilayer, or moving against its concentration gradient. - Usually this process is required to move a substance across the plasma membrane against the concentration gradient – from a lower concentration to a higher concentration (the opposite of simple diffusion) to enable the accumulation of material in a compartment. - Like carrier-mediated facilitated diffusion, active transport requires transport proteins that combine specifically and reversibly with the transported substances. - Two types of active transporters: 1. Primary active transporter: ATP, an energy carrier molecule, supplies the required energy to change the transporter’s shape thus helping to move the molecule across the membrane 2. Secondary active transporters: input energy comes from the potential energy stored in a secondary molecule’s concentration gradient. This means that when the secondary molecule travels through the membrane along its concentration gradient (high to low), energy is released, which is utilized by the other molecule and giving it the extra momentum to move against it concentration gradient

Answer 20

- A type of active transports in which the energy needed to drive the transport process is provided directly by hydrolysis of ATP - This step causes the protein to change its shape in such a manner that it pumps the bound solute across the membrane.

Answer 21

- All cells have ion pumps. These are carrier proteins that require energy to exchange ions across the plasma membrane to ensure there is a difference in intracellular and extracellular concentration. - Some examples are calcium and hydrogen pumps - The most commonly studied ion pump is the sodium-potassium exchange pump which ensures a higher extracellular concentration of sodium ions (Na+) and a higher intercellular concentration of potassium ions (K+).

Answer 22

- Also known as cotransport - A type of active transport that uses a cotransport protein to couple the “downhill” (down its concentration gradient) movement of one solute to the “uphill” (against its concentration gradient) movement of another solute. - The concentration gradient that is the source of energy for secondary active transport is created by primary active transport—in many cases by the sodium-potassium exchange pump. By moving sodium across the plasma membrane against its concentration gradient, the pump stores energy (in the gradient). Then, just as water held back by a dam can do work as it flows downward, a substance pumped across a membrane can do work as it leaks back, propelled “downhill” along its concentration gradient.

Answer 23

- When cells work together collectively in the body, we call them tissue and often refer to them as one of the 4 primary or basic types. - The four basic types of tissue are: 1. epithelial 2. connective 3. muscle 4. nerve

Answer 24

- Also known as epithelium (plural: epithelia) - Function: (1) protection, (2) absorption, (3) filtration, (4) excretion, (5) secretion, and (6) sensory reception - Location: covers the body surfaces, covers and lines the body cavities and interns organs, compose glands - Distinguishing features: lacks blood vessels - Epithelial cells fit closely together to form ‘sheets’ which line or cover surfaces of the body. - Generally these cells are easily regenerated or replaced. - They are always attached to underlying connective tissue, which supports them and supplies them with nutrients for growth. - There are many classifications of epithelial tissue, distinguished by the shape and arrangement of the cells and the reasons for this arrangement.

Answer 25

- The name of each epithelium has two parts. - The first name indicates the number of cell layers present. Based on the number of cell layers, there are simple and stratified epithelia - Both types of cell layers have a basal surface (near the base or interior of a structure) and apical surface (the free, exposed surface that faces the external environment or the lumen of a body cavity) - Simple epithelia consist of a single cell layer. They are typically found where absorption, secretion, and filtration occur and a thin epithelial barrier is desirable. - Stratified epithelia, composed of two or more cell layers stacked on top of each other, are common in high-abrasion areas where protection is important, such as the skin surface and the lining of the mouth. - An epithelium’s second name describes the shape of its cells. Epithelial cells vary in height, and on that basis, there are three common shapes of epithelial cells: * Squamous cells (skwa′mus) are flattened and scale-like (squam = scale). * Cuboidal cells (ku-boi′dahl) are boxlike, approximately as tall as they are wide. * Columnar cells (kŏ-lum′nar) are tall and column shaped.

Answer 26

- Function: bind, support, protect, fill spaces, store fat, produce blood cells - Location: widely distributed throughout the body - Distinguishing features: matrix between cells, good blood supply, all types originate from mesenchyme (an embyonic tissue) - There is more connective tissue in our body than any other tissue type, with a great diversity in the sub-groupings of connective tissue (CT), but they all have some similarities. - The most abundant connective tissue is aerola or loose CT. - This type of tissue provides a base for epithelium to grow upon (often referred to as the basement membrane) and is the basis of membranes and other structures that hold us together. - Generally the cells are sparse (they are not closely packed like epithelial tissue cells) and there are relatively large spaces between them. - These spaces contain materials/ substances that are usually produced by the cells and is collectively called the extracellular matrix (ECM). - The ECM usually contains protein fibres (the most abundant is collagen which has the role of connecting or holding the tissue together) and a ‘sea’ of thickened fluid called ground substance.

