National 5 Biology-Transport Across Cell Membranes

NinaJasT
Flashcards by NinaJasT, updated more than 1 year ago
NinaJasT
Created by NinaJasT over 6 years ago
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CfE Higher Biology (Unit 1-Cell Biology) Flashcards on National 5 Biology-Transport Across Cell Membranes , created by NinaJasT on 12/28/2014.

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Question Answer
What is the cell membrane composed of? Phospholipids and proteins.
What is the cell membrane known to be? Selectively permeable-it only allows molecules that are small enough to pass through it.
What is a concentration gradient? A difference in concentration of a substance.
Describe what passive transport of a substance is The movement of its molecules from a region of high concentration to a region of low concentration, down a concentration gradient. This does not require additional energy.
Give two examples of passive transport Diffusion and osmosis.
What is the difference between diffusion and osmosis? Osmosis is the movement of water through a selectively permeable membrane, whereas diffusion is the movement of a substance.
Give three examples of substances that enter most cells through diffusion Oxygen, glucose and amino acids.
Give two examples of substances that leave most cells through diffusion Carbon dioxide and urea.
Why is diffusion important? It helps to provide the cell with raw materials and helps to remove waste products.
Describe what active transport of a substance is The movement of molecules from a region of low concenration to a region of high concentration against a concentration gradient. This requires additional energy (ATP).
Why does active tranpsort require additional energy? To allow membrane proteins to move molecules against the concentration gradient.
What happens to an animal cell in a hypotonic solution? Water is taken into the cell through osmosis and it bursts.
What happens to an animal cell in a hypertonic solution? Water will be lost by osmosis and the cell shrinks.
What happens to an animal cell in an isotonic solution? No gain or loss in water, and therefore the cell remains unchanged.
What happens to a plant cell if it is placed in a hypotonic solution? It will take up water by osmosis and become turgid-the vacuole swells and cell membrane and cytoplasm are pushed against the cell wall.
What happens to a plant cell placed in a hypertonic solution? It will lose water by osmosis and become plasmolysed-vacuole shrinks, and the cell membrane pulls away from the cell wall, tissue is flaccid.
Describe the role of protein molecules in osmosis and active transport In osmosis, protein molecules allow the passage of water molecules in pores. In active transport, proteins act as carriers.
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