Cells and Tissues (11)

Distinguish between facilitated diffusion and active transport

FD = Passive, H-L, Large complex (proteins), movement of molecules. AT = Active, L-H, Solutes (glucose) , movement of molecules

Define the 4 functions of the cell membrane

Form external barrier: Separates cytoplasm and extracellular fluid, Regulates passage of materials: controls what goes in and out of the cell. Sensitivity: Contains receptor proteins that are sensitive to extracellular environment, Structure: Attached to microfilaments which support the cell

Define simple diffusion

The passive movement of molecules with the concentration gradient across a plasma membrane from an area of high concentration to area of low concentration until evenly distributed.

How is the body organised

cells, tissues, organs, organ systems, organism

List the 4 basic tissue types

Connective, epithelial, muscle, nervous

Function of the mitochondria

Site for cellular respiration (production of ATP) that is used for the cells activities. Double membrane structure that is highly folded creating a large surface area for chemical reactions to occur.

Function of the nucleus

Contains deoxyribonucleic acid (DNA) that codes for the production of proteins. Proteins are produced by following the code outlined by the nitrogenous bases. This is how the nucleus controls the structure and function of the cell.

Function of the cytosol

Liquid portion of the cytoplasm, contains nutrients and minerals which provide for the cells organelles. 75-95% water, made up of dissolved substances and insoluble substances suspended in fluid.

Describe how the concentration gradient can affect the exchange of materials.

The greater the concentration gradient the quicker diffusion will take place. The smaller the concentration gradient the slower diffusion will take place.

Function of the nuclear pores

Small gaps in the nuclear membrane that allows larger substances in and out of the nucleus.

Function of inclusions

Any substance in the cell that is not an organelle. E.g. hemoglobin in red blood cells is a chemical structure which helps in the transportation of oxygen and carbon dioxide.

Describe how the physical and chemical nature of materials can affect the transport across the membrane

Cell membrane is a selectively permeable bi-layer. Larger molecules and water soluble molecules cannot diffuse through so they can enter through channel or carrier proteins or vesicular transport depending on the concentration gradient and the energy requirements. Small hydrophobic lipid soluble substances can diffuse through.

List and describe the 3 basic processes that result in transport of materials into and out of cells

Diffusion: movement of materials from a high concentration to a low concentration. Carrier - mediated transport: The movement of materials across the cell membrane using channel or carrier proteins. Vesicular transport: movement of substances in and out of the cell in membrane bound sacs.

Define the term selectively permeable

Allows certain ions and molecules to pass through but restricts the movement of others.

Define active transport

Requires energy (ATP), from low to high concentration, water soluble substance use carrier proteins, e.g glucose, amino acids

Function of the cytoplasm

Jelly-like consistency that suspends organelles (protects and absorbs movement). Fills space between nucleus and cell membrane.

What are cells?

The basic structural and functional unit of a living organism.

Distinguish between simple diffusion and osmosis

Similarities: Passive, high to low concentration, movement of molecules across selectively permeable membrane. Differences: osmosis is only the movement of water molecules

Outline the differences between active and passive transport

Active: uses energy, against concentration gradient, Passive: no energy used, with the concentration gradient

List the basic parts of a cell

Cell membrane, cytoplasm (cytosol and organelles), cytoskeleton and inclusions

Describe the general requirements of a cell

In the human body cells need to be in a stable environment in which they are continually supplied with the materials they need, and continually removing the waste products they produce. Cells continually need oxygen and glucose, while continually removing carbon dioxide and water. The amount of materials and organelles required by a cell varies depending on the cells role and type.

Function of the golgi body

Modifies and packages proteins into vesicles. These vesicles can then travel through the cell to meet intracellular needs. Or they can move through the cytoplasm, fuse with the cell membrane and expel its contents into the extracellular environment.

Function of cytoskeleton

Framework made of protein fibres that provides a transport network (mesh-like) and helps suspend the organelles. Allows for the movement of substances within the cell from organelle to organelle. Microtubules: Hollow rods that keep organelles in place. Microfilaments: Assist in the movement of materials around the cytoplasm.

Function of lysosome

Engulfs pathogens and dead/old organelles, breaks them down, to be expelled from the cell via exocytosis. Macrophage that contains digestive enzymes that can break down large molecules. Can also join with vesicles and break down there contents.

Function of cell membrane

Phospholipid bi-layer made up of phosphate heads and lipid tails. Separates intracellular fluid from extracellular fluid. Selectively permeable, controls the movement of substances in and out of the cell.

Define facilitated diffusion

Passive movement of molecules across the cell membrane using carrier or channel proteins, using no energy from and area of high concentration to an area of low concentration. Larger more complex molecules, proteins, water soluble substances.

Function of centrioles

Found near the nucleus, produce spindle fibres that attach to chromosomes during cellular divison.

Describe process of exocytosis

Contents of a vesicle inside the cell is passed through into the extracellular environment. A vesicle formed inside the cell travels through the cytoplasm fuses with the cell membrane expelling it's contents. E.g. Mucus, digestive enzymes

Function of organelles

A structure inside the cell that has a particular job.

Nuclear membrane

Separates the cytoplasm from the nucleus. A selectively permeable membrane bound structure that controls the movement of substances in and out of the nucleus.

Describe the process of endocytosis

The taking in of substances from outside the cell. The cell membrane folds around the substance until it is fully enclosed forming a vesicle which then pinches off and is suspended in cytoplasm. When the substance is a solid it is phagocytosis, and when it is a liquid it is pinocytosis. E.g. cell debris, cholesterol, micro-organisms

Function of rough endoplasmic reticulum

Ribosomes found on the surface, plays a role in protein synthesis as it stores and transports proteins. Has surface area for chemical reactions to occur and channels to store and transport molecules.

Define osmosis

The passive movement of water molecules with the concentration gradient across a plasma membrane from an are of high concentration of water molecules to an area of low concentration of water molecules until evenly distributed.

Function of the nucleolus

Contains ribonucleic acid (RNA), produces proteins, and plays a role in protein synthesis.

Function of ribosomes

Produce proteins through protein synthesis, the joining of amino acids to create proteins. Found free floating in the cytoplasm or on the surface of the rough endoplasmic reticulum.

Define the term tissue

A group of cells similar in structure that work together to perform a particular function.

Function of smooth endoplasmic reticulum

No ribosomes on the surface, stores and transports molecules. These molecules may be needed for future use by the cell or removed from the cell later. Has surface area for chemical reactions to occur and channels for storing and transporting molecules.

Outline the role of channel proteins in diffusion.

Water-soluble molecules must diffuse through channel pathways so they can cross the cell membrane without coming into contact with the hydrophobic lipid tails in the cell membrane. Very small in diameter water and ions can easily get through but larger molecules cannot.

Describe the characteristics of carrier proteins.

Carrier proteins are only open on one side of the membrane at a time. When the specific substance binds to the binding site within the protein, the protein changes shape and opens to the other side. The substance can then be released on the side opposite to where is entered. Specific, can become saturated, regulated by hormones.

Describe how the surface area to volume ratio limits cell size.

Cells are very small which means they have a high surface area to volume ratio. If cells were larger the ratio would be smaller and the cell membrane would not be able to support the needs of the cell because the cells volume would be too large in comparison to the surface area of the cell membrane.