Answer 27

- the differences between the sub-groups of CT is due to the differences in the ECM produced. It is in these spaces where structures such as blood vessels, nerves and other cells roam. - If required the cells can replicate in order to regenerate additional ECM particularly if tissue is injured. - We require connective tissue with its variable ECM for: - Establishing a structural framework for the body - Transporting fluids and dissolved materials - Protecting delicate organs - Supporting, surrounding, and interconnecting other types of tissue - Storing energy reserves, especially in the form of triglycerides - Defending the body from invading microorganisms

Answer 28

- Function: movement - Location: attached to the bones, in the walls of hollow internal organs, heart - Distinguishing features: contractile - Muscle tissues can shorten in length, or contract. - Contraction of muscle tissue produces movement within the body. - There are 3 types of muscle tissue: 1. skeletal muscle that is attached to bones, 2. smooth muscle tissue that is found in walls of hollow organs, 3. and cardiac muscle which is the main tissue of the heart. - In each case the cells of muscle tissue are able to shorten on command, and therefore produce movement.

Answer 29

- Muscle composed of cylindrical multinucleate cells with obvious striations - The muscles attached to the body’s skeleton - Voluntary muscle, meaning muscle under strict nervous control - Skeletal muscle cells, also called muscle fibers, are long, cylindrical cells that contain many peripherally located nuclei. - Their obvious banded, or striated, appearance reflects the precise alignment of their myofilaments

Answer 30

- Spindle-shaped cells with one centrally located nucleus and no externally visible stations (bands) - Found mainly in the walls of hollow organs other than the heart: - Digestive tract organs - Urinary tract organs - Uterus - Blood vessel - Named because its cells have no visible striations

Answer 31

- Specialized muscle of the heart and found only in the walls of the heart. - Its contractions help propel blood through the blood vessels to all parts of the body. - Like skeletal muscle cells, cardiac muscle cells are striated. - However, cardiac cells differ structurally in that they are: 1. Generally uninucleate (one nucleus) with the nucleus situated centrally 2. Branching cells that fit together tightly at unique junctions called intercalated discs

Answer 32

- Function: transmit impulses for coordination, regulation of body functions, integration and sensory reception and controls body functions - Location: brain, spinal cord, nerves - Distinguishing features: cells connect to each other and other body parts - Nervous tissue allows us to regulate and control body functions by transmitting electrical signals. - It is made up of 2 major cell types: neurons and a number of different neuroglial cells/tissues.

Answer 33

Connective tissue

Answer 34

Epithelial Tissue

Answer 35

Muscle tissue

Answer 36

Nerve tissue

Answer 37

- It is made up of 2 major cell types: neurons and a number of different neuroglial cells/tissues. - Neurons are highly specialized nerve cells that generate and conduct nerve impulses. - Typically, they are branching cells with cytoplasmic extensions or processes that enable them to: * Respond to stimuli (via processes called dendrites) * Transmit electrical impulses over substantial distances within the body (via processes called axons) - Nerve cells are usually bundled together with many other neurons to produce a nerve or nervous tissue. - However, there is always support cells present as well in the form of neuroglia, and these cells generally make up around 50% of the tissue weight. - Glial cells or neuroglia are nonconducting cells that support, insulate, and protect the delicate neurons. - The astrocytes, oligodendrocytes, microglia and myelin-forming cells are examples of neuroglia.

Answer 38

- the multicellular sheets of tissue that separate organs and line our body cavities. - These membranes incorporate both a superficial epithelial sheet and connective layer known as the lamina propria - There are 4 types of membranes: 1. Mucous membrane: also known as mucosae; membranes that form the linings of the body cavities open to the exterior (digestive, urinary and reproductive tracts) 2. Synovial membrane: consists of only connective tissue 3. Serous membrane: also known as serosae; the moist membranes found in closed ventral body cavities 4. Cutaneous membrane (only external membrane; dry surface; waterproof): pertaining to the skin - Each of the membrane categories, with the exception of the cutaneous membrane (the skin), produce a fluid - It is the epithelial tissue that is responsible for producing this secretion, whether it is serous fluid, synovial fluid or mucus. - Goblet cells secrete this fluid to maintain a moist surface and lubricate - Serous membrane systems, which line the body cavity and cover the organs within, ensure organs can move within the cavity with minimal friction developing.

Week 2: Cells Flashcards

(63 cards)