Ocr Biology (Cell Membranes)

Front 1

Describe the 3 functions of the membrane at the surface of the cell.

Back 1

>Separating cell contents from the outside environment
>Controls which substances enter and leave the cell
>Cell recognition and signalling

Front 2

Describe the 3 functions of the membrane within the cell.

Back 2

>Divide cell into compartments making different functions more efficient
>Can form vesicles
>Control which substances enter and leave the organelle.

Front 3

Describe the 'fluid mosaic' structure.

Back 3

>Phospholipid molecules form a continuous fluid bilayer
>Various protein molecules are scattered through the bilayer some can move around
>Glycoproteins (protein molecules have a carbohydrate part attached)
>Glycolipids (phospholipid molecules have a carbohydrate part attached)
>Cholesterol

Front 4

Describe the role of cholesterol in the cell membrane.

Back 4

Cholesterol molecules fit between phospholipid tails to make the membrane more rigid/more complete so water molecules and ions cannot pass easily through the membrane.

Front 5

Describe the role of phospholipids in the cell membrane.

Back 5

Front 6

Describe the role of glycolipids and glycoproteins in the cell membrane.

Back 6

>Cell signalling and recognition
>Glycoproteins can bind cells together in tissues.
>Some receptor sites allow hormones to bind with the cell which causes the cell to respond in some way.

Front 7

Outline the effects of changing temperature on membrane structure and permeability.

Back 7

Increase in temperature gives molecules more kinetic energy so they move faster. This increased movements of phospholipids makes membranes more permeable.

Front 8

Describe the role of channel proteins in the cell membrane.

Back 8

Allows the movement of molecules that are usually too large and too hydrophylic to cross the membrane.

Front 9

Describe the role of carrier proteins in the cell membrane.

Back 9

Actively moves some substances across membrane using ATP.

Front 10

Explain the term 'cell signalling'.

Back 10

One cell releases a messenger molecule, which travels to another cell where it binds to a receptor on the target cell membrane because the two have complimentary shapes, causing the target cell to respond in some way.

Front 11

Explain the role of membrane bound receptors where hormones bind.

Back 11

Hormones bind to a receptor because their shapes are complimentary e.g. glucagon is released when there's not enough glucose in the blood. It binds to receptors on liver cells, causing them to break down stores of glycogen to glucose.

Front 12

Explain the role of membrane bound receptors where drugs bind.

Back 12

Drugs bind to a receptor because their shapes are complimentary. They either trigger a response or block the receptor and prevent it working.

Front 13

a) What is the meaning of passive transport?
b) List 3 types.

Back 13

a) No energy needed
b)>Diffusion
>Osmosis
>Facilitated diffusion

Front 14

What 6 things does diffusion depend on?

Back 14

>Temperature - the hotter the more kinetic energy
>The concentration gradient - the higher, the faster the rate of diffusion
>Thickness of exchange surface - thinner surface the faster the rate of diffusion
>Surface area - larger the area the faster diffusion
>Moving/stirring - increases kinetic energy
>Size of molecule

Front 15

Define diffusion.

Back 15

The movement of molecules from a region of high concentration of that molecule to a region of lower concentration of that molecule down a concentration gradient.

Front 16

Define facilitated diffusion in carrier proteins.

Back 16

Shaped so a specific molecule can fit in at the membrane surface, once the molecule is in, the protein changes shape to allow molecule through to other side.

Front 17

Describe active transport.

Back 17

Refers to the movement of molecules across membranes, which use ATP to drive protein pumps within the membrane.

Front 18

Define endocytosis.

Back 18

The bulk movement of materials into a cell.

Front 19

Define exocytosis.

Back 19

The bulk movement of materials out of a cell.

Front 20

Define Phago.

Back 20

Solid material.

Front 21

Define Pino.

Back 21

Liquid material.

Front 22

List the differences between active transport and facilitated diffusion.

Back 22

>Active transport only carries molecules one way
>Uses ATP
>Can carry molecules opposite to concentration gradient
>Faster
>Molecules can be accumulated.

Front 23

Define osmosis.

Back 23

The movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane.

Front 24

Define water potential.

Back 24

A measure of the tendency of water molecules to diffuse from one place to another.

Front 25

If an animal cell is placed in pure water what will happen.

Back 25

The water will enter the cell by osmosis causing it to swell and eventually the membrane will burst (haemolysed).

Front 26

If an plant cell is placed in pure water what will happen.

Back 26

The water will enter the cell by osmosis causing it to swell, the membrane will push on the the cell wall (turgid). Will not burst due to cell wall.

Front 27

If an animal cell is placed in a concentrated salt or sugar solution (water potential lower than cell contents) what will happen.

Back 27

Water molecules move in to out by osmosis. Cell will shrink and membrane will wrinkle up (crenated).

Front 28

If an plant cell is placed in a concentrated salt or sugar solution (water potential lower than cell contents) what will happen.

Back 28

Water molecules move in to out by osmosis. Cytoplasm and vacuole will shrink, cell surface membrane will pull away from cell wall (plasmolysed)

Front 29

Define solute.

Back 29

A solid that dissolves in a liquid.

Front 30

Define solvent.

Back 30

A liquid that dissolves solids.

Front 31

Define solution.

Back 31

A liquid containing dissolved solids

Front 32

Describe what the cell cycle consists of.

Back 32

Mitosis only occupies a small percentage of the cell cycle the remaining being copying and checking genetic information on DNA and processes associated with growth.

Front 33

Describe the four stages of mitosis.

Back 33

Prophase - replicated chromosomes supercoil (shorten and thicken), nuclear envelope breaks down and disappears. Centriole divides into two and each daughter centriole moves to opposite poles of cell to form spindle
Metaphase - replicated chromosomes move to the central region of spindle and each become attached to spindle thread by its centromere
Anaphase - the replicated sister chromatids that make up chromosomes are separated from each other when the centromere holding them together splits. Sisters become individual chromosomes, spindle fibres shorten pulling chromatids (now chromosomes) further apart towards poles.
Telophase - as sister chromatids (now chromosomes) reach the poles a new nuclear envelope forms around each. The spindle breaks down and disappears and the chromosomes uncoil
Cytokinesis.

Front 34

Explain the significance of mitosis for growth.

Back 34

Multicellular organisms grow by producing new genetically identical extra cells.

Front 35

Explain the significance of mitosis for repair.

Back 35

Damaged cells need to be replaced by new ones that are genetically identical.

Front 36

Define cytokinesis.

Back 36

The cell splitting into two new cells at the end of mitosis.

Front 37

Define stem cell.

Back 37

Cell with the potential to become any one of the different cell types found in the fully grown organism. Can be described as omnipotent or totipotent.

Front 38

Explain the process of budding in yeast.

Back 38

Cells of yeast undergo cytokinesis by producing a small bud that nips off the cell, in a process called budding.

Front 39

State the two ways in which mitosis and meiosis differ.

Back 39

>Meiosis produces cells containing half the number of chromosomes
>Meiosis produces cells that are genetically different from each other and from parent cell

Front 40

Define the term differentiation with reference to the production of erythrocytes.

Back 40

>Start out as stem cells from bone marrow
>Loses nucleus, mitochondria, golgi apparatus and roughER
>Packed full of the protein haemoglobin
>Cell changes shape, becoming bioconcave discs capable of transporting oxygen

Front 41

Define the term differentiation with reference to the production of neutrophilis.

Back 41

>Start as stem cells from bone marrow
>Keep nucleus
>Cytoplasm appears granular due to huge amounts lysosomes being produced
>All potent enzymes in lysosomes enable neutrophilis to be specialised for killing (ingesting) invading microorganisms.

Front 42

Define differentiation.

Back 42

Refers to the changes occuring in cells of a multicellular organism so that each different type of cell becomes specialised to perform a specific function.

Front 43

Define the term tissue.

Back 43

A collection of cells that are similar to each other and perform a common function.

Front 44

Define the term organ.

Back 44

A collection of tissues working together to perform a particular function.

Front 45

Define the term organ systems.

Back 45

A number of organs working together to perform an overall life function e.g. excretory systems and reproductive systems.

Front 46

Explain the function of sperm cells.

Back 46

>Have many mitochondria to produce ATP which provides energy for movement
>Have an undulipodium for movement
>Have enzymes to digest membrane around egg

Front 47

Explain the function of root hair cells.

Back 47

Have a large surface area to maximise uptake of minerals and water.

Front 48

Define the term differentiation with reference to the production of xylem vesssels.

Back 48

>Starts as meristem cells such as cambium
>Meristem cells produce small cells that elongate
>Walls become waterproofed by lignin which kills cells contents
>Ends of cell breaks down to form long tubes with wide lumen
>Good for transporting water and minerals up plant as well as supporting plant
>Consist of xylem vessels with parenchyma cells and fibres

Front 49

Define the term differentiation with reference to the production of phloem sieve tubes.

Back 49

>Starts as meristem cells such as cambium
>Meristem tissue produces cells that elongate and line up end to end to form long tubes
>Ends form sieve plates
>Plates allow movement of materials up or down tubes
>Next to sieve tube is a companion cell, which is very metabolic. Important in moving products up and down plant

Front 50

Explain how cells are organised into the squamous epithelial tissue.

Back 50

>Thin flattened cells
>Ideal for fluids to pass over
>Short diffusion pathway due to thickness
>Held in place by basement membrane, secreted by epithelial made of collagen and glycoproteins

Front 51

Explain how cells are organised into the ciliated epithelial tissue.

Back 51

>Made up of column shaped cells
>Part of cell surface that is exposed in tube space (lumen) is covered with cilia

Front 52

Define locomotion.

Back 52

>Muscular and skeletal systems work together in order for movement to take place
>Nervous system instructs muscles to coordinate
>Muscles and nerves need energy to work
>They require a supply of nutrients and oxygen from circulatory system
>Which in turn receives these chemicals from digestive and ventilation systems.

Front 53

Define mitosis.

Back 53

The process of nuclear division where two genetically identical nucei are formed from one parent cell nucleus.

Front 54

Define facilitated diffusion in channel proteins.

Back 54

Basically form pores in membrane which are often shaped to allow only one type of molecule through, many are gated meaning they open and close